Lint Report

Overview

	Correctness
1	OldTargetApi: Target SDK attribute is not targeting latest version
5	GradleDependency: Obsolete Gradle Dependency
	Performance
4	ObsoleteSdkInt: Obsolete SDK_INT Version Check
1	UnusedResources: Unused resources
	Internationalization
1	SetTextI18n: TextView Internationalization
5	HardcodedText: Hardcoded text
	Included Additional Checks (29)
	Disabled Checks (39)

Target SDK attribute is not targeting latest version

../../build.gradle.kts:13: Not targeting the latest versions of Android; compatibility modes apply. Consider testing and updating this version. Consult the android.os.Build.VERSION_CODES javadoc for details.

 10     defaultConfig {
 11         applicationId = "de.duffy.screencast"
 12         minSdk = 24
 13         targetSdk = 35                                                                              
 14         versionCode = 3
 15         versionName = "1.2"
 16     }

When your application runs on a version of Android that is more recent than your targetSdkVersion specifies that it has been tested with, various compatibility modes kick in. This ensures that your application continues to work, but it may look out of place. For example, if the targetSdkVersion is less than 14, your app may get an option button in the UI.

To fix this issue, set the targetSdkVersion to the highest available value. Then test your app to make sure everything works correctly. You may want to consult the compatibility notes to see what changes apply to each version you are adding support for: https://developer.android.com/reference/android/os/Build.VERSION_CODES.html as well as follow this guide:
https://developer.android.com/distribute/best-practices/develop/target-sdk.html

More info:

Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.
To suppress this error, use the issue id "OldTargetApi" as explained in the Suppressing Warnings and Errors section.

OldTargetApi Correctness Warning Priority 6/10

Obsolete Gradle Dependency

../../build.gradle.kts:49: A newer version of androidx.core:core-ktx than 1.13.1 is available: 1.19.0

 46 
 47 dependencies {
 48     testImplementation("junit:junit:4.13.2")
 49     implementation("androidx.core:core-ktx:1.13.1")                                                 
 50     implementation("androidx.appcompat:appcompat:1.7.0")
 51     implementation("com.google.android.material:material:1.12.0")
 52     implementation("androidx.constraintlayout:constraintlayout:2.1.4")

../../build.gradle.kts:50: A newer version of androidx.appcompat:appcompat than 1.7.0 is available: 1.8.0

 47 dependencies {
 48     testImplementation("junit:junit:4.13.2")
 49     implementation("androidx.core:core-ktx:1.13.1")
 50     implementation("androidx.appcompat:appcompat:1.7.0")                                            
 51     implementation("com.google.android.material:material:1.12.0")
 52     implementation("androidx.constraintlayout:constraintlayout:2.1.4")
 53     implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.8.7")

../../build.gradle.kts:51: A newer version of com.google.android.material:material than 1.12.0 is available: 1.14.0

 48     testImplementation("junit:junit:4.13.2")
 49     implementation("androidx.core:core-ktx:1.13.1")
 50     implementation("androidx.appcompat:appcompat:1.7.0")
 51     implementation("com.google.android.material:material:1.12.0")                                   
 52     implementation("androidx.constraintlayout:constraintlayout:2.1.4")
 53     implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.8.7")
 54 }

../../build.gradle.kts:52: A newer version of androidx.constraintlayout:constraintlayout than 2.1.4 is available: 2.2.2

 49     implementation("androidx.core:core-ktx:1.13.1")
 50     implementation("androidx.appcompat:appcompat:1.7.0")
 51     implementation("com.google.android.material:material:1.12.0")
 52     implementation("androidx.constraintlayout:constraintlayout:2.1.4")                              
 53     implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.8.7")
 54 }

../../build.gradle.kts:53: A newer version of androidx.lifecycle:lifecycle-runtime-ktx than 2.8.7 is available: 2.11.0

 50     implementation("androidx.appcompat:appcompat:1.7.0")
 51     implementation("com.google.android.material:material:1.12.0")
 52     implementation("androidx.constraintlayout:constraintlayout:2.1.4")
 53     implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.8.7")                                
 54 }

GradleDependency Correctness Warning Priority 4/10

Obsolete SDK_INT Version Check

../../src/main/java/de/duffy/screencast/CastService.kt:255: Unnecessary; SDK_INT is always >= 24

 252         CastState.running.postValue(false)
 253         CastState.viewers.postValue(0)
 254         CastState.url.postValue("")
 255         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {                                       
 256             stopForeground(STOP_FOREGROUND_REMOVE)
 257         } else {
 258             @Suppress("DEPRECATION") stopForeground(true)

../../src/main/java/de/duffy/screencast/NetworkUtil.kt:20: Unnecessary; SDK_INT is never < 24

 17   }
 18 
 19   private fun fromConnectivityManager(context: Context): String? {
 20       if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) return null                              
 21       return try {
 22           val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
 23           val network = cm.activeNetwork ?: return null

../../src/main/java/de/duffy/screencast/NetworkUtil.kt:47: Unnecessary; SDK_INT is always >= 24

 44   /** Ist ueberhaupt ein WLAN aktiv? Ohne WLAN nuetzt der Stream wenig. */
 45   fun isOnWifi(context: Context): Boolean = try {
 46       val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
 47       if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {                                       
 48           val caps = cm.getNetworkCapabilities(cm.activeNetwork ?: return false) ?: return false
 49           caps.hasTransport(android.net.NetworkCapabilities.TRANSPORT_WIFI) ||
 50               caps.hasTransport(android.net.NetworkCapabilities.TRANSPORT_ETHERNET)

../../src/main/java/de/duffy/screencast/ScreenEncoder.kt:72: Unnecessary; SDK_INT is always >= 24

  69            }
  70            // Standbild trotzdem weitersenden, sonst laeuft der Puffer im Player leer.
  71            setLong(MediaFormat.KEY_REPEAT_PREVIOUS_FRAME_AFTER, 250_000L)
  72            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {                                   
  73                setInteger(MediaFormat.KEY_PRIORITY, 0) // Echtzeit
  74            }
  75            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {

This check flags version checks that are not necessary, because the minSdkVersion (or surrounding known API level) is already at least as high as the version checked for.

Similarly, it also looks for resources in -vNN folders, such as values-v14 where the version qualifier is less than or equal to the minSdkVersion, where the contents should be merged into the best folder.
Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.
To suppress this error, use the issue id "ObsoleteSdkInt" as explained in the Suppressing Warnings and Errors section.

ObsoleteSdkInt Performance Warning Priority 6/10

Unused resources

../../src/main/res/values/strings.xml:26: The resource R.string.connect_browser appears to be unused

 23     <string name="disconnect">Verbindung trennen</string>
 24     <string name="protocol">Protokoll</string>
 25     <string name="connect_direct">Zum Fernseher verbinden</string>
 26     <string name="connect_browser">Über Browser-Adresse</string>                                    
 27 
 28     <plurals name="viewers">
 29         <item quantity="one">%d Gerät schaut zu</item>

UnusedResources Performance Warning Priority 3/10

TextView Internationalization

../../src/main/java/de/duffy/screencast/DeviceActivity.kt:179: Do not concatenate text displayed with setText. Use resource string with placeholders.

 176 
 177   private fun addDevice(title: String, subtitle: String, enabled: Boolean, onClick: () -> Unit) {
 178       val button = MaterialButton(this, null, com.google.android.material.R.attr.materialButtonOutlinedStyle)
 179       button.text = "$title\n$subtitle"                                                           
 180       button.isAllCaps = false
 181       button.isEnabled = enabled
 182       button.setPadding(40, 30, 40, 30)

When calling TextView#setText
* Never call Number#toString() to format numbers; it will not handle fraction separators and locale-specific digits properly. Consider using String#format with proper format specifications (%d or %f) instead.
* Do not pass a string literal (e.g. "Hello") to display text. Hardcoded text can not be properly translated to other languages. Consider using Android resource strings instead.
* Do not build messages by concatenating text chunks. Such messages can not be properly translated.

More info: https://developer.android.com/guide/topics/resources/localization.html

To suppress this error, use the issue id "SetTextI18n" as explained in the Suppressing Warnings and Errors section.

SetTextI18n Internationalization Warning Priority 6/10

Hardcoded text

../../src/main/res/layout/activity_main.xml:175: Hardcoded string "Sparsam", should use @string resource

 172                     style="@style/Widget.Material3.Chip.Filter"
 173                     android:layout_width="wrap_content"
 174                     android:layout_height="wrap_content"
 175                     android:text="Sparsam" />                                                       
 176 
 177                 <com.google.android.material.chip.Chip
 178                     android:id="@+id/chip_hd"

../../src/main/res/layout/activity_main.xml:183: Hardcoded string "Ausgewogen", should use @string resource

 180                     android:layout_width="wrap_content"
 181                     android:layout_height="wrap_content"
 182                     android:checked="true"
 183                     android:text="Ausgewogen" />                                                    
 184 
 185                 <com.google.android.material.chip.Chip
 186                     android:id="@+id/chip_fhd"

../../src/main/res/layout/activity_main.xml:190: Hardcoded string "Scharf", should use @string resource

 187                     style="@style/Widget.Material3.Chip.Filter"
 188                     android:layout_width="wrap_content"
 189                     android:layout_height="wrap_content"
 190                     android:text="Scharf" />                                                        
 191             </com.google.android.material.chip.ChipGroup>
 192 
 193             <TextView

../../src/main/res/layout/activity_main.xml:214: Hardcoded string "30 fps", should use @string resource

 211                     android:layout_width="wrap_content"
 212                     android:layout_height="wrap_content"
 213                     android:checked="true"
 214                     android:text="30 fps" />                                                        
 215 
 216                 <com.google.android.material.chip.Chip
 217                     android:id="@+id/chip_fps60"

../../src/main/res/layout/activity_main.xml:221: Hardcoded string "60 fps", should use @string resource

 218                     style="@style/Widget.Material3.Chip.Filter"
 219                     android:layout_width="wrap_content"
 220                     android:layout_height="wrap_content"
 221                     android:text="60 fps" />                                                        
 222             </com.google.android.material.chip.ChipGroup>
 223 
 224             <TextView

HardcodedText Internationalization Warning Priority 5/10

Included Additional Checks

This card lists all the extra checks run by lint, provided from libraries, build configuration and extra flags. This is included to help you verify whether a particular check is included in analysis when configuring builds. (Note that the list does not include the hundreds of built-in checks into lint, only additional ones.)

DetachAndAttachSameFragment

When doing a FragmentTransaction that includes both attach() and detach() operations being committed on the same fragment instance, it is a no-op. The reason for this is that the FragmentManager optimizes all operations within a single transaction so the attach() and detach() cancel each other out and neither is actually executed. To get the desired behavior, you should separate the attach() and detach() calls into separate FragmentTransactions.

Vendor: Android Open Source Project
Identifier: androidx.fragment
Feedback: https://issuetracker.google.com/issues/new?component=460964

DialogFragmentCallbacksDetector

When using a DialogFragment, the setOnCancelListener and setOnDismissListener callback functions within the onCreateDialog function __must not be used__ because the DialogFragment owns these callbacks. Instead the respective onCancel and onDismiss functions can be used to achieve the desired effect.

Vendor: Android Open Source Project
Identifier: androidx.fragment
Feedback: https://issuetracker.google.com/issues/new?component=460964

EnsureInitializerMetadata

When a library defines a Initializer, it needs to be accompanied by a corresponding <meta-data> entry in the AndroidManifest.xml file.

Vendor: Android Open Source Project
Identifier: androidx.startup
Feedback: https://issuetracker.google.com/issues/new?component=823348

EnsureInitializerNoArgConstr

Every Initializer must have a no argument constructor.

Vendor: Android Open Source Project
Identifier: androidx.startup
Feedback: https://issuetracker.google.com/issues/new?component=823348

ExperimentalAnnotationRetention

Experimental annotations defined in Java source should use default (CLASS) retention, while Kotlin-sourced annotations should use BINARY retention.

Vendor: Android Open Source Project
Identifier: androidx.annotation.experimental
Feedback: https://issuetracker.google.com/issues/new?component=459778

FragmentAddMenuProvider

The Fragment lifecycle can result in a Fragment being active longer than its view. This can lead to unexpected behavior from lifecycle aware objects remaining active longer than the Fragment's view. To solve this issue, getViewLifecycleOwner() should be used as a LifecycleOwner rather than the Fragment instance once it is safe to access the view lifecycle in a Fragment's onCreateView, onViewCreated, onActivityCreated, or onViewStateRestored methods.

Vendor: Android Open Source Project
Identifier: androidx.fragment
Feedback: https://issuetracker.google.com/issues/new?component=460964

FragmentBackPressedCallback

Vendor: Android Open Source Project
Identifier: androidx.fragment
Feedback: https://issuetracker.google.com/issues/new?component=460964

FragmentLiveDataObserve

When observing a LiveData object from a fragment's onCreateView, onViewCreated, onActivityCreated, or onViewStateRestored method getViewLifecycleOwner() should be used as the LifecycleOwner rather than the Fragment instance. The Fragment lifecycle can result in the Fragment being active longer than its view. This can lead to unexpected behavior from LiveData objects being observed longer than the Fragment's view is active.

Vendor: Android Open Source Project
Identifier: androidx.fragment
Feedback: https://issuetracker.google.com/issues/new?component=460964

FragmentTagUsage

FragmentContainerView replaces the <fragment> tag as the preferred way of adding fragments via XML. Unlike the <fragment> tag, FragmentContainerView uses a normal FragmentTransaction under the hood to add the initial fragment, allowing further FragmentTransaction operations on the FragmentContainerView and providing a consistent timing for lifecycle events.

More info: https://developer.android.com/reference/androidx/fragment/app/FragmentContainerView.html

Vendor: Android Open Source Project
Identifier: androidx.fragment
Feedback: https://issuetracker.google.com/issues/new?component=460964

InvalidFragmentVersionForActivityResult

In order to use the ActivityResult APIs you must upgrade your Fragment version to 1.3.0. Previous versions of FragmentActivity failed to call super.onRequestPermissionsResult() and used invalid request codes

More info: https://developer.android.com/training/permissions/requesting#make-the-request

Vendor: Android Open Source Project
Identifier: androidx.activity
Feedback: https://issuetracker.google.com/issues/new?component=527362

NullSafeMutableLiveData

This check ensures that LiveData values are not null when explicitly declared as non-nullable.

Kotlin interoperability does not support enforcing explicit null-safety when using generic Java type parameters. Since LiveData is a Java class its value can always be null even when its type is explicitly declared as non-nullable. This can lead to runtime exceptions from reading a null LiveData value that is assumed to be non-nullable.

Vendor: Android Open Source Project
Identifier: androidx.lifecycle
Feedback: https://issuetracker.google.com/issues/new?component=413132

RepeatOnLifecycleWrongUsage

The repeatOnLifecycle APIs should be used when the View is created, that is in the onCreate lifecycle method for Activities, or onViewCreated in case you're using Fragments.

Vendor: Android Open Source Project
Identifier: androidx.lifecycle
Feedback: https://issuetracker.google.com/issues/new?component=413132

UnsafeLifecycleWhenUsage

If the Lifecycle is destroyed within the block of Lifecycle.whenStarted or any similar Lifecycle.when method is suspended, the block will be cancelled, which will also cancel any child coroutine launched inside the block. As as a result, If you have a try finally block in your code, the finally might run after the Lifecycle moves outside the desired state. It is recommended to check the Lifecycle.isAtLeast before accessing UI in finally block. Similarly, if you have a catch statement that might catch CancellationException, you should check the Lifecycle.isAtLeast before accessing the UI. See documentation of Lifecycle.whenStateAtLeast for more details

Vendor: Android Open Source Project
Identifier: androidx.lifecycle
Feedback: https://issuetracker.google.com/issues/new?component=413132

UnsafeOptInUsageError

This API has been flagged as opt-in with error-level severity.

Any declaration annotated with this marker is considered part of an unstable or
otherwise non-standard API surface and its call sites should accept the opt-in
aspect of it by using the @OptIn annotation, using the marker annotation --
effectively causing further propagation of the opt-in aspect -- or configuring
the UnsafeOptInUsageError check's options for project-wide opt-in.

To configure project-wide opt-in, specify the opt-in option value in lint.xml
as a comma-delimited list of opted-in annotations:

<lint>
    <issue id="UnsafeOptInUsageError">
        <option name="opt-in" value="com.foo.ExperimentalBarAnnotation" />
    </issue>
</lint>

Vendor: Android Open Source Project
Identifier: androidx.annotation.experimental
Feedback: https://issuetracker.google.com/issues/new?component=459778

UnsafeOptInUsageWarning

This API has been flagged as opt-in with warning-level severity.

Any declaration annotated with this marker is considered part of an unstable or
otherwise non-standard API surface and its call sites should accept the opt-in
aspect of it by using the @OptIn annotation, using the marker annotation --
effectively causing further propagation of the opt-in aspect -- or configuring
the UnsafeOptInUsageWarning check's options for project-wide opt-in.

To configure project-wide opt-in, specify the opt-in option value in lint.xml
as a comma-delimited list of opted-in annotations:

<lint>
    <issue id="UnsafeOptInUsageWarning">
        <option name="opt-in" value="com.foo.ExperimentalBarAnnotation" />
    </issue>
</lint>

Vendor: Android Open Source Project
Identifier: androidx.annotation.experimental
Feedback: https://issuetracker.google.com/issues/new?component=459778

UnsafeRepeatOnLifecycleDetector

The repeatOnLifecycle APIs should be used with the viewLifecycleOwner in Fragments as opposed to lifecycleOwner.

Vendor: Android Open Source Project
Identifier: androidx.fragment
Feedback: https://issuetracker.google.com/issues/new?component=460964

UseAndroidAlpha

ColorStateList uses app:alpha without android:alpha

Vendor: Android Open Source Project
Identifier: androidx.appcompat
Feedback: https://issuetracker.google.com/issues/new?component=460343

UseAppTint

ImageView or ImageButton uses android:tint instead of app:tint

Vendor: Android Open Source Project
Identifier: androidx.appcompat
Feedback: https://issuetracker.google.com/issues/new?component=460343

UseCompatLoadingForColorStateLists

Use Compat loading of color state lists

Vendor: Android Open Source Project
Identifier: androidx.appcompat
Feedback: https://issuetracker.google.com/issues/new?component=460343

UseCompatLoadingForDrawables

Use Compat loading of drawables

Vendor: Android Open Source Project
Identifier: androidx.appcompat
Feedback: https://issuetracker.google.com/issues/new?component=460343

UseCompatTextViewDrawableApis

Use Compat loading of compound text view drawables

Vendor: Android Open Source Project
Identifier: androidx.appcompat
Feedback: https://issuetracker.google.com/issues/new?component=460343

UseCompatTextViewDrawableXml

TextView uses android: compound drawable attributes instead of app: ones

Vendor: Android Open Source Project
Identifier: androidx.appcompat
Feedback: https://issuetracker.google.com/issues/new?component=460343

UseGetLayoutInflater

Using LayoutInflater.from(Context) can return a LayoutInflater that does not have the correct theme.

Vendor: Android Open Source Project
Identifier: androidx.fragment
Feedback: https://issuetracker.google.com/issues/new?component=460964

UseRequireInsteadOfGet

AndroidX added new "require____()" versions of common "get___()" APIs, such as getContext/getActivity/getArguments/etc. Rather than wrap these in something like requireNotNull(), using these APIs will allow the underlying component to try to tell you _why_ it was null, and thus yield a better error message.

Vendor: Android Open Source Project
Identifier: androidx.fragment
Feedback: https://issuetracker.google.com/issues/new?component=460964

UseSupportActionBar

Use AppCompatActivity.setSupportActionBar

Vendor: Android Open Source Project
Identifier: androidx.appcompat
Feedback: https://issuetracker.google.com/issues/new?component=460343

UseSwitchCompatOrMaterialCode

Use SwitchCompat from AppCompat or MaterialSwitch from Material library

Vendor: Android Open Source Project
Identifier: androidx.appcompat
Feedback: https://issuetracker.google.com/issues/new?component=460343

UseSwitchCompatOrMaterialXml

Use SwitchCompat from AppCompat or MaterialSwitch from Material library

Vendor: Android Open Source Project
Identifier: androidx.appcompat
Feedback: https://issuetracker.google.com/issues/new?component=460343

UsingOnClickInXml

Old versions of the platform do not properly support resolving android:onClick

Vendor: Android Open Source Project
Identifier: androidx.appcompat
Feedback: https://issuetracker.google.com/issues/new?component=460343

WrongRequiresOptIn

Experimental features defined in Kotlin source code must be annotated with the Kotlin
@RequiresOptIn annotation. Using androidx.annotation.RequiresOptIn will prevent the
Kotlin compiler from enforcing its opt-in policies.

Vendor: Android Open Source Project
Identifier: androidx.annotation.experimental
Feedback: https://issuetracker.google.com/issues/new?component=459778

Disabled Checks

One or more issues were not run by lint, either because the check is not enabled by default, or because it was disabled with a command line flag or via one or more lint.xml configuration files in the project directories.

AppCompatMethod

Disabled By: Default

When using the appcompat library, there are some methods you should be calling instead of the normal ones; for example, getSupportActionBar() instead of getActionBar(). This lint check looks for calls to the wrong method.

More info: https://developer.android.com/topic/libraries/support-library/

Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

AppLinksAutoVerify

Disabled By: Default

Ensures that app links are correctly set and associated with website.

More info: https://g.co/appindexing/applinks

BackButton

Disabled By: Default

According to the Android Design Guide,

"Other platforms use an explicit back button with label to allow the user to navigate up the application's hierarchy. Instead, Android uses the main action bar's app icon for hierarchical navigation and the navigation bar's back button for temporal navigation."

This check is not very sophisticated (it just looks for buttons with the label "Back"), so it is disabled by default to not trigger on common scenarios like pairs of Back/Next buttons to paginate through screens.

More info: https://d.android.com/r/studio-ui/designer/material/design

ConvertToWebp

Disabled By: Default

The WebP format is typically more compact than PNG and JPEG. As of Android 4.2.1 it supports transparency and lossless conversion as well. Note that there is a quickfix in the IDE which lets you perform conversion.

Previously, launcher icons were required to be in the PNG format but that restriction is no longer there, so lint now flags these.
Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

DalvikOverride

Disabled By: Default

The Dalvik virtual machine will treat a package private method in one class as overriding a package private method in its super class, even if they are in separate packages.

If you really did intend for this method to override the other, make the method protected instead.

If you did not intend the override, consider making the method private, or changing its name or signature.

Note that this check is disabled be default, because ART (the successor to Dalvik) no longer has this behavior.

DefaultEncoding

Disabled By: Default

Some APIs will implicitly use the default system character encoding instead of UTF-8 when converting to or from bytes, such as when creating a default FileReader.

This is usually not correct; you only want to do this if you need to read files created by other programs where they have deliberately written in the same encoding. The default encoding varies from platform to platform and can vary from locale to locale, so this makes it difficult to interpret files containing non-ASCII characters.

We recommend using UTF-8 everywhere.

Note that on Android, the default file encoding is always UTF-8 (see https://developer.android.com/reference/java/nio/charset/Charset#defaultCharset() for more), so this lint check deliberately does not flag any problems in Android code, since it is always safe to rely on the default character encoding there.

DuplicateStrings

Disabled By: Default

Duplicate strings can make applications larger unnecessarily.

This lint check looks for duplicate strings, including differences for strings where the only difference is in capitalization. Title casing and all uppercase can all be adjusted in the layout or in code.

More info: https://developer.android.com/reference/android/widget/TextView.html#attr_android:inputType

EasterEgg

Disabled By: Default

An "easter egg" is code deliberately hidden in the code, both from potential users and even from other developers. This lint check looks for code which looks like it may be hidden from sight.

ExpensiveAssertion

Disabled By: Default

In Kotlin, assertions are not handled the same way as from the Java programming language. In particular, they're just implemented as a library call, and inside the library call the error is only thrown if assertions are enabled.

This means that the arguments to the assert call will always be evaluated. If you're doing any computation in the expression being asserted, that computation will unconditionally be performed whether or not assertions are turned on. This typically turns into wasted work in release builds.

This check looks for cases where the assertion condition is nontrivial, e.g. it is performing method calls or doing more work than simple comparisons on local variables or fields.

You can work around this by writing your own inline assert method instead:

@Suppress("INVISIBLE_REFERENCE", "INVISIBLE_MEMBER")
inline fun assert(condition: () -> Boolean) {
    if (_Assertions.ENABLED && !condition()) {
        throw AssertionError()
    }
}

In Android, because assertions are not enforced at runtime, instead use this:

inline fun assert(condition: () -> Boolean) {
    if (BuildConfig.DEBUG && !condition()) {
        throw AssertionError()
    }
}

Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

IconExpectedSize

Disabled By: Default

There are predefined sizes (for each density) for launcher icons. You should follow these conventions to make sure your icons fit in with the overall look of the platform.

More info: https://d.android.com/r/studio-ui/designer/material/iconography

ImplicitSamInstance

Disabled By: Default

Kotlin's support for SAM (single accessor method) interfaces lets you pass a lambda to the interface. This will create a new instance on the fly even though there is no explicit constructor call. If you pass one of these lambdas or method references into a method which (for example) stores or compares the object identity, unexpected results may happen.
Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

InvalidPackage

Disabled By: Default

This check scans through libraries looking for calls to APIs that are not included in Android.

When you create Android projects, the classpath is set up such that you can only access classes in the API packages that are included in Android. However, if you add other projects to your libs/ folder, there is no guarantee that those .jar files were built with an Android specific classpath, and in particular, they could be accessing unsupported APIs such as java.applet.

This check scans through library jars and looks for references to API packages that are not included in Android and flags these. This is only an error if your code calls one of the library classes which wind up referencing the unsupported package.

KotlinPropertyAccess

Disabled By: Default

For a method to be represented as a property in Kotlin, strict “bean”-style prefixing must be used.

Accessor methods require a get prefix or for boolean-returning methods an is prefix can be used.

More info: https://android.github.io/kotlin-guides/interop.html#property-prefixes

KotlincFE10

Disabled By: Default

K2, the new version of Kotlin compiler, which encompasses the new frontend, is coming. Try to avoid using internal APIs from the old frontend if possible.

LambdaLast

Disabled By: Default

To improve calling this code from Kotlin, parameter types eligible for SAM conversion should be last.

More info: https://android.github.io/kotlin-guides/interop.html#lambda-parameters-last

LintDocExample

Disabled By: Default

Lint's tool for generating documentation for each issue has special support for including a code example which shows how to trigger the report. It will pick the first unit test it can find and pick out the source file referenced from the error message, but you can instead designate a unit test to be the documentation example, and in that case, all the files are included.

To designate a unit test as the documentation example for an issue, name the test testDocumentationExample, or if your detector reports multiple issues, testDocumentationExample<Id>, such as testDocumentationExampleMyId.

LintImplPsiEquals

Disabled By: Default

You should never compare two PSI elements for equality with equals; use isEquivalentTo(PsiElement) instead.

LintImplUnexpectedDomain

Disabled By: Default

This checks flags URLs to domains that have not been explicitly allowed for use as a documentation source.

LogConditional

Disabled By: Default

The BuildConfig class provides a constant, DEBUG, which indicates whether the code is being built in release mode or in debug mode. In release mode, you typically want to strip out all the logging calls. Since the compiler will automatically remove all code which is inside a if (false) check, surrounding your logging calls with a check for BuildConfig.DEBUG is a good idea.

If you really intend for the logging to be present in release mode, you can suppress this warning with a @SuppressLint annotation for the intentional logging calls.

MangledCRLF

Disabled By: Default

On Windows, line endings are typically recorded as carriage return plus newline: \r\n.

This detector looks for invalid line endings with repeated carriage return characters (without newlines). Previous versions of the ADT plugin could accidentally introduce these into the file, and when editing the file, the editor could produce confusing visual artifacts.

More info: https://bugs.eclipse.org/bugs/show_bug.cgi?id=375421

MinSdkTooLow

Disabled By: Default

The value of the minSdkVersion property is too low and can be incremented without noticeably reducing the number of supported devices.
Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

NegativeMargin

Disabled By: Default

Margin values should be positive. Negative values are generally a sign that you are making assumptions about views surrounding the current one, or may be tempted to turn off child clipping to allow a view to escape its parent. Turning off child clipping to do this not only leads to poor graphical performance, it also results in wrong touch event handling since touch events are based strictly on a chain of parent-rect hit tests. Finally, making assumptions about the size of strings can lead to localization problems.

NewerVersionAvailable

Disabled By: Default

This detector checks with a central repository to see if there are newer versions available for the dependencies used by this project. This is similar to the GradleDependency check, which checks for newer versions available in the Android SDK tools and libraries, but this works with any MavenCentral dependency, and connects to the library every time, which makes it more flexible but also much slower.
Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

NoHardKeywords

Disabled By: Default

Do not use Kotlin’s hard keywords as the name of methods or fields. These require the use of backticks to escape when calling from Kotlin. Soft keywords, modifier keywords, and special identifiers are allowed.

For example, ActionEvent's getWhen() method requires backticks when used from Kotlin:

val timestamp = event.`when`

More info: https://android.github.io/kotlin-guides/interop.html#no-hard-keywords

NoOp

Disabled By: Default

This check looks for code which looks like it's a no-op -- usually leftover expressions from interactive debugging, but in some cases bugs where you had intended to do something with the expression such as assign it to a field.

This check can be configured via the following options:

pure-getters (default is false):
Whether to assume methods with getter-names have no side effects.

Getter methods (where names start with get or is, and have non-void return types, and no arguments) should not have side effects. With this option turned on, lint will assume that is the case and will list any getter calls whose results are ignored as suspicious code.

To configure this option, use a `lint.xml` file in the project or source folder using an <option> block like the following:

 1 <lint>
 2     <issue id="NoOp">
 3         <option name="pure-getters" value="false" />                                                
 4     </issue>
 5 </lint>

PermissionNamingConvention

Disabled By: Default

Permissions should be prefixed with an app's package name, using reverse-domain-style naming. This prefix should be followed by .permission., and then a description of the capability that the permission represents, in upper SNAKE_CASE. For example, com.example.myapp.permission.ENGAGE_HYPERSPACE.

Following this recommendation avoids naming collisions, and helps clearly identify the owner and intention of a custom permission.

Registered

Disabled By: Default

Activities, services and content providers should be registered in the AndroidManifest.xml file using <activity>, <service> and <provider> tags.

If your activity is simply a parent class intended to be subclassed by other "real" activities, make it an abstract class.

More info: https://developer.android.com/guide/topics/manifest/manifest-intro.html

RequiredSize

Disabled By: Default

All views must specify an explicit layout_width and layout_height attribute. There is a runtime check for this, so if you fail to specify a size, an exception is thrown at runtime.

It's possible to specify these widths via styles as well. GridLayout, as a special case, does not require you to specify a size.

SelectableText

Disabled By: Default

If a <TextView> is used to display data, the user might want to copy that data and paste it elsewhere. To allow this, the <TextView> should specify android:textIsSelectable="true".

This lint check looks for TextViews which are likely to be displaying data: views whose text is set dynamically.
Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

StopShip

Disabled By: Default

Using the comment // STOPSHIP can be used to flag code that is incomplete but checked in. This comment marker can be used to indicate that the code should not be shipped until the issue is addressed, and lint will look for these. In Gradle projects, this is only checked for non-debug (release) builds.

In Kotlin, the TODO() method is also treated as a stop ship marker; you can use it to make incomplete code compile, but it will throw an exception at runtime and therefore should be fixed before shipping releases.
Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

StringFormatTrivial

Disabled By: Default

Every call to String.format creates a new Formatter instance, which will decrease the performance of your app. String.format should only be used when necessary--if the formatted string contains only trivial conversions (e.g. b, s, c) and there are no translation concerns, it will be more efficient to replace them and concatenate with +.

SyntheticAccessor

Disabled By: Default

A private inner class which is accessed from the outer class will force the compiler to insert a synthetic accessor; this means that you are causing extra overhead. This is not important in small projects, but is important for large apps running up against the 64K method handle limit, and especially for libraries where you want to make sure your library is as small as possible for the cases where your library is used in an app running up against the 64K limit.
Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

TypographyQuotes

Disabled By: Default

Straight single quotes and double quotes, when used as a pair, can be replaced by "curvy quotes" (or directional quotes). Use the right single quotation mark for apostrophes. Never use generic quotes ", ' or free-standing accents `, ´ for quotation marks, apostrophes, or primes. This can make the text more readable.

More info: https://en.wikipedia.org/wiki/Quotation_mark

Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

UnknownNullness

Disabled By: Default

To improve referencing this code from Kotlin, consider adding explicit nullness information here with either @NonNull or @Nullable.

This check can be configured via the following options:

ignore-deprecated (default is false):
Whether to ignore classes and members that have been annotated with @Deprecated.

Normally this lint check will flag all unannotated elements, but by setting this option to true it will skip any deprecated elements.

To configure this option, use a `lint.xml` file in the project or source folder using an <option> block like the following:

 1 <lint>
 2     <issue id="UnknownNullness">
 3         <option name="ignore-deprecated" value="false" />                                           
 4     </issue>
 5 </lint>

More info: https://developer.android.com/kotlin/interop#nullability_annotations

Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

UnsupportedChromeOsHardware

Disabled By: Default

The <uses-feature> element should not require this unsupported large screen hardware feature. Any <uses-feature> not explicitly marked with required="false" is necessary on the device to be installed on. Ensure that any features that might prevent it from being installed on a ChromeOS, large screen, or foldable device are reviewed and marked as not required in the manifest.

More info: https://developer.android.com/topic/arc/manifest.html#incompat-entries

Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

UnusedIds

Disabled By: Default

This resource id definition appears not to be needed since it is not referenced from anywhere. Having id definitions, even if unused, is not necessarily a bad idea since they make working on layouts and menus easier, so there is not a strong reason to delete these.

The unused resource check can ignore tests. If you want to include resources that are only referenced from tests, consider packaging them in a test source set instead.

You can include test sources in the unused resource check by setting the system property lint.unused-resources.include-tests =true, and to exclude them (usually for performance reasons), use lint.unused-resources.exclude-tests =true.

Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

ValidActionsXml

Disabled By: Default

Ensures that an actions XML file is properly formed
Note: This issue has an associated quickfix operation in Android Studio and IntelliJ IDEA.

VulnerableCordovaVersion

Disabled By: Default

The version of Cordova used in the app is vulnerable to security issues. Please update to the latest Apache Cordova version.

More info: https://cordova.apache.org/announcements/2015/11/20/security.html

WrongThreadInterprocedural

Disabled By: Default

Searches for interprocedural call paths that violate thread annotations in the program. Tracks the flow of instantiated types and lambda expressions to increase accuracy across method boundaries.

More info: https://developer.android.com/guide/components/processes-and-threads.html#Threads

Suppressing Warnings and Errors

Lint errors can be suppressed in a variety of ways:

1. With a @SuppressLint annotation in the Java code
2. With a tools:ignore attribute in the XML file
3. With a //noinspection comment in the source code
4. With ignore flags specified in the build.gradle file, as explained below
5. With a lint.xml configuration file in the project
6. With a lint.xml configuration file passed to lint via the --config flag
7. With the --ignore flag passed to lint.

To suppress a lint warning with an annotation, add a @SuppressLint("id") annotation on the class, method or variable declaration closest to the warning instance you want to disable. The id can be one or more issue id's, such as "UnusedResources" or {"UnusedResources","UnusedIds"}, or it can be "all" to suppress all lint warnings in the given scope.

To suppress a lint warning with a comment, add a //noinspection id comment on the line before the statement with the error.

To suppress a lint warning in an XML file, add a tools:ignore="id" attribute on the element containing the error, or one of its surrounding elements. You also need to define the namespace for the tools prefix on the root element in your document, next to the xmlns:android declaration:
xmlns:tools="http://schemas.android.com/tools"

To suppress a lint warning in a build.gradle file, add a section like this:

android {
    lintOptions {
        disable 'TypographyFractions','TypographyQuotes'
    }
}

Here we specify a comma separated list of issue id's after the disable command. You can also use warning or error instead of disable to change the severity of issues.

To suppress lint warnings with a configuration XML file, create a file named lint.xml and place it at the root directory of the module in which it applies.

The format of the lint.xml file is something like the following:

<?xml version="1.0" encoding="UTF-8"?>
<lint>
    <!-- Ignore everything in the test source set -->
    <issue id="all">
        <ignore path="\*/test/\*" />
    </issue>

    <!-- Disable this given check in this project -->
    <issue id="IconMissingDensityFolder" severity="ignore" />

    <!-- Ignore the ObsoleteLayoutParam issue in the given files -->
    <issue id="ObsoleteLayoutParam">
        <ignore path="res/layout/activation.xml" />
        <ignore path="res/layout-xlarge/activation.xml" />
        <ignore regexp="(foo|bar)\.java" />
    </issue>

    <!-- Ignore the UselessLeaf issue in the given file -->
    <issue id="UselessLeaf">
        <ignore path="res/layout/main.xml" />
    </issue>

    <!-- Change the severity of hardcoded strings to "error" -->
    <issue id="HardcodedText" severity="error" />
</lint>

To suppress lint checks from the command line, pass the --ignore flag with a comma separated list of ids to be suppressed, such as:
$ lint --ignore UnusedResources,UselessLeaf /my/project/path

For more information, see https://developer.android.com/studio/write/lint.html#config