When I use codes generated by android studio automatically and ViewBinding together, the programme will crash.
ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main)) { v, insets ->
val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
insets
}// this is what android studio generate
val binding=ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
When I delete the first part( setOnApplyWindowInsetsListener ), the programme will run properly.
I have no idea what’s going wrong
here’s what logcat says, I copy them all and the error is at the bottom
2024-07-18 11:20:36.777 20996-20996 ziparchive com.example.uiwidgettest W Unable to open '/data/app/~~pqSil-xEI7VW0FmbjVGwVA==/com.example.uiwidgettest-Q-RcIuNwpvivt9LzMFW-IA==/base.dm': No such file or directory
2024-07-18 11:20:36.777 20996-20996 ziparchive com.example.uiwidgettest W Unable to open '/data/app/~~pqSil-xEI7VW0FmbjVGwVA==/com.example.uiwidgettest-Q-RcIuNwpvivt9LzMFW-IA==/base.dm': No such file or directory
2024-07-18 11:20:36.873 20996-20996 nativeloader com.example.uiwidgettest D Configuring clns-6 for other apk /data/app/~~pqSil-xEI7VW0FmbjVGwVA==/com.example.uiwidgettest-Q-RcIuNwpvivt9LzMFW-IA==/base.apk. target_sdk_version=34, uses_libraries=, library_path=/data/app/~~pqSil-xEI7VW0FmbjVGwVA==/com.example.uiwidgettest-Q-RcIuNwpvivt9LzMFW-IA==/lib/x86_64, permitted_path=/data:/mnt/expand:/data/user/0/com.example.uiwidgettest
2024-07-18 11:20:36.896 20996-20996 GraphicsEnvironment com.example.uiwidgettest V Currently set values for:
2024-07-18 11:20:36.896 20996-20996 GraphicsEnvironment com.example.uiwidgettest V angle_gl_driver_selection_pkgs=[]
2024-07-18 11:20:36.896 20996-20996 GraphicsEnvironment com.example.uiwidgettest V angle_gl_driver_selection_values=[]
2024-07-18 11:20:36.896 20996-20996 GraphicsEnvironment com.example.uiwidgettest V Global.Settings values are invalid: number of packages: 0, number of values: 0
2024-07-18 11:20:36.896 20996-20996 GraphicsEnvironment com.example.uiwidgettest V Neither updatable production driver nor prerelease driver is supported.
2024-07-18 11:20:37.034 20996-20996 AppCompatDelegate com.example.uiwidgettest D Checking for metadata for AppLocalesMetadataHolderService : Service not found
2024-07-18 11:20:37.157 20996-20996 le.uiwidgettest com.example.uiwidgettest W Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (unsupported, reflection, allowed)
2024-07-18 11:20:37.159 20996-20996 le.uiwidgettest com.example.uiwidgettest W Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (unsupported, reflection, allowed)
2024-07-18 11:20:37.163 20996-20996 TransactionExecutor com.example.uiwidgettest E Failed to execute the transaction: tId:-695490178 ClientTransaction{
tId:-695490178 transactionItems=[
tId:-695490178 LaunchActivityItem{activityToken=android.os.BinderProxy@7bb8227,intent=Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.example.uiwidgettest/.MainActivity },ident=95817982,info=ActivityInfo{5dc30a0 com.example.uiwidgettest.MainActivity},curConfig={1.0 310mcc260mnc [en_US] ldltr sw411dp w411dp h731dp 420dpi nrml long port finger qwerty/v/v dpad/v winConfig={ mBounds=Rect(0, 0 - 1080, 1920) mAppBounds=Rect(0, 0 - 1080, 1920) mMaxBounds=Rect(0, 0 - 1080, 1920) mDisplayRotation=ROTATION_0 mWindowingMode=fullscreen mActivityType=undefined mAlwaysOnTop=undefined mRotation=ROTATION_0} s.8 fontWeightAdjustment=0},overrideConfig={1.0 310mcc260mnc [en_US] ldltr sw411dp w411dp h731dp 420dpi nrml long port finger qwerty/v/v dpad/v winConfig={ mBounds=Rect(0, 0 - 1080, 1920) mAppBounds=Rect(0, 0 - 1080, 1920) mMaxBounds=Rect(0, 0 - 1080, 1920) mDisplayRotation=ROTATION_0 mWindowingMode=fullscreen mActivityType=standard mAlwaysOnTop=undefined mRotation=ROTATION_0} s.3 fontWeightAdjustment=0},deviceId=0,referrer=com.android.shell,procState=2,state=null,persistentState=null,pendingResults=null,pendingNewIntents=null,sceneTransitionInfo=null,profilerInfo=null,assistToken=android.os.BinderProxy@9f86f5d,shareableActivityToken=android.os.BinderProxy@fa3f0d2,activityWindowInfo=ActivityWindowInfo{isEmbedded=false, taskBounds=Rect(0, 0 - 1080, 1920), taskFragmentBounds=Rect(0, 0 - 1080, 1920)}}
tId:-695490178 ResumeActivityItem{mActivityToken=android.os.BinderProxy@7bb8227,procState=-1,updateProcState=false,isForward=true,shouldSendCompatFakeFocus=false}
tId:-695490178 Target activity: com.example.uiwidgettest.MainActivity
tId:-695490178 ]
tId:-695490178 }
2024-07-18 11:20:37.163 20996-20996 AndroidRuntime com.example.uiwidgettest D Shutting down VM
2024-07-18 11:20:37.166 20996-20996 AndroidRuntime com.example.uiwidgettest E FATAL EXCEPTION: main
Process: com.example.uiwidgettest, PID: 20996
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.uiwidgettest/com.example.uiwidgettest.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnApplyWindowInsetsListener(android.view.View$OnApplyWindowInsetsListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4047)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4234)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:112)
at android.app.servertransaction.TransactionExecutor.executeNonLifecycleItem(TransactionExecutor.java:174)
at android.app.servertransaction.TransactionExecutor.executeTransactionItems(TransactionExecutor.java:109)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:81)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2635)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loopOnce(Looper.java:232)
at android.os.Looper.loop(Looper.java:317)
at android.app.ActivityThread.main(ActivityThread.java:8699)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:580)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:886)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnApplyWindowInsetsListener(android.view.View$OnApplyWindowInsetsListener)' on a null object reference
at androidx.core.view.ViewCompat$Api21Impl.setOnApplyWindowInsetsListener(ViewCompat.java:4840)
at androidx.core.view.ViewCompat.setOnApplyWindowInsetsListener(ViewCompat.java:2537)
at com.example.uiwidgettest.MainActivity.onCreate(MainActivity.kt:18)
at android.app.Activity.performCreate(Activity.java:8980)
at android.app.Activity.performCreate(Activity.java:8958)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1526)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4029)
... 13 more
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The main reason of this crash is finding the view before you set the layout.
findViewById(R.id.main)
Solution
- Make sure your parent view in layout xml has
mainid.
If it’s auto-generated by IDE, it should automatically added like this.
android:id="@+id/main"
- Set content view before
setOnApplyWindowInsetsListener.
val binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main)) { v, insets - >
val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
insets
}
If you don’t want to set id to your parent layout, you can still get parent view of your layout like this.
findViewById(android.R.id.content)
Or if you want to use view binding, you can use binding.root instead.
Explanation
When you create Empty views activity from IDE, it generated a full screen edge to edge activity like this.
enableEdgeToEdge()
setContentView(R.layout.activity_main)
ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main)) { v, insets - >
val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
insets
}
-
enableEdgeToEdge()is a Kotlin extension that enables the edge-to-edge display (full screen) for your activity. -
Since your activity is now edge to edge, you need to apply padding to your parent view so that its contents (child views) fit inside the system bars (status bars and navigation bars) and Toolbar.
If you don’t want to make your activity edge to edge, you can safely remove these auto generated codes.