im using a device for android studio and after a while app crashes and i get this error. anybody knows what the problem is?

Question

03/30 03:30:23: Launching 'app' on HMD Global Nokia 3.1 Plus.
$ adb shell am start -n "com.example.myfirstproject/com.example.myfirstproject.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Connected to process 4242 on device 'hmd_global-nokia_3_1_plus-ROOGADA910318089'.
Capturing and displaying logcat messages from application. This behavior can be disabled in the "Logcat output" section of the "Debugger" settings page.
W/.myfirstprojec: Accessing hidden method Landroid/graphics/drawable/Drawable;->getOpticalInsets()Landroid/graphics/Insets; (light greylist, linking)
    Accessing hidden field Landroid/graphics/Insets;->left:I (light greylist, linking)
    Accessing hidden field Landroid/graphics/Insets;->right:I (light greylist, linking)
    Accessing hidden field Landroid/graphics/Insets;->top:I (light greylist, linking)
    Accessing hidden field Landroid/graphics/Insets;->bottom:I (light greylist, linking)
I/DecorView: It non-support bigbang
I/PhoneWindow: isNeedChangeNaviBarColor taskInfo: [android.app.ActivityManager$RunningTaskInfo@faeee23] size: 1
I/PhoneWindow: isAPPNeedChange pkgName: com.example.myfirstproject needKeep: false
    isNeedChangeNaviBarColor false
    generateLayout mNavigationBarColor: ff000000
    generateLayout isLightNavi false, Visibility: 0
W/.myfirstprojec: Accessing hidden method Landroid/view/View;->getAccessibilityDelegate()Landroid/view/View$AccessibilityDelegate; (light greylist, linking)
W/.myfirstprojec: Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (light greylist, reflection)
W/.myfirstprojec: Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (light greylist, reflection)
W/.myfirstprojec: Accessing hidden method Landroid/widget/TextView;->getTextDirectionHeuristic()Landroid/text/TextDirectionHeuristic; (light greylist, linking)
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.myfirstproject, PID: 4242
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myfirstproject/com.example.myfirstproject.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2946)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3081)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1838)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6715)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:911)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at com.example.myfirstproject.MainActivity.onCreate(MainActivity.kt:20)
        at android.app.Activity.performCreate(Activity.java:7136)
        at android.app.Activity.performCreate(Activity.java:7127)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2926)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3081) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1838) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:193) 
        at android.app.ActivityThread.main(ActivityThread.java:6715) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:911)

Can you post the part of your activity code that calls `setOnClickListener()`? Because the button you're calling it on is `null`. Also, JavaScript is a separate language. — , Mar 30 '20 at 10:52

score 0 · Answer 1 · answered Mar 30 '20 at 11:13

0

Inside onCreate() at line 20 in your MainActivity, you have set onCLickListner to a button which is causing null pointer exception. It would be more helpful if you post your code here.

answered Mar 30 '20 at 11:13

Vinay Kharayat

87
2
9

score 0 · Answer 2 · answered Mar 30 '20 at 11:56

You have problem in MainActivity.kt

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at com.example.myfirstproject.MainActivity.onCreate(MainActivity.kt:20)

You should check MainActivity.kt line no. 20 on setOnClickListenern

im using a device for android studio and after a while app crashes and i get this error. anybody knows what the problem is?

2 Answers2