받기 "java.lang.IllegalStateException는 : 안드로이드에 대한 방법을 실행할 수 없습니다 : onclick을"

Question

오류 ...

E/AndroidRuntime: FATAL EXCEPTION: main 
Process: com.example.vaidish.myapplication, PID: 12727 
java.lang.IllegalStateException: Could not execute method for android:onClick 
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293) 
    at android.view.View.performClick(View.java:6256) 
    at android.view.View$PerformClick.run(View.java:24697) 
    at android.os.Handler.handleCallback(Handler.java:789) 
    at android.os.Handler.dispatchMessage(Handler.java:98) 
    at android.os.Looper.loop(Looper.java:164) 
    at android.app.ActivityThread.main(ActivityThread.java:6567) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767) 
Caused by: java.lang.reflect.InvocationTargetException 
    at java.lang.reflect.Method.invoke(Native Method) 
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
    at android.view.View.performClick(View.java:6256) 
    at android.view.View$PerformClick.run(View.java:24697) 
    at android.os.Handler.handleCallback(Handler.java:789) 
    at android.os.Handler.dispatchMessage(Handler.java:98) 
    at android.os.Looper.loop(Looper.java:164) 
    at android.app.ActivityThread.main(ActivityThread.java:6567) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources$Theme android.content.Context.getTheme()' on a null object reference 
    at android.app.AlertDialog.resolveDialogTheme(AlertDialog.java:224) 
    at android.app.AlertDialog$Builder.<init>(AlertDialog.java:454) 
    at com.example.vaidish.myapplication.Background.<init>(Background.java:25) 
    at com.example.vaidish.myapplication.MainActivity.userLogin(MainActivity.java:56) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
    at android.view.View.performClick(View.java:6256) 
    at android.view.View$PerformClick.run(View.java:24697) 
    at android.os.Handler.handleCallback(Handler.java:789) 
    at android.os.Handler.dispatchMessage(Handler.java:98) 
    at android.os.Looper.loop(Looper.java:164) 
    at android.app.ActivityThread.main(ActivityThread.java:6567) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767) 

Answer 1

당신의 사고의 근본 원인이 비트입니다 :

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources$Theme android.content.Context.getTheme()' on a null object reference 
    at android.app.AlertDialog.resolveDialogTheme(AlertDialog.java:224) 
    at android.app.AlertDialog$Builder.<init>(AlertDialog.java:454) 
    at com.example.vaidish.myapplication.Background.<init>(Background.java:25) 

생성자에 null을 전달한다고 말합니다.

new AlertDialog.Builder(null) 

또는 당신이 좋아, 실수로 그 일을 할 수 있습니다 : 당신은 같이 명시 적으로 그 일을 할 수 귀하의 Background 클래스의

new AlertDialog.Builder(mContext) 

체크 라인 (25), 당신은 비를 전달하고 있는지 확인 -null Context 인스턴스를 빌더에 보냅니다.