com.kami2017.app.MainActivity.onCreateのAndroidスタジオエラー

Question

Error: 

02/01 14:12:04: Launching app 
$ adb push /Users/Kamran/AndroidStudioProjects/App/app/build/outputs/apk/app-debug.apk /data/local/tmp/com.kami2017.app 
$ adb shell pm install -r "/data/local/tmp/com.kami2017.app" 
Success 


$ adb shell am start -n "com.kami2017.app/com.kami2017.app.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER 
Client not ready yet..Waiting for process to come online 
Connected to process 2284 on device emulator-5554 
W/System: ClassLoader referenced unknown path: /data/app/com.kami2017.app-1/lib/x86 

      [ 02-01 14:12:28.511 1531: 1552 D/   ] 
      HostConnection::get() New Host Connection established 0x85a8d240, tid 1552 
I/InstantRun: Instant Run Runtime started. Android package is com.kami2017.app, real application class is null. 
W/System: ClassLoader referenced unknown path: /data/app/com.kami2017.app-1/lib/x86 
W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable 
D/AndroidRuntime: Shutting down VM 


        --------- beginning of crash 
E/AndroidRuntime: FATAL EXCEPTION: main 
        Process: com.kami2017.app, PID: 2284 
        java.lang.RuntimeException: Unable to start activity ComponentInfo{com.kami2017.app/com.kami2017.app.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.webkit.WebSettings android.webkit.WebView.getSettings()' on a null object reference 
         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665) 
         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
         at android.app.ActivityThread.-wrap12(ActivityThread.java) 
         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
         at android.os.Handler.dispatchMessage(Handler.java:102) 
         at android.os.Looper.loop(Looper.java:154) 
         at android.app.ActivityThread.main(ActivityThread.java:6119) 
         at java.lang.reflect.Method.invoke(Native Method) 
         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
        Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.webkit.WebSettings android.webkit.WebView.getSettings()' on a null object reference 
         at com.kami2017.app.MainActivity.onCreate(MainActivity.java:17) 
         at android.app.Activity.performCreate(Activity.java:6679) 
         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) 
         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618) 
         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)  
         at android.app.ActivityThread.-wrap12(ActivityThread.java)  
         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)  
         at android.os.Handler.dispatchMessage(Handler.java:102)  
         at android.os.Looper.loop(Looper.java:154)  
         at android.app.ActivityThread.main(ActivityThread.java:6119)  
         at java.lang.reflect.Method.invoke(Native Method)  
         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)  
         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)  
Application terminated. 

Answer 1

あなたのWebViewのIDはXMLファイルではないと思います。そのWebViewにアクセスしようとしています。

はFYI次のリンクを検討してください： Getting void android.webkit.WebView.loadUrl while loading webview in dialog in Android?

Answer 2

あなたのWebViewがnullです。あなたのアクティビティでXMLファイルからwebview用のインスタンスを作成しましたか？

WebView myWebView = (WebView) findViewById(R.id.webview); 
WebSettings webSettings = myWebView.getSettings(); 

それとも、プログラムで新しいWebViewを作成する必要があります：java.lang.NullPointerExceptionが：によって引き起こさ

WebView webView = new WebView(this);