當我按下按鈕時，Android應用程序崩潰

-2

嘿傢伙，所以當我打這個特定的按鈕，它應該帶我到另一個佈局。然而，每次我點擊它，整個應用程序崩潰。下面是該網頁即時試圖去的onCreate方法：當我按下按鈕時，Android應用程序崩潰

protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_bench_data_entry); 
     //opens the database 
     openDB(); 
     //Initializes and declares the sensors, and accelerometer 
     mInitialized = false; 
     mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE); 
     mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); 
     mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL); 
     // tv.setText("Aasfdaf"); 

    }

這裏是的onClick的按鈕，我按：

public void onClick_Bench(View v){ 
     //Intent to create a new activity 
     Intent intent = new Intent(MainMenuActivity.this, BenchDataEntry.class); 
     //Goes to the Data Entry Screen 
     startActivity(intent); 
    }

，這裏是錯誤日誌中我收到的時候我按下按鈕：

08-08 17:30:30.785 31113-31113/com.example.jacob.repcapture E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.example.jacob.repcapture, PID: 31113 
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.jacob.repcapture/com.example.jacob.repcapture.BenchDataEntry}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2327) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
      at android.app.ActivityThread.-wrap11(ActivityThread.java) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:148) 
      at android.app.ActivityThread.main(ActivityThread.java:5422) 
      at java.lang.reflect.Method.invoke(Native Method) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference 
      at android.app.Activity.findViewById(Activity.java:2096) 
      at com.example.jacob.repcapture.BenchDataEntry.<init>(BenchDataEntry.java:49) 
      at java.lang.Class.newInstance(Native Method) 
      at android.app.Instrumentation.newActivity(Instrumentation.java:1067) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2317) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
            at android.app.ActivityThread.-wrap11(ActivityThread.java) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:148) 
            at android.app.ActivityThread.main(ActivityThread.java:5422) 
            at java.lang.reflect.Method.invoke(Native Method) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

來源

2016-08-08 jvangore31

'findViewById'必須在'onCreate'方法內。不在其外面。請參閱BenchDataEntry.java的第49行 –

實際上，只需通過執行_act.runOnUiThread _act爲Activity變量或此操作，就可以在UI線程上調用findViewById。另外，如果您最終在兩個單獨的線程上運行並初始化ui，則必須使用線程併發性，並確保您使用鎖定和條件來同步運行的功能代碼和UI代碼。我在下面的答案第二，確保做一個重建。 – JQluv

我認爲錯誤未在這些代碼塊的logcat約android.view.View android.view.Window.findViewById（INT）」上的空對象引用

首先 - 在build-menu下執行clean project，並重新啓動模擬器。之後，我的情況異常消失了。其次 - 檢查FindviewById項目您還需要在onCreate中初始化它們。

來源

2016-08-08 22:47:13

當我按下按鈕時，Android應用程序崩潰

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