Question

嘿伙计们，所以当我点击这个特定的按钮时，它应该带我到另一个布局。但是，每当我点击它，整个应用程序崩溃。这是我试图访问的页面的onCreate方法：

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");

  }

这是我按下按钮的onClick：

 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);
    }

这是我按下按钮时得到的错误日志：

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)

Answer 1

我认为错误不在这些代码中阻止logcat关于空对象引用的android.view.View android.view.Window.findViewById（int）'

首先 - 在build-menu下清理项目，然后重启模拟器。在那之后，异常在我的情况下消失了。第二步 - 检查FindviewById项目您还需要在onCreate中初始化它们。

当我点击按钮时Android应用程序崩溃

1 个答案: