使用更新的GridView在活动中按下后退按钮时，应用程序崩溃-Java 学习之路

在我的应用程序中，我发起了一项活动，并从那里开始了另在第二个活动中，我展示了一个填充了数据的GridView . 然后，用户可以按下按钮删除附加到GridView的所有数据 . 每当用户删除数据然后按“返回”按钮时，应用程序崩溃并发生致命异常 . 在下面的代码中，logcat指示崩溃发生在ReloadGridView方法中 . 实际上有try ... catch在这段代码中，但这并不能防止致命错误 .

我花了一天时间试图弄清楚造成这种情况的原因，但还没有成功 . 只有在删除附加到适配器的基础数据并按下“后退”按钮时才会出现此问题 . 此代码在Android 4.1上运行 . 注意：这是一组简化的代码 . 所有必要的东西都被删除了，以便更容易专注于问题 .

@Override
public void onCreate(Bundle savedInstanceState)
{
  private ArrayList data = new ArrayList();
  private MyAdapter adapterData;
  private GridView gvData;

  // Setup the GridView.
  gvData = (GridView) findViewById(R.id.gvData);

  adapterData = new MonitorDataAdapter();
  gvData.setAdapter(adapterData);

  new Thread(null, new LoadMyDataRunnable(0, false), "LoadMyDataRunnable").start();
}

private class LoadMyDataRunnable implements Runnable
{
  @Override
  public void run()
  {
    data = GetMyData();

    ReloadGridView reloadGridView = new ReloadGridView();
    runOnUiThread(reloadGridView);
  }
}

private class ReloadGridView implements Runnable
{
  @Override
  public void run()
  {

// Tried the following and many other things but a fatal exeption occurs here when the Back button is pressed:
//        adapterData = new MyAdapter();
//        gvData.setAdapter(adapterData);
//        if (data.size() == 0)
//          gvData.setAdapter(null);
  }
}


// Button to delete data.
btnDelete.setOnClickListener(new OnClickListener()
{
  @Override
  public void onClick(View v)
  {
    // Delete the data.
    SomeMethodToDeleteData();
    new Thread(null, new LoadMyDataRunnable(0, false), "LoadMyDataRunnable").start();
  }
}

日志：

07-08 11:28:15.421: E/AndroidRuntime(27415): FATAL EXCEPTION: MonitorDevice.ReloadGridView.run_d99af1dd-b961-4a1f-bea5-4e4bb986e107
07-08 11:28:15.421: E/AndroidRuntime(27415): java.lang.NullPointerException
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.AbsListView.obtainView(AbsListView.java:2269)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.GridView.onMeasure(GridView.java:1030)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.View.measure(View.java:15222)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:617)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:399)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.View.measure(View.java:15222)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.View.measure(View.java:15222)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.View.measure(View.java:15222)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.View.measure(View.java:15222)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.View.measure(View.java:15222)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2165)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.View.measure(View.java:15222)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1870)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1106)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1279)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1004)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4238)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.Choreographer.doCallbacks(Choreographer.java:555)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.Choreographer.doFrame(Choreographer.java:525)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.os.Handler.handleCallback(Handler.java:615)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.os.Handler.dispatchMessage(Handler.java:92)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.os.Looper.loop(Looper.java:137)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at android.app.ActivityThread.main(ActivityThread.java:4838)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at java.lang.reflect.Method.invokeNative(Native Method)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at java.lang.reflect.Method.invoke(Method.java:511)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
07-08 11:28:15.421: E/AndroidRuntime(27415):    at dalvik.system.NativeStart.main(Native Method)
07-08 11:28:15.971: E/WifiHW(427): wifi_send_command : SIGNAL_POLL ; interface index=0;
07-08 11:28:18.981: E/WifiHW(427): wifi_send_command : SIGNAL_POLL ; interface index=0;
07-08 11:28:22.001: E/WifiHW(427): wifi_send_command : SIGNAL_POLL ; interface index=0;
07-08 11:28:25.011: E/WifiHW(427): wifi_send_command : SIGNAL_POLL ; interface index=0;
07-08 11:28:28.031: E/WifiHW(427): wifi_send_command : SIGNAL_POLL ; interface index=0;

使用更新的GridView在活动中按下后退按钮时，应用程序崩溃

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