Question

我正在制作一个应用程序，它看起来运行得很好，但应用程序有一些错误。每当我触摸视图并将手指移到视图外并释放时，它就会崩溃。

以下是我的问题的解释：！[在此输入图像说明] [1]

以下是我的一些代码可能是问题：

public class Game extends View implements OnTurnBasedMatchUpdateReceivedListener  {

public Game(GameActivity activity){
    super(activity);
    this.mGameActivity = activity;
    this.mGameBoard    = new GameBoard(activity);
    this.setFocusable(true);
    this.setFocusableInTouchMode(true);
    this.setClickable(true);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
    // TODO Auto-generated method stub
    // TODO Subtract movementpoints
    int eventCode = event.getAction();
    switch(eventCode){
    case MotionEvent.ACTION_DOWN:
        return true;
    case MotionEvent.ACTION_MOVE:
        return true;
    case MotionEvent.ACTION_UP:
        return true;
    default:
        return true;            
    }
}

以下是错误日志：

04-08 23:00:47.585: E/InputEventReceiver(18313): Exception dispatching input event.
04-08 23:00:47.585: E/MessageQueue-JNI(18313): Exception in MessageQueue callback: handleReceiveCallback
04-08 23:00:47.620: E/MessageQueue-JNI(18313): java.lang.NullPointerException
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at com.boentertainment.quizgame.Game.onTouchEvent(Game.java:199)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.View.dispatchTouchEvent(View.java:7713)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2216)
04-08 23:00:47.620: E/MessageQueue-JNI(18313):  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1959)

Answer 1

您需要学习调试应用程序。然后你可以做导致bug的事情，并在那时看到变量的值。另一个有用的东西是日志系统。如果您正在使用Eclipse，可以在此处找到更多信息：How to Debug Android application line by line using Eclipse?

如果您打算在将来为每个案例实现代码，那么您的开关肯定需要break-statements：

switch(eventCode){
case MotionEvent.ACTION_DOWN:
    return true;
    break;
case MotionEvent.ACTION_MOVE:
    return true;
    break;
case MotionEvent.ACTION_UP:
    return true;
    break;
default:
    return true;            
}

显示java.lang.NullPointerException; android.view.View.dispatchTouchEvent（View.java:7713）

1 个答案: