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您好已更改 Opencv 示例，仅在用户触摸屏幕时添加操作。代码有树类。FdActivity 扩展了 Activity，FdViewBase 扩展了 SurfaceView 并实现了 SurfaceHolder.Callback，最后 FdView 扩展了 FdViewBase。

FdActivity的onCreate方法：

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);            
        setContentView(new FdView(this));        
      }

FdViewBase 在类构造函数中有方法调用'setFocusable(true);' .
最后是 onTouchEvent 代码：

public boolean onTouchEvent(MotionEvent event) {                  
         //   if (event.getAction() == MotionEvent.ACTION_DOWN) 
              Log.i(TAG,"DOWN");                
            Log.i(TAG,"/\");
            return true;
        }

以这种方式，代码不会发生编译或执行错误，但如果我取消注释 if 语句，我会收到以下错误消息：

04-16 21:59:06.011: I/OpenCV_NativeCamera(8952): ### Camera FPS ### [780] Frames, 12.84 FPS
    04-16 21:59:06.662: D/AndroidRuntime(8952): Shutting down VM
    04-16 21:59:06.662: W/dalvikvm(8952): threadid=1: thread exiting with uncaught exception (group=0x40018560)
    04-16 21:59:06.732: E/AndroidRuntime(8952): FATAL EXCEPTION: main
    04-16 21:59:06.732: E/AndroidRuntime(8952): java.lang.NullPointerException
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at org.opencv.samples.fd.FdActivity.onTouchEvent(Unknown Source)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at android.app.Activity.dispatchTouchEvent(Activity.java:2099)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1721)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at android.view.ViewRoot.deliverPointerEvent(ViewRoot.java:2200)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1884)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at android.os.Handler.dispatchMessage(Handler.java:99)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at android.os.Looper.loop(Looper.java:130)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at android.app.ActivityThread.main(ActivityThread.java:3835)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at java.lang.reflect.Method.invokeNative(Native Method)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at java.lang.reflect.Method.invoke(Method.java:507)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)
    04-16 21:59:06.732: E/AndroidRuntime(8952):     at dalvik.system.NativeStart.main(Native Method)
    04-16 21:59:07.432: I/OpenCV_NativeCamera(8952): ### Camera FPS ### [810] Frames, 21.09 FPS
    04-16 21:59:08.864: I/OpenCV_NativeCamera(8952): ### Camera FPS ### [840] Frames, 21.00 FPS
    04-16 21:59:12.588: I/OpenCV_NativeCamera(8952): ### Camera FPS ### [870] Frames, 8.04 FPS
    04-16 21:59:13.168: I/Process(8952): Sending signal. PID: 8952 SIG: 9

我不知道为什么会这样，似乎事件源不可见。

Eclipse 没有显示任何警告或错误消息，LogCat 中也没有出现其他错误。所以有人知道为什么会这样吗？

谢谢=]

4

2 回答 2

1 
setContentView(new FdView(this));

替换上面的代码如下

View view = new FdView(this);
view.setOnTouchListener(this);
setContentView(view);

这是因为您没有将 ontouch 设置为任何视图。

于 2012-04-17T02:28:44.533 回答
0

尝试false从你那里返回 onTouchEvent() 监听器。

当您返回时true，该事件不会进一步传播，并且可能会导致 NPE。

于 2012-04-17T01:28:05.977 回答