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当检测到单击视图时，我想为结果调用 startactivity。

对于视图上的单击，我在视图的 ontouch 方法中编写了以下条件

@Override public boolean onTouchEvent(MotionEvent ev) {


if (!mSupportsZoom && !mSupportsPan) return false;


mScaleDetector.onTouchEvent(ev);

final int action = ev.getAction();
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN: {
    final float x = ev.getX();
    final float y = ev.getY();

    mLastTouchX = x;
    mLastTouchY = y;
    mActivePointerId = ev.getPointerId(0);

    break;
}

case MotionEvent.ACTION_MOVE: {
    final int pointerIndex = ev.findPointerIndex(mActivePointerId);
    final float x = ev.getX(pointerIndex);
    final float y = ev.getY(pointerIndex);

    if (mSupportsPan && !mScaleDetector.isInProgress()) {
        final float dx = x - mLastTouchX;
        final float dy = y - mLastTouchY;

        mPosX += dx;
        mPosY += dy;
        //mFocusX = mPosX;
        //mFocusY = mPosY;

        invalidate();
    }

    mLastTouchX = x;
    mLastTouchY = y;

    break;
}

case MotionEvent.ACTION_UP: {

    final float x = ev.getX();
    final float y = ev.getY();

    touchupX=x;
    touchupY=y;

    if(mLastTouchX == touchupX && mLastTouchY == touchupY){ //this is my condition to detect single tap on the view

        PinchZoomPanActivity2.tapped(null, 100); //method for startactivityfor result which is in main activity

    }

    mActivePointerId = INVALID_POINTER_ID;
    break;
}

case MotionEvent.ACTION_CANCEL: {
    mActivePointerId = INVALID_POINTER_ID;
    break;
}

case MotionEvent.ACTION_POINTER_UP: {
    final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) 
            >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
    final int pointerId = ev.getPointerId(pointerIndex);
    if (pointerId == mActivePointerId) {

        final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
        mLastTouchX = ev.getX(newPointerIndex);
        mLastTouchY = ev.getY(newPointerIndex);
        mActivePointerId = ev.getPointerId(newPointerIndex);
    }
    break;
}
}

return true;
}

mainactivity 中的 tapped 方法如下

static void tapped(Activity activity, int requestCode){

activity.startActivityForResult(new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.INTERNAL_CONTENT_URI), 1);
}

但这不起作用，因为它因错误空指针异常而取消了赎回权。

请建议我的代码有什么问题。

4

2 回答 2

2 
PinchZoomPanActivity2.tapped(null, 100);

您正在为活动传递 null 。因此，被窃听的函数尝试对其调用 startActivityForResult 并失败，因为它为空。

于 2013-08-01T05:11:28.820 回答
0

最终起作用的代码是我在视图中添加了 this.getcontext()，

PinchZoomPanActivity2.tapped(this.getContext(), 100);

活动如下

static void tapped(Context context, int requestCode){

((Activity) context).startActivityForResult(new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.INTERNAL_CONTENT_URI), 1);
}
于 2013-08-01T05:27:20.537 回答