Android移动ImageView

我在网上搜索了一个简单的解决方案来自由移动ImageView.我终于找到了一些产生完美结果的代码：

public class MainActivity extends Activity implements View.OnTouchListener {

    private int _xDelta;
    private int _yDelta;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ImageView j = (ImageView)findViewById(R.id.j);

        j.setOnTouchListener(this);

    }

    public boolean onTouch(View view,MotionEvent event) {
        final int X = (int) event.getRawX();
        final int Y = (int) event.getRawY();
        ImageView j = (ImageView)findViewById(R.id.j);
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
                _xDelta = (int) (X - j.getTranslationX());
                _yDelta = (int) (Y - j.getTranslationY());
                break;
            case MotionEvent.ACTION_UP:
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                break;
            case MotionEvent.ACTION_POINTER_UP:
                break;
            case MotionEvent.ACTION_MOVE:
                RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view.getLayoutParams();

                j.setTranslationX(X - _xDelta);
                j.setTranslationY(Y - _yDelta);
                break;
        }

        return true;
    }}

由于我不知道我的代码是如何工作的,我想看看是否有更好的解决方案.

最佳答案

正如谷歌建议的那样,如果您定位Android 3.0及更高版本,则可以使用DragListener.

对于pre-Honeycomb版本,您可以使用以下内容：

// The ‘active pointer’ is the one currently moving our object.
private int mActivePointerId = INVALID_POINTER_ID;

@Override
public boolean onTouchEvent(MotionEvent ev) {
    // Let the ScaleGestureDetector inspect all events.
    mScaleDetector.onTouchEvent(ev);

    final int action = MotionEventCompat.getActionMasked(ev); 

    switch (action) { 
    case MotionEvent.ACTION_DOWN: {
        final int pointerIndex = MotionEventCompat.getActionIndex(ev); 
        final float x = MotionEventCompat.getX(ev,pointerIndex); 
        final float y = MotionEventCompat.getY(ev,pointerIndex); 

        // Remember where we started (for dragging)
        mLastTouchX = x;
        mLastTouchY = y;
        // Save the ID of this pointer (for dragging)
        mActivePointerId = MotionEventCompat.getPointerId(ev,0);
        break;
    }

    case MotionEvent.ACTION_MOVE: {
        // Find the index of the active pointer and fetch its position
        final int pointerIndex = 
                MotionEventCompat.findPointerIndex(ev,mActivePointerId);  

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

        // Calculate the distance moved
        final float dx = x - mLastTouchX;
        final float dy = y - mLastTouchY;

        mPosX += dx;
        mPosY += dy;

        invalidate();

        // Remember this touch position for the next move event
        mLastTouchX = x;
        mLastTouchY = y;

        break;
    }

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

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

    case MotionEvent.ACTION_POINTER_UP: {

        final int pointerIndex = MotionEventCompat.getActionIndex(ev); 
        final int pointerId = MotionEventCompat.getPointerId(ev,pointerIndex); 

        if (pointerId == mActivePointerId) {
            // This was our active pointer going up. Choose a new
            // active pointer and adjust accordingly.
            final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
            mLastTouchX = MotionEventCompat.getX(ev,newPointerIndex); 
            mLastTouchY = MotionEventCompat.getY(ev,newPointerIndex); 
            mActivePointerId = MotionEventCompat.getPointerId(ev,newPointerIndex);
        }
        break;
    }
    }       
    return true;
}

正如谷歌here所建议的那样.

原文链接：https://www.f2er.com/android/430975.html

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