Question

我已经实现了一个可移动的图像视图，我可以用手指和缩放来移动。我使用拖放框架移动它（因为我还需要它拖放），我有一个ScaleGestureDetector.SimpleOnScaleGestureListener来处理缩放。 MovableImageView扩展了普通ImageView表单Android。当用户触摸图像视图时，调用方法onTouchEvent(MotionEvent event)。此方法如下所示：

public boolean onTouchEvent(MotionEvent event)
{
   scaleDetector.onTouchEvent(event);
   startDragNDrop();
   return true;
}

startDragNDrop()看起来像这样：

private void startDragNDrop() {
    // Create a new ClipData.
    // This is done in two steps to provide clarity. The convenience method
    // ClipData.newPlainText() can create a plain text ClipData in one step.

    // Create a new ClipData.Item from the ImageView object's tag
    ClipData.Item item = new ClipData.Item(mediaItem.getMediaIdentifier());

    // Create a new ClipData using the tag as a label, the plain text MIME type, and
    // the already-created item. This will create a new ClipDescription object within the
    // ClipData, and set its MIME type entry to "text/plain"
    String[] mimeType =  {ClipDescription.MIMETYPE_TEXT_PLAIN};
    ClipData dragData = new ClipData((CharSequence) this.getTag(),mimeType,item);

    // Instantiates the drag shadow builder.
    DragShadowBuilder myShadow = new ZPACDragShadowBuilder(this);

    actualyDraggedView = this;

    // Starts the drag
    this.startDrag(dragData,  // the data to be dragged
                   myShadow,  // the drag shadow builder
                   null,      // no need to use local data
                   0);        // flags (not currently used, set to 0)
}

它基本上创建了dragshadow并开始拖动操作。

在scaleDetector.onTouchEvent(event)之后调用的onScale()的实现如下：

public boolean onScale(ScaleGestureDetector detector) {
    float scaleFactor = MovableImageView.this.SCALE_FACTOR;
    scaleFactor *= detector.getScaleFactor();

    // Don't let the object get too small or too large.
    scaleFactor = Math.max(0.1f, Math.min(scaleFactor, 2.0f));

    int width = (int) (MovableImageView.this.getWidth()*scaleFactor);
    int height = (int) (MovableImageView.this.getHeight()*scaleFactor);

    Log.e("MovableImageView", "Scale Gesture Captured. Scaling Factor " + scaleFactor + " old width " + MovableImageView.this.getWidth() + ", new width " + width);

    AbsoluteLayout.LayoutParams layoutParams = new AbsoluteLayout.LayoutParams(width, height, MovableImageView.this.getLeft(), MovableImageView.this.getTop());

    parentLayout.updateViewLayout(MovableImageView.this, layoutParams);
    invalidate();
    return true;
}

字段SCALE_FACTOR是一个浮点数，值为1.f。 parentLayout是一个扩展的AbsoluteLayout，用于管理屏幕上ImageView的位置和大小。

我的问题是缩放不起作用，只有拖放。不执行缩放，仅在视图周围移动。如果我注释掉了linke startDragNDrop()，那么缩放就可以了，但显然不是在视图中移动。有没有人有更好的想法将这些与图像视图中的东西结合起来？

Answer 1

你的onScaleBegin方法是否返回false？当我尝试做类似的事情时，Eclipse创建了一个返回false的onScaleBegin方法。这告诉Android忽略其余的缩放手势。为了让Android调用onScale和onScaleEnd，我不得不让onScaleBegin返回true。我遇到的另一个问题是，即使onScaleBegin返回true，根据Android reference for OnScaleGestureListener onScale也可能永远不会被调用。因此，我将缩放计算放在onScaleEnd中。这个解决方案对我有用，因为我只想为每个捏合或展开手势调整一次缩放。

Answer 2

我为你所追求的目标取得了类似的成果。也许该片段会帮助你：

在onClickListener（）中：

AnimatorSet scale = resizeAnimation(v, 1.2f);
scale.addListener(new AnimatorListenerAdapter() {
    @Override
    public void onAnimationEnd(Animator animation) {
        super.onAnimationEnd(animation);
        v.startDrag(dragData,  // the data to be dragged
                new MyDragShadowBuilder(v),  // the drag shadow builder
                v,
                0          // flags (not currently used, set to 0)
        );
    }
});
scale.start();

ResizeAnimation（）：

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
private AnimatorSet resizeAnimation(View view, float scale) {
    ObjectAnimator scaleX = ObjectAnimator.ofFloat(view, "scaleX", scale);
    ObjectAnimator scaleY = ObjectAnimator.ofFloat(view, "scaleY", scale);
    AnimatorSet animSetXY = new AnimatorSet();
    animSetXY.playTogether(scaleX, scaleY);
    animSetXY.setDuration(200);
    animSetXY.setInterpolator(new AccelerateDecelerateInterpolator());
    return animSetXY;
}

MyDragShadowBuilder：

private static class MyDragShadowBuilder extends View.DragShadowBuilder {

    // The drag shadow image, defined as a drawable thing
    private static Drawable shadow;
    int width, height;

    public MyDragShadowBuilder(View v) {

        width = (int) (v.getWidth() * 1.2f);
        height = (int) (v.getHeight() * 1.2f);
        v.setDrawingCacheEnabled(true);
        v.setDrawingCacheQuality(View.DRAWING_CACHE_QUALITY_LOW); //Quality of the snapshot
        Bitmap snapshot;
        try {
            snapshot = Bitmap.createBitmap(v.getDrawingCache()); // You can tell how to crop the snapshot and whatever in this method
            shadow = new BitmapDrawable(snapshot);
        } finally {
            v.setDrawingCacheEnabled(false);
        }
        v.setDrawingCacheEnabled(false);
    }

    @Override
    public void onProvideShadowMetrics (Point size, Point touch){

        int halfWidth = width /2, halfHeight = height /2;
        shadow.setBounds(0, 0, width, height);
        size.set(width, height);
        touch.set(halfWidth, halfHeight);
}

@Override
public void onDrawShadow(Canvas canvas) {
    shadow.draw(canvas);
}

}

结合拖放和缩放

2 个答案: