android - Android Market 中的 TextView 展开动画

Question

谁能指出如何在 Android Market 动画中制作 Description TextView 的展开动画的解决方案？ TextView 包裹在 FrameLayout 中，单击“更多”标签后会展开。

Answer 1

解决方案:

private static int measureViewHeight( View view2Expand, View view2Measure ) {
    try {
        Method m = view2Measure.getClass().getDeclaredMethod("onMeasure", int.class, int.class);
        m.setAccessible(true);
        m.invoke(view2Measure,
                    MeasureSpec.makeMeasureSpec(view2Expand.getWidth(), MeasureSpec.AT_MOST),
                    MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
    } catch (Exception e) {
        return -1;
    }

    int measuredHeight = view2Measure.getMeasuredHeight();
    return measuredHeight;
}

static public void expandOrCollapse( View view2Expand, View view2Measure,
        int collapsedHeight ) {
    if (view2Expand.getHeight() < collapsedHeight)
        return;

    int measuredHeight = measureViewHeight(view2Expand, view2Measure);

    if (measuredHeight < collapsedHeight)
        measuredHeight = collapsedHeight;

    final int startHeight = view2Expand.getHeight();
    final int finishHeight = startHeight <= collapsedHeight ?
            measuredHeight : collapsedHeight;

    view2Expand.startAnimation(new ExpandAnimation(view2Expand, startHeight, finishHeight));
}

class ExpandAnimation extends Animation {
    private final View _view;
    private final int _startHeight;
    private final int _finishHeight;

    public ExpandAnimation( View view, int startHeight, int finishHeight ) {
        _view = view;
        _startHeight = startHeight;
        _finishHeight = finishHeight;
        setDuration(220);
    }

    @Override
    protected void applyTransformation( float interpolatedTime, Transformation t ) {
        final int newHeight = (int)((_finishHeight - _startHeight) * interpolatedTime + _startHeight);
        _view.getLayoutParams().height = newHeight;
        _view.requestLayout();
    }

    @Override
    public void initialize( int width, int height, int parentWidth, int parentHeight ) {
        super.initialize(width, height, parentWidth, parentHeight);
    }

    @Override
    public boolean willChangeBounds( ) {
        return true;
    }
};