TextView expand animation like in Android Market

问题:

Can anyone point to solution how to make expand animation of Description TextView in Android Market animation? There are TextView wrapped into FrameLayout which expands after clicking on 'More' label.

回答1:

Solution:

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;
    }
};