Android:添加带有展开动画的 View (不闪烁)

Question

我想使用展开动画向 View 组添加一个 View ，因此添加的 View 开始时非常小，并且占用越来越多的空间，直到达到其最大尺寸(可能在此过程中移动其他 View )。

在尝试了不同的方法之后，我想出了下面的解决方案。投票是否对您有帮助，或者请发布更好的选择。我相信一定有更简单的方法来做到这一点。

有关更多信息，请参阅 this one 等帖子和 this one .

下面是我如何添加 View 并启动动画:

// Trick: set height to 1 so the view doesn't take its full size at the beginning.
// (0 doesn't work, I don't know why)
container.addView(view, LayoutParams.MATCH_PARENT, 1);
Animation expansion = createExpansion(view);
expansion.setDuration(200);
view.startAnimation(expansion);

createExpansion() 方法:

public static Animation createExpansion(View view) {

    return new SizedHeightScaleAnimation(view, 0, 1,
            Animation.RELATIVE_TO_SELF, 0f,
            Animation.RELATIVE_TO_SELF, 0f);
}

最后是 SizedHeightScaleAnimation 动画类:

/**
 * Like {@link ScaleAnimation} for height scaling that also resizes the view accordingly,
 * so it takes the right amount of space while scaling.
 */
public class SizedHeightScaleAnimation extends ScaleAnimation {

    private float fromHeight;
    private float toHeight;
    private View viewToScale;

    public SizedHeightScaleAnimation(View viewToScale, float fromY, float toY) {
        super(1, 1, fromY, toY);
        init(viewToScale, fromY, toY);
    }

    public SizedHeightScaleAnimation(View viewToScale, float fromY, float toY, float pivotX, float pivotY) {
        super(1, 1, fromY, toY, pivotX, pivotY);
        init(viewToScale, fromY, toY);
    }

    public SizedHeightScaleAnimation(View viewToScale, float fromY, float toY, int pivotXType, float pivotXValue, int pivotYType, float pivotYValue) {
        super(1, 1, fromY, toY, pivotXType, pivotXValue, pivotYType, pivotYValue);
        init(viewToScale, fromY, toY);
    }

    private void init(View viewToScale, float fromY, float toY) {

        this.viewToScale = viewToScale;
        viewToScale.measure(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
        fromHeight = viewToScale.getMeasuredHeight() * fromY;
        toHeight = viewToScale.getMeasuredHeight() * toY;
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        super.applyTransformation(interpolatedTime, t);

        final int newHeight = (int) (fromHeight * (1 - interpolatedTime) + toHeight * interpolatedTime);

        viewToScale.getLayoutParams().height = newHeight;
        viewToScale.requestLayout();
    }
}

顺便说一句，您可以通过这种方式创建折叠效果:

public static Animation createCollapse(View view) {

    return new SizedHeightScaleAnimation(view, 1, 0,
            Animation.RELATIVE_TO_SELF, 0f,
            Animation.RELATIVE_TO_SELF, 0f);
}

当您使用它时，您可能希望在动画完成后从其父 View 中删除 View :

Animation collapse = createCollapse(view);
collapse.setDuration(200);

collapse.setAnimationListener(new AnimationListener() {
    @Override
    public void onAnimationEnd(Animation animation) {
        final ViewGroup parent = (ViewGroup) view.getParent();
        parent.removeView(view);
    }

    ... other overrides ...
});

view.startAnimation(collapse);

Answer 1

这可能会更简单一些:

public void expand(final View view) {
    view.getLayoutParams().height = 0;

    Animation a = new Animation() {
        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t)
        {
            view.getLayoutParams().height = (int)(mTargetHeight * interpolatedTime);
            view.requestLayout();
        }

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

    a.setDuration(1000);
    view.startAnimation(a);
}