Android动画 - 仿58同城加载动画

效果图

58LoadingView.gif

分析动画

首先分析动画，如上图所示：
动画分为三部分，分别为上方跳动部分，中间阴影部分，和下方文字部分。

• 上方跳动部分，三个几何图形，实现上抛下落（平移），上抛过程中几何图形进行旋转，到达最底部时，变换几何图形
• 中间阴影部分，一个椭圆，进行缩放
• 下方文字部分居中

进行绘制

主要运用Drawable动画进行绘制。

public class ShapeLoadingDrawable extends Drawable implements Animatable{
} 

先将上方部分三个几何图和中间部分椭圆形绘制出来

    //画圆
    private void drawCircle(Canvas canvas) {
        mPaint.setColor(Color.parseColor("#aa738ffe"));
        canvas.drawCircle(mWidth / 2, mHeight / 2, radius, mPaint);
    }
    //画正方形
    private void drawRect(Canvas canvas) {
        mPaint.setColor(Color.parseColor("#aae84e49"));
        canvas.drawRect(mWidth / 2 -rectLength/2, mHeight / 2 - rectLength/2, mWidth / 2 + rectLength/2, mHeight / 2 + rectLength/2, mPaint);
    }

    //画三角形
    private void drawTriangle(Canvas canvas) {
        mPaint.setColor(Color.parseColor("#aa72d572"));
        Path path = new Path();
        path.moveTo(mWidth / 2, mHeight / 2 - rectLength/2);
        path.lineTo((float) (mWidth / 2 - Math.sqrt(Math.pow(rectLength,2) / 3)), mHeight / 2 + rectLength/2);
        path.lineTo((float) (mWidth / 2 + Math.sqrt(Math.pow(rectLength,2) / 3)), mHeight / 2 + rectLength/2);
        path.close();
        canvas.drawPath(path, mPaint);
    }
    
    //画椭圆
    private void drawShadow(Canvas canvas) {
        mPaint.setColor(Color.parseColor("#25808080"));
        canvas.scale(scale, scale, mWidth / 2, mHeight / 2 + 90);
        canvas.drawArc(mWidth / 2 - rectLength/2, mHeight / 2 + 80, mWidth / 2 + 50, mHeight / 2 + 100, 0, 360, false, mPaint);
    }

进行动画部分代码编写，主要运用ValueAnimator

• 分析动画：两个部分的动画，一个是上面几何图形的下落上抛动画，一个是中间阴影指示器放大缩小的动画，如果能这样组合就算实现了: 当几何图形下落时配合阴影放大，当几何图形上抛时配合中间阴影缩小。当几何图形下落到最低点时，变换几何图形

    /**
     * 上抛动画
     */
    private void upAnimation() {
        final ValueAnimator upAnimation = ValueAnimator.ofFloat(0, -200);
        upAnimation.setInterpolator(new DecelerateInterpolator(1.2f));
        //为动画设置更新时候的监听
        upAnimation.addUpdateListener(new 
    ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                translateY = (float) upAnimation.getAnimatedValue();
                //刷新
                invalidateSelf();
            }
        });
        
        //监听动画结束，进行下落动画
        upAnimation.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                downAnimation();
            }
        });
        
        //缩放动画
        final ValueAnimator scaleAnimation = ValueAnimator.ofFloat(1, 0.3f);
        scaleAnimation.setInterpolator(new DecelerateInterpolator(1.2f));
        scaleAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                scale = (float) scaleAnimation.getAnimatedValue();
            }
        });

        //三角形旋转动画
        final ValueAnimator rotateTriangleAnimation = ValueAnimator.ofFloat(0, 120);
        rotateTriangleAnimation.setInterpolator(new DecelerateInterpolator(1.2f));
        rotateTriangleAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                rotateTriangle = (float) rotateTriangleAnimation.getAnimatedValue();
            }
        });
        //正方形旋转动画
        final ValueAnimator rotateRectAnimation = ValueAnimator.ofFloat(0, 180);
        rotateRectAnimation.setInterpolator(new DecelerateInterpolator(1.2f));
        rotateRectAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                rotateRect = (float) rotateRectAnimation.getAnimatedValue();
            }
        });


        upAnimatorSet = new AnimatorSet();
        upAnimatorSet.setDuration(300);
        upAnimatorSet.playTogether(upAnimation, scaleAnimation, rotateTriangleAnimation, rotateRectAnimation);
        upAnimatorSet.start();

    }

    
   /**
     * 下落动画
     */
    private void downAnimation() {
        final ValueAnimator downAnimation = ValueAnimator.ofFloat(-200, 0);
        downAnimation.setInterpolator(new DecelerateInterpolator(1.2f));
        downAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                translateY = (float) downAnimation.getAnimatedValue();
                invalidateSelf();
            }
        });

        downAnimation.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                upAnimation();
                exchangeDraw();
            }
        });


        final ValueAnimator scaleAnimation = ValueAnimator.ofFloat(0.3f, 1);
        scaleAnimation.setInterpolator(new DecelerateInterpolator(1.2f));
        scaleAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                scale = (float) scaleAnimation.getAnimatedValue();
            }
        });
        downAnimatorSet = new AnimatorSet();
        downAnimatorSet.setDuration(500);
        downAnimatorSet.playTogether(downAnimation, scaleAnimation);
        downAnimatorSet.start();
    }

动画使用

在ImageView中设置drawable即可

ShapeLoadingDrawable shapeLoadingDrawable = new ShapeLoadingDrawable();
imageView.setImageDrawable(shapeLoadingDrawable);
shapeLoadingDrawable.start();