一个很酷的加载loading效果，自定义LeafLoadingView实现，LeafLoadingView继承view,
本例子主要由以下几点构成
（1）：RotateAnimation实现叶子旋转
（2）：叶子飘动
（3）：当前进度绘制当前进度条
大体实现源码如下：
?@Override
??? protected void onDraw(Canvas canvas) {
??????? super.onDraw(canvas);

??????? // 绘制进度条和叶子
??????? // 之所以把叶子放在进度条里绘制，主要是层级原因
??????? drawProgressAndLeafs(canvas);
??????? // drawLeafs(canvas);

??????? canvas.drawBitmap(mOuterBitmap, mOuterSrcRect, mOuterDestRect, mBitmapPaint);

??????? postInvalidate();
??? }

??? private void drawProgressAndLeafs(Canvas canvas) {

??????? if (mProgress >= TOTAL_PROGRESS) {
??????????? mProgress = 0;
??????? }
??????? // mProgressWidth为进度条的宽度，根据当前进度算出进度条的位置
??????? mCurrentProgressPosition = mProgressWidth * mProgress / TOTAL_PROGRESS;
??????? // 即当前位置在图中所示1范围内
??????? if (mCurrentProgressPosition < mArcRadius) {
??????????? Log.i(TAG, "mProgress = " + mProgress + "---mCurrentProgressPosition = "
??????????????????? + mCurrentProgressPosition
??????????????????? + "--mArcProgressWidth" + mArcRadius);
??????????? // 1.绘制白色ARC，绘制orange ARC
??????????? // 2.绘制白色矩形

??????????? // 1.绘制白色ARC
??????????? canvas.drawArc(mArcRectF, 90, 180, false, mWhitePaint);

??????????? // 2.绘制白色矩形
??????????? mWhiteRectF.left = mArcRightLocation;
??????????? canvas.drawRect(mWhiteRectF, mWhitePaint);

??????????? // 绘制叶子
??????????? drawLeafs(canvas);

??????????? // 3.绘制棕色 ARC
??????????? // 单边角度
??????????? int angle = (int) Math.toDegrees(Math.acos((mArcRadius - mCurrentProgressPosition)
??????????????????? / (float) mArcRadius));
??????????? // 起始的位置
??????????? int startAngle = 180 - angle;
??????????? // 扫过的角度
??????????? int sweepAngle = 2 * angle;
??????????? Log.i(TAG, "startAngle = " + startAngle);
??????????? canvas.drawArc(mArcRectF, startAngle, sweepAngle, false, mOrangePaint);
??????? } else {
??????????? Log.i(TAG, "mProgress = " + mProgress + "---transfer-----mCurrentProgressPosition = "
??????????????????? + mCurrentProgressPosition
??????????????????? + "--mArcProgressWidth" + mArcRadius);
??????????? // 1.绘制white RECT
??????????? // 2.绘制Orange ARC
??????????? // 3.绘制orange RECT
??????????? // 这个层级进行绘制能让叶子感觉是融入棕色进度条中

??????????? // 1.绘制white RECT
??????????? mWhiteRectF.left = mCurrentProgressPosition;
??????????? canvas.drawRect(mWhiteRectF, mWhitePaint);
??????????? // 绘制叶子
??????????? drawLeafs(canvas);
??????????? // 2.绘制Orange ARC
??????????? canvas.drawArc(mArcRectF, 90, 180, false, mOrangePaint);
??????????? // 3.绘制orange RECT
??????????? mOrangeRectF.left = mArcRightLocation;
??????????? mOrangeRectF.right = mCurrentProgressPosition;
??????????? canvas.drawRect(mOrangeRectF, mOrangePaint);

??????? }

??? }

??? /**
???? * 绘制叶子
???? *
???? * @param canvas
???? */
??? private void drawLeafs(Canvas canvas) {
??????? mLeafRotateTime = mLeafRotateTime <= 0 ? LEAF_ROTATE_TIME : mLeafRotateTime;
??????? long currentTime = System.currentTimeMillis();
??????? for (int i = 0; i < mLeafInfos.size(); i++) {
??????????? Leaf leaf = mLeafInfos.get(i);
??????????? if (currentTime > leaf.startTime && leaf.startTime != 0) {
??????????????? // 绘制叶子－－根据叶子的类型和当前时间得出叶子的（x，y）
??????????????? getLeafLocation(leaf, currentTime);
??????????????? // 根据时间计算旋转角度
??????????????? canvas.save();
??????????????? // 通过Matrix控制叶子旋转
??????????????? Matrix matrix = new Matrix();
??????????????? float transX = mLeftMargin + leaf.x;
??????????????? float transY = mLeftMargin + leaf.y;
??????????????? Log.i(TAG, "left.x = " + leaf.x + "--leaf.y=" + leaf.y);
??????????????? matrix.postTranslate(transX, transY);
??????????????? // 通过时间关联旋转角度，则可以直接通过修改LEAF_ROTATE_TIME调节叶子旋转快慢
??????????????? float rotateFraction = ((currentTime - leaf.startTime) % mLeafRotateTime)
??????????????????????? / (float) mLeafRotateTime;
??????????????? int angle = (int) (rotateFraction * 360);
??????????????? // 根据叶子旋转方向确定叶子旋转角度
??????????????? int rotate = leaf.rotateDirection == 0 ? angle + leaf.rotateAngle : -angle
??????????????????????? + leaf.rotateAngle;
??????????????? matrix.postRotate(rotate, transX
??????????????????????? + mLeafWidth / 2, transY + mLeafHeight / 2);
??????????????? canvas.drawBitmap(mLeafBitmap, matrix, mBitmapPaint);
??????????????? canvas.restore();
??????????? } else {
??????????????? continue;
??????????? }
??????? }
??? }

?