StackScrollLayout

1.直接将/StackscrollLayout/build/outputs/aar/StackscrollLayout-release.aar放入lib目录下,
并修改build.gradle文件
repositories {
 flatDir {
 dirs 'libs'
 }
}
dependencies {
 compile fileTree(dir: 'libs', include: ['*.jar'])
 testCompile 'junit:junit:4.12'
 compile 'com.android.support:appcompat-v7:23.3.0'
 compile(name:'StackscrollLayout-release',ext:'aar');
}
2.如需修改源代码, 请在项目中导入StackscrollLayout这个module, 并做如下配置
build.gradle
dependencies {
 ... 
 compile project(':StackscrollLayout')
 ...
}
settings.gradle
include ':StackscrollLayout'

1.初始化
stackViewAdapter = new StackViewAdapter(LayoutInflater.from(this)); // 创建一个adapter
stackViewAdapter.setData(getData()); // 为Adapter绑定数据
mStackScroller.setAdapter(stackViewAdapter); //为Scroller设置adapter
mStackScroller.setOnItemClickListener(onStackItemClickListener); // 绑定点击事件
stackViewAdapter继承StackViewBaseAdapter实现了ListAdapter, SpinnerAdapter接口,
所以这里的adapter实现逻辑与ListView的adapter基本一样, 刷新数据时只要调下stackViewAdapter的notifyDataSetChanged即可
adapter的实现逻辑主要在StackScrollLayout.java与StackViewBaseAdapter.java中
2.一些方法 
展开: stackScrollPanelView.expand(false);
关闭: stackScrollPanelView.collapse(false);
其中括号里的参数为delay, false表示直接执行操作, true表示延迟一段时间后执行
改delay的值可以在PanelView修改对应delay参数
3.核心代码
第一次点击屏幕时,由于此时view未展开,Touch事件首先被父类PanelView拦截处理:
代码:PanelView的ActionDown中return true拦截该事件;
Action_Down ---> (mExpandedHeight == 0 || PanelView正在进行展开或收合动画) Touch事件首先被父类PanelView拦截处理: 
 然后onTouchEvent的ActionMove方法:此处主要处理下拉时更新View的状态
 final float newHeight = Math.max(0, h + mInitialOffsetOnTouch);
 setExpandedHeightInternal(newHeight);
 setExpandedHeightInternal->onHeightUpdated->mStackScroller.setStackHeight(expandedHeight),这里最终实现下拉展开效果
Action_Down ---> (PanelView已经全部展开时) 最后会交友StackScrollLayout的onScrollTouch函数处理
overScrollBy:随手指拖拽
overScrollDown:向下拖拽到达顶部时,继续向下拖拽
overScrollUp:向上拖拽到达底部时,继续向上拖拽
setOverScrollAmount ---> onOverScrolled --> applyCurrentState ---> StackScrollState的apply()方法,
apply方法是处理view的层叠效果的
updateChildren() ->StackScrollAlgorithm的getStackScrollState ---> 调用findNumberOfItemsInTopStackAndUpdateState计算即将被完全遮挡的view 的index
然后再调用updatePositionsForState方法计算每个View的currentYPosition = childViewState.yTranslation + childHeight + mPaddingBetweenElements;
4.版本兼容问题
 API21一下不支持elevation,所以API21以下的View层进行了下处理:
 StackScrollLayout.java
 @Override
 protected void dispatchDraw(Canvas canvas) { // 重绘View的涂层
 if (Define.SDK_INT < 21) {
 for (int i = getChildCount() - 1; i >= 0; i--) {
 View child = getChildAt(i);
 drawChild(canvas, child, getDrawingTime());
 }
 } else {
 super.dispatchDraw(canvas);
 }
 }
 ExpandableView.java
 @Override
 protected void dispatchDraw(Canvas canvas) { // 重绘View边缘的阴影
 if (Define.SDK_INT < 21) {
 super.dispatchDraw(canvas);
 
 canvas.save();
 Paint paint = new Paint();
 paint.setColor(Color.TRANSPARENT);
 paint.setAlpha(currentAlpha);
 paint.setStrokeWidth(0);
 
 Shader shader = new LinearGradient(0, getHeight() - shadowRadius, 0, getHeight(),
 new int[] {shadowStartColor, shadowEndColor}, null, Shader.TileMode.MIRROR);
 paint.setShader(shader);
 canvas.drawRect(0, getHeight() - shadowRadius, getWidth(), getHeight(), paint);
 
 canvas.restore();
 } else {
 super.dispatchDraw(canvas);
 }
 }