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public class AbsorbOnScrollListener extends RecyclerView.OnScrollListener {
private final FrameLayout vpShow;
private int[] absorbPos;
private View[] absorbViews;
private FrameLayout[] itemViews;
private View placeholderView;
private View contentView;
public AbsorbOnScrollListener(FrameLayout vpShow, int... absorbPos) {
if (absorbPos == null || absorbPos.length == 0)
throw new IllegalStateException("absorbPos is not null or empty");
this.absorbPos = absorbPos;
this.vpShow = vpShow;
absorbViews = new View[absorbPos.length];
itemViews = new FrameLayout[absorbPos.length];
}
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int pos = 0;
try {
//GridLayoutManager 继承LinearLayoutManager 所以也支持GridLayoutManager
pos = ((LinearLayoutManager) (recyclerView.getLayoutManager())).findFirstVisibleItemPosition();
} catch (Exception e) {
e.printStackTrace();
throw new IllegalStateException("仅仅支持继承LinearLayoutManager的布局!");
}
//缓存list中断头view
for (int i = 0; i < absorbPos.length; i++) {
if (pos == absorbPos[i] && itemViews[i] == null) {
try {
itemViews[i] = (FrameLayout) recyclerView.findViewHolderForLayoutPosition(pos).itemView;
} catch (Exception e) {
e.printStackTrace();
throw new IllegalStateException("断头的itemView必须是FrameLayout!");
}
absorbViews[i] = itemViews[i].getChildAt(0);
}
}
int showPos = findShowPos(pos);
if (showPos == -1) {//啥也不显示
if (placeholderView != null && placeholderView.getParent() != null) {
restoreItemView(0);
contentView = null;
}
} else {
if (placeholderView == null)
placeholderView = new View(recyclerView.getContext());
//找到对应的位置
int arrayPos = 0;
for (int i = 0; i < absorbPos.length; i++) {
if (showPos == absorbPos[i]) {
arrayPos = i;
break;
}
}
if (!(contentView != null && contentView == absorbViews[arrayPos])) {
//如果断头view不改变的话仅仅更改位置 主要是节省了操作
//找到之前那个itemView 还原了
for (int i = 0; i < absorbViews.length; i++) {
if (absorbViews[i] != null && absorbViews[i] == contentView) {
restoreItemView(i);
break;
}
}
//ItemView的狸猫换太子 显示在VP中
itemViews[arrayPos].removeView(absorbViews[arrayPos]);
placeholderView.setLayoutParams(absorbViews[arrayPos].getLayoutParams());
placeholderView.getLayoutParams().height = absorbViews[arrayPos].getHeight();
itemViews[arrayPos].addView(placeholderView);
addContentView(absorbViews[arrayPos]);
}
//位移计算!
if (showPos != absorbPos[absorbPos.length - 1]) {//最后的那个不进行位移
int next = absorbPos[arrayPos + 1];
if (recyclerView.findViewHolderForLayoutPosition(next) == null)
absorbViews[arrayPos].setTranslationY(0);
else {
View targetView = recyclerView.findViewHolderForLayoutPosition(next).itemView;
if (targetView.getTop() <= absorbViews[arrayPos].getHeight())
absorbViews[arrayPos].setTranslationY(targetView.getTop() - absorbViews[arrayPos].getHeight());
}
}
}
}
private void restoreItemView(int i) {
itemViews[i].removeView(placeholderView);
vpShow.removeView(absorbViews[i]);
absorbViews[i].setTranslationY(0);
itemViews[i].addView(absorbViews[i]);
}
private void addContentView(View absorbView) {
vpShow.addView(absorbView);
contentView = absorbView;
}
// 3,6,9为例 [1,3)show 无 ,[3,6)show 3,[6,9)show 6,>=9 show 9,
private int findShowPos(int pos) {
for (int i = 0; i < absorbPos.length; i++) {
if (pos < absorbPos[i]) {
if (i == 0)//[1,3)show 无
return -1;
//[3,6)show 3,[6,9)show 6
System.out.println("Absorb_ i:" + i + "\t itemViews[i-1].getTop()" + itemViews[i - 1].getTop());
return findWithOutDecTop(i, "Absorb_显示:" + (i - 1), "Absorb_显示:无", "Absorb_显示:" + (i - 2));
}
}
// >=9 show 9
return findWithOutDecTop(absorbPos.length, "Absorb_显示 Last:" + (absorbPos.length - 1), "Absorb_显示 Last:无", "Absorb_显示 Last:" + (absorbPos.length - 2));
}
private int findWithOutDecTop(int i, String x, String x2, String x3) {
// getTop如果<=0的时候 才显示这个位置的断头
if (itemViews[i - 1].getTop() <= 0) {//注意:getTop不包括 dector
QuickConfig.i(x);
return absorbPos[i - 1];
} else {//不然还是显示上一个位置的断头
if (i - 2 < 0) {//上一个位置是无的情况
QuickConfig.i(x2);
return -1;
}
QuickConfig.i(x3);
return absorbPos[i - 2];
}
}
}
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