今天开始讲RecycleView的系列教程。分割线，分组，局部刷新，动态添加，缓存原理，抖音效果，瀑布流。嵌套，动画等等
分析：
1.滑动过半的判断PagerSnapHelper
2.滑动过半添加在哪，通过自定义layoutManager
3.得到滑动的view，和position
4.初始化和销毁的时机 recycleVIewchild销毁
监听滑动的位置：
publicvoidonScrollStateChanged(intstate) {
switch(state) {
caseRecyclerView.SCROLL_STATE_IDLE:
ViewviewIdle=mPagerSnapHelper.findSnapView(this);
intpositionIdle=getPosition(viewIdle);
if(mOnViewPagerListener!=null&&getChildCount()==1) {
mOnViewPagerListener.onPageSelected(positionIdle,positionIdle==getItemCount()-1);
}
break;
caseRecyclerView.SCROLL_STATE_DRAGGING:
ViewviewDrag=mPagerSnapHelper.findSnapView(this);
intpositionDrag=getPosition(viewDrag);
break;
caseRecyclerView.SCROLL_STATE_SETTLING:
ViewviewSettling=mPagerSnapHelper.findSnapView(this);
intpositionSettling=getPosition(viewSettling);
break;
}
}
监听recycleVIew子child销毁
privateRecyclerView.OnChildAttachStateChangeListenermChildAttachStateChangeListener=newRecyclerView.OnChildAttachStateChangeListener() {
@Override
publicvoidonChildViewAttachedToWindow(Viewview) {
if(mOnViewPagerListener!=null&&getChildCount()==1) {
mOnViewPagerListener.onInitComplete();
}
}
@Override
publicvoidonChildViewDetachedFromWindow(Viewview) {
if(mDrift>=0){
if(mOnViewPagerListener!=null)mOnViewPagerListener.onPageRelease(true,getPosition(view));
}else{
if(mOnViewPagerListener!=null)mOnViewPagerListener.onPageRelease(false,getPosition(view));
}
}
};
PagerSnapHelper找到view
ViewviewSettling=mPagerSnapHelper.findSnapView(this);
通过view得到Positon
源码：
public class DouyinLayoutManagerextends LinearLayoutManager {
private static final StringTAG ="ViewPagerLayoutManager";
private PagerSnapHelpermPagerSnapHelper;
private OnViewPagerListenermOnViewPagerListener;
private RecyclerViewmRecyclerView;
private int mDrift;//位移，用来判断移动方向
public DouyinLayoutManager(Context context, int orientation) {
super(context, orientation, false);
init();
}
public DouyinLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
init();
}
private void init() {
mPagerSnapHelper =new PagerSnapHelper();
}
@Override
public void onAttachedToWindow(RecyclerView view) {
super.onAttachedToWindow(view);
mPagerSnapHelper.attachToRecyclerView(view);
this.mRecyclerView = view;
mRecyclerView.addOnChildAttachStateChangeListener(mChildAttachStateChangeListener);
}
@Override
public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
super.onLayoutChildren(recycler, state);
//
}
/**
* 滑动状态的改变
* 缓慢拖拽-> SCROLL_STATE_DRAGGING
* 快速滚动-> SCROLL_STATE_SETTLING
* 空闲状态-> SCROLL_STATE_IDLE
* @param state
*/
@Override
public void onScrollStateChanged(int state) {
switch (state) {
case RecyclerView.SCROLL_STATE_IDLE:
View viewIdle =mPagerSnapHelper.findSnapView(this);
int positionIdle = getPosition(viewIdle);
if (mOnViewPagerListener !=null && getChildCount() ==1) {
mOnViewPagerListener.onPageSelected(positionIdle,positionIdle == getItemCount() -1);
}
break;
case RecyclerView.SCROLL_STATE_DRAGGING:
View viewDrag =mPagerSnapHelper.findSnapView(this);
int positionDrag = getPosition(viewDrag);
break;
case RecyclerView.SCROLL_STATE_SETTLING:
View viewSettling =mPagerSnapHelper.findSnapView(this);
int positionSettling = getPosition(viewSettling);
break;
}
}
/**
* 监听竖直方向的相对偏移量
* @param dy
* @param recycler
* @param state
* @return
*/
@Override
public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
this.mDrift = dy;
return super.scrollVerticallyBy(dy, recycler, state);
}
/**
* 监听水平方向的相对偏移量
* @param dx
* @param recycler
* @param state
* @return
*/
@Override
public int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state) {
this.mDrift = dx;
return super.scrollHorizontallyBy(dx, recycler, state);
}
/**
* 设置监听
* @param listener
*/
public void setOnViewPagerListener(OnViewPagerListener listener){
this.mOnViewPagerListener = listener;
}
private RecyclerView.OnChildAttachStateChangeListenermChildAttachStateChangeListener =new RecyclerView.OnChildAttachStateChangeListener() {
@Override
public void onChildViewAttachedToWindow(View view) {
if (mOnViewPagerListener !=null && getChildCount() ==1) {
mOnViewPagerListener.onInitComplete();
}
}
@Override
public void onChildViewDetachedFromWindow(View view) {
if (mDrift >=0){
if (mOnViewPagerListener !=null)mOnViewPagerListener.onPageRelease(true,getPosition(view));
}else {
if (mOnViewPagerListener !=null)mOnViewPagerListener.onPageRelease(false,getPosition(view));
}
}
};
}
public class DouyinActivityextends AppCompatActivity {
private static final StringTAG ="ViewPagerActivity";
private RecyclerViewmRecyclerView;
private MyAdaptermAdapter;
private DouyinLayoutManagermLayoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_pager_layout_manager);
initView();
initListener();
}
private void initView() {
mRecyclerView = findViewById(R.id.recycler);
mLayoutManager =new DouyinLayoutManager(DouyinActivity.this, OrientationHelper.VERTICAL);
mAdapter =new MyAdapter();
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.setAdapter(mAdapter);
}
private void initListener(){
mLayoutManager.setOnViewPagerListener(new OnViewPagerListener() {
@Override
public void onInitComplete() {
Log.e(TAG,"onInitComplete");
playVideo(0);
}
@Override
public void onPageRelease(boolean isNext,int position) {
Log.e(TAG,"释放位置:"+position +" 下一页:"+isNext);
int index =0;
if (isNext){
index =0;
}else {
index =1;
}
releaseVideo(index);
}
@Override
public void onPageSelected(int position,boolean isBottom) {
Log.e(TAG,"选中位置:"+position+" 是否是滑动到底部:"+isBottom);
playVideo(0);
}
});
}
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