[英]How to detect when user have scrolled to the top most item in a RecyclerView
我尝试编写以下代码
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if(dy > 0){
//scrolling up
} else {
//scrolling down
int pastVisibleItems = linearLayoutManager.findFirstVisibleItemPosition();
if (pastVisibleItems == 0) {
Toast.makeText(getContext(),"Top most item",Toast.LENGTH_SHORT).show();
}
}
}
但它不起作用。 我也尝试使用android的SwipeRefreshLayout来做这个,因为它做了我想要的,它能够检测用户何时滚动到最顶层的项目。 我决定不使用它,因为我似乎无法阻止加载指示器弹出(我不想看到加载指示器出来)。
所以,基本上我想做的是:
知道怎么做到这一点?
谢谢。
用以下代码替换您的代码:
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int pastVisibleItems = linearLayoutManager.findFirstCompletelyVisibleItemPosition();
if (pastVisibleItems == 0) {
Toast.makeText(getContext(),"Top most item",Toast.LENGTH_SHORT).show();
}
}
它对我有用,如果你有任何错误然后评论。
我自己解决了我的问题。 我使用下面的代码
private boolean isUserScrolling = false;
private boolean isListGoingUp = true;
然后在RecyclerView OnScrollListener中
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
//detect is the topmost item visible and is user scrolling? if true then only execute
if(newState == RecyclerView.SCROLL_STATE_DRAGGING){
isUserScrolling = true;
if(isListGoingUp){
//my recycler view is actually inverted so I have to write this condition instead
if(linearLayoutManager.findLastCompletelyVisibleItemPosition() + 1 == list.size()){
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
@Override
public void run() {
if(isListGoingUp) {
if (linearLayoutManager.findLastCompletelyVisibleItemPosition() + 1 == list.size()) {
Toast.makeText(getContext(),"exeute something", Toast.LENGTH_SHORT).show();
}
}
}
},50);
//waiting for 50ms because when scrolling down from top, the variable isListGoingUp is still true until the onScrolled method is executed
}
}
}
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if(isUserScrolling){
if(dy > 0){
//means user finger is moving up but the list is going down
isListGoingUp = false;
}
else{
//means user finger is moving down but the list is going up
isListGoingUp = true;
}
}
}
你能做到这很容易使用Code
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if(newState == RecyclerView.SCROLL_STATE_DRAGGING) {
isUserScrolling = true;
}
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if(isUserScrolling){
if(dy > 0){
//Scroll list Down
}
else{
if(!recyclerView.canScrollVertically(-1)){
//This Your Top View do Something
}
}
}
}
});
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