[英]How to detect when user have scrolled to the top most item in a RecyclerView
我嘗試編寫以下代碼
@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。 我也嘗試使用android的SwipeRefreshLayout來做這個,因為它做了我想要的,它能夠檢測用戶何時滾動到最頂層的項目。 我決定不使用它,因為我似乎無法阻止加載指示器彈出(我不想看到加載指示器出來)。
所以,基本上我想做的是:
知道怎么做到這一點?
謝謝。
用以下代碼替換您的代碼:
@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();
}
}
它對我有用,如果你有任何錯誤然后評論。
我自己解決了我的問題。 我使用下面的代碼
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;
}
}
}
你能做到這很容易使用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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