我有一个水平布局的回收视图,一次只有一个视图可见:
mRecyclerView = findViewById(R.id.rvmain);
mRecyclerView.setOnFlingListener(null);
final SnapHelper snapHelper = new LinearSnapHelper();
snapHelper.attachToRecyclerView(mRecyclerView);
mLayoutManager = new LinearLayoutManager(this,LinearLayoutManager.HORIZONTAL,false);
mRecyclerView.setLayoutManager(mLayoutManager);
mAdapter = new MainActivityRVAdapter(postsModels,MainActivity.this);
mRecyclerView.setAdapter(mAdapter);
使用onScrolllistener,每次滚动时我想知道起始位置和结束位置。怎么知道
我知道这将是了解新职位的一些事情:
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
// get newstate position
if(newState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {
View centerView = snapHelper.findSnapView(mLayoutManager);
if(centerView != null){
int pos = mLayoutManager.getPosition(centerView);
Log.e("Snapped Item Position:",""+pos);
}
}
}
如何在滚动开始之前知道位置
然后我想比较两者并做一些事情,我应该在哪里使用该代码。
我尝试按照提到的解决方案:
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if(count == 0) {
View centerView = snapHelper.findSnapView(mLayoutManager);
if(centerView != null){
initial_position = mLayoutManager.getPosition(centerView);
//initial_position2 = ((LinearLayoutManager)mRecyclerView.getLayoutManager()).findFirstVisibleItemPosition();
Log.e("Initial Item Position:",""+initial_position);
//Log.e("Initial Item Position2:",""+initial_position2);
}
}
count ++;
// get newstate position
if(newState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {
View centerView = snapHelper.findSnapView(mLayoutManager);
if(centerView != null){
int pos = mLayoutManager.getPosition(centerView);
count = 0; // in idle state clear the count again
Log.e("Snapped Item Position:",""+pos);
}
}
}
我得到的结果是:
E/Initial Item Position:: 0
E/Snapped Item Position:: 1
E/Initial Item Position:: 1
E/Snapped Item Position:: 1
E/Initial Item Position:: 1
E/Snapped Item Position:: 1
E/Initial Item Position:: 1
E/Snapped Item Position:: 1
初始位置的最终值与滚动开始时的值不同
并且它返回多次位置。我不想检查所有多个位置的最终位置和初始位置之间的差异。我只想最后检查一下。
我的问题的解决方案
正如我所见,即使我滚动一个位置,onScrollListener 也会运行 4 次。我发现无法控制它运行的次数,但我只想在它第一次运行时做一些事情。我希望运行一段代码 if pos != initial_position。我第一次看到的是真的,后来就变成假的了。
我的问题是,每当我到达与之前的视图不同的任何视图时,我想重置字体。
最终代码:
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if(count == 0) {
View centerView = snapHelper.findSnapView(mLayoutManager);
if(centerView != null){
initial_position = mLayoutManager.getPosition(centerView);
//initial_position2 = ((LinearLayoutManager)mRecyclerView.getLayoutManager()).findFirstVisibleItemPosition();
Log.e("Initial Item Position:",""+initial_position);
//Log.e("Initial Item Position2:",""+initial_position2);
}
count ++;
}
// get newstate position
if(newState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {
View centerView = snapHelper.findSnapView(mLayoutManager);
if(centerView != null){
int pos = mLayoutManager.getPosition(centerView);
if(pos != initial_position ){
TextView textView2 = (TextView) centerView.findViewById(R.id.postsmodel_description);
if(textsize == 0){
textsize = textView2.getTextSize();
}
textView2.setTextSize(pixelsToSp(textsize));
}
count = 0; // in idle state clear the count again
Log.e("Snapped Item Position:",""+pos);
}
}
}