如何知道以前的位置和新的位置？

Question

我有一个水平布局的 recyclerview，一次只能看到一个视图：

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，每次滚动我都想知道开始位置和结束位置。怎么知道

我知道知道新职位会很有趣：

    @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);
            }
        }
    }

如何知道滚动开始前的位置

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。

我按照提到的解决方案试过了：

@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不相同

并且它 returns 多次定位。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。我只是想最后看看。

我的问题的解决方案

正如我所见，即使我将 onScrollListener 运行s 滚动一个位置 4 次。我发现没有办法控制它运行的次数，但我只想在它第一次运行时才做某事。如果 pos != initial_position，我正在寻找运行代码。我第一次看到是真的，后来是假的。

我的问题是，每当我登陆任何与之前的视图不同的视图时，我都想重置字体。

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);
            }
        }


    }

Answer 1

int count = 0; //field variable
int initial_position;  

@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
    super.onScrollStateChanged(recyclerView, newState);

    if(count == 0) {
       initial_position = mLayoutManager.findFirstVisibleItemPosition();
   }

    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);
        }
    }
}

initial_position = 起始位置

pos = 结束位置

编码愉快:)

如何知道以前的位置和新的位置？

how to know the previous and new positions?

android

android-recyclerview

onscrolllistener