Android ExpandableListView：如何检测滚动何时到达列表的底部/末尾

Question

我正在我的应用程序上实现ExpandableListView，并尝试检测滚动何时到达ExpandableListView 的底部。我试过使用onScrollListener 和onScrollChangedListener。

对于onScrollListener，它被调用的次数太多，无法接受。

但是对于onScrollChangedListener，这似乎是我想要的。问题是ExpandableListView 没有 1 个子级别而是 2 个子级别，我无法找到一种方法来识别最后一个可见元素。

是否有人已经在ExpandableListView 上实现了这种行为？

Answer 1

试试这个解决方案 Detect when RecyclerView reaches the bottom most position while scrolling - 检查 Kaustubh Bhagwat 的答案

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

        if (!recyclerView.canScrollVertically(1)) {
            Toast.makeText(YourActivity.this, "Last", Toast.LENGTH_LONG).show();

        }
    }
});

Answer 2

您可以通过获取最后一组展开时的位置来完成

expandableListView.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {
        @Override
        public boolean onGroupClick(ExpandableListView parent, View v, int groupPosition, long id) {
            if(groupPosition == expandableListView.getExpandableListAdapter().getGroupCount()){
            // your code goes here
            }
            return false;
        }
    });

Answer 3

试试下面的示例：-

activity_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">

<ExpandableListView
    android:id="@+id/elvMain"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
</ExpandableListView>

</LinearLayout>

MainActivity.java：

public class MainActivity extends AppCompatActivity {
ArrayList<String> mainGroupList;
HashMap<String, ArrayList<String>> mainChildList;
CustomAdapter mainAdapter;
ExpandableListView elvMain;
int newDataSet = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    elvMain = findViewById(R.id.elvMain);
    mainGroupList = new ArrayList<>();
    mainChildList = new HashMap<>();
    for(int i = 0; i < 20; i++){
        ArrayList<String> tmpList = new ArrayList<>();
        for(int j = 0; j< 17; j++){
            tmpList.add("Child " + j);
        }
        mainChildList.put("Group " + i, tmpList);
        mainGroupList.add("Group " + i);
    }
    mainAdapter = new CustomAdapter(this, mainGroupList, mainChildList);
    elvMain.setAdapter(mainAdapter);

    elvMain.setOnScrollListener(new AbsListView.OnScrollListener() {
        @Override
        public void onScrollStateChanged(AbsListView absListView, int i) {}
        @Override
        public void onScroll(AbsListView absListView, int i, int i1, int i2) {
            if(i2 == i + i1){
                View lastView = absListView.getChildAt(i1 - 1);
                if(lastView.getBottom() == absListView.getBottom()){
                    try{
                        String viewTag = lastView.getTag().toString();
                        if(viewTag.equals("Group")){
                            Toast.makeText(getApplicationContext(),
                                    "No more data, unless expanded the last group!!",
                                    Toast.LENGTH_SHORT).show();
                            //elvMain.expandGroup(mainAdapter.getGroupCount() - 1);
                        }
                    }catch(Exception e){
                        addNewData();
                    }
                }
            }
        }
    });
}

private void addNewData(){
    newDataSet++;
    for(int i = 0; i < 5; i++){
        ArrayList<String> tmpList = new ArrayList<>();
        for(int j = 0; j< 7; j++){
            tmpList.add("Child " + j);
        }
        mainChildList.put("Added " + newDataSet + ",Group " + i, tmpList);
        mainGroupList.add("Added " + newDataSet + ",Group " + i);
    }
    mainAdapter.notifyDataSetChanged();
}
}

CustomAdapter.java：

public class CustomAdapter extends BaseExpandableListAdapter {
ArrayList<String> groupList;
HashMap<String, ArrayList<String>> childList;
LayoutInflater inflater;

public CustomAdapter(Context context, ArrayList<String> groupList, HashMap<String, ArrayList<String>> childList) {
    this.inflater = LayoutInflater.from(context);
    this.groupList = groupList;
    this.childList = childList;
}

@Override
public int getGroupCount() {
    return groupList.size();
}

@Override
public int getChildrenCount(int i) {
    return childList.get(groupList.get(i)).size();
}

@Override
public String getGroup(int i) {
    return groupList.get(i);
}

@Override
public String getChild(int i, int i1) {
    return childList.get(groupList.get(i)).get(i1);
}

@Override
public long getGroupId(int i) {
    return i;
}

@Override
public long getChildId(int i, int i1) {
    return 0;
}

@Override
public boolean hasStableIds() {
    return false;
}

@Override
public View getGroupView(int i, boolean b, View view, ViewGroup viewGroup) {
    if(view == null) view = inflater.inflate(android.R.layout.simple_list_item_1, null);
    TextView textView = view.findViewById(android.R.id.text1);
    textView.setText(getGroup(i));
    view.setTag("Group");
    return view;
}

@Override
public View getChildView(int i, int i1, boolean b, View view, ViewGroup viewGroup) {
    if(view == null) view = inflater.inflate(android.R.layout.simple_list_item_1, null);
    TextView textView = view.findViewById(android.R.id.text1);
    textView.setText(getChild(i, i1));
    return view;
}

@Override
public boolean isChildSelectable(int i, int i1) {
    return false;
}
}

在这个示例中，我使用 setTag() 来识别视图是“组”。如果您对组视图和子视图使用不同的布局，那么您可以使用 findViewById() 来查找组视图内的视图，因此您的适配器不会发生任何变化。

另外，在try-catch中，你可以注释掉Toast()，并启用代码elvMain.expandGroup(mainAdapter.getGroupCount() - 1);，它会在列表滚动到底部时自动展开最后一个组，所以ExpandableListView 变得无穷无尽。

希望有帮助！