如果多次单击某个选项，是否可以只获取 setOnItemClickListener 的单个值而不是获取多个值？

Question

我有一个清单，我想将清单中所有选中的项目发送到 Firebase 数据库。我已将它发送到数据库，但有一个问题。如果该项目被选中、取消选中并再次选中，该值将被发送到数据库两次。

    listView.setAdapter(adapter);
    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> adapterView, View view, int i, 
    long l) 
    {
       String selectedItem = ((TextView) view).getText().toString();
       selectedItems.add(selectedItem);

       if (unselectedItems.contains(selectedItem)) {
       unselectedItems.remove(selectedItem);
    }
    }
    });

    public void showSelectedItems(View view) {

    FirebaseUser user = mAuth.getCurrentUser();
    String presentStudents = "";

    for (int i = 0; i < selectedItems.size(); i++) {
        dbPresentRef.child(selectedItems.get(i)).push().setValue("Present");
        presentStudents += "-" + selectedItems.get(i) + "\n";
    }
    }

Answer 1

只需在将 [=b12=] 添加到您的 selectedItems 列表之前添加一个 if 条件。

listView.setAdapter(adapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, 
long l) 
{
   String selectedItem = ((TextView) view).getText().toString();
   if(!selectedItems.contains(selectedItem)){
    selectedItems.add(selectedItem); 
   }


   if (unselectedItems.contains(selectedItem)) {
   unselectedItems.remove(selectedItem);
}
}
});

public void showSelectedItems(View view) {

FirebaseUser user = mAuth.getCurrentUser();
String presentStudents = "";

for (int i = 0; i < selectedItems.size(); i++) {
    dbPresentRef.child(selectedItems.get(i)).push().setValue("Present");
    presentStudents += "-" + selectedItems.get(i) + "\n";
}
}

如果多次单击某个选项，是否可以只获取 setOnItemClickListener 的单个值而不是获取多个值？

Is there a way for only getting a single value for a setOnItemClickListener instead of getting multiple values if an option is clicked multiple times?

android

listview

onitemclick

firebase-realtime-database