Android ChildEventListener必须实现onChildChanged
这快把我逼疯了。我使用的是“onchildaded”,如果我将其切换为“onChildChanged”,那么它会要求我切换回“onchildaded”。我不知道它为什么这样做 这是我的密码:Android ChildEventListener必须实现onChildChanged,android,firebase-realtime-database,Android,Firebase Realtime Database,这快把我逼疯了。我使用的是“onchildaded”,如果我将其切换为“onChildChanged”,那么它会要求我切换回“onchildaded”。我不知道它为什么这样做 这是我的密码: Query queryRecycler = mDatabase.limitToLast(5); queryRecycler.addChildEventListener(new ChildEventListener() { public void onChildAdd
Query queryRecycler = mDatabase.limitToLast(5);
queryRecycler.addChildEventListener(new ChildEventListener() {
public void onChildAdded(DataSnapshot dataSnapshot, String previousKey) {
messageList.add(dataSnapshot.getValue(Message.class));
mMessageAdapter.notifyDataSetChanged();
}
});
完全错误是:
类“从ChildEventListener派生的匿名类”必须为
声明抽象或实现抽象方法
“ChildEventListener”中的“onChildChanged(DataSnapshot,String)”
您可能希望将
@Override
注释添加到实现的方法.onChildChanged()
,否则它将不会被识别为抽象方法的实现。草案内容如下:
指示方法声明旨在重写超类型中的方法声明
您可能希望将@Override
注释添加到实现的方法.onChildChanged()
,否则它将不会被识别为抽象方法的实现。草案内容如下:
指示方法声明旨在重写超类型中的方法声明
如果要实现,应该重写onChildAdded、onChildChanged、onChildRemoved和onChildMoved。即使你不想要它。(源代码示例)
如果要实现,应该重写onChildAdded、onChildChanged、onChildRemoved和onChildMoved。即使你不想要它。(源代码示例)
ChildEventListener childEventListener = new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String previousChildName) {
Log.d(TAG, "onChildAdded:" + dataSnapshot.getKey());
// A new comment has been added, add it to the displayed list
Comment comment = dataSnapshot.getValue(Comment.class);
// ...
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String previousChildName) {
Log.d(TAG, "onChildChanged:" + dataSnapshot.getKey());
// A comment has changed, use the key to determine if we are displaying this
// comment and if so displayed the changed comment.
Comment newComment = dataSnapshot.getValue(Comment.class);
String commentKey = dataSnapshot.getKey();
// ...
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
Log.d(TAG, "onChildRemoved:" + dataSnapshot.getKey());
// A comment has changed, use the key to determine if we are displaying this
// comment and if so remove it.
String commentKey = dataSnapshot.getKey();
// ...
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String previousChildName) {
Log.d(TAG, "onChildMoved:" + dataSnapshot.getKey());
// A comment has changed position, use the key to determine if we are
// displaying this comment and if so move it.
Comment movedComment = dataSnapshot.getValue(Comment.class);
String commentKey = dataSnapshot.getKey();
// ...
}
@Override
public void onCancelled(DatabaseError databaseError) {
Log.w(TAG, "postComments:onCancelled", databaseError.toException());
Toast.makeText(mContext, "Failed to load comments.",
Toast.LENGTH_SHORT).show();
}
};
ref.addChildEventListener(childEventListener);