java - 交易导致 Activity 召回 Firebase Android

Question

当我点击我的rate_btn 启动此交易功能时。

它工作正常，但在此过程中它再次重新运行我的类 Activity (每次使用事务时我的类 Activity 都会重新运行)因此重置所有内容，如我的 msg_ID。

例如，每次调用此类 Activity 时，我的 msg_ID 都会更改(由于使用随机)，因此当我运行事务时它有效但作为返回，它也运行了类 Activity ，因此改变了我的 < strong>msg_ID 也是。

这是一个场景:

so when click this "rate" button it does the rating on the current msg_ID but when I click on it again, it rates a different msg_ID because of my get random msg_ID. I think this is caused when I call the onComplete method.

当我点击rate_btn

现在类(class)重新开始，我再次点击 rate_btn。

它投票赞成第一个 msg_id 然后当我再次点击 rate_btn 它投票赞成第二个键(因为它重新调用了类 Activity 和 msg_id 已更改)

这是交易代码:

rate_btn.setOnClickListener(new OnClickListener(){
public void onClick(View v){
        Firebase upvoteref = new Firebase("https://myapp.firebaseio.com/"+msgID+"/upvotes"); 

        upvoteref.runTransaction(new Transaction.Handler() {
            @Override
            public Transaction.Result doTransaction(final MutableData currentData) {
                if (currentData.getValue() == null) {
                    currentData.setValue(1);
                } else {
                    currentData.setValue((Long) currentData.getValue() + 1);
                }

                return Transaction.success(currentData);
            }

            public void onComplete(FirebaseError firebaseError, boolean committed, DataSnapshot currentData) {
                if (firebaseError != null) {
                    System.out.println("Firebase counter increment failed.");
                } else {
                    System.out.println("Firebase counter increment succeeded.");
                }
            }
        });
    }

下面是获取随机 id 的代码:

    String msgID; //this variable is declare at the start of the class as a global variable.

    Firebase ref = new Firebase("https://myapp.firebaseio.com/"+msgID); 

    ref.addValueEventListener(new ValueEventListener() {

        public void onDataChange(DataSnapshot snapshot) {
            Iterable<DataSnapshot> ds = snapshot.getChildren();

            //getting maximum number of children
            long allNum = snapshot.getChildrenCount();
            int maxNum = (int)allNum;

            //getting the random integer from number of children
            int randomNum = new Random().nextInt(maxNum);

            Iterator<DataSnapshot> ids = ds.iterator();

            int count = 0;

            //has next will check if there are values in the next iteration , while count is used as a position substitute.
            while(ids.hasNext() && count < randomNum) {
                ids.next();
                count ++; // used as positioning.
            }           

            Map<String, Object> newPost = (Map<String, Object>) ids.next().getValue(); // ids will take the value in the iterator (iterate at key) 
            //getting the message from the key
            msgID = newPost.get("id").toString();
        }

有什么想法吗？

Answer 1

由于每次调用事务时消息 ID 都会更改，这是因为 addValueEventListener(它在调用事务时接受更改)。因此，为了解决这个问题，我添加了 addListenerForSingleValueEvent 而不是 addValueEventListener 并且它起作用了。

例如:

 ref.addListenerForSingleValueEvent(new ValueEventListener() {

    public void onDataChange(DataSnapshot snapshot) {
        Iterable<DataSnapshot> ds = snapshot.getChildren();

        //getting maximum number of children
        long allNum = snapshot.getChildrenCount();
        int maxNum = (int)allNum;

        //getting the random integer from number of children
        int randomNum = new Random().nextInt(maxNum);

        Iterator<DataSnapshot> ids = ds.iterator();

        int count = 0;

        //has next will check if there are values in the next iteration , while count is used as a position substitute.
        while(ids.hasNext() && count < randomNum) {
            ids.next();
            count ++; // used as positioning.
        }           

        Map<String, Object> newPost = (Map<String, Object>) ids.next().getValue(); // ids will take the value in the iterator (iterate at key) 
        //getting the message from the key
        msgID = newPost.get("id").toString();
    }`