使用Firebase for Android更新特定的按键 [英] Update specific keys using Firebase for Android

问题描述

我有一个Firebase数据创建如下

 任务
 -K1NRz9l5PU_0R8ltgXz 
描述：test1 
状态：PENDING
 -K1NRz9l5PU_0CFDtgXz 
描述：test2
状态：PENDING
  

我需要将第二个对象的状态从PENDING更新为COMPLETED。我正在使用 updateChildren 方法，但是它向子任务添加了一个新节点。

如何更新第二个节点的状态，而不创建一个新的节点？

这是我的代码截至目前，

//在按钮上点击侦听器

  {
 
 Firebase m_objFireBaseRef =新的Firebase（AppConstants.FIREBASE_URL） ; 
最终Firebase objRef = m_objFireBaseRef.child（tasks）; 
地图< String，Object> taskMap = new HashMap< String，Object>（）; 
 taskMap.put（Status，COMPLETED）; 
 objRef.updateChildren（taskMap）; //我应该使用setValue（）...？ 
 
}）; 
  

解决方案

您没有指定任务的任务ID你要更新。

 字符串taskId =-K1NRz9l5PU_0CFDtgXz; 
 
 Firebase m_objFireBaseRef =新的Firebase（AppConstants.FIREBASE_URL）; 
 Firebase objRef = m_objFireBaseRef.child（tasks）; 
 Firebase taskRef = objRef.child（taskId）; 
地图< String，Object> taskMap = new HashMap< String，Object>（）; 
 taskMap.put（Status，COMPLETED）; 
 taskRef.updateChildren（taskMap）; 
  

或者，您可以调用 setValue（）关于你想要更新的财产

 字符串taskId =-K1NRz9l5PU_0CFDtgXz; 
 
 Firebase m_objFireBaseRef =新的Firebase（AppConstants.FIREBASE_URL）; 
 Firebase objRef = m_objFireBaseRef.child（tasks）; 
 Firebase taskRef = objRef.child（taskId）; 
 Firebase statusRef = taskRef.child（状态）; 
 statusRef.setValue（COMPLETED）; 
  

或者：

  Firebase m_objFireBaseRef =新的Firebase（AppConstants.FIREBASE_URL）; 
 Firebase objRef = m_objFireBaseRef.child（tasks）; 
 objRef.child（taskId）.child（Status）。setValue（COMPLETED）; 
  

更新

需要根据状态跟踪ID的意思。但是如果你想同步处于 Pending 状态的所有任务，你可以这样做：

  Firebase m_objFireBaseRef =新的Firebase（AppConstants.FIREBASE_URL）; 
 Firebase objRef = m_objFireBaseRef.child（tasks）; 
 Query pendingTasks = objRef.orderByChild（Status）。equalTo（PENDING）; 
（DataSnapshot snapshot：tasksSnapshot.getChildren（））
 public void onDataChange（DataSnapshot tasksSnapshot）{
 $ pendingBasks.addListenerForSingleValueEvent（new ValueEventListener（）{
 @Override 
 $ b $ （完成）; 
} 
} 
 @覆盖
 public void onCancelled（FirebaseError firebaseError）{
 System.out.println（The read failed：+ firebaseError.getMessage（））; 
} 
}）; 
  

I have a Firebase data created as follows

tasks
-K1NRz9l5PU_0R8ltgXz
   Description: "test1"
   Status: "PENDING"
 -K1NRz9l5PU_0CFDtgXz
   Description: "test2"
   Status: "PENDING"

I need to update the 2nd object's status from PENDING to COMPLETED. I am using the updateChildren method but it is added a new node to the tasks child.

How do I update the status of the 2nd node without creating a new node?

Here is my code as of now,

//on a button click listener

  {

    Firebase m_objFireBaseRef = new Firebase(AppConstants.FIREBASE_URL);        
    final Firebase objRef = m_objFireBaseRef.child("tasks");    
    Map<String,Object> taskMap = new HashMap<String,Object>();
    taskMap.put("Status", "COMPLETED");
    objRef.updateChildren(taskMap); //should I use setValue()...?

 });

解决方案

You're not specifying the task id of the task that you want to update.

String taskId = "-K1NRz9l5PU_0CFDtgXz";

Firebase m_objFireBaseRef = new Firebase(AppConstants.FIREBASE_URL);        
Firebase objRef = m_objFireBaseRef.child("tasks");
Firebase taskRef = objRef.child(taskId);
Map<String,Object> taskMap = new HashMap<String,Object>();
taskMap.put("Status", "COMPLETED");
taskRef.updateChildren(taskMap);

Alternatively, you can just call setValue() on the property you want to update

String taskId = "-K1NRz9l5PU_0CFDtgXz";

Firebase m_objFireBaseRef = new Firebase(AppConstants.FIREBASE_URL);        
Firebase objRef = m_objFireBaseRef.child("tasks");
Firebase taskRef = objRef.child(taskId);
Firebase statusRef = taskRef.child("Status");
statusRef.setValue("COMPLETED");

Or:

Firebase m_objFireBaseRef = new Firebase(AppConstants.FIREBASE_URL);        
Firebase objRef = m_objFireBaseRef.child("tasks");
objRef.child(taskId).child("Status").setValue("COMPLETED");

Update

Not sure what "I need to track the ID based on the status" means. But if you want to synchronize all tasks that are in status Pending, you'd do:

Firebase m_objFireBaseRef = new Firebase(AppConstants.FIREBASE_URL);        
Firebase objRef = m_objFireBaseRef.child("tasks");
Query pendingTasks = objRef.orderByChild("Status").equalTo("PENDING");
pendingTasks.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot tasksSnapshot) {
        for (DataSnapshot snapshot: tasksSnapshot.getChildren()) {
            snapshot.getRef().child("Status").setValue("COMPLETED");
        }
    }
    @Override
    public void onCancelled(FirebaseError firebaseError) {
        System.out.println("The read failed: " + firebaseError.getMessage());
    }
});

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