Question

我尝试从Firebase实时数据库中读取多个不同的对象。如果我只在数据库中添加一种对象，它就可以工作。如果我添加其他对象，Android应用程序不会中断 - 但似乎不再有任何内容。

例如，我有一个活动，它包含一个包含Machine类型对象的列表。此对象保存在Firebase数据库中。

现在我按照这个逻辑阅读对象：

public ArrayList<Machine> readMachines(){
    DatabaseReference mDatabaseRef = FirebaseDatabase.getInstance().getReference();
    ChildEventListener childEventListener = mDatabaseRef.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            machines.clear();
            if (dataSnapshot.getKey().equals("Machine")) {
                for (DataSnapshot snap : dataSnapshot.getChildren()) {
                    String key = snap.getKey();
                    Machine m = snap.getValue(Machine.class);
                    machines.add(m);
                }
            }
        }

        //OTHER OVERRIDE METHODS
    });
    return machines;
}

此刻此工作正常。如果我添加另一个维护对象的对象，则整个系统会中断。

我不明白这个问题，因为我检查dataSnapshot键是否符合＆＃34; Machine＆＃34; -key。

以下是接收维护对象的逻辑：

public ArrayList<RepairHistory> readMaintenance(final String machineID){
    DatabaseReference mDatabaseRef = FirebaseDatabase.getInstance().getReference();
    ChildEventListener childEventListener = mDatabaseRef.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            histories.clear();
            if(dataSnapshot.getKey().equals("Maintenance")){
                for(DataSnapshot snap: dataSnapshot.getChildren()){
                    String key = snap.getKey();
                    RepairHistory history = snap.getValue(RepairHistory.class);
                    if(history.getS_machineID().equals(machineID)){
                        histories.add(history);
                    }

                }
            }
        }

        //OTHER OVERRIDE METHODS
    });
    return histories;
}

我使用以下代码将数据保存到数据库：

public void saveMachine(Machine machine){
    DatabaseReference refDatabase = FirebaseDatabase.getInstance().getReference();
    String keyID  = refDatabase.child("Machine").push().getKey();
    machine.setI_ID(keyID);
    refDatabase.child("Machine").child(keyID).setValue(machine);
}

所以我的问题是，为什么在向数据库添加维护时打破读取逻辑？如果我添加维护，我的数据库看起来像这样： Maintanance是机器的钥匙，我知道哪种机器的维护。

    {
  "Machine" : {
    "-KdVxzbMt9nZJUuLQ-Wh" : {
      "i_ID" : "-KdVxzbMt9nZJUuLQ-Wh",
      "i_uID" : "UxCvQy2ifmYh7gkT2gxVGYjwwGg1",
      "s_MachineLocation" : "Maschinen Standort",
      "s_Machinentyp" : "Maschinen Typ",
      "s_Name" : "Arturs Machine"
    }
  },
  "Maintenance" : {
    "-Kdu_CCqdKBH5P_P4Fwd" : {
      "d_repairDate" : {
        "date" : 26,
        "day" : 0,
        "hours" : 11,
        "minutes" : 29,
        "month" : 1,
        "seconds" : 53,
        "time" : 1488104993199,
        "timezoneOffset" : -60,
        "year" : 117
      },
      "s_Description" : "Example\n",
      "s_ID" : "-Kdu_CCqdKBH5P_P4Fwd",
      "s_author" : "UxCvQy2ifmYh7gkT2gxVGYjwwGg1",
      "s_machineID" : "-KdVxzbMt9nZJUuLQ-Wh"
    }
  }
}

这是RepairHisto的类：

package logical;

导入android.graphics.Bitmap;

import java.io.Serializable; import java.util.Date;

公共类RepairHistory实现Serializable {

private Date d_repairDate = new Date();
private String s_ID;
private String s_Description;
private String s_machineID;
private RepairImage r_image;
private String s_author;
private Bitmap image;



public RepairHistory() {
}

public RepairHistory(Date d_repairDate, String s_ID, String s_Description, String s_machineID, RepairImage r_image, String s_author, Bitmap image) {
    this.d_repairDate = d_repairDate;
    this.s_ID = s_ID;
    this.s_Description = s_Description;
    this.s_machineID = s_machineID;
    this.r_image = r_image;
    this.s_author = s_author;
    this.image = image;
}

public Bitmap getImage() {
    return image;
}

public void setImage(Bitmap image) {
    this.image = image;
}

public String getS_ID() {
    return s_ID;
}

public void setS_ID(String s_ID) {
    this.s_ID = s_ID;
}

public String getS_machineID() {
    return s_machineID;
}

public void setS_machineID(String s_machineID) {
    this.s_machineID = s_machineID;
}

public Date getD_repairDate() {
    return d_repairDate;
}

public void setD_repairDate(Date d_repairDate) {
    this.d_repairDate = d_repairDate;
}

public String getS_Description() {
    return s_Description;
}

public void setS_Description(String s_Description) {
    this.s_Description = s_Description;
}

public RepairImage getR_image() {
    return r_image;
}

public void setR_image(RepairImage r_image) {
    this.r_image = r_image;
}

public String getS_author() {
    return s_author;
}

public void setS_author(String s_author) {
    this.s_author = s_author;
}

}

Firebase读取多个对象

0 个答案: