如何遍历Android中的Firebase结构？

Question

我需要遍历Firebase架构以获取每个的数据workouts并在RecyclerView中显示它。现在，我无法使用侦听器遍历Firebase中的Schema，也无法通过名为的POJO类来获取它Program。

Firebase的JSON

{
  "subscriptions" : {
    "han@gmail,com" : {
      "-KDnhRwHjssOejrqyenP" : {
        "category" : "Strength",
        "goal" : "This workout can be done while on the phone!",
        "length" : 1,
        "title" : "Hello Workouts",
        "weeks" : {
          "week1" : [ "High Knees", "Jumping Jacks", "Wall sit", "Pushups", "Sit-ups", "Step ups", "Squats", "Tricep dips on chair", "Plank", "High Knees running in place", "Lunges", "Pushup and rotation", "Side plank (alternate per round)", "Alternating Push-Up Plank", "Chest Expander", "Diamond Push-ups", "Dive Bomber Push-ups", "Butt Kickers", "Lying Triceps Lifts", "One Arm Side Push-up", "Overhead Arm Clap", "Overhead Press", "Power Circles", "Push-up and Rotation", "T Push-ups", "Reverse Plank", "Spiderman Push-up", "T Raise", "Tricep Dips", "Wall Push-ups", "Wide Arm Push-ups", "Burpees" ]
        }
      },
      "-KDni3TN4NMyGXePyp92" : {
        "category" : "Strength",
        "goal" : "This workout can be done by a BABUJI",
        "length" : 1,
        "title" : "Indian Workouts",
        "weeks" : {
          "week1" : [ "Diamond Pushups", "Jackknives", "Plyo Lunges", "Plyo Squats", "Single leg plank (alternate per round)", "Plyo Lunges", "Pushup and rotation", "Weighted side plank (alternate per round)", "Alternating Push-Up Plank", "Chest Expander", "Diamond Push-ups", "Dive Bomber Push-ups", "One Arm Side Push-up", "Overhead Press", "Push-up and Rotation", "T Push-ups", "Spiderman Push-up", "Wide Arm Push-ups", "Burpee Pushups" ]
        }
      }
    },
    "obama@gmsil,com" : {
      "-KDnfjROKeFAL9wccsxY" : {
        "category" : "Mobility",
        "goal" : "afternoon body weight workout",
        "length" : 1,
        "title" : "Afternoon HiiT",
        "weeks" : {
          "week1" : [ "High Knees", "Squats", "Lunges", "Diamond Push-ups", "Lying Triceps Lifts" ]
        }
      },
      "-KDps90Dn6XtJc6Co00b" : {
        "category" : "Strength",
        "goal" : "goal",
        "length" : 1,
        "title" : "title",
        "weeks" : {
          "week1" : [ "Diamond Pushups", "Jackknives", "Plyo Lunges", "Plyo Squats", "Single leg plank (alternate per round)", "Plyo Lunges", "Pushup and rotation", "Weighted side plank (alternate per round)", "Alternating Push-Up Plank", "Chest Expander", "Diamond Push-ups", "Dive Bomber Push-ups", "One Arm Side Push-up", "Overhead Press", "Push-up and Rotation", "T Push-ups", "Spiderman Push-up", "Wide Arm Push-ups", "Burpee Pushups" ]
        }
      }
    }
  }
  }

侦听器代码

    public void FB(){
ref.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot snapshot) {
                    for (DataSnapshot postSnapshot: snapshot.getChildren()) {
                        System.out.println(postSnapshot.getValue());
    //Program post = proSnapshot.getValue(Program.class);
                    }
                }
                @Override
                public void onCancelled(FirebaseError firebaseError) {
                    System.out.println("The read failed: " + firebaseError.getMessage());
                }
            });
        }

LOGCAT

03-28 08：52：53.966 23584-23584 / com.android.sam I /
System.out：{-KDni3TN4NMyGXePyp92 = {weeks = {week1 = [Diamond
Pushups，Jackknives，Plyo Lunges，Plyo
Squats，单腿板（备用）每轮），Plyo刺针，俯卧撑和旋转，配重侧板（每轮备用），交替俯卧撑板，扩胸器，钻石俯卧撑，潜水轰炸俯卧撑，单臂俯卧撑，高架俯卧撑，俯卧撑和旋转，T俯卧撑，蜘蛛侠俯卧撑，宽臂俯卧撑，Burpee俯卧撑]}，标题=印度锻炼，类别=力量，长度=
1，目标=此锻炼可以由BABUJI完成}，-KDnhRwHjssOejrqyenP = {weeks = {week1 =
[高膝盖，跳起的杰克，坐在墙壁上，俯卧撑，仰卧起坐，加高俯卧撑，蹲坐，Tricep俯卧在椅子上，木板，高位膝盖就位，滑刺，俯卧撑和旋转，侧板（每轮交替），交替式俯卧撑板，扩胸器，钻石俯卧撑，潜水轰炸机俯卧撑，对接踢腿，卧式三头肌举高，单臂侧俯卧撑，高架手臂拍打，高架俯卧撑，动力圈，俯卧撑和旋转，T俯卧撑，反向木板，蜘蛛侠俯卧撑，T上升，三头肌俯卧撑，墙壁俯卧撑，宽臂俯卧撑，Burbures]}，标题=你好锻炼，类别=力量，长度=
1，目标=此锻炼可以在电话上进行！ }}

03-28 08：52：53.967 23584-23584 / com.android.sam I /
System.out：{-KDnfjROKeFAL9wccsxY = {weeks = {week1 =
[高膝盖，下蹲，肺，钻石俯卧撑，卧式肱三头肌训练器]] }，标题=下午HitT，类别=移动性，长度=
1，目标=下午体重锻炼}，-KDps90Dn6XtJc6Co00b = {weeks = {week1 = [Diamond
Pushups，Jackknives，Plyo Lunges，Plyo
Squats，单腿木板（每人备用）圆形），Plyo刺，俯卧撑和旋转，配重侧板（每轮交替），交替俯卧撑板，扩胸器，钻石俯卧撑，潜水轰炸俯卧撑，单臂侧俯卧撑，高架俯卧撑，俯卧撑俯卧撑，T俯卧撑，蜘蛛侠俯卧撑，宽臂俯卧撑，Burpee俯卧撑]}，标题=标题，类别=强度，长度=
1，目标=目标}}

程式库

public class Program {
    private String title;

    private String goal;

    private String category;

    private int length;

    HashMap<String, ArrayList<String>> weeks;

    /**
     * Required public constructor
     */
    public Program() {
    }

    public Program(String title, String goal,  String category, int length, HashMap<String, ArrayList<String>> weeks) {
        this.title = title;
        this.goal = goal;
        this.category = category;
        this.length = length;
        this.weeks = weeks;
    }

    public String getTitle() {
        return title;
    }

    public String getGoal() {
        return goal;
    }

    public String getCategory() {
        return category;
    }
    public int getLength() {
        return length;
    }
    public HashMap<String, ArrayList<String>> getweeks() {
        return weeks;
    }    
}

Answer 1

正如@ReazMurshed所说的，您快到了。但是您无法在树中迭代一个级别。似乎ref指向subscriptionsJSON中的节点。在此之下，您有用户，然后有推送ID。因此，您需要执行一个双循环：

ref.addListenerForSingleValueEvent(new ValueEventListener) {
  public void onDataChange(DataSnapshot snapshot) {
    if (dataSnapshot.exists()) {
      for (DataSnapshot userSnapshot : snapshot.getChildren()) {
        for (DataSnapshot programSnapshot : userSnapshot.getChildren()) {
          Program program = programSnapshot.getValue(Program.class);
      }
    }
  }

  public void onCancelled(FirebaseError firebaseError) {

  }
});