java - 如何在 Android 中遍历 Firebase 结构？

Question

我需要遍历 Firebase 架构来获取每个锻炼的数据并将其显示在 RecyclerView 中。现在我无法使用监听器遍历 Firebase 中的架构并通过名为 Program 的 POJO 类获取它。

来自 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" ]
        }
      }
    }
  }
  }

监听器代码

    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, 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]}, title=Indian Workouts, category=Strength, length=1, goal=This workout can be done by a BABUJI}, -KDnhRwHjssOejrqyenP={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]}, title=Hello Workouts, category=Strength, length=1, goal=This workout can be done while on the phone!}}

03-28 08:52:53.967 23584-23584/com.android.sam I/System.out: {-KDnfjROKeFAL9wccsxY={weeks={week1=[High Knees, Squats, Lunges, Diamond Push-ups, Lying Triceps Lifts]}, title=Afternoon HiiT, category=Mobility, length=1, goal=afternoon body weight workout}, -KDps90Dn6XtJc6Co00b={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]}, title=title, category=Strength, length=1, goal=goal}}

Program.java

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，你就快到了。但是您无法迭代树中的一层。 ref 似乎指向 JSON 中的 subscriptions 节点。在其下您有用户，然后您有推送 ID。所以你需要做一个双循环:

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) {

  }
});