java.lang.ClassCastException：java.util.HashMap无法强制转换为Ride

Question

DatabaseReference ridesRef = database.getReference("rides");
ridesRef.equalTo(from).orderByChild("from").addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Log.i(TAG, "dataSnapshot.getChildrenCount(): " + dataSnapshot.getChildrenCount());
        if (dataSnapshot.getChildrenCount() > 0) {
            ArrayList<Ride> value = (ArrayList<Ride>) dataSnapshot.getValue();

            Log.i(TAG, value.toString());

            for (Ride r : value) { // error occurs here
                Log.i(TAG, "r.getTime:" + r.getTime());
                Log.i(TAG, "getFrom:" + r.getFrom());
            }
        }
    }
});

日志输出为：

  

09-02 18：08：25.070 23651-23651 I / RidesFragment：   dataSnapshot.getChildrenCount（）：1

     

09-02 18：08：25.070 23651-23651 I / RidesFragment：[{to = Hackerscher   Markt，userID = 0，time = 1472831718565，regular = false，price = 0，   chosenUserID = 0，active = true，places = 1，from = Hauptbahnhof Berlin，   meetingPointDescription = blaues ei}]

public class Ride {
    private String from;
    private String to;
    private long time;
    private int places;
    private String meetingPointDescription;
    private boolean regularly;
    private boolean active;
    private float price;
    private int userID;
    private int chosenUserID;

    public Ride() {
        // Default constructor required for calls to DataSnapshot.getValue(Ride.class)
    }

    public Ride(String from, String to, long time, int places, String meetingPointDescription, boolean regularly,
                boolean active, float price, int userID, int chosenUserID) {
        this.from = from;
        this.to = to;
        this.time = time;
        this.places = places;
        this.meetingPointDescription = meetingPointDescription;
        this.regularly = regularly;
        this.active = active;
        this.price = price;
        this.userID = userID;
        this.chosenUserID = chosenUserID;
    }

    // automatically generated getters and setters...
}

Answer 1

我第三次回答自己的问题：/

ArrayList<Ride> value = (ArrayList<Ride>) dataSnapshot.getValue();

必须替换为

GenericTypeIndicator<ArrayList<Ride>> t = new GenericTypeIndicator<ArrayList<Ride>>() {};
ArrayList<Ride> value = dataSnapshot.getValue(t);

一切都按预期工作。