android - 在模型类中定义构造函数(使用 Cloud Firestore 获取数据)

Question

我在 Cloud Firestore 中添加了一些数据 enter image description here

其中我有字符串标题、字符串描述、字符串[] 照片

我想在 MyClass.class 中获取该数据，所以我在类(class)中提供了Parameterized Constructor 和 Getter & Setters。

但是报错说不支持转换为数组，请改用列表

这是我的逻辑部分代码:

FirebaseFirestore db = FirebaseFirestore.getInstance();

        db.collection("gallery")
                .get()
                .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                    @Override
                    public void onComplete(@NonNull Task<QuerySnapshot> task) {
                        if (task.isSuccessful()) {
                            for (QueryDocumentSnapshot document : task.getResult()) {
                                Log.d("MyTag", document.getId() + " => " + document.getData());
                                MyClass obj = document.toObject(MyClass.class);
                            }
                        } else {
                            Log.d("Main", "Error getting documents: ", task.getException());
                        }
                    }
                });

这是我的类(class):

public class MyClass {

    String title;
    String desc;
    String[] photos;

    public MyClass(){}

    public MyClass(String title, String desc, String[] photos) {
        this.title = title;
        this.desc = desc;
        this.photos = photos;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public String[] getPhotos() {
        return photos;
    }

    public void setPhotos(String[] photos) {
        this.photos = photos;
    }

我在 MyClass obj = document.toObject(MyClass.class) 收到这个错误 :

FATAL EXCEPTION: main
                  Process: com.developtrainmaintain.firebaserecycle, PID: 3836
                  java.lang.RuntimeException: Could not deserialize object. Converting to Arrays is not supported, please use Lists instead (found in field 'photos')
                      at com.google.android.gms.internal.firebase-firestore.zzko.zzb(Unknown Source)
                      at com.google.android.gms.internal.firebase-firestore.zzko.zza(Unknown Source)
                      at com.google.android.gms.internal.firebase-firestore.zzko.zza(Unknown Source)
                      at com.google.android.gms.internal.firebase-firestore.zzko.zzb(Unknown Source)
                      at com.google.android.gms.internal.firebase-firestore.zzko$zza.zza(Unknown Source)
                      at com.google.android.gms.internal.firebase-firestore.zzko.zza(Unknown Source)
                      at com.google.android.gms.internal.firebase-firestore.zzko.zza(Unknown Source)
                      at com.google.firebase.firestore.DocumentSnapshot.zza(Unknown Source)
                      at com.google.firebase.firestore.QueryDocumentSnapshot.zza(Unknown Source)
                      at com.google.firebase.firestore.DocumentSnapshot.toObject(Unknown Source)
                      at com.google.firebase.firestore.QueryDocumentSnapshot.toObject(Unknown Source)
                      at com.developtrainmaintain.firebaserecycle.MainActivity$1.onComplete(MainActivity.java:48)
                      at com.google.android.gms.tasks.zzj.run(Unknown Source)
                      at android.os.Handler.handleCallback(Handler.java:733)
                      at android.os.Handler.dispatchMessage(Handler.java:95)
                      at android.os.Looper.loop(Looper.java:136)
                      at android.app.ActivityThread.main(ActivityThread.java:5017)
                      at java.lang.reflect.Method.invokeNative(Native Method)
                      at java.lang.reflect.Method.invoke(Method.java:515)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
                      at dalvik.system.NativeStart.main(Native Method)

请帮我解决这个问题:(

Answer 1

您看到的错误消息是这样的:

Could not deserialize object. Class com.developtrainmaintain.firebaserecycle.MyClass does not define a no-argument constructor. If you are using ProGuard, make sure these constructors are not stripped

所有 JavaBean 类型的对象都应该有一个无参数的构造函数，这样就可以创建它们的新实例，而不必猜测如何在构造函数中传递参数。因此，向您的类添加一个无参数构造函数:

public MyClass() {}