在模型类中定义构造函数（使用Cloud Firestore获取数据） [英] Defining Constructors in Model Class (Get Data with Cloud Firestore)

问题描述

我在 Cloud Firestore 中添加了一些数据在此处输入图像说明

I added some data in Cloud Firestore enter image description here

其中我有String标题，String desc，String []照片

in which I am having String title, String desc, String[] photos

我想要在 MyClass.class 中获取数据，因此我提供了 Parameterized Constructor 和 Getter&设置器。

I want to get that data in MyClass.class so I provided Parameterized Constructor and Getter & Setters in the class.

但是错误提示不支持转换为数组，请改用列表

这是我逻辑部分的代码：

This is my code for logical part:

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());
                        }
                    }
                });

这是我的课程：

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）
：

And I am getting this error at MyClass obj = document.toObject(MyClass.class) :

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)

请帮助我解决此问题：（

推荐答案

您看到的错误消息是：

无法反序列化对象。 com.developtrainmaintain.firebaserecycle.MyClass类未定义无参数构造函数。如果您使用的是ProGuard，请确保这些构造函数没有被剥夺

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类型对象都应具有no-arg构造函数，以便有可能创建它们的新实例，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的构造函数：

All JavaBean type objects should have a no-arg constructor so it's possible to create a new instance of them without having to guess how to pass parameters in the constructor. So add a no-arg constructor to your class:

public MyClass() {}

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