Question

我在 Cloud Firestore enter image description here

中添加了一些数据

其中我有String title，String desc，String [] photos

我想在 MyClass.class 中获取该数据，因此我提供了参数化构造函数和 Getter＆amp;在课堂上安装。

但错误表示转换为阵列不支持，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());
                        }
                    }
                });

这是我的班级：

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上收到此错误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)

请帮我解决这个问题：（

Answer 1

您看到的错误消息是：

无法反序列化对象。 com.developtrainmaintain.firebaserecycle.MyClass类没有定义无参构造函数。如果您使用的是ProGuard，请确保这些构造函数未被剥离

所有JavaBean类型对象都应该有一个no-arg构造函数，因此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。所以在你的类中添加一个no-arg构造函数：

public MyClass() {}

Answer 2

由于您在类中提供了参数化构造函数，因此默认情况下没有参数构造函数不再可用。定义一个无参数构造函数，然后它应该工作

package com.mikadosolutions.training.spring.di;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;

public class LaunchTraining    
{

    public static void main(String args[])
    {
        ApplicationContext context = new FileSystemXmlApplicationContext("TrainingConfig.xml");
        Workshop trainingWorkshop = (Workshop) context.getBean("trainingWorkshop");
        trainingWorkshop.conductWorkshop();
    }
}

Answer 3

public class MyClass {

    String title;
    String desc;
    ArrayList<String> photos;

    public MyClass(){}

    public MyClass(String title, String desc, ArrayList<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 ArrayList<String> getPhotos() {
        return photos;
    }

    public void setPhotos(ArrayList<String> photos) {
        this.photos = photos;
    }
}

Firebase或FireStore不支持使用列表或映射类而不是数组

在模型类中定义构造函数（使用Cloud Firestore获取数据）

3 个答案: