android - 如何在 firebase 数据库中保存对象？

Question

我无法将对象添加到 firebase 实时数据库。我尝试了以下代码。但是当这段代码执行时 userRef.child("Users").child(Integer.toString(random.nextInt(100))).setValue(newUser);我的应用程序崩溃了。

    public class MainActivity extends AppCompatActivity {

    private FirebaseAuth mAuth;
    private DatabaseReference userRef;
    EditText nameEditText;
    EditText passEditText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        nameEditText = (EditText) findViewById(R.id.nameEditText);
        passEditText = (EditText) findViewById(R.id.passEditText);

        mAuth = FirebaseAuth.getInstance();
        //        signInAnonymously();
                mAuth.signInAnonymously().addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {

                    }

                    public void onFailure(Throwable throwable) {
                        throw new RuntimeException(throwable);
                    }
                });
    }
    public void createUser(View view){

        Random random = new Random();



        userRef = FirebaseDatabase.getInstance().getReference();



        String userN = String.valueOf(nameEditText.getText());
        String pass = String.valueOf(passEditText.getText());


        UserDetails newUser = new UserDetails(userN,pass);

        userRef.child("Users").child(Integer.toString(random.nextInt(100))).setValue(newUser);


    }
@IgnoreExtraProperties
public class UserDetails{

    public String userName;
    public String password;

    public UserDetails(){

    }

    public UserDetails(String userName, String userPass){

        this.userName = userName;
        this.password = userPass;
        Log.i("Check", this.userName);

    }

    public String getUserName() {
        return userName;
    }

    public String getPassword() {
        return password;
    }
}
}

这是 logcat 错误消息。

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.crossappfactory.username, PID: 20144
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:4785)
at android.view.View$PerformClick.run(View.java:19884)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5343)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)
                   Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:4785) 
at android.view.View$PerformClick.run(View.java:19884) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:135) 
at android.app.ActivityThread.main(ActivityThread.java:5343) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700) 
                   Caused by: com.google.firebase.database.DatabaseException: Invalid key: this$0. Keys must not contain '/', '.', '#', '$', '[', or ']'
at com.google.android.gms.internal.zzaiw.zziv(Unknown Source)
at com.google.android.gms.internal.zzaiw.zzau(Unknown Source)
at com.google.firebase.database.DatabaseReference.zza(Unknown Source)
at com.google.firebase.database.DatabaseReference.setValue(Unknown Source)
at com.crossappfactory.username.MainActivity.createUser(MainActivity.java:63)
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
at android.view.View.performClick(View.java:4785) 
at android.view.View$PerformClick.run(View.java:19884) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:135) 
at android.app.ActivityThread.main(ActivityThread.java:5343) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)

Answer 1

解决方案很简单，将UserDetails类标记为静态，这样编译器就不会生成额外的字段:

public static class UserDetails {

解释为什么需要这样做，以防您感兴趣。

错误消息说明了问题所在，但在这种情况下有点难以解析:“无效键:this$0。键不能包含'/'、'.'、'#'、'$'、'[ ', 或 ']'"

它说 this$0，这是对您的 UserDetails 对象的引用。 $0 表示它是 MainActivity 的内部类。当你创建一个内部类时，该类的实例会得到一个额外的隐藏字段，引用它们的包含对象，这样你就可以在 UserDetails 的代码中说 this.MainActivity .但是 Firebase SDK 无法处理这个额外的隐藏字段，因此会引发异常。