Question

（对不起我的英语不好），我正在尝试从Firebase数据库加载数据。该应用程序运行正常，还可以从Firebase数据库加载数据。但随后该应用开始崩溃。我不知道该怎么解决。

这是MainActivity。this

public class MainActivity extends AppCompatActivity {


    CircleImageView profileImage;

    FirebaseAuth mAuth;
    FirebaseAuth.AuthStateListener listener;
    FirebaseDatabase userDatabase;
    DatabaseReference reference;
    FirebaseUser user;
    String firebaseid;

    private String email, name, phone, password, image;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        getSupportActionBar().hide();

        profileImage = findViewById(R.id.profile_image);
        username = findViewById(R.id.userName);

        userDatabase = FirebaseDatabase.getInstance();
        reference = userDatabase.getReference();
        mAuth = FirebaseAuth.getInstance();
        user = mAuth.getCurrentUser();

        assert user != null;
        firebaseid = user.getUid();

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                for (DataSnapshot ds : dataSnapshot.getChildren()){
                    information.setName(ds.child(firebaseid).getValue(RegisterModel.class).getName());
                    information.setPoints(ds.child(firebaseid).getValue(RegisterModel.class).getPoints());
                    information.setImage(ds.child(firebaseid).getValue(RegisterModel.class).getImage());

                    username.setText(information.getName());
                    totalPoints.setText(Integer.toString(information.getPoints()));
                    String image = information.getImage();

                    try {
                        Picasso.get().load(image).into(profileImage);
                    } catch (Exception e){
                        Picasso.get().load(R.drawable.user).into(profileImage);
                    }

                }

            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

                Toasty.error(MainActivity.this, "Error: "+ databaseError.getMessage(),
                        Toasty.LENGTH_SHORT, true).show();
            }
        });

    }


}

这是Logcat

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.marsad.app.model.RegisterModel.getName()' on a null object reference
        at com.marsad.app.MainActivity$13.onDataChange(MainActivity.java:290)
        at com.google.firebase.database.core.ValueEventRegistration.fireEvent(com.google.firebase:firebase-database@@19.2.1:75)
        at com.google.firebase.database.core.view.DataEvent.fire(com.google.firebase:firebase-database@@19.2.1:63)
        at com.google.firebase.database.core.view.EventRaiser$1.run(com.google.firebase:firebase-database@@19.2.1:55)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:192)
        at android.app.ActivityThread.main(ActivityThread.java:6711)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:549)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:826)

这是Firebase数据库结构（JSON）

{
  "Users" : {
    "nftLFXoEzPNyTt4OnZByVGClWJM2" : {
      "email" : "test@gmail.com",
      "image" : "https://firebasestorage.googleapis.com/v0/b/earning-app-27780.appspot.com/o/UsersProfileImages%2F1581504377418.jpg?alt=media&token=14484015-3b3c-4ff4-aa1c-7b5f3ffbe695",
      "name" : "Marsad",
      "password" : "123456",
      "phone" : "03012345678"
    }
  }
}

我不知道该如何解决。有人告诉我如何解决这个错误

Answer 1

为用户提供正确的参考。您忘记显示节点用户。我在您的Json响应中找不到积分

reference.child("Users").addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

        for (DataSnapshot ds : dataSnapshot.getChildren()){
            information.setName(ds.child("name").getValue(String.class));
            information.setImage(ds.child("image").getValue(String.class));
            username.setText(information.getName());
            String image = information.getImage();
            try {
                Picasso.get().load(image).into(profileImage);
            } catch (Exception e){
                Picasso.get().load(R.drawable.user).into(profileImage);
            }

        }

    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {

        Toasty.error(MainActivity.this, "Error: "+ databaseError.getMessage(),
                Toasty.LENGTH_SHORT, true).show();
    }
});

Answer 2

以下内容将获取数据库根节点的DatabaseReference

reference = userDatabase.getReference();

您需要的是获取对/Users路径的引用

reference = userDatabase.getReference("Users);

尝试在空对象引用上

2 个答案: