ANDROID_ID调用空对象错误Firebase数据库

Question

我是Android应用程序开发的新手。我一直在尝试使用Firebase电子邮件和密码验证来构建应用程序，并尝试在注册过程中将手机的ANDROID_ID保存在Firebase数据库中。

但每当我打开SignUp Activity时，应用程序都会关闭并在Logcat中显示以下错误：

java.lang.RuntimeException：无法实例化活动ComponentInfo {com.rimikri.smartpedi / com.rimikri.smartpedi.SignUpActivity}：java.lang.NullPointerException：尝试调用虚拟方法'android.content.ContentResolver android.content.Context。对空引用引用的getContentResolver（）'

这是我的SignUp活动：

public class SignUpActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText editTextName;
    private FirebaseAuth mAuth;
    public String androidId = Settings.Secure.getString(getContentResolver(), Settings.Secure.ANDROID_ID);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_signup);
        editTextName = findViewById(R.id.edit_text_name);
        mAuth = FirebaseAuth.getInstance();
    }

    private void registerUser() {
        final String name = editTextName.getText().toString().trim();
        mAuth.createUserWithEmailAndPassword(email, password)
            .addOnCompleteListener(new OnCompleteListener < AuthResult > () {
                @Override
                public void onComplete(@NonNull Task < AuthResult > task) {
                    if (task.isSuccessful()) {

                        User user = new User(
                            name,
                            androidId
                        );

                        FirebaseDatabase.getInstance().getReference("Users")
                            .child(FirebaseAuth.getInstance().getCurrentUser().getUid())
                            .setValue(user).addOnCompleteListener(new OnCompleteListener < Void > () {
                                @Override
                                public void onComplete(@NonNull Task < Void > task) {
                                    //
                                }
                            });

                    } else {
                        //
                    }
                }
            });
    }
}

我拥有的班级User是：

public class User {
    public String name;


    public User() {

    }

    public User(String name) {
        this.name = name;
    }
}

我该如何获得ANDROID_ID？

Answer 1

在androidId方法中获取你的onCreate()

试试这个

public class SignUpActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText editTextName;
    private FirebaseAuth mAuth;
    public String androidId;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_signup);
        editTextName = findViewById(R.id.edit_text_name);
        mAuth = FirebaseAuth.getInstance();
        androidId = Settings.Secure.getString(getContentResolver(), Settings.Secure.ANDROID_ID);
    }

    private void registerUser() {
        final String name = editTextName.getText().toString().trim();
        mAuth.createUserWithEmailAndPassword(email, password)
            .addOnCompleteListener(new OnCompleteListener < AuthResult > () {
                @Override
                public void onComplete(@NonNull Task < AuthResult > task) {
                    if (task.isSuccessful()) {

                        User user = new User(
                            name,
                            androidId
                        );

                        FirebaseDatabase.getInstance().getReference("Users")
                            .child(FirebaseAuth.getInstance().getCurrentUser().getUid())
                            .setValue(user).addOnCompleteListener(new OnCompleteListener < Void > () {
                                @Override
                                public void onComplete(@NonNull Task < Void > task) {
                                    //
                                }
                            });

                    } else {
                        //
                    }
                }
            });
    }
}