java - 将登录状态存储在 SharedPreference 中

Question

这个问题已经有答案了:

How to keep android applications always be logged in state? (9 个回答)

已关闭 3 年前。

我正在制作 Android 应用程序，并使用注册、登录和注销屏幕。我需要的是保存登录状态。如果用户登录一次，那么他将永远不会再次登录，直到注销。我用SharedPareference但我面临着很多问题。

这是我的代码:

public class LoginPage extends AppCompatActivity {
    private SharedPreferences sharedPreferences;
    Button login, register, database;
    EditText username;
    EditText password;
    TextView msg;
    String db_username;
    MyDBManager db;

    static final int REGISTRATION_REQUEST = 1;  // The request code

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.loginpage);
        db = new MyDBManager(this);

        msg = (TextView) findViewById(R.id.msg);
        login = (Button) findViewById(R.id.button);
        register = (Button) findViewById(R.id.button2);
        database = (Button) findViewById(R.id.button3);
        username = (EditText) findViewById(R.id.user);
        password = (EditText) findViewById(R.id.pass);


        // Click and move to the next activity
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                    db.open();
                    Cursor c = db.getUser(username.getText().toString(), password.getText().toString());
                    if (c.moveToFirst()) {
                        db.close();
                        Intent intent = new Intent(LoginPage.this, Menu.class);
                        intent.putExtra("Username", username.getText().toString());
                        startActivity(intent); // call Login Activity
                }
                else
                {
                    db.close();

                    // set error message when the username and/or password is not valid
                    msg.setText("Unable to login: wrong username or password!");
                    // Stay at the current activity.
                }
                 {

                }




                }
            });





        // Click and move to the next activity
        register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(LoginPage.this, Registration.class);
                startActivityForResult(intent, REGISTRATION_REQUEST);
            }
        });

        // Click and move to the next activity
        database.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(LoginPage.this, Database.class);
                startActivity(intent);
            }
        });


    }


    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == REGISTRATION_REQUEST) {
            //if(resultCode == Registration.RESULT_OK){
            Log.d("Pikatchu", "User successfully registered!");
            Bundle res = data.getExtras();
            String result = res.getString("result");
            System.out.println(result);
            msg.setText(result);

        }
    }


}

您能否提供一些建议，为什么我的代码不起作用？

Answer 1

当用户登录时将 boolean 登录存储到共享首选项中，并在启动期间检查用户是否登录，然后您可以导航到必要的路线， boolean 登录默认值应为 false