Android 如何使用共享首選項檢查用戶登錄或注銷

Question

這是我的 MainActivity.java，用於使用共享首選項無需注冊即可登錄系統。 當我單擊登錄按鈕時，它會將輸入數據保存到首選項中。 現在我需要使用 session 來檢查用戶登錄或未注銷。 但我無法做到這一點。 請幫我。 提前謝謝👍

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.ConnectivityManager;
import android.preference.PreferenceManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import api.syntech.com.crmapp.MenuItem.Dashboard;

//login class
public class MainActivity extends AppCompatActivity {

    private EditText Email, Password;
    private Button btn_signin;
    private TextView errordia;
    private SharedPreferences pref;
    private static final String FILE_NAME = "UserInfo";
    private String PARAM_ONE = "Email";
    private String PARAM_TWO = "Password";
    private String PARAM_THREE = "userLoggedInState";
    private boolean isUserLoggedIn;


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

        Email = (EditText)findViewById(R.id.email);
        Password = (EditText)findViewById(R.id.password);
        btn_signin = (Button)findViewById(R.id.btn_login);
        errordia = (TextView)findViewById(R.id.errordia);
        //SharedPref
        btn_signin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SaveData();
                Login();
            }
        });
    }

    private void SaveData(){
        String mEmail = Email.getText().toString();
        String mPass = Password.getText().toString();

        if (mEmail.equals("faruk") && mPass.equals("1234")){
            SharedPreferences pref = getApplicationContext().getSharedPreferences(FILE_NAME, MODE_PRIVATE);
            SharedPreferences.Editor editor = pref.edit();
            editor.putString(PARAM_ONE, mEmail);
            editor.putString(PARAM_TWO, mPass);
            editor.putBoolean(PARAM_THREE, true);
            editor.commit();
            Toast.makeText(getApplicationContext(), "Data is saved successfully", Toast.LENGTH_LONG).show();

        } else {
            Toast.makeText(getApplicationContext(), "Provide Valid Information",Toast.LENGTH_LONG).show();
        }

    }

    private void LoadData(){
        SharedPreferences pref = getApplicationContext().getSharedPreferences(FILE_NAME, MODE_PRIVATE);
        String saved_email = pref.getString(PARAM_ONE, null);
        String saved_password = pref.getString(PARAM_TWO, null);
        errordia.setText("Email : " + saved_email + " Password: " + saved_password);
    }

    private void Login(){
        SharedPreferences pref = getApplicationContext().getSharedPreferences(FILE_NAME, MODE_PRIVATE);
        if (pref.contains(PARAM_ONE) && pref.contains(PARAM_TWO)){
            Intent intent = new Intent(MainActivity.this, MenuPage.class);
            startActivity(intent);
        }
    }
}

Answer 1

當用戶注銷或應用程序停止或銷毀時，嘗試將第三個參數設為 false：

 private void LogOut(){
           SharedPreferences pref = getApplicationContext().getSharedPreferences(FILE_NAME, MODE_PRIVATE);
                SharedPreferences.Editor editor = pref.edit();
                editor.putBoolean(PARAM_THREE, false);
                editor.commit();

            }
     @Override
        protected void onDestroy() {
            super.onDestroy();
                LogOut();
        }

現在在你的 onCreate()

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

   SharedPreferences pref = getApplicationContext().getSharedPreferences(FILE_NAME, MODE_PRIVATE);
   if(pref.getBoolean(PARAM_THREE, false))
    {
        Login(); 
    }

    else{
    setContentView(R.layout.activity_main);
    Email = (EditText)findViewById(R.id.email);
    Password = (EditText)findViewById(R.id.password);
    btn_signin = (Button)findViewById(R.id.btn_login);
    errordia = (TextView)findViewById(R.id.errordia);
    btn_signin.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            SaveData();
            Login();
        }
    });
 }
}

Answer 2

Add thge logout button on your app.
When user click on logout clear the SharedPreferences login data.

SharedPreferences sharedPreferences = getSharedPreferences(FILE_NAME, Context.MODE_PRIVATE);
SharedPreferences.Editor edit = sharedPreferences.edit();
edit.clear().commit();