android - 应用程序关闭后Android用户登录错误

Question

我正在使用 SharedPreferences 来保存凭据，这可以正常工作，但是当应用程序被杀死时，会要求用户再次登录。

保存凭据后，如果应用程序被终止，则不应要求用户登录。任何帮助，将不胜感激。

public class MyActivity extends Activity {
     public static final String PREFS_NAME = "myFile";
     private String user; 
     private String userName; 

     @Override 
     public void onRestart(){
           super.onRestart();
           userName = null;
           user=null;

           //Retrieve the preferences.
           SharedPreferences credentials = getSharedPreferences(PREFS_NAME,MODE_PRIVATE); 

           user = credentials.getString(userName, null);
           //Check for stored preferences.  
           if (user!=null) {
              Intent j = new Intent(getApplicationContext(), MainActivity.class);
              startActivity(j);
              finish(); 

           } 

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // setting default screen to login.xml
        setContentView(R.layout.layout_login_new);

        //Initializing the fields from XML layout.

        final Button login_btn = (Button) findViewById(R.id.btnLogin);

        //Retrieve the preferences.
        SharedPreferences credentials = getSharedPreferences(PREFS_NAME,MODE_PRIVATE);
        final SharedPreferences.Editor editor = credentials.edit(); 
        userName = null;
        user=null;


        //retrieve the stored values.
        user = credentials.getString(userName, null);
        //Check for stored preferences. 
        if (user!=null){
            Intent j = new Intent(getApplicationContext(), MainActivity.class);
            j.putExtra("user_name", user);
            startActivity(j);
            finish(); 
        }    

        //Listener for the login button.
            login_btn.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    Intent j = new Intent(getApplicationContext(), MainActivity.class);
                    // Verify the username and password.
                    if ( 
                            (username_login.getText().toString()).equals("test")&&(password_login.getText().toString()).equals("test")){
                        //Store the credentials in sharedPreferences.
                        user=username_login.getText().toString();
                        editor.putString(userName, username_login.getText().toString()).commit();

                            j.putExtra("user_name", user);
                        startActivity(j);
                        finish(); 
                        }
                    else{
                        Display_error_msg();
                        }
                }
            });

Answer 1

您的做法有一些错误，您没有提交共享首选项值，并且没有适当的标签用于存储和检索。看看这段代码

if ((username_login.getText().toString()).equals("test")&&(password_login.getText().toString()).equals("test")){
    //Store the credentials in sharedPreferences.
    user=username_login.getText().toString();
    editor.putString("UserName", username_login.getText().toString()).commit();

    editor.commit();  //// changes will be effect after commit only

    j.putExtra("user_name", user);
    startActivity(j);
    finish(); 
} else {
    Display_error_msg();
}

在另一个活动中

public class MyActivity extends Activity {
     public static final String PREFS_NAME = "myFile";
     private String user; 
     private String userName; 

     @Override 
     public void onRestart(){
         super.onRestart();
         userName = "UserName";
         user=null;

         //Retrieve the preferences.
         SharedPreferences credentials = getSharedPreferences(PREFS_NAME,MODE_PRIVATE); 

         user = credentials.getString(userName, null);
         //Check for stored preferences. 
         if (user!=null){
             Intent j = new Intent(getApplicationContext(), MainActivity.class);
             startActivity(j);
             finish(); 
         } 
 }

Answer 2

使用onResume()而不是onRestart()检查用户登录。

这些是活动的生命周期，而不是应用程序的。即， onRestart() 并不意味着应用程序重启。