Question

我有两个活动..首先是Loginactivity如果按钮点击然后我将值存储在sahred prefrences和第二个activtty中（Firstscreen我啊按钮注销如果我点击它然后重新移动存储的sharedpreferences值...

....退出应用程序并重新启动应用程序后，如果我打印然后共享首选项存储值正在打印...（如果我注销然后完全删除值）

public class LoginActivity extends ActionBarActivity {


 User myApplication;

    EditText username,passwordField;
    Button login;
    CheckBox check;

    SharedPreferences settings;
    SharedPreferences.Editor editor;
    String userStored;
    String passwordStored;
     boolean checked =false;
     boolean checkboxvalue;
     public static final String PREFS_NAME = "Shared_File";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.login);




login.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub




        //  settings = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());


                settings = getSharedPreferences(PREFS_NAME,Context.MODE_PRIVATE);               
                editor = settings.edit();                                   
                editor.putString("User_Shared", username.getText().toString());
                editor.putString("Pass_Shared", passwordField.getText().toString());                
                //editor.putBoolean("Checkbox_Click", true);

                editor.commit();

                userStored = settings.getString("User_Shared",null);
                passwordStored =settings.getString("Pass_Shared", null);                     


                System.out.println("userStored :::" +userStored + " :::::::pasword :::::::" +passwordStored  );

                 Intent intent =  new Intent(getApplicationContext(),FirstScreen.class);
                 startActivity(intent);

            }   


    }
});



}
}           





public class FirstScreen extends Activity {


    Button logout;

    SharedPreferences settings;
    SharedPreferences.Editor editor;
    public static final String PREFS_NAME = "Shared_File";

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.firstscreen);




  logout =(Button)findViewById(R.id.logout);

  logout.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub

    //  settings = PreferenceManager.getDefaultSharedPreferences(getApplicationContext()); 

        settings =getSharedPreferences(PREFS_NAME,Context.MODE_PRIVATE);
        editor = settings.edit();   

           try {

               editor.remove("User_Shared");
               editor.remove("Pass_Shared");


                   editor.clear();
               editor.commit();
        }

           catch (NullPointerException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } 
           catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } 


    Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
            //intent.putExtra("Logout", logout);

        startActivity(intent);



    }
});



}
}

Answer 1

这与活动生命周期有关。您应该将与SharedPreferences相关的代码放在onPause方法中。您的代码的错误在于它将键值对存储在SharedPreferences对象中，但是当您按下后退按钮或活动退出其活动状态时会被删除。所以，试试我的建议。祝你好运。希望，这很有益。

Answer 2

很容易放

editor.putString("User_Shared", null);

一切都会正常。

应用程序重新启动时，共享首选项值将再次显示

2 个答案: