SharedPreferences不起作用

Question

i'm having little problems using the SharedPreferences. I want to save and later load strings to/from the Preferences. I initialize my prefs in the onCreate-method:

prefs = this.getSharedPreferences("com.example.android_test", Activity.MODE_PRIVATE);

I do saving in another method:

    public void saveUser()
    {   
        prefs.edit().putString("username", username);
        prefs.edit().putString("password", password);
        prefs.edit().apply();
    }

And loading in yet another method:

    public void loadUser()
    {
        username = prefs.getString("username", "default");
        password = prefs.getString("password", "test");
    }

And those are my Test-Methods:

    public void showUser(View v) 
    {
       loadUser();
       text.setText(username);
    }

    public void addUser(View v)
    {
        changeUser(eingabe.getText().toString(),"newpass");
    }

    public void changeUser(String user, String pass)
    {
        username = user;
        password = pass;
        saveUser();
    }

username and password are global, private Strings, eingabe is an EditText and text is a TextView. However, when executing showUser() i only get the defaultvalue displayed to the TextView, even if im using saveUser with different usernames... No crash or anything... its just only the defaultvalue being shown...

Answer 1

您忘记了进行编辑：

prefs.edit().putString("username", username).commit();

Answer 2

 prefs.edit().putString("username", username);
 prefs.edit().putString("password", password);

Change this each time edit will return diffrent instance so your changes wont get committed.

Editor editor = prefs.edit();
editor.putString("username", username);
editor.putString("password", password);
editor.commit();

Try this.

Unlike commit(), which writes its preferences out to persistent storage synchronously, apply() commits its changes to the in-memory SharedPreferences immediately but starts an asynchronous commit to disk and you won't be notified of any failures. If another editor on this SharedPreferences does a regular commit() while a apply() is still outstanding, the commit() will block until all async commits are completed as well as the commit itself.

Answer 3

Ok, apply is same as commit , it only writes the preferences atomically making it thread safe. (It requires API Level 9 though, so be careful)

See the documentation

The problem is what Rajesh CP is saying. You need to create an editor pointer and then apply:

Editor editor = prefs.edit();
editor.putString("username", username);
editor.putString("password", password);
editor.apply();

Else, every time you create a new instance of the editor and when you apply the changes, the editor that is being instructed to apply the changes, doesn't have any changes