SharedPreferences基本使用

位于android.content目录下的
SharedPreferences

| android.content.SharedPreferences |

Class Overview

Interface for accessing and modifying preference data returned by . For any particular set of preferences, there is a single instance of this class that all clients share. Modifications to the preferences must go through an object to ensure the preference values remain in a consistent state and control when they are committed to storage. Objects that are returned from the various get methods must be treated as immutable by the application.

To write values:

1. Call [edit()] to get a `[SharedPreferences.Editor]
2. Add values with methods such as [putBoolean()] and [putString()].
3. Commit the new values with [commit()]

To read values, use [SharedPreferences] methods such as [getBoolean()] and [getString()].

Here is an example that saves a preference for silent keypress mode in a calculator:

public class Calc extends Activity {
    public static final String PREFS_NAME = "MyPrefsFile";

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

       // Restore preferences
       SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
       boolean silent = settings.getBoolean("silentMode", false);
       setSilent(silent);
    }

    @Override
    protected void onStop(){
       super.onStop();

      // We need an Editor object to make preference changes.
      // All objects are from android.context.Context
      SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
      SharedPreferences.Editor editor = settings.edit();
      editor.putBoolean("silentMode", mSilentMode);

      // Commit the edits!
      editor.commit();
    }
}

sp存储的目录：data/data下 包名 下 shared_prefs 下的一个XML文件 存储方式是键值对

image.png

 public class MainActivity extends Activity {
 
    private EditText et_input;//输入的文本
    private SharedPreferences sp;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //初始化视图
        initView();
        //回显操作
        reShow();
    }
 
    /**
     * 回显操作
     */
    private void reShow() {
        //从sp中取数据
        String con = sp.getString("content", "");
        et_input.setText(con);
    }
 
    /**
     * 初始化视图
     */
    private void initView() {
        et_input = (EditText) findViewById(R.id.et_input);
        //实例化sp
        sp = getSharedPreferences("config.xml", 0);
    }
 
    /**
     * 点击保存数据
     * @param v
     */
    @SuppressLint({ "NewApi", "ShowToast" })
    public void clickSave(View v) {
//      System.out.println("按钮被点击了");
        //拿到文本内容
        String et_con = et_input.getText().toString().trim();
        if (et_con.isEmpty()) {
            Toast.makeText(MainActivity.this, "请输入文本内容", 0).show();
            return;
        }
        //保存数据到sp
        Editor edit = sp.edit();
        edit.putString("content", et_con);
        //提交
        edit.commit();
        System.out.println("保存数据成功");
    }
}