Android數(shù)據(jù)持久化之Preferences機(jī)制詳解

package com.example.data_sharedpreferences;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends Activity {
  private TextView text;
  private Button button;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // 寫入數(shù)據(jù)
    writeData();
    text = (TextView) findViewById(R.id.text);
    button = (Button) findViewById(R.id.button0);
    button.setOnClickListener(new OnClickListener() {
      @Override
      public void onClick(View v) {
        // TODO Auto-generated method stub
        // 讀取數(shù)據(jù)
        readData();
      }
    });
  }
  /**
   * 寫入數(shù)據(jù)
   */
  public void writeData() {
    // 設(shè)置權(quán)限為私有MODE_PRIVATE
    SharedPreferences sp_p = this.getSharedPreferences("ct_sp_private",
        Context.MODE_PRIVATE);
    // 通過(guò)SharedPreferences對(duì)象的編輯器對(duì)象Editor來(lái)實(shí)現(xiàn)存入數(shù)據(jù)
    SharedPreferences.Editor editor = sp_p.edit();
    // 通過(guò)該編輯器函數(shù)設(shè)置鍵值
    editor.putString("username", "marry_private");
    // 提交數(shù)據(jù)，并將數(shù)據(jù)寫入xml文件中
    editor.commit();
    // 設(shè)置為只讀
    SharedPreferences sp_or = this.getSharedPreferences("ct_sp_private",
        Context.MODE_WORLD_READABLE);
    sp_or.edit().putString("username", "marry_only_read").commit();
    // 設(shè)置為只寫
    SharedPreferences sp_ow = this.getSharedPreferences("ct_sp_private",
        Context.MODE_WORLD_WRITEABLE);
    sp_ow.edit().putString("username", "marry_only_write").commit();
    // 設(shè)置為可讀可寫
    SharedPreferences sp_x = this.getSharedPreferences("ct_sp_private",
        Context.MODE_WORLD_READABLE + Context.MODE_WORLD_WRITEABLE);
    sp_x.edit().putString("username", "marry_write_read").commit();
  }
  /**
   * 讀取數(shù)據(jù)
   * 通過(guò)SharedPreferences對(duì)象的鍵key可以獲取到對(duì)應(yīng)key的鍵值value。對(duì)于不同類型的鍵值有不同的函數(shù)：getBoolean
   * ,getInt,getFloat,getLong.
   */
  public void readData() {
    // TODO Auto-generated method stub
    text.setText("private_username:"
        + this.getSharedPreferences("ct_cp_private", 0).getString(
            "username", "marry_private")
        + "\r\n"
        + "read_username:"
        + this.getSharedPreferences("ct_cp_private", 0).getString(
            "username", "marry_only_read")
        + "\r\n"
        + "write_username:"
        + this.getSharedPreferences("ct_cp_private", 0).getString(
            "username", "marry_only_write")
        + "\r\n"
        + "write_read_username:"
        + this.getSharedPreferences("ct_cp_private", 0).getString(
            "username", "marry_write_read") + "\r\n");
  }
  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
  }
}

package com.example.data_sharedpreferences2;
import com.example.data_sharedpreferences2.R;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager.NameNotFoundException;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
/**
 * 該程序的功能是訪問(wèn)data_sharedpreferences應(yīng)用 Sharedpreferences訪問(wèn)另一個(gè)應(yīng)用的條件：
 * 1、被訪問(wèn)的應(yīng)用權(quán)限為可讀或者可寫 2、必須要知道被訪問(wèn)應(yīng)用的包名
 *
 * @author marry
 *
 */
public class MainActivity extends Activity {
  private TextView text;
  private Button button;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    text = (TextView) findViewById(R.id.text);
    button = (Button) findViewById(R.id.button0);
    button.setOnClickListener(new OnClickListener() {
      @Override
      public void onClick(View v) {
        // 訪問(wèn)應(yīng)用1,并讀取應(yīng)用1的數(shù)據(jù)
        try {
          // 獲得要訪問(wèn)應(yīng)用的context
          Context ortherContext = createPackageContext(
              "com.example.data_sharedpreferences", 0);
          // 通過(guò)ortherContext.getSharedPreferences打開(kāi)應(yīng)用1的文件
          text.setText("private_username:"
              + ortherContext.getSharedPreferences(
                  "ct_cp_private", 0).getString("username",
                  "marry_private")
              + "\r\n"
              + "read_username:"
              + ortherContext.getSharedPreferences(
                  "ct_cp_private", 0).getString("username",
                  "marry_only_read")
              + "\r\n"
              + "write_username:"
              + ortherContext.getSharedPreferences(
                  "ct_cp_private", 0).getString("username",
                  "marry_only_write")
              + "\r\n"
              + "write_read_username:"
              + ortherContext.getSharedPreferences(
                  "ct_cp_private", 0).getString("username",
                  "marry_write_read") + "\r\n");
        } catch (NameNotFoundException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }
      }
    });
  }
  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
  }
}