Android学习笔记十六.Android数据存储与IO.SharedPreferences

package com.example.android_sharedprefences_1;
import java.text.SimpleDateFormat;
import java.util.Date;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
public class SharedPreferencesTest extends Activity {
 SharedPreferences preferences;
 SharedPreferences.Editor editor;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
 //1.获取只能被本应用程序读、写的SharedPreferences对象
  preferences=getSharedPreferences("jiangdongguo",Context.MODE_PRIVATE);	//实例化一个SharedPreferences对象
  editor=preferences.edit();	 //实例化一个SharedPreferences.Editor对象
 
  Button read=(Button)findViewById(R.id.readBtn);
  Button write=(Button)findViewById(R.id.writeBtn);
 //2.读取SharedPreferences中的数据:读取字符串、int类型数据
  read.setOnClickListener(new OnClickListener(){
   @Override
   public void onClick(View v) {
    String time=preferences.getString("time", null);	//获取键值为time的数据
    int randNum=preferences.getInt("random", 0);	 //获取键值为random的数据
    String result=(time==null?"您暂时还未写入数据":"写入时间为:"+time+"\n上次生成的随机数为:"+randNum);
    Toast.makeText(SharedPreferencesTest.this, result, Toast.LENGTH_SHORT).show();
   }
  });
 //3.利用SharedPreferences.Editor向Preferences写入数据
  write.setOnClickListener(new OnClickListener(){
   @Override
   public void onClick(View v) {
    SimpleDateFormat sdf=new SimpleDateFormat("yyyy年MM月dd日"+"hh:mm:ss");
    editor.putString("time",sdf.format(new Date()));	//存入当前时间到time键
    editor.putInt("random", (int)(Math.random()*100));	//存入一个随机数
    editor.commit();	 //提交所有存入的数据
   }
   
  });
 }
}

/*实现功能：计算应用程序被打开的次数*/ 
package com.example.android_sharedprefences_2;
import android.support.v7.app.ActionBarActivity; 
import android.widget.Toast;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
public class Usecount extends ActionBarActivity {
 SharedPreferences preferences;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
 //1.获取本应用程序的SharedPreferences,其文件名为count
  preferences=getSharedPreferences("count",Context.MODE_WORLD_READABLE);
 //2.读取SharedPreferences里的count数据（默认值为0）,并显示
  int count=preferences.getInt("count", 0);	    
  Toast.makeText(this, "程序被使用了"+count+"次。",Toast.LENGTH_SHORT).show();
 //3.存储count次数到SharedPreferences里(应用每打开依次，count+1)
  Editor editor=preferences.edit();
  editor.putInt("count", ++count);
 //4.提交数据
  editor.commit();
 }
}

/*实现：读取其他应用程序所保存的SharedPreferences数据*/
package com.example.android_sharedpreferences_3;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.pm.PackageManager.NameNotFoundException;
import android.os.Bundle;
import android.widget.TextView;
public class ReadOtherPreferences extends Activity {
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  Context useCount=null;
  try{
  //1.获取其他程序所对应的Context
   useCount=createPackageContext("com.example.android_sharedprefences_2",Context.CONTEXT_IGNORE_SECURITY);
  }
  catch(NameNotFoundException e)
  {
   e.printStackTrace();
  }
  //2.使用其他程序的Context获取对应的SharedPreferences
  SharedPreferences prefs=useCount.getSharedPreferences("count", Context.MODE_WORLD_READABLE);
  //3.读取数据并显示
  int count=prefs.getInt("count", 0);
  TextView show=(TextView)findViewById(R.id.show);
  show.setText("UseCount应用程序以前被使用了"+count+"次。");
 }
}