Android下文件访问的权限

* 默认情况下，Android中，应用程序的文件时私有的，其他应用程序不可以读取私有的文件
* 底层用的时Linux文件的权限

- rw- rw- ---
      
        - ：文件
        r:只读  readable
        w:只写  writeable
        x: 可执行

第一位：文件类型
        234位：应用程序对自己文件的权限
        567位：同组用户对这个文件的操作权限
        8910位：其他应用程序对文件的权限

package com.example.filemode;
import java.io.FileOutputStream;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      Button btn1 = (Button) findViewById(R.id.btn1);
      Button btn2 = (Button) findViewById(R.id.btn2);
      Button btn3 = (Button) findViewById(R.id.btn3);
      Button btn4 = (Button) findViewById(R.id.btn4);
      // 设置监听事件
      btn1.setOnClickListener(this);
      btn2.setOnClickListener(this);
      btn3.setOnClickListener(this);
      btn4.setOnClickListener(this);
   }
   @Override
   public void onClick(View v) {
      try {
         FileOutputStream fos = null;
         switch (v.getId()) {
            case R.id.btn1:// 私有
                fos = this.openFileOutput("private.txt", MODE_PRIVATE);
                break;
            case R.id.btn2:// 只读
                fos = this.openFileOutput("readable.txt", MODE_WORLD_READABLE);
                break;
            case R.id.btn3:// 只写
                fos = this.openFileOutput("writeable.txt", MODE_WORLD_WRITEABLE);
                break;
            case R.id.btn4:// 可读可写
                fos = this.openFileOutput("public.txt",MODE_WORLD_READABLE + MODE_WORLD_WRITEABLE);
                break;
            default:
                break;
         }
         fos.write("呵呵".getBytes());
         fos.close();
         Toast.makeText(this, "文件保存成功，哈哈。。。", 0).show();
      } catch (Exception e) {
         e.printStackTrace();
         Toast.makeText(this, "文件保存失败楼", 0).show();
      }
   }
}

---

package com.example.readwrite;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends Activity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
   }
   public void read(View v){
      try {
         File file = new File("/data/data/com.example.filemode/files/public.txt");
         FileInputStream fis = new FileInputStream(file);
         BufferedReader br = new BufferedReader(new InputStreamReader(fis));
         String text = br.readLine();
         br.close();
         Toast.makeText(this, "哈哈："+text, 0).show();
      } catch (Exception e) {
         e.printStackTrace();
         Toast.makeText(this, "无权读取文件", 0).show();
      }
   }

   public void write(View v){
      File file = new File("/data/data/com.example.filemode/files/public.txt");
      try {
         FileOutputStream fos = new FileOutputStream(file);
         fos.write("LoaderMan".getBytes());
         fos.close();
         Toast.makeText(this, "嘿嘿", 0).show();
      } catch (Exception e) {
         e.printStackTrace();
         Toast.makeText(this, "失败了！", 0).show();
      }
   }
}

---