public void save()
{
    try {
      FileOutputStream outStream=this.openFileOutput("a.txt",Context.MODE_WORLD_READABLE);
      outStream.write(text.getText().toString().getBytes());
      outStream.close();
      Toast.makeText(MyActivity.this,"Saved",Toast.LENGTH_LONG).show();
    } catch (FileNotFoundException e) {
      return;
    }
    catch (IOException e){
      return ;
    }
}

public void load()
{
  try {
    FileInputStream inStream=this.openFileInput("a.txt");
    ByteArrayOutputStream stream=new ByteArrayOutputStream();
    byte[] buffer=new byte[1024];
    int length=-1;
    while((length=inStream.read(buffer))!=-1)  {
      stream.write(buffer,0,length);
    }
    stream.close();
    inStream.close();
    text.setText(stream.toString());
    Toast.makeText(MyActivity.this,"Loaded",Toast.LENGTH_LONG).show();
  } catch (FileNotFoundException e) {
    e.printStackTrace();
  }
  catch (IOException e){
    return ;
  }
}

mksdcard 2048M D:\AndroidTool\sdcard.img

<!– 在SDCard中創(chuàng)建與刪除文件權(quán)限 –>
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
<!– 往SDCard寫入數(shù)據(jù)權(quán)限 –>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
   File sdCardDir = Environment.getExternalStorageDirectory();//獲取SDCard目錄
   File saveFile = new File(sdCardDir, "a.txt");
   FileOutputStream outStream = new FileOutputStream(saveFile);
   outStream.write("test".getBytes());
   outStream.close();
}

File sdCardDir = new File("/sdcard"); //獲取SDCard目錄
File saveFile = new File(sdCardDir, "itcast.txt"); 
//上面兩句代碼可以合成一句： File saveFile = new File("/sdcard/a.txt");
FileOutputStream outStream = new FileOutputStream(saveFile);
outStream.write("test".getBytes());
outStream.close();

public class MainActivity extends Activity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  }
  public void button(View view){
    Person p = new Person();
    p.setAge(10);
    p.setName("Lee");
    saveObject(p, "MainActivity.dat");
  }
  public void button2(View view){
    Person p = (Person) readObject("MainActivity.dat");
    System.out.println(p.getAge());
  }
  public boolean saveObject(Serializable ser, String file) {
    FileOutputStream fos = null;
    ObjectOutputStream oos = null;
    try{
      fos = openFileOutput(file, MODE_PRIVATE);
      oos = new ObjectOutputStream(fos);
      oos.writeObject(ser);
      oos.flush();
      return true;
    }catch(Exception e){
      e.printStackTrace();
      return false;
    }finally{
      try {
        oos.close();
      } catch (Exception e) {}
      try {
        fos.close();
      } catch (Exception e) {}
    }
  }
  /**
   * 讀取對(duì)象
   * @param file
   * @return
   * @throws IOException
   */
  public Serializable readObject(String file){
    FileInputStream fis = null;
    ObjectInputStream ois = null;
    try{
      fis = openFileInput(file);
      ois = new ObjectInputStream(fis);
      return (Serializable)ois.readObject();
    }catch(FileNotFoundException e){
    }catch(Exception e){
      e.printStackTrace();
      //反序列化失敗 - 刪除緩存文件
      if(e instanceof InvalidClassException){
        File data = getFileStreamPath(file);
        data.delete();
      }
    }finally{
      try {
        ois.close();
      } catch (Exception e) {}
      try {
        fis.close();
      } catch (Exception e) {}
    }
    return null;
  }
}
class Person implements Serializable{
  int age;
  String name;
  public int getAge() {
    return age;
  }
  public void setAge(int age) {
    this.age = age;
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
}