文章标题

首先，大家在学习的过程中记得大概的看下源码：源码在:     安装目录\sdk\sources\android-18\android\app\ContextImpl.java

@Override
public FileOutputStream openFileOutput(String name, int mode)
throws FileNotFoundException {
final boolean append = (mode&MODE_APPEND) != 0;
File f = makeFilename(getFilesDir(), name);
try {
FileOutputStream fos = new FileOutputStream(f, append);
setFilePermissionsFromMode(f.getPath(), mode, 0);
return fos;
} catch (FileNotFoundException e) {
}

    File parent = f.getParentFile();    parent.mkdir();    FileUtils.setPermissions(        parent.getPath(),        FileUtils.S_IRWXU|FileUtils.S_IRWXG|FileUtils.S_IXOTH,        -1, -1);    FileOutputStream fos = new FileOutputStream(f, append);    setFilePermissionsFromMode(f.getPath(), mode, 0);    return fos;}

下面是具体的使用（借鉴：http://blog.csdn.net/janronehoo/article/details/6960137）
package demo.filerw.service;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

import android.content.Context;
import android.os.Environment;

/**
* 文件操作类
* @author janrone
* @website http://hujl.sinaapp.com
*/
public class FileService {

private Context context;  public FileService(Context context) {      this.context = context;  }  //存储数据到文件  public void saveName(String name) throws Exception{      //context.getFilesDir();// 得到存放文件的系统目录 /data/data/<package name>/files      //context.getCacheDir(); //缓存目录  /data/data/<package name>/cache      FileOutputStream outputStream=context.openFileOutput("deomfilerw.txt", Context.MODE_APPEND);      outputStream.write(name.getBytes());      outputStream.close();  }  //存储数据到sdcard  public void saveNameToSDCard(String name) throws Exception{      Environment.getExternalStorageDirectory(); //得到sdcard目录      File file=new File("/sdcard","demosdcard.txt");      FileOutputStream outputStream=new FileOutputStream(file);      outputStream.write(name.getBytes());      outputStream.close();  }  // 读取数据  public String getName() throws Exception{      FileInputStream inputStream=context.openFileInput("deomfilerw.txt");      ByteArrayOutputStream outStream=new ByteArrayOutputStream();      byte[] buffer=new byte[1024];      int len=0;      while ((len=inputStream.read(buffer))!=-1){          outStream.write(buffer, 0, len);      }      outStream.close();      byte[] data=outStream.toByteArray();      String name=new String(data);      return name;  }  

}

事件监听类可以放到外边
[java] view plaincopy
package demo.filerw.clicklistener;

import android.app.Activity;
import android.content.Context;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import demo.filerw.R;
import demo.filerw.service.FileService;

public class ClickListener implements OnClickListener {

private FileService fileService;  private EditText editText;  private TextView show_text;  private Context context;  public ClickListener(Context context) {      this.context=context;      fileService = new FileService(context);      Activity activity = (Activity) context;      editText = (EditText) activity.findViewById(R.id.edit_name);      show_text = (TextView) activity.findViewById(R.id.show_text);  }  @Override  public void onClick(View v) {      // TODO Auto-generated method stub      switch (v.getId()) {      case R.id.ok_button:          String name=editText.getText().toString();          try {              fileService.saveName(name);              Toast.makeText(context, R.string.ok_succee, Toast.LENGTH_SHORT).show();          } catch (Exception e) {              // TODO Auto-generated catch block              e.printStackTrace();              //Toast.makeText(contex, R.string.ok_error, Toast.LENGTH_SHORT).show();          }          break;      case R.id.read_button:          try {              String name1 =fileService.getName();              show_text.setText(name1);          } catch (Exception e) {              // TODO Auto-generated catch block              e.printStackTrace();              Toast.makeText(context, R.string.read_error, Toast.LENGTH_SHORT).show();          }          break;      }  }  

}
Activity
[java] view plaincopy
package demo.filerw;

import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
import demo.filerw.clicklistener.ClickListener;

public class FileRWActivity extends Activity {

private Button ok_button;  private Button read_button;  /** Called when the activity is first created. */  @Override  public void onCreate(Bundle savedInstanceState) {      super.onCreate(savedInstanceState);      setContentView(R.layout.main);      ok_button = (Button) findViewById(R.id.ok_button);      read_button = (Button) findViewById(R.id.read_button);      ok_button.setOnClickListener(new ClickListener(this));      read_button.setOnClickListener(new ClickListener(this));  }  

}

main.xml
[java] view plaincopy