1.由于需要删除文件,因此需要如下权限: 
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission> 
2.核心代码  
package com.example.deleteyoumi; 
import java.io.File; 
import android.os.Bundle; 
import android.os.Handler; 
import android.os.Message; 
import android.app.Activity; 
import android.view.Menu; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.Toast; 
/* 
*@author: ZhengHaibo 
*web: http://blog.csdn.net/nuptboyzhb 
*mail: zhb931706659@126.com 
*2013-4-28 Nanjing,njupt,China 
*/ 
public class DeleteYouMiMainActivity extends Activity implements 
OnClickListener { 
private Button deleteButton; 
private final static String youmiPathString = "/mnt/sdcard/Android/data/.youmicache/";//文件夹的路径 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.activity_delete_you_mi_main); 
deleteButton = (Button) findViewById(R.id.delete_youmi); 
deleteButton.setOnClickListener(this); 
} 
@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
// Inflate the menu; this adds items to the action bar if it is present. 
getMenuInflater().inflate(R.menu.delete_you_mi_main, menu); 
return true; 
} 
@Override 
public void onClick(View v) { 
// TODO Auto-generated method stub 
switch (v.getId()) { 
case R.id.delete_youmi: 
File file = new File(youmiPathString); 
DeleteFile(file); 
mHandler.sendEmptyMessage(1); 
break; 
default: 
break; 
} 
} 
Handler mHandler = new Handler() { 
public void handleMessage(Message msg) { 
switch (msg.what) { 
case 0: 
Toast.makeText(getApplicationContext(), "文件或文件夹不存在", Toast.LENGTH_LONG).show(); 
break; 
case 1: 
Toast.makeText(getApplicationContext(), "删除成功!", Toast.LENGTH_LONG).show(); 
break; 
default: 
break; 
} 
}; 
}; 
/** 
* 递归删除文件和文件夹 
* 
* @param file 
* 要删除的根目录 
*/ 
public void DeleteFile(File file) { 
if (file.exists() == false) { 
mHandler.sendEmptyMessage(0); 
return; 
} else { 
if (file.isFile()) { 
file.delete(); 
return; 
} 
if (file.isDirectory()) { 
File[] childFile = file.listFiles(); 
if (childFile == null || childFile.length == 0) { 
file.delete(); 
return; 
} 
for (File f : childFile) { 
DeleteFile(f); 
} 
file.delete(); 
} 
} 
} 
} 
 3.拓展 本文是以删除为例。当然,对于遍历某文件夹下的所有文件均可用这个方法。如搜索.mp3文件等。