Android 删除指定文件代码

package com.tware.pdfdrop;

import java.io.File;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;

public class PdfDropActivity extends Activity{
    /** Called when the activity is first created. */
	TextView textview;
	
	@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
 
        textview = (TextView)findViewById(R.id.v_file_list);

        View clsbtn = findViewById(R.id.btn_clean);
        clsbtn.setOnClickListener(new OnClickListener(){
        	public void onClick(View v)
        	{

       			File f = new File("/sdcard");
       			
       			File[] fl = f.listFiles();
       			for (int i=0; i