package com.wenhao.test.sddemo;import java.io.File;import android.app.Activity;import android.os.Bundle;import android.os.Environment;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.Toast;public class MainDemo extends Activity {    /** Called when the activity is first created. */        private Button button = null;    private File path;        @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                   button = (Button)findViewById(R.id.mybutton);                //检测SD卡是否存在        if (Environment.getExternalStorageState().equals(                Environment.MEDIA_MOUNTED)) {            path = Environment.getExternalStorageDirectory();        }else{            Toast.makeText(this, "没有SD卡", Toast.LENGTH_LONG).show();            finish();        }                button.setOnClickListener(new OnClickListener() {                        @Override            public void onClick(View v) {                // TODO Auto-generated method stub                                                getAllFiles(path);            }        });            }        // 遍历接收一个文件路径，然后把文件子目录中的所有文件遍历并输出来     private void getAllFiles(File root){          File files[] = root.listFiles();          if(files != null){              for (File f : files){                  if(f.isDirectory()){                      getAllFiles(f);                  }else{                      System.out.println(f);                  }              }          }      }        }