得到SD卡的文件目录

、SDCard文件浏览器的制作：

1、原理：利用File对象的listFile()方法获得File[]数组。将数组产生的信息填充在listview中。

核心代码中的重要方法：

1. listFiles()
2. isFile()
3. isDirectory()
4. getAbsolutePath()
5. getParentFile()
   主要的逻辑代码，点击文件可以进行相应的操作，例如查看图片，查看文件等
   

   package com.hht.homework_sdcardfilebrowser;
   
   import java.io.File;
   import java.util.ArrayList;
   import java.util.HashMap;
   import java.util.List;
   import java.util.Map;
   
   import android.app.Activity;
   import android.content.Intent;
   import android.net.Uri;
   import android.os.Bundle;
   import android.view.Menu;
   import android.view.View;
   import android.webkit.MimeTypeMap;
   import android.widget.AdapterView;
   import android.widget.AdapterView.OnItemClickListener;
   import android.widget.ListView;
   import android.widget.SimpleAdapter;
   import android.widget.TextView;
   import android.widget.Toast;
   
   public class MainActivity extends Activity {
   
   	private TextView textView_main_show;
   	private ListView listView_main_filelist;
   
   	private File currentFile = null;
   
   	private File[] arrCurrentFiles = null;
   
   	@Override
   	protected void onCreate(Bundle savedInstanceState) {
   		super.onCreate(savedInstanceState);
   		setContentView(R.layout.activity_main);
   		textView_main_show = (TextView) findViewById(R.id.textView_main_show);
   		listView_main_filelist = (ListView) findViewById(R.id.listView_main_filelist);
   		if (SDCardHelper.isSDcardMounted()) {
   			currentFile = new File(SDCardHelper.getSDCardPath());
   			fillListView(currentFile);
   		} else {
   			Toast.makeText(MainActivity.this, "SDCARD不存在！", Toast.LENGTH_LONG)
   
   			.show();
   		}
   		listView_main_filelist
   				.setOnItemClickListener(new OnItemClickListener() {
   
   					@Override
   					public void onItemClick(AdapterView parent, View view,
   							int position, long id) {
   						// TODO Auto-generated method stub
   						if (arrCurrentFiles[position].isDirectory()) {
   							File[] arrSubFiles = arrCurrentFiles[position]
   									.listFiles();
   							if (arrSubFiles.length == 0) {
   								Toast.makeText(MainActivity.this, "您点击的是空目录！",
   
   								Toast.LENGTH_SHORT).show();
   							} else {
   								fillListView(arrCurrentFiles[position]);
   							}
   						} else {
   							String extension = MimeTypeMap
   									.getFileExtensionFromUrl(arrCurrentFiles[position]
   											.getAbsolutePath());
   							// setTitle(extension);
   							Intent intent = new Intent();
   							intent.setAction(android.content.Intent.ACTION_VIEW);
   							if (extension.equals("jpg")
   									|| extension.equals("gif")
   									|| extension.equals("png")
   									|| extension.equals("bmp")
   									|| extension.equals("jpeg")) {
   								intent.setDataAndType(
   										Uri.fromFile(arrCurrentFiles[position]),
   										"image/*");
   							} else if (extension.equals("mp3")
   									|| extension.equals("mp4")
   									|| extension.equals("mpg")
   									|| extension.equals("avi")
   									|| extension.equals("3gp")
   									|| extension.equals("mpeg")) {
   								intent.setDataAndType(
   										Uri.fromFile(arrCurrentFiles[position]),
   										"video/*");
   							} else if (extension.equals("au")
   									|| extension.equals("mid")) {
   								intent.setDataAndType(
   										Uri.fromFile(arrCurrentFiles[position]),
   										"audio/*");
   							} else if (extension.equals("txt")
   									|| extension.equals("xml")
   									|| extension.equals("log")
   									|| extension.equals("html")) {
   								intent.setDataAndType(
   										Uri.fromFile(arrCurrentFiles[position]),
   										"text/*");
   							} else {
   								intent.setDataAndType(
   										Uri.fromFile(arrCurrentFiles[position]),
   										"text/*");
   							}
   							startActivity(intent);
   						}
   
   					}
   				});
   	}
   
   	@Override
   	public boolean onCreateOptionsMenu(Menu menu) {
   		// Inflate the menu; this adds items to the action bar if it is present.
   		getMenuInflater().inflate(R.menu.main, menu);
   		return true;
   	}
   
   	public void clickButton(View v) {
   		switch (v.getId()) {
   		case R.id.button_main_back:
   			if (!currentFile.getAbsolutePath().equals(
   					SDCardHelper.getSDCardPath())) {
   				File file = currentFile.getParentFile();
   
   				fillListView(file);
   			}
   
   			break;
   
   		default:
   			break;
   		}
   
   	}
   
   	public void fillListView(File file) {
   
   		currentFile = file;
   		arrCurrentFiles = currentFile.listFiles();
   
   		List> list = new ArrayList>();
   		for (int i = 0; i < arrCurrentFiles.length; i++) {
   			Map map = new HashMap();
   			if (arrCurrentFiles[i].isDirectory()) {
   				map.put("imgId", R.drawable.folder);
   			} else {
   				map.put("imgId", R.drawable.file);
   			}
   			map.put("filename", arrCurrentFiles[i].getName());
   			list.add(map);
   		}
   
   		SimpleAdapter adapter = new SimpleAdapter(MainActivity.this, list,
   				R.layout.item_listview_main,
   				new String[] { "imgId", "filename" }, new int[] {
   						R.id.imageView_item_listview_type,
   						R.id.textView_item_listview_filename });
   		listView_main_filelist.setAdapter(adapter);
   		textView_main_show.setText(currentFile.getAbsolutePath());
   
   	}
   
   }