android 获取sd卡根目录下的指定文件

1.首先开启读取sd卡权限:

 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

2.判断sd卡是否存在:

boolean sdCardExist = Environment.getExternalStorageState()               .equals(android.os.Environment.MEDIA_MOUNTED);

3.获取根目录下指定文件(以图片做列子)

 //获得SD卡根目录路径
 sdDir =Environment.getExternalStorageDirectory();
 String sdpath = sdDir.getAbsolutePath(); 
 //获取指定图片路径
 String filepath = sdpath + File.separator + "hand.jpg";
File file = new File(filepath);
//创建一个imageView对象
 ImageView imageView = new ImageView(this);
 if (file.exists()) {
 Bitmap bm = BitmapFactory.decodeFile(filepath);
 // 将图片显示到ImageView中
 imageView.setImageBitmap(bm);
 ll.addView(imageView);}

4.附上完整代码:

 File sdDir = null;
 //判断sd卡是否存在
 boolean sdCardExist = Environment.getExternalStorageState()            .equals(android.os.Environment.MEDIA_MOUNTED);
 if(sdCardExist){
   //获得SD卡根目录路径
    sdDir = Environment.getExternalStorageDirectory();
    String sdpath = sdDir.getAbsolutePath();
    //获取指定图片路径
    String filepath = sdpath + File.separator +"hand.jpg";
    File file = new File(filepath);
    //创建一个imageView对象
    ImageView imageView = new ImageView(this);
    if (file.exists()) {
      Bitmap bm = BitmapFactory.decodeFile(filepath);
      // 将图片显示到ImageView中
        imageView.setImageBitmap(bm);
        ll.addView(imageView);}
  }