获取SD卡中的图片资源并显示

1. ImageView iv = (ImageView) findViewById(R.id.image_test); 
2. Bitmap bit = BitmapFactory.decodeFile("/sdcard/dcd/images/xinwen.gif"); 
3. iv.setImageBitmap(bit);

button.setBackgroundDrawable(new BitmapDrawable(BitmapFactory.decodeFile("图片路径")));      

SD卡根目录：

String DATABASE_PATH = android.os.Environment.getExternalStorageDirectory().getAbsolutePath();