sd卡上的圖片資料夾名稱是Pictures
獲取sd卡根路徑下的api

String path = Environment.getExternalStorageDirectory().getAbsolutePath()+"/"+"Pictures"+"/"+"01.jpg";//獲取視訊路徑

1先加讀取sd卡許可權

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

2程式碼

	private  List<String> mListString =getImagePathFromSD();
	private ImageSwitcher mImagSwitcher ;

	mImagSwitcher  = (ImageSwitcher) findViewById(R.id.imagV_ad);
		if(mImagSwitcher!=null){
			mImagSwitcher.setFactory(new ViewSwitcher.ViewFactory() {
	            @Override
	            public View makeView() {
	                // makeView返回的是當前需要顯示的ImageView控制元件，用於填充進ImageSwitcher中
	                return new ImageView(SpeechMainActivity.this);
	            }
	        });
		}
	if(mImagSwitcher!=null){
			        mImagSwitcher.postDelayed(new Runnable() {
			            int currentIndex= 0;
			            @Override
			            public void run() {
//				                mImagSwitcher.setImageResource(images[currentIndex]);
			            		Log.d(TAG, "mListString:"+mListString.get(currentIndex));
				                Bitmap bit = BitmapFactory.decodeFile(mListString.get(currentIndex));
				                Drawable drawable = new BitmapDrawable(bit);
				                mImagSwitcher.setBackgroundDrawable(drawable); 
				                if(currentIndex ==(mListString.size() - 1))
				                    currentIndex = 0;
				                else
				                    currentIndex++;
				                mImagSwitcher.postDelayed(this,1000);
			            }
			        },200);
				}		




	
	 /** 
     * 從sd卡獲取圖片資源 
     * @return 
     */  
    private List<String> getImagePathFromSD() {  
        // 圖片列表  
        List<String> imagePathList = new ArrayList<String>();  
        // 得到sd卡內image資料夾的路徑   File.separator(/)   
//        String path = Environment.getExternalStorageDirectory().getAbsolutePath()+"/"+"Pictures"+"/"+"01.jpg";//獲取視訊路徑
    	
        String filePath = Environment.getExternalStorageDirectory().getAbsolutePath() +"/"+"Pictures";
        // 得到該路徑資料夾下所有的檔案  
        File fileAll = new File(filePath);  
        File[] files = fileAll.listFiles();  
        // 將所有的檔案存入ArrayList中,並過濾所有圖片格式的檔案  
        for (int i = 0; i < files.length; i++) {  
            File file = files[i];  
            if (checkIsImageFile(file.getPath())) {  
                imagePathList.add(file.getPath());  
            }  
        }  
        // 返回得到的圖片列表  
        return imagePathList;  
    }  
    /** 
    * 檢查副檔名，得到圖片格式的檔案 
    * @param fName  檔名 
    * @return 
    */  
   @SuppressLint("DefaultLocale")  
   private boolean checkIsImageFile(String fName) {  
       boolean isImageFile = false;  
       // 獲取副檔名  
       String FileEnd = fName.substring(fName.lastIndexOf(".") + 1,  
               fName.length()).toLowerCase();  
       if (FileEnd.equals("jpg") || FileEnd.equals("png") || FileEnd.equals("gif")  
               || FileEnd.equals("jpeg")|| FileEnd.equals("bmp") ) {  
           isImageFile = true;  
       } else {  
           isImageFile = false;  
       }  
       return isImageFile;  
   }