判断SD卡剩余空间是否可用

	private static final long LOW_STORAGE_THRESHOLD = 1024 * 1024 * 10;

	public static long getAvailableStorage() {		

		String storageDirectory = null;		
		storageDirectory = Environment.getExternalStorageDirectory().toString();
		
		Log.d(TAG, "getAvailableStorage. storageDirectory : " + storageDirectory);
		
		try {
			StatFs stat = new StatFs(storageDirectory);
			avaliableSize = ((long) stat.getAvailableBlocks() * (long) stat.getBlockSize());
			Log.d(TAG, "getAvailableStorage. avaliableSize : " + avaliableSize);
			return avaliableSize;
		} catch (RuntimeException ex) {
			// if we can't stat the filesystem then we don't know how many
			// free bytes exist. It might be zero but just leave it
			// blank since we really don't know.
			Log.e(TAG, "getAvailableStorage - exception. return 0");
			return 0;
		}
    }

	public static boolean checkAvailableStorage() {
		Log.d(TAG,"checkAvailableStorage E");
		
		if(getAvailableStorage() < LOW_STORAGE_THRESHOLD) {
			return false;
		}
		
		return true;
	}