判断是否有SDCard存在并获取目录 .

File file = null;
// 判断SDCard是否存在
String status = Environment.getExternalStorageState();
boolean isSDCardExist = status.equals(Environment.MEDIA_MOUNTED);
//如果存在则获取SDCard目录
if(isSDCardExist){
file = Environment.getExternalStorageDirectory();
}