public static boolean sdCardIsAvailable() {
 //首先判斷外部存儲(chǔ)是否可用
 if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
  File sd = new File(Environment.getExternalStorageDirectory().getPath());
  Log.e("qq", "sd = " + sd);//sd = /storage/emulated/0
  return sd.canWrite();
 } else {
  return false;
 }

public String getSDPath() {
 File sdDir = null;
  //判斷sd卡是否存在
boolean sdCardExist = Environment.getExternalStorageState()
.equals(android.os.Environment.MEDIA_MOUNTED); 
if (sdCardExist) {
sdDir = Environment.getExternalStorageDirectory();//獲取根目錄
Log.e("qq", "外部存儲(chǔ)可用..." + sdDir.toString());
}
return sdDir.toString();
}
//使用
private void saveInRoot() {
 if (getSDPath()!=null) {
  //String fileName = getSDPath() + "/";
  //File file = new File(fileName,"123111");//參數(shù)
  //if (!file.mkdir()) {
   //Toast.makeText(ExternalStoreActivity.this, "目錄已存在...", Toast.LENGTH_SHORT).show();
  //} else {
   //Toast.makeText(ExternalStoreActivity.this, "創(chuàng)建新目錄...", Toast.LENGTH_SHORT).show();
  //}
 }
}

public File getAlbumStorageDir(String fileName) {
 // Get the directory for the user's public pictures directory.
 //在 Environment.DIRECTORY_DOWNLOADS 目錄下創(chuàng)建名為fileName的文件夾 刷新查看
 File file =
  new File(Environment.getExternalStoragePublicDirectory(Environment.
   DIRECTORY_DOWNLOADS), fileName);//參數(shù)2是文件名稱
 //mkdirs()可以創(chuàng)建多級(jí)目錄
 //mkdir()只能創(chuàng)建一級(jí)目錄
 if (!file.mkdir()) {
  Log.e(LOG_TAG, "Directory not created");
  Toast.makeText(ExternalStoreActivity.this, "目錄已存在...", Toast.LENGTH_SHORT).show();
 } else {
  Toast.makeText(ExternalStoreActivity.this, "創(chuàng)建新目錄...", Toast.LENGTH_SHORT).show();
 }
 return file;
}