compile 'com.github.bumptech.glide:glide:3.7.0'

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

public class SDFileHelper {  private Context context;  public SDFileHelper() {  }  public SDFileHelper(Context context) {    super();    this.context = context;  }  //Glide保存圖片  public void savePicture(final String fileName, String url){    Glide.with(context).load(url).asBitmap().toBytes().into(new SimpleTarget<byte[]>() {      @Override      public void onResourceReady(byte[] bytes, GlideAnimation<? super byte[]> glideAnimation) {        try {          savaFileToSD(fileName,bytes);        } catch (Exception e) {          e.printStackTrace();        }      }    });  }  //往SD卡寫入文件的方法  public void savaFileToSD(String filename, byte[] bytes) throws Exception {    //如果手機已插入sd卡,且app具有讀寫sd卡的權限    if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {      String filePath = Environment.getExternalStorageDirectory().getCanonicalPath()+"/budejie";      File dir1 = new File(filePath);      if (!dir1.exists()){        dir1.mkdirs();      }      filename = filePath+ "/" + filename;      //這里就不要用openFileOutput了,那個是往手機內存中寫數據的      FileOutputStream output = new FileOutputStream(filename);      output.write(bytes);      //將bytes寫入到輸出流中      output.close();      //關閉輸出流      Toast.makeText(context, "圖片已成功保存到"+filePath, Toast.LENGTH_SHORT).show();    } else Toast.makeText(context, "SD卡不存在或者不可讀寫", Toast.LENGTH_SHORT).show();  }}

 SDFileHelper helper = new SDFileHelper(MainActivity.this); helper.savePicture("bg.jpg",url);