最近有个需求需要下载封面图片保存到本地，并且同步到相册中。
利用Glide、Rxjava封装下以便复用。

//保存网络图片到相册
    public static void saveImageUrlToGallery(Context context, String url,OnListener listener) {
        Observable.just(url).map(new Func1<String, File>() {
            @Override
            public File call(String s) {
                File file = null;
                try {
                    file = Glide.with(context).load(s).downloadOnly(Target.SIZE_ORIGINAL, Target.SIZE_ORIGINAL).get();
                } catch (Exception e) {
                    e.printStackTrace();
                }
                return file;
            }
        }).subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Action1<File>() {
                    @Override
                    public void call(File file) {
                        if (file != null) {
                            saveImageToGallery(context,file.getAbsolutePath());
                            listener.onSuccess(null);
                        }else {
                            listener.onFail();
                        }
                    }
                });
    }

    //保存图片到相册
    public static void saveImageToGallery(Context context, String path) {
        File file = new File(path);
        //其次把文件插入到系统图库
        try {
            String filename = path.substring(path.lastIndexOf('/') + 1);
            MediaStore.Images.Media.insertImage(context.getContentResolver(),
                    file.getAbsolutePath(), filename, null);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        // 通知图库更新
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            MediaScannerConnection.scanFile(context, new String[]{file.getAbsolutePath()}, null,
                    new MediaScannerConnection.OnScanCompletedListener() {
                        public void onScanCompleted(String path, Uri uri) {
                            Intent mediaScanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
                            mediaScanIntent.setData(uri);
                            context.sendBroadcast(mediaScanIntent);
                        }
                    });
        } else {
            String relationDir = file.getParent();
            File file1 = new File(relationDir);
            context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.fromFile(file1.getAbsoluteFile())));
        }
    }