在Android 開發視訊的時候，通常都需要顯示視訊列表，而視訊列表通常都有一張視訊縮圖，那麼它是怎麼獲取的呢，

關於網路視訊的縮圖的實現方案主要有兩種：

1、後臺返回視訊時順便連縮圖的路徑都返回給你了，這樣前端壓力輕鬆。
2、後臺是返回視訊路徑，關於縮圖，前端從視訊中獲取。

那麼如何從視訊中獲取縮圖呢？

1、關於本地視訊的縮圖，官方有提供解決方案：
ThumbnailUtils.createVideoThumbnail(String filePath, int kind)；
方法便可以獲取：

Bitmap bitmap= BitmapUtil.createVideoThumbnail(url,MediaStore.Video.Thumbnails.MINI_KIND);

2、那麼網路視訊怎麼獲取呢？
經過分析MediaMetadataRetriever類，發現有一個方法，setDataSource(String uri, Map

    /**
     * Sets the data source (URI) to use. Call this
     * method before the rest of the methods in this class. This method may be
     * time-consuming.
     *
     * @param uri The URI of the input media.
     * @param headers the headers to
 
 be sent together with the request for the data
     * @throws IllegalArgumentException If the URI is invalid.
     */
    public void setDataSource(String uri,  Map<String, String> headers)
            throws IllegalArgumentException {
        int i = 0;
        String[] keys = new String[headers.size()];
        String
 
[] values = new String[headers.size()];
        for (Map.Entry<String, String> entry: headers.entrySet()) {
            keys[i] = entry.getKey();
            values[i] = entry.getValue();
            ++i;
        }

        _setDataSource(
                MediaHTTPService.createHttpServiceBinderIfNecessary(uri),
                uri,
                keys,
                values);
    }

這個方法說明了是獲取網路的資料，瞭解了原始碼就好辦，我們就依葫蘆畫瓢，自己建立一個類模仿一個方法出來：

這個方法，呼叫了retriever.setDataSource(filePath,new Hashtable

/**
     * Create a video thumbnail for a video. May return null if the video is
     * corrupt or the format is not supported.
     *
     * @param filePath the path of video file
     * @param kind could be MINI_KIND or MICRO_KIND
     */
    public static Bitmap createVideoThumbnail(String filePath, int kind) {
        Bitmap bitmap = null;
        MediaMetadataRetriever retriever = new MediaMetadataRetriever();
        try {
            if (filePath.startsWith("http://")
                    || filePath.startsWith("https://")
                    || filePath.startsWith("widevine://")) {
                retriever.setDataSource(filePath,new Hashtable<String, String>());
            }else {
                retriever.setDataSource(filePath);
            }
            bitmap = retriever.getFrameAtTime(-1);
        } catch (IllegalArgumentException ex) {
            // Assume this is a corrupt video file
            ex.printStackTrace();
        } catch (RuntimeException ex) {
            // Assume this is a corrupt video file.
            ex.printStackTrace();
        } finally {
            try {
                retriever.release();
            } catch (RuntimeException ex) {
                // Ignore failures while cleaning up.
                ex.printStackTrace();
            }
        }

        if (bitmap == null) return null;

        if (kind == MediaStore.Images.Thumbnails.MINI_KIND) {
            // Scale down the bitmap if it's too large.
            int width = bitmap.getWidth();
            int height = bitmap.getHeight();
            int max = Math.max(width, height);
            if (max > 512) {
                float scale = 512f / max;
                int w = Math.round(scale * width);
                int h = Math.round(scale * height);
                bitmap = Bitmap.createScaledBitmap(bitmap, w, h, true);
            }
        } else if (kind == MediaStore.Images.Thumbnails.MICRO_KIND) {
            bitmap = ThumbnailUtils.extractThumbnail(bitmap,
                    96,
                    96,
                    ThumbnailUtils.OPTIONS_RECYCLE_INPUT);
        }
        return bitmap;
    }

這樣就可以獲取網路視訊縮圖了，可能還存在版本相容上沒做相容，歡迎提出意見