android显示视频预览

读sd卡中的mp4文件的权限

   fun showVideo() {
   		// 比如显示sdcard对应app的data中的kongfu.mp4
        val video: String = getExternalFilesDir("")!!.getAbsolutePath() + "/kongfu.mp4"
        val file: File = File(video)
        if (!file.exists()) {
            Log.e(TAG, "file:${video} not exists")
            return
        }

        lifecycleScope.launch(Dispatchers.Main) {
            val firstframe = getFirstframeDrawable(video)
            if (firstframe != null) {
            	// iv_first_frame是一个ImageView
                iv_first_frame.setVisibility(View.VISIBLE)
                iv_first_frame.setImageBitmap(firstframe)
            }
        }
    }

    
    private suspend fun getFirstframeDrawable(url: String): Bitmap? {
        val mmr = MediametadataRetriever()
        Log.d(TAG, "video_url = $url")
        return try {
            mmr.setDataSource(url)
            mmr.frameAtTime
        } catch (e: Exception) {
            e.printStackTrace()
            null
        }
    }

如果这么调 mmr.setDataSource(url, HashMap())
会提示如下错误：
android java.lang.RuntimeException: setDataSource failed: status = 0xFFFFFFEA

作者：帅得不敢出门