基于Android扫描sd卡与系统文件的介绍

如果你做过多媒体应用，一定会苦恼过，怎样获取sd卡中的多媒体文件。android还是很强大的，如果你知道怎么调用android的api，万事就ok了。
当手机或模拟器开机时，会调用android的mediascanner，扫描sd卡和内存里的文件。以下是log信息。

12-13 15:39:11.062: verbose/mediaplayerservice(67): create new media retriever from pid 349<br>
12-13 15:39:11.082: debug/mediascannerservice(349): getdefaultlocale =zh_cn
12-13 15:39:11.122: debug/surfaceflinger(102): layer::requestbuffer(this=0x7c8c68), index=1, pid=12866, w=309, h=192 success
12-13 15:39:11.142: info/mediascanner(349): moriginalcount = 14, prune thumb flag = false<br>
12-13 15:39:11.142: debug/mediascanner(349):  prescan time: 44ms<br>
12-13 15:39:11.142: debug/mediascanner(349):     scan time: 13ms<br>
12-13 15:39:11.142: debug/mediascanner(349): postscan time: 2ms<br>
12-13 15:39:11.142: debug/mediascanner(349):    total time: 59ms<br>
12-13 15:39:11.152: debug/mediaprovider(349): un-lock thumbnail worker<br>
12-13 15:39:11.152: debug/mediaprovider(349): un-lock thumbnail worker<br>
12-13 15:39:11.182: debug/mediascannerservice(349): done scanning volume external

那么扫描后的记录它保存到哪里了呢。哈。你觉得在哪里呢？data/data/com.android.media/providers/databases/external
它存了些什么信息呢，拉出来看看吧：

那么，我们直接使用contentprovider就可以直接获取到sd卡中多媒体的信息了，你还用去listfile么？还用去自己解析媒体文件中的信息么(时长，文件名，专辑名。。应有尽有哦)？

cursor cursor = context.getcontentresolver().query(<br>    mediastore.audio.media.external_content_uri,<br>    new string[] { mediastore.audio.media._id, mediastore.audio.media.display_name, mediastore.audio.media.title,<br>      mediastore.audio.media.duration, mediastore.audio.media.artist, mediastore.audio.media.album,<br>      mediastore.audio.media.year, mediastore.audio.media.mime_type, mediastore.audio.media.size, mediastore.audio.media.data}<br>    , "_size>?", new string[]{1024*1024+""},null);

好了，最后一个问题<br> 当你往sd卡中添加一些多媒体文件的时候，android没有自动将它刷新到数据库中。那么我们怎么让它手动刷新呢，如下：

intentfilter intentfilter = new intentfilter(intent.action_media_scanner_started);
        intentfilter.addaction(intent.action_media_scanner_finished);
        intentfilter.adddatascheme("file");
        scanreceiver = new scansdfilesreceiver();
        registerreceiver(scanreceiver, intentfilter);
        sendbroadcast(new intent(intent.action_media_mounted, uri.parse("file://" + environment.getexternalstoragedirectory())));

 
private class scansdfilesreceiver extends broadcastreceiver {
        public void onreceive(context context, intent intent) {
            string action = intent.getaction();
            if (intent.action_media_scanner_started.equals(action)) {
                scanhandler.sendemptymessage(started);
            }
            if (intent.action_media_scanner_finished.equals(action)) {
                scanhandler.sendemptymessage(finished);
            }
        }
    }

 
private handler scanhandler = new handler() {
        public void handlemessage(message msg) {
            super.handlemessage(msg);
            switch (msg.what) {
            case started:
                mydialog scandialog = new mydialog(locallist.this);
                scanalertdialog = scandialog.scanfile();
                scanalertdialog.show();
                log.i(tag, "showing");
                break;
            case finished:
                arraylist<song> tempsongs = readfilelist.readdatafromsd(locallist.this, local);
                if (tempsongs != null && tempsongs.size()>0) {
                    if (songs != null && songs.size()>0) {
                        songs.clear();
                        songs.addall(tempsongs);
                        songadapter.notifydatasetchanged();
                    }else {
                        songs = new arraylist<song>();
                        songs.addall(tempsongs);
                        initsong_lv();
                    }
                }else {
                    toast.maketext(locallist.this, "sd卡中没有歌曲，请添加后再扫描", toast.length_short).show();
                }
                log.i(tag, "finish");
                if (scanalertdialog!=null && scanalertdialog.isshowing()) {
                    scanalertdialog.dismiss();
                }
                unregisterreceiver(scanreceiver);
                break;
            case dismiss:
                log.i(tag, "dismiss");
                if (scanalertdialog!=null && scanalertdialog.isshowing()) {
                    scanalertdialog.dismiss();
                }
            default:
                break;
            }