DownloadManager使用

DownloadManager介绍

简介

DownloadManager是一个系统下载服务，提供了一套下载API，并可以通知栏显示下载进度。

API使用

获取DownloadManager对象

DownloadManager是一个系统服务，通过以下方式获取：

    private DownloadManager mDownloadManager;
    mDownloadManager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);

初始化DownloadManager.Request

        DownloadManager.Request request = new DownloadManager.Request(Uri.parse(info.apkUrl));
        String subPath = info.appName + "_" + info.apkVersion + ".apk";
        request.setDestinationInExternalPublicDir("download", subPath);
        request.setTitle(info.appName);
        request.setMimeType("application/vnd.android.package-archive");
        request.allowScanningByMediaScanner();
        request.setVisibleInDownloadsUi(false);
        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE);

发送Request

将Request对象加入队列，系统就会自动启动下载，并返回一个唯一的id

    mDownloadId = mDownloadManager.enqueue(request);

DownloadManager.Query查询下载进度

下载进度需要主动去查询，API并没有提供回调的接口：

    private int[] getBytesAndStatus(long downloadId) {
        int[] bytesAndStatus = new int[]{-1, -1, 0};
        DownloadManager.Query query = new DownloadManager.Query().setFilterById(downloadId);
        Cursor c = null;
        try {
            c = mDownloadManager.query(query);
            if (c != null && c.moveToFirst()) {
                bytesAndStatus[0] = c.getInt(c.getColumnIndexOrThrow(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
                bytesAndStatus[1] = c.getInt(c.getColumnIndexOrThrow(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));
                bytesAndStatus[2] = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
            }
        } finally {
            if (c != null) {
                c.close();
            }
        }
        return bytesAndStatus;
    }

取消下载

传入之前返回的id即可取消本次下载操作

    mDownloadManager.remove(mDownloadId);

广播监听下载完成

AndroidManifest.xml中声明接收器：

        <receiver android:name="com.android.launcher3.promoted.AppDownloadBroadcastReceiver">
            <intent-filter>
                <action android:name="android.intent.action.DOWNLOAD_COMPLETE" />
                <action android:name="android.intent.action.DOWNLOAD_NOTIFICATION_CLICKED" />
            </intent-filter>
        </receiver>

public class AppDownloadBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();

        if (action.equals(DownloadManager.ACTION_DOWNLOAD_COMPLETE)) {
            long downloadId = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
            DownloadManager downloadManager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
                DownloadManager.Query query = new DownloadManager.Query();
                query.setFilterById(downloadId);
                Cursor c = downloadManager.query(query);
                boolean downloadSuccess = false;
                String localPath = null;
                String encodePath = null;
                if (c != null && c.moveToFirst()) {
                    downloadSuccess = (c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS)) == downloadManager.STATUS_SUCCESSFUL);
                    int fileUriId = c.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI);
                    String fileUri = c.getString(fileUriId);
                    LogUtils.d(TAG, "fileUri = "+fileUri);
                    if (Utilities.ATLEAST_N) {
                        if (fileUri != null) {
                            localPath = Uri.parse(fileUri).getPath();
                            encodePath = Uri.parse(fileUri).getEncodedPath();
                        }
                    }else {
                        localPath = c.getString(c.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME));
                    }
                }

        } else if (action.equals(DownloadManager.ACTION_NOTIFICATION_CLICKED)) {

        }
    }
}

小结

DownloadManager作为系统组件，对于单个文件的下载很方便，但是对于需求复杂，或者批量并发下载的场景，不是很适合，有一定局限性，希望Google后面会给予更多的完善。