Android你要的DownloadManager

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实现样式

• DownloadManager 是android官方下载通道，一般都是没有问题的，坑点就是不同厂商会做不同的优化，所以要注意Download 文件夹是否初始化（PS：外置卡可能没有Download文件夹）。

• 如果定制Rom不支持DownloadManager,最好的方式是跳转到浏览器进行下载，但是如何检测DownloadManager是否可用，我也是参考了别人的代码，如果有遇到问题的朋友，可以进行相关交流，参考链接放在文章尾部。

• 大体思路解析

  • 下载完成之后，如果APP仍然在运行，则直接监听下载完成广播，直接启动APP

  • 如果系统DownloadManager仍然正在下载，然而APP被杀死（APP启动后，下载线程先检测是否存在下载任务，有重复利用的任务时候，不新建任务：PS，android3.0之后，首次安装未启动，或者被强制杀死的APP，静态广播注册是接收不到系统广播的，所以只能在APP被启动的时候检测）

• 打开APP，启动更新线程的时候，检测是否存在
  • DownloadManager 会保存各种下载状态任务（等待下载,下载中...,暂停,下载失败，下载成功），我们只要查询出这些状态下的任务，重复利用就进行了相当大的优化。
  • 测试主要发现华为Mate9机型启动下载任务会延时，进行相关优化，发现还是存在相应的问题，于是采用浏览器下载进行兼容。（PS：估计国内其他机型也会遇到类似的问题，当然自己实现下载通道也是可以的）

• 查询手机DownloadManager 任务，确认下载任务是否已经存在

public CursorBean queryProcess(String fileName) {
CursorBean targetBean = null;
if (TextUtils.isEmpty(fileName)) {
return targetBean;
}
int status_query = DownloadManager.STATUS_PENDING | DownloadManager.STATUS_RUNNING
| DownloadManager.STATUS_PAUSED | DownloadManager.STATUS_SUCCESSFUL | DownloadManager.STATUS_FAILED;
Cursor c = null;
try {
c = getCursor(true, status_query);
while (c.moveToNext()) {
CursorBean queryBean = new CursorBean();
long downId = c.getLong(c.getColumnIndex(DownloadManager.COLUMN_ID));
int reason = c.getInt(c.getColumnIndexOrThrow(DownloadManager.COLUMN_REASON));
int status = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
String uri = c.getString(c.getColumnIndex(DownloadManager.COLUMN_URI));
String title = c.getString(c.getColumnIndex(DownloadManager.COLUMN_TITLE));
String local_url = c.getString(c.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));
String media_type = c.getString(c.getColumnIndex(DownloadManager.COLUMN_MEDIA_TYPE));
String description = c.getString(c.getColumnIndex(DownloadManager.COLUMN_DESCRIPTION));
long timeStamp = c.getLong(c.getColumnIndex(DownloadManager.COLUMN_LAST_MODIFIED_TIMESTAMP));

            Log.d("download-kk", "description | " + description + "\r\n"
                    + "uri | " + uri + "\r\n"
                    + "media_type |" + media_type + "\r\n"
                    + "local_url |" + local_url + "\r\n");
            String filePath = getDownloadFile(c);
            queryBean.setId(downId);
            queryBean.setTitle(title);
            queryBean.setFile(filePath);
            queryBean.setStatus(status);
            queryBean.setTimeStamp(timeStamp);
            if (!TextUtils.isEmpty(filePath) && fileName.contains(fileName)) {
                if (reason != DownloadManager.PAUSED_WAITING_TO_RETRY
                        && reason != DownloadManager.STATUS_FAILED
                        && reason != DownloadManager.STATUS_PAUSED) {
                    if (null == targetBean) {
                        targetBean = new CursorBean();
                    }
                    if (timeStamp > targetBean.getTimeStamp()) {
                        if (targetBean != null && targetBean.getId() != 0) {
                            getDownloadMgr().remove(downId);
                        }
                        targetBean = queryBean;
                    }
                } else {
                    try {
                        getDownloadMgr().remove(downId);
                    } catch (Exception ex) {
                        ex.printStackTrace();
                    }
                }
            }
        }

    } catch (Exception ex) {
        ex.printStackTrace();
    } 

* 启动新的下载任务(注意开始的初始化文件夹，这个是一个坑)

public long download(String title, String defName, String url) {
try {
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).mkdirs();
final Uri parse = Uri.parse(url);
final DownloadManager.Request request = new DownloadManager.Request(parse);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
request.allowScanningByMediaScanner();
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
}
request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_MOBILE | DownloadManager.Request.NETWORK_WIFI);
request.setAllowedOverRoaming(false);
request.setMimeType(MimeTypeMap.getSingleton().getMimeTypeFromExtension(MimeTypeMap.getFileExtensionFromUrl(url)));
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setVisibleInDownloadsUi(true);
request.setTitle(String.valueOf(title));
//set this to fileName
url = getFileName(defName, parse);
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, url);
return ((DownloadManager) mContext.getSystemService(Context.DOWNLOAD_SERVICE)).enqueue(request);
} catch (Exception e) {
e.printStackTrace();
}
return -1;
}

 * 重复利用已经存在的任务

@Override
public void run() {
String fileName = mLoadMgr.getFileName(DEF_APP_NAME, mUrl);
CursorBean historyBean = mLoadMgr.queryProcess(fileName);
if (historyBean != null && historyBean.getId() != -1) {//证明有下载的线程
int status = historyBean.getStatus();
switch (status) {
case DownloadManager.STATUS_SUCCESSFUL:
long timeDiff = System.currentTimeMillis() - historyBean.getTimeStamp();
double hour = (timeDiff) / 1000D / 60D / 60D;//时效是一个小时
boolean exists = new File(historyBean.getFile()).exists();
if (hour <= 1 && timeDiff > 0 && exists) {
if (mHandler != null) {
Message msg = Message.obtain();
msg.what = PROCESS;
msg.obj = new Integer(100);
mHandler.sendMessage(msg);
}
mLoadMgr.install(historyBean.getFile(), AUTHORITY_PATH);
} else {
mLoadId = mLoadMgr.reload(mLoadId, mLoadName, DEF_APP_NAME, mUrl);
}
break;
case DownloadManager.STATUS_PENDING:
case DownloadManager.STATUS_RUNNING:
case DownloadManager.STATUS_PAUSED:
mLoadId = historyBean.getId();
break;
default:
mLoadId = mLoadMgr.reload(mLoadId, mLoadName, DEF_APP_NAME, mUrl);
break;
}

    } else {
        mLoadId = mLoadMgr.reload(mLoadId, mLoadName, DEF_APP_NAME, mUrl);
    }
}

*****
[Demo工程下载地址]
--http://git.oschina.net/jiake_xiaoyu/downloadmanager

[浏览器下载APP：参考]
--http://www.cnblogs.com/liyiran/p/6393813.html
[DownloadStatus]
http://blog.csdn.net/lonewolf521125/article/details/41477023