最近做SDK开发，有个简单的下载功能，为了方便及不增加第三方库，遂采用了系统的DownloadManager来处理下载任务。
官网的说明：
The download manager is a system service that handles long-running HTTP downloads. Clients may request that a URI be downloaded to a particular destination file. The download manager will conduct the download in the background, taking care of HTTP interactions and retrying downloads after failures or across connectivity changes and system reboots.
Apps that request downloads through this API should register a broadcast receiver for ACTION_NOTIFICATION_CLICKED to appropriately handle when the user clicks on a running download in a notification or from the downloads UI.
Note that the application must have the Manifest.permission.INTERNET permission to use this class.
Instances of this class must be obtained using Context.getSystemService(Class) with the argument DownloadManager.class or Context.getSystemService(String) with the argument Context.DOWNLOAD_SERVICE.
下载状态：
DownloadManager.STATUS_PAUSED：下载暂停
DownloadManager.STATUS_PENDING：下载延迟
DownloadManager.STATUS_RUNNING：正在下载
DownloadManager.STATUS_SUCCESSFUL：下载完成
DownloadManager.STATUS_FAILED：下载失败
文件信息：
DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR：已下载文件大小
DownloadManager.COLUMN_TOTAL_SIZE_BYTES：文件总大小
广播：
DownloadManager.ACTION_NOTIFICATION_CLICKED：下载通知点击事件广播
最后代码如下
public class DownloadHelper {
private static final String TAG = "DownloadHelper";
private boolean debug = false;
private Context context;
/**
* 系统下载管理器
*/
private DownloadManager mDownloadManager;
/**
* 下载ID
*/
private long mDownloadId;
/**
* 文件名
*/
private String fileName;
/**
* 文件下载地址
*/
private String downloadUrl;
private boolean downloading;
/**
* 通知栏点击事件，点击进入下载详情
*/
private BroadcastReceiver mDownloadDetailsReceiver;
private final Runnable mQueryProgressRunnable = new Runnable() {
@Override
public void run() {
queryProgress();
if (downloading) {
mHandler.postDelayed(mQueryProgressRunnable, 1000);
}
}
};
private final Handler mHandler = new Handler(Looper.getMainLooper());
private DownloadListener downloadListener;
public interface DownloadListener {
void onStart();
void onProgress(long soFarSize, long totalSize);
void onFinish(String fileFullPath, long totalSize);
void onFailed();
}
public void setDownloadListener(DownloadListener listener) {
this.downloadListener = listener;
}
private DownloadHelper(Context context, String fileName, String downloadUrl) {
this.context = context;
this.fileName = fileName;
this.downloadUrl = downloadUrl;
}
public static DownloadHelper getInstance(Context context, String fileName, String downloadUrl) {
DownloadHelper helper = new DownloadHelper(context, fileName, downloadUrl);
helper.registerReceiver();
return helper;
}
/**
* 注册广播
*/
private void registerReceiver() {
mDownloadDetailsReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (DownloadManager.ACTION_NOTIFICATION_CLICKED.equals(action)) {
showDownloadList();
}
}
};
context.registerReceiver(mDownloadDetailsReceiver, new IntentFilter(DownloadManager.ACTION_NOTIFICATION_CLICKED));
}
/**
* 显示下载列表
*/
public void showDownloadList() {
Intent downloadIntent = new Intent(DownloadManager.ACTION_VIEW_DOWNLOADS);
if (downloadIntent.resolveActivity(context.getPackageManager()) != null) {
context.startActivity(downloadIntent);
}
}
/**
* 开始下载
*/
public void startDownload(String mimeType) {
if (downloadListener != null) downloadListener.onStart();
mDownloadManager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(downloadUrl));
request..setAllowedOverMetered(true)
.setAllowedOverRoaming(true)
.setTitle("Downloading " + fileName) // 通知栏标题
.setMimeType(mimeType)
.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE)
// .setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, fileName)
.setDestinationInExternalFilesDir(ContextUtils.getContext(), Environment.DIRECTORY_DOWNLOADS, fileName)
.allowScanningByMediaScanner();
try {
mDownloadId = mDownloadManager.enqueue(request); // 加入下载队列
if (mDownloadId != 0) {
startQueryProgress();
}
} catch (IllegalArgumentException e) {
if (downloadListener != null) downloadListener.onFailed();
// "更新失败", "请在设置中开启下载管理"
Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
intent.setData(Uri.parse("package:" + "com.android.providers.downloads"));
if (intent.resolveActivity(context.getPackageManager()) != null) {
context.startActivity(intent);
}
}
}
/**
* 查询下载进度
*/
private void queryProgress() {
// 通过ID向下载管理查询下载情况，返回一个cursor
Cursor c = mDownloadManager.query(new DownloadManager.Query().setFilterById(mDownloadId));
if (c != null && c.moveToFirst()) {
int status = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
logDebug("下载状态：" + status);
switch (status) {
case DownloadManager.STATUS_PAUSED: //下载暂停， 由系统触发
case DownloadManager.STATUS_PENDING: //下载延迟， 由系统触发
break;
case DownloadManager.STATUS_RUNNING: //正在下载， 由系统触发
long soFarSize = c.getLong(c.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
long totalSize = c.getLong(c.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));
if (totalSize > 0) {
logDebug(String.format("total:%s soFar:%s ", totalSize, soFarSize) + soFarSize * 1.0f / totalSize);
if (downloadListener != null) {
downloadListener.onProgress(soFarSize, totalSize);
}
}
break;
case DownloadManager.STATUS_SUCCESSFUL: //下载完成， 由系统触发
stopQueryProgress();
File downloadDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
totalSize = c.getLong(c.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));
if (downloadListener != null) {
String fullName = downloadDir.getPath() + File.separator + fileName;
logDebug(fullName);
downloadListener.onFinish(fullName, totalSize);
}
break;
case DownloadManager.STATUS_FAILED: //下载失败， 由系统触发
if (downloadListener != null) downloadListener.onFailed();
break;
}
} else {
stopQueryProgress();
if (downloadListener != null) downloadListener.onFailed();
}
closeCursor(c);
}
private void closeCursor(Cursor cursor) {
if (cursor != null && !cursor.isClosed()) {
cursor.close();
}
}
private void logDebug(String msg) {
if (debug) {
Log.e(TAG, msg);
}
}
/**
* 移除下载并删除下载文件
*/
public void removeDownload() {
mDownloadManager.remove(mDownloadId);
stopQueryProgress();
}
/**
* 开始查询下载进度
*/
private void startQueryProgress() {
downloading = true;
mHandler.post(mQueryProgressRunnable);
}
/**
* 停止查询下载进度
*/
private void stopQueryProgress() {
downloading = false;
mHandler.removeCallbacks(mQueryProgressRunnable);
}
public boolean isDownloading() {
return downloading;
}
public void onDestroy() {
try {
stopQueryProgress(); //停止查询下载进度
context.unregisterReceiver(mDownloadDetailsReceiver);
} catch (Exception ex) {
//java.lang.IllegalArgumentException: Receiver not registered:
}
}
}