downloadmanager时Android系统下载器，使用系统下载器可以避免用stream流读入内存可能导致的内存溢出问题。以下为downloadmanager初始化部分。apkurl为下载网络路径。Environment.DIRECTORY_DOWNLOADS 为系统的下载路径。即下载至外部存储。
mDownloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
String apkUrl = "https://qd.myapp.com/myapp/qqteam/AndroidQQ/mobileqq_android.apk";
Uri resource = Uri.parse(apkUrl);
DownloadManager.Request request = new DownloadManager.Request(resource);
//下载的本地路径，表示设置下载地址为SD卡的Download文件夹，文件名为mobileqq_android.apk。
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "mobileqq_android.apk");
request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_MOBILE | DownloadManager.Request.NETWORK_WIFI);
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setVisibleInDownloadsUi(true);
request.setDescription("xiazaizhong");
//end 一些非必要的设置
id = mDownloadManager.enqueue(request);
//下载后的本地uri
uri = mDownloadManager.getUriForDownloadedFile(id);
enqueue方法为添加到下载队列，同时返回的id用于contentobserver监听下载进度.下载进度监听代码如下：
private DownloadContentObserver observer = new DownloadContentObserver();
class DownloadContentObserver extends ContentObserver {
public DownloadContentObserver() {
super(handler);
}
@Override
public void onChange(boolean selfChange) {
// updateView();
if (scheduledExecutorService != null) {
scheduledExecutorService.scheduleWithFixedDelay(runnable, 0, 3, TimeUnit.SECONDS);
}
}
}
public static ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(3);
public void updateView() {
int[] bytesAndStatus = getBytesAndStatus(id);
int currentSize = bytesAndStatus[0];//当前大小
int totalSize = bytesAndStatus[1];//总大小
int status = bytesAndStatus[2];//下载状态 1开始 2下载中 8下载完成
Message.obtain(handler, 0, currentSize, totalSize, status).sendToTarget();
}
public 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;
}
设置 DownloadContentObserver类监听下载进度，可在其重写的 onchange方法中更新UI，即updataView方法，但此会返回大量数据，在下载量大时可使用ScheduledExecutorService 设定定时任务，注册定时任务设定间隔时间查询进度，downloadcontentobserver需要在onresume 和 ondestroy方法中注册和注销代码在下，getBytesAndStatus方法获取队列中数组当前下载的进度 包括当前大小总大小，下载状态等。
注销和注册downloadcontentobserver的代码
private static final Uri CONTENT_URI = Uri.parse("content://downloads/my_downloads");
getContentResolver().registerContentObserver(CONTENT_URI, true, observer);
getContentResolver().unregisterContentObserver(observer);
定时任务中执行的runable 为更新UI的 updateView方法
Runnable runnable = new Runnable() {
@Override
public void run() {
try {
updateView();
} catch (Exception e) {
e.printStackTrace();
}
}
};
最后即是updateView方法中发送message的handeler代码，message可传入两个bundle参数和一个object对象。从handler中取出可以更新UI 或逻辑操作了，注意声明handler时传入了 mainlooper，这样不用再特地主线程中更新UI，测试中下载完成时状态码为8，具体使用时可再次测试。下载结束后可将定时任务关闭置空。
private Handler handler = new Handler(Looper.getMainLooper()) {
@Override
public void handleMessage(@NonNull @NotNull Message msg) {
super.handleMessage(msg);
if (scheduledExecutorService != null) {
int currentSize = msg.arg1;
int totalSize = msg.arg2;
Object object = msg.obj;
tvDownload.setText(String.valueOf(((float) (currentSize / totalSize)) * 100));
if ((Integer) object == 8) {
scheduledExecutorService.shutdownNow();
scheduledExecutorService = null;
Toast.makeText(ControlerActivity.this, "下载完成", Toast.LENGTH_SHORT).show();
}
Log.e(TAG, "handleMessage:" + currentSize + " " + totalSize + " " + object.toString());
}
}
};
最后测试下载的本地的uri是否正确，文件下载是否成功 Environment.getExternalStoragePublicDirectory获取外部存储的下载路径。还有下载完成点击通知跳转和下载完成监听功能不再详述。
File file=new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS)+"/mobileqq_android.apk");
if (file.exists()) {
Log.e(TAG, "exists yes"+file.length());
}else {
Log.e(TAG, "exists no" );
}