我已经创建了一个简单的应用程序，应该可以下载大型zip文件。经过一些研发，我得出的结论是我必须使用Download Manager来实现这一目标。 如果设备重新启动或互联网连接不稳定，我希望下载自动恢复。现在，该代码能够按预期下载大文件，但是如果Internet连接出现波动或系统重新启动，它将停止下载。
活动：
public class MainActivity extends ActionBarActivity {
String Download_path = "http://wickedbrains.com/map/mumbai.zip";
String Download_ID = "DOWNLOAD_ID";
SharedPreferences preferenceManager;
DownloadManager downloadManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
preferenceManager = PreferenceManager.getDefaultSharedPreferences(this);
downloadManager = (DownloadManager)getSystemService(DOWNLOAD_SERVICE);
Button btnDownload = (Button)findViewById(R.id.download);
btnDownload.setOnClickListener(new Button.OnClickListener(){
@Override
public void onClick(View arg0) {
// Locate storage location
String filepath = "";
File folder = new File(
Environment.getExternalStorageDirectory() + "/osmdroid");
boolean success = true;
if (!folder.exists()) {
success = folder.mkdir();
}
if (success) {
// Do something on success
filepath = Environment.getExternalStorageDirectory()
.getPath() + "/osmdroid";
// Deleting if zip file exists
File folder2 = Environment.getExternalStorageDirectory();
String fileName = folder2.getPath() + "/osmdroid/mumbai.zip";
File myFile = new File(fileName);
if(myFile.exists())
myFile.delete();
}
//Starting download manager to download file
Uri Download_Uri = Uri.parse(Download_path);
DownloadManager.Request request = new DownloadManager.Request(Download_Uri);
long download_id = downloadManager.enqueue(request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI |DownloadManager.Request.NETWORK_MOBILE)
.setAllowedOverRoaming(false)
.setTitle("Test")
.setDescription("Map Download")
.setDestinationInExternalPublicDir("/osmdroid","mumbai.zip"));
// long download_id = downloadManager.enqueue(request);
//Save the download id
Editor PrefEdit = preferenceManager.edit();
PrefEdit.putLong(Download_ID, download_id);
PrefEdit.commit();
}});
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
IntentFilter intentFilter = new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE);
registerReceiver(downloadReceiver, intentFilter);
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
unregisterReceiver(downloadReceiver);
}
private BroadcastReceiver downloadReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context arg0, Intent arg1) {
// TODO Auto-generated method stub
DownloadManager.Query query = new DownloadManager.Query();
query.setFilterById(preferenceManager.getLong(Download_ID, 0));
Cursor cursor = downloadManager.query(query);
if(cursor.moveToFirst()){
int columnIndex = cursor.getColumnIndex(DownloadManager.COLUMN_STATUS);
int status = cursor.getInt(columnIndex);
int columnReason = cursor.getColumnIndex(DownloadManager.COLUMN_REASON);
int reason = cursor.getInt(columnReason);
if(status == DownloadManager.STATUS_SUCCESSFUL){
//Retrieve the saved download id
long downloadID = preferenceManager.getLong(Download_ID, 0);
ParcelFileDescriptor file;
try {
file = downloadManager.openDownloadedFile(downloadID);
Toast.makeText(MainActivity.this,
"File Downloaded: " + file.toString(),
Toast.LENGTH_LONG).show();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Toast.makeText(MainActivity.this,
e.toString(),
Toast.LENGTH_LONG).show();
}
}else if(status == DownloadManager.STATUS_FAILED){
Toast.makeText(MainActivity.this,
"FAILED!\n" + "reason of " + reason,
Toast.LENGTH_LONG).show();
}else if(status == DownloadManager.STATUS_PAUSED){
Toast.makeText(MainActivity.this,
"PAUSED!\n" + "reason of " + reason,
Toast.LENGTH_LONG).show();
}else if(status == DownloadManager.STATUS_PENDING){
Toast.makeText(MainActivity.this,
"PENDING!",
Toast.LENGTH_LONG).show();
}else if(status == DownloadManager.STATUS_RUNNING){
Toast.makeText(MainActivity.this,
"RUNNING!",
Toast.LENGTH_LONG).show();
}
}
}
};
}
我要去哪里错了？我应该怎么做才能启用下载的恢复功能？
引用文档，
下载管理器将在后台进行下载，处理HTTP交互，并在发生故障或在连接更改和系统重新启动后重试下载。
我想是Download Manager，默认情况下会重试。
如果遇到问题，可以使用DownloadManager.Query类并查询COLUMN_STATUS和COLUMN_REASON以获取下载状态
编辑：
dm = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
Request request = new Request( YOUR_DOWNLOAD_URL );
long enqueue = dm.enqueue(request);
enqueue更像是下载要求ID。您可以使用该队列获取下载进度/状态
Query query = new Query();
query.setFilterById(enqueue);
Cursor c = dm.query(query);
if (c.moveToFirst()) {
int downloadStatus = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
if (DownloadManager.STATUS_SUCCESSFUL == downloadStatus) {
// download succeded
} else if (DownloadManager.STATUS_FAILED == downloadStatus){
String failedReason = c.getString(c.getColumnIndex(DownloadManager.COLUMN_REASON));
// handle failures
}
}
没有亲自测试代码。但是应该可以。
尝试获取下载失败的原因。例如，它是否可以在网络交换机wifi-> data
上运行（（如果您的错误原因是1008，这里似乎有一个已报告的错误
https://code.google.com/p/android/issues/detail?id=18462，
进一步：
[我确认此问题在2020年仍然存在，当在模拟器中进行测试并启用WiFi时，始终出现此错误（即使在Android 10中也是如此。
在模拟器中关闭WiFi似乎可以解决问题。