Android 4 学习（14）：Internet Resources

参考《Professional Android 4 Development》

使用Internet资源

打开URI

String myFeed = getString(R.string.my_feed);
try {
　　URL url = new URL(myFeed);
　　// Create a new HTTP URL connection
　　URLConnection connection = url.openConnection();
　　HttpURLConnection httpConnection = (HttpURLConnection)connection;
　　int responseCode = httpConnection.getResponseCode();
　　if (responseCode == HttpURLConnection.HTTP_OK) {
　　　　InputStream in = httpConnection.getInputStream();
　　　　processStream(in);
　　}
}catch (MalformedURLException e) {
　　Log.d(TAG, “Malformed URL Exception.”);
}catch (IOException e) {
　　Log.d(TAG, “IO Exception.”);
}

使用Download Manager

Download Manager是一个系统服务，可以这样获取：

String serviceString = Context.DOWNLOAD_SERVICE;
DownloadManager downloadManager;
downloadManager = (DownloadManager)getSystemService(serviceString);

开始下载

下载实际是将一个Download请求加入到下载队列的过程：

String serviceString = Context.DOWNLOAD_SERVICE;
DownloadManager downloadManager;
downloadManager = (DownloadManager)getSystemService(serviceString);
Uri uri = Uri.parse(“http://developer.android.com/shareables/icon_templates-v4.0.zip”);
DownloadManager.Request request = new Request(uri);
long reference = downloadManager.enqueue(request);

设置“限Wifi条件下下载”：

request.setAllowedNetworkTypes(Request.NETWORK_WIFI);

下载结束

IntentFilter filter = new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE);
BroadcastReceiver receiver = new BroadcastReceiver() {
　　@Override
　　public void onReceive(Context context, Intent intent) {
　　　　long reference = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
　　　　if (myDownloadReference == reference) {
　　　　　　// Do something with downloaded file.
　　　　}
　　}
};

registerReceiver(receiver, filter);

修改下载文件夹

以写入SD卡为例，首先要获得写SD卡的权限：

<uses-permission android:name=”android.permission.WRITE_EXTERNAL_STORAGE”/>

设置存储路径：

request.setDestinationUri(Uri.fromFile(f));

存储文件：

request.setDestinationInExternalFilesDir(this, Environment.DIRECTORY_DOWNLOADS, “Bugdroid.png”);

取消或删除下载:

downloadManager.remove(REFERENCE_1, REFERENCE_2, REFERENCE_3);

获取下载信息

@Override
public void onReceive(Context context, Intent intent) {
　　long reference = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
　　if (reference == myDownloadReference) {
　　　　Query myDownloadQuery = new Query();
　　　　myDownloadQuery.setFilterById(reference);
　　　　Cursor myDownload = downloadManager.query(myDownloadQuery);
　　　　if (myDownload.moveToFirst()) {
　　　　　　int fileNameIdx = myDownload.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME);
　　　　　　int fileUriIdx = myDownload.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI);
　　　　　　String fileName = myDownload.getString(fileNameIdx);
　　　　　　String fileUri = myDownload.getString(fileUriIdx);
　　　　// TODO Do something with the file.
　　　　}
　　　　myDownload.close();
　　}
}