Android：在下载数据时处理意外的互联网断开 [英] Android: handle unexpected internet disconnect while downloading data
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问题描述
注意：我在一个线程中调用这个函数，以便UI不会被阻止。 p>
public static boolean getFromRemote（String link，String fileName，Context context）{
boolean dataReceived = false;
ConnectivityManager connec =（ConnectivityManager）context.getSystemService（Context.CONNECTIVITY_SERVICE）;
if（connec.getNetworkInfo（0）.isConnected（）|| connec.getNetworkInfo（1）.isConnected（））{
try {
HttpClient httpClient = new DefaultHttpClient ）;
HttpGet httpGet = new HttpGet（link）;
HttpParams params = httpClient.getParams（）;
HttpConnectionParams.setConnectionTimeout（params，30000）;
HttpConnectionParams.setSoTimeout（params，30000）;
HttpResponse响应;
response = httpClient.execute（httpGet）;
int statusCode = response.getStatusLine（）。getStatusCode（）;
if（statusCode == 200）{
HttpEntity entity = response.getEntity（）;
InputStream in = null;
OutputStream output = null;
尝试{
in = entity.getContent（）;
String secondLevelCacheDir = context.getCacheDir（）+ fileName;
文件imageFile = new File（secondLevelCacheDir）;
output = new FileOutputStream（imageFile）;
IOUtilities.copy（in，output）;
output.flush（）;
} catch（IOException e）{
Log.e（SAVING，无法加载xml，e）;
} finally {
IOUtilities.closeStream（in）;
IOUtilities.closeStream（output）;
dataReceived = true;
}
}
} catch（SocketTimeoutException e）{
//处理未连接到客户端！
Log.d（SocketTimeoutException Thrown，e.toString（））;
dataReceived = false;
} catch（ClientProtocolException e）{
//处理未连接到客户端！
Log.d（ClientProtocolException Thrown，e.toString（））;
dataReceived = false;
} catch（MalformedURLException e）{
// TODO自动生成的catch块
e.printStackTrace（）;
dataReceived = false;
Log.d（MalformedURLException Thrown，e.toString（））;
} catch（IOException e）{
// TODO自动生成的catch块
e.printStackTrace（）;
dataReceived = false;
Log.d（IOException Thrown，e.toString（））;
}
}
return dataReceived;
}
解决方案
在开始网络通信之前检查网络是否可用的以下代码片段（预防胜于治疗？）。一旦通信开始，我只能希望网络保持可用。如果没有，我将捕获异常并向用户显示一条消息。
public boolean isNetworkAvailable（）{
Context context = getApplicationContext（）;
ConnectivityManager连接=（ConnectivityManager）context.getSystemService（Context.CONNECTIVITY_SERVICE）;
if（connectivity == null）{
boitealerte（this.getString（R.string.alert），getSystemService rend null）;
} else {
NetworkInfo [] info = connectivity.getAllNetworkInfo（）;
if（info！= null）{
for（int i = 0; i< info.length; i ++）{
if（info [i] .getState（）== NetworkInfo .State.CONNECTED）{
return true;
}
}
}
}
return false;
}
您可以附加任何线程的DefaultThreadHandler，如果有任何异常，将使用
//使用静态函数附加一个线程的处理程序
Thread.setDefaultUncaughtExceptionHandler（handler）;
//创建一个处理程序
private Thread.UncaughtExceptionHandler handler =
new Thread.UncaughtExceptionHandler（）{
public void uncaughtException（Thread thread，Throwable ex）{
Log.e（TAG，未捕获的例外，ex）;
showDialog（ex）;
}
};
void showDialog（Throwable t）{
AlertDialog.Builder builder = new AlertDialog.Builder（mContext）;
builder
.setTitle（Exception）
.setMessage（t.toString（））
.setPositiveButton（Okay，null）
.show（） ;
}
I have here a function that downloads data from a remote server to file. I am still not confident with my code. My question is, what if while reading the stream and saving the data to a file and suddenly I was disconnected in the internet, will these catch exceptions below can really catch that kind of incident? If not, can you suggest how to handle this kind of incident?
Note: I call this function in a thread so that the UI won't be blocked.
public static boolean getFromRemote(String link, String fileName, Context context){
boolean dataReceived = false;
ConnectivityManager connec = (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
if (connec.getNetworkInfo(0).isConnected() || connec.getNetworkInfo(1).isConnected()){
try {
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(link);
HttpParams params = httpClient.getParams();
HttpConnectionParams.setConnectionTimeout(params, 30000);
HttpConnectionParams.setSoTimeout(params, 30000);
HttpResponse response;
response = httpClient.execute(httpGet);
int statusCode = response.getStatusLine().getStatusCode();
if (statusCode == 200){
HttpEntity entity = response.getEntity();
InputStream in = null;
OutputStream output = null;
try{
in = entity.getContent();
String secondLevelCacheDir = context.getCacheDir() + fileName;
File imageFile = new File(secondLevelCacheDir);
output= new FileOutputStream(imageFile);
IOUtilities.copy(in, output);
output.flush();
} catch (IOException e) {
Log.e("SAVING", "Could not load xml", e);
} finally {
IOUtilities.closeStream(in);
IOUtilities.closeStream(output);
dataReceived = true;
}
}
}catch (SocketTimeoutException e){
//Handle not connecting to client !!!!
Log.d("SocketTimeoutException Thrown", e.toString());
dataReceived = false;
} catch (ClientProtocolException e) {
//Handle not connecting to client !!!!
Log.d("ClientProtocolException Thrown", e.toString());
dataReceived = false;
}catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
dataReceived = false;
Log.d("MalformedURLException Thrown", e.toString());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
dataReceived = false;
Log.d("IOException Thrown", e.toString());
}
}
return dataReceived;
}
解决方案
I use the following snippet to check if Network is Available before I start a network communication(Prevention better than cure?). Once the communication starts, I can only hope that the network remains available throughout. If not, I would catch Exception thrown and display a message to the user.
public boolean isNetworkAvailable() {
Context context = getApplicationContext();
ConnectivityManager connectivity = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
if (connectivity == null) {
boitealerte(this.getString(R.string.alert),"getSystemService rend null");
} else {
NetworkInfo[] info = connectivity.getAllNetworkInfo();
if (info != null) {
for (int i = 0; i < info.length; i++) {
if (info[i].getState() == NetworkInfo.State.CONNECTED) {
return true;
}
}
}
}
return false;
}
You can attach a DefaultThreadHandler with any thread which would be used if any exception go uncaught in the exception-raising code.
[EDIT: Adding sample code]
//attaching a Handler with a thread using the static function
Thread.setDefaultUncaughtExceptionHandler(handler);
//creating a Handler
private Thread.UncaughtExceptionHandler handler=
new Thread.UncaughtExceptionHandler() {
public void uncaughtException(Thread thread, Throwable ex) {
Log.e(TAG, "Uncaught exception", ex);
showDialog(ex);
}
};
void showDialog(Throwable t) {
AlertDialog.Builder builder=new AlertDialog.Builder(mContext);
builder
.setTitle("Exception")
.setMessage(t.toString())
.setPositiveButton("Okay", null)
.show();
}
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