我有一个应用程序需要连接到 Internet 才能执行某些操作，但是当没有可用的 Internet 时它会崩溃。我读到我需要使用 try catch 括号以防万一没有互联网。正如您在 AsyncTask 中看到的那样，我尝试使用它，但它不起作用。我不知道为什么。应用程序崩溃。如何处理 try catch 将它放在我的代码中的什么位置？
如果应用程序在进程进行时丢失了 Internet 连接，那又会怎样。我应该如何处理这件事，这样我的应用程序就不会崩溃。非常感谢。
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.home);
lv = (ListView) findViewById(R.id.mybookslistview);
new connectToServer().execute();
}
class connectToServer extends AsyncTask<Void, Void, Void>{
CustomListViewAdapter adapter;
HttpResponse response;
@Override
protected Void doInBackground(Void... params) {
ids_list.clear();
names_list.clear();
writers_list.clear();
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(link);
ArrayList<NameValuePair> list = new ArrayList<NameValuePair>();
list.add(new BasicNameValuePair(word, connectionPurpose));
try {
post.setEntity(new UrlEncodedFormEntity(list, HTTP.UTF_8));
response = client.execute(post);
BufferedReader br = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
sb = new StringBuffer();
String tempVar = "";
while((tempVar = br.readLine()) != null){
sb.append(tempVar);
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
//Get data from stringbuffer and put it in array list
if(!sb.toString().trim().contentEquals("null")){
content_array = sb.toString().split(",");
for(int s = 0; s < content_array.length; s++){
if(content_array[s].contains("-")){
String temp[] = content_array[s].split("-");
ids_list.add(temp[0].trim());
names_list.add(temp[1].trim());
writers_list.add(temp[2].trim());
}
}
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
connManager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);
mWifi = connManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
if(!mWifi.isConnected()){
adb = new AlertDialog.Builder(Home.this);
adb.setMessage("لا يوجد إنترنت. قم بتفعيل الإنترنت ثم حاول مرة أخرى.");
adb.setPositiveButton("حاول مجددا", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface arg0, int arg1) {
new connectToServer().execute();
}
});
adb.setNegativeButton("إغلاق التطبيق", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
});
//It shows dialog if no connection
adb.create().show();
}else{
list = new ArrayList<Home.ListViewItem>();
for(x = 0; x < ids_list.size(); x++){
list.add(new ListViewItem(){{bookName = names_list.get(x); writerName = writers_list.get(x);}});
}
adapter = new CustomListViewAdapter(Home.this, list);
lv.setAdapter(adapter);
if(sb.toString().trim().contentEquals("null")){
Toast.makeText(Home.this, "لا توجد نتائج.", Toast.LENGTH_LONG).show();
}
}
这是我的日志：
java.net.UnknownHostException: Unable to resolve host "globalmall.ca": No address associated with hostname
at java.net.InetAddress.lookupHostByName(InetAddress.java:424)
at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
at java.net.InetAddress.getAllByName(InetAddress.java:214)
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)
at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:670)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:509)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
at readit.Mansour.inc.Home$connectToServer.doInBackground(Home.java:106)
at readit.Mansour.inc.Home$connectToServer.doInBackground(Home.java:1)
at android.os.AsyncTask$2.call(AsyncTask.java:287)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
at java.util.concurrent.FutureTask.run(FutureTask.java:137)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
at java.lang.Thread.run(Thread.java:856)
Caused by: libcore.io.GaiException: getaddrinfo failed: EAI_NODATA (No address associated with hostname)
at libcore.io.Posix.getaddrinfo(Native Method)
at libcore.io.ForwardingOs.getaddrinfo(ForwardingOs.java:55)
at java.net.InetAddress.lookupHostByName(InetAddress.java:405)
... 18 more
Caused by: libcore.io.ErrnoException: getaddrinfo failed: ENETUNREACH (Network is unreachable)
... 21 more
threadid=13: thread exiting with uncaught exception (group=0x40e582a0)