我得到了一个AsyncTask，应该检查对主机名的网络访问。但是doInBackground()永远不会超时。有人知道吗?
public class HostAvailabilityTask extends AsyncTask<String, Void, Boolean> {
private Main main;
public HostAvailabilityTask(Main main) {
this.main = main;
}
protected Boolean doInBackground(String... params) {
Main.Log("doInBackground() isHostAvailable():"+params[0]);
try {
return InetAddress.getByName(params[0]).isReachable(30);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return false;
}
protected void onPostExecute(Boolean... result) {
Main.Log("onPostExecute()");
if(result[0] == false) {
main.setContentView(R.layout.splash);
return;
}
main.continueAfterHostCheck();
}
}
if(isConnected()){
Toast.makeText(getApplication(),"Thank you",Toast.LENGTH_SHORT).show();
}
else{
AlertDialog.Builder builder =
new AlertDialog.Builder(this, R.style.AppCompatAlertDialogStyle);
builder.setTitle("Amar Bhat");
builder.setMessage("Oops...You are not connected to Internet!!!");
builder.setPositiveButton("OK", null);
builder.setNegativeButton("Cancel", null);
builder.show();
//Toast.makeText(getApplication(),"You are not connected",Toast.LENGTH_SHORT).show();
}
//And outside the class define isConnected()
public boolean isConnected(){
ConnectivityManager connMgr = (ConnectivityManager) getSystemService(Activity.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isConnected())
return true;
else
return false;
}
// In minifest add these permission
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
下面是一些现代代码，使用AsynTask来解决android崩溃的问题，当你尝试在主线程上连接并为用户引入一个带有冲洗和重复选项的警报。
class TestInternet extends AsyncTask<Void, Void, Boolean> {
@Override
protected Boolean doInBackground(Void... params) {
try {
URL url = new URL("http://www.google.com");
HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
urlc.setConnectTimeout(3000);
urlc.connect();
if (urlc.getResponseCode() == 200) {
return true;
}
} catch (MalformedURLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
return false;
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}
return false;
}
@Override
protected void onPostExecute(Boolean result) {
if (!result) { // code if not connected
AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setMessage("An internet connection is required.");
builder.setCancelable(false);
builder.setPositiveButton(
"TRY AGAIN",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
new TestInternet().execute();
}
});
AlertDialog alert11 = builder.create();
alert11.show();
} else { // code if connected
doMyStuff();
}
}
}
...
new TestInternet().execute();
在我目前所见过的所有方法中，最短、最干净的方法应该是:
public final static boolean isConnected( Context context )
{
final ConnectivityManager connectivityManager =
(ConnectivityManager) context.getSystemService( Context.CONNECTIVITY_SERVICE );
final NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
return networkInfo != null && networkInfo.isConnected();
}
PS:这不会ping任何主机，它只是检查连接状态，所以如果你的路由器没有互联网连接，而你的设备连接到它，这个方法将返回true，尽管你没有互联网。
对于实际的测试，我建议执行一个HttpHead请求(例如到www.google.com)并检查状态，如果它是200 OK，一切正常，并且您的设备有互联网连接。
if(isConnected()){
Toast.makeText(getApplication(),"Thank you",Toast.LENGTH_SHORT).show();
}
else{
AlertDialog.Builder builder =
new AlertDialog.Builder(this, R.style.AppCompatAlertDialogStyle);
builder.setTitle("Amar Bhat");
builder.setMessage("Oops...You are not connected to Internet!!!");
builder.setPositiveButton("OK", null);
builder.setNegativeButton("Cancel", null);
builder.show();
//Toast.makeText(getApplication(),"You are not connected",Toast.LENGTH_SHORT).show();
}
//And outside the class define isConnected()
public boolean isConnected(){
ConnectivityManager connMgr = (ConnectivityManager) getSystemService(Activity.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isConnected())
return true;
else
return false;
}
// In minifest add these permission
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
我已经尝试了近5+不同的android方法，发现这是谷歌提供的最佳解决方案，特别是android:
try {
HttpURLConnection urlConnection = (HttpURLConnection)
(new URL("http://clients3.google.com/generate_204")
.openConnection());
urlConnection.setRequestProperty("User-Agent", "Android");
urlConnection.setRequestProperty("Connection", "close");
urlConnection.setConnectTimeout(1500);
urlConnection.connect();
if (urlConnection.getResponseCode() == 204 &&
urlConnection.getContentLength() == 0) {
Log.d("Network Checker", "Successfully connected to internet");
return true;
}
} catch (IOException e) {
Log.e("Network Checker", "Error checking internet connection", e);
}
它比任何其他可用的解决方案都更快、高效和准确。
