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();
}
}
不要检查WIFI连接或移动数据连接，试着点击任何托管域。以便您可以检查WIFI/Mobile连接是否具有连接公共互联网的能力。
如果您的移动设备能够连接到所提供的公共域，则将返回以下内容。
boolean isReachable()
{
boolean connected = false;
String instanceURL = "Your trusted domain name";
Socket socket;
try {
socket = new Socket();
SocketAddress socketAddress = new InetSocketAddress(instanceURL, 80);
socket.connect(socketAddress, 5000);
if (socket.isConnected()) {
connected = true;
socket.close();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
socket = null;
}
return connected;
}
希望对大家有所帮助。
Android提供了ConnectivityManager类来了解互联网连接状态。下面的方法将是非常有用的，以了解互联网连接状态。
首先在AndroidManifest.xml中添加INTERNET和ACCESS_NETWORK_STATE权限
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
然后使用下面的方法检查设备是否连接到互联网。如果设备已连接到互联网，此方法将返回true。
public boolean isInternetAvailable(Context context) {
ConnectivityManager connectivityManager = (ConnectivityManager)
context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = connectivityManager.getActiveNetworkInfo();
return activeNetwork != null
&& activeNetwork.isConnectedOrConnecting();
}
参考链接:—http://www.androidtutorialshub.com/android-check-internet-connection-status/
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。
Jetpack组成/芬兰湾的科特林
根据Levite的回答，我们可以在Jetpack Compose中使用这个组合:
val DNS_SERVERS = listOf("8.8.8.8", "1.1.1.1", "4.2.2.4")
const val INTERNET_CHECK_DELAY = 3000L
@Composable
fun InternetAwareComposable(
dnsServers: List<String> = DNS_SERVERS,
delay: Long = INTERNET_CHECK_DELAY,
successContent: (@Composable () -> Unit)? = null,
errorContent: (@Composable () -> Unit)? = null,
onlineChanged: ((Boolean) -> Unit)? = null
) {
suspend fun dnsAccessible(
dnsServer: String
) = try {
withContext(Dispatchers.IO) {
Runtime.getRuntime().exec("/system/bin/ping -c 1 $dnsServer").waitFor()
} == 0
} catch (e: Exception) {
false
}
var isOnline by remember { mutableStateOf(false) }
LaunchedEffect(Unit) {
while (true) {
isOnline = dnsServers.any { dnsAccessible(it) }
onlineChanged?.invoke(isOnline)
delay(delay)
}
}
if (isOnline) successContent?.invoke()
else errorContent?.invoke()
}
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();
只需创建下面的类来检查internet连接:
public class ConnectionStatus {
private Context _context;
public ConnectionStatus(Context context) {
this._context = context;
}
public boolean isConnectionAvailable() {
ConnectivityManager connectivity = (ConnectivityManager) _context
.getSystemService(Context.CONNECTIVITY_SERVICE);
if (connectivity != null) {
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;
}
}
该类仅包含一个返回连接状态布尔值的方法。因此，简单来说，如果该方法找到一个到Internet的有效连接，则返回值为true，否则为false，如果没有找到有效连接。
MainActivity中的下面的方法调用前面描述的方法的结果，并提示用户进行相应的操作:
public void addListenerOnWifiButton() {
Button btnWifi = (Button)findViewById(R.id.btnWifi);
iia = new ConnectionStatus(getApplicationContext());
isConnected = iia.isConnectionAvailable();
if (!isConnected) {
btnWifi.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(Settings.ACTION_WIFI_SETTINGS));
Toast.makeText(getBaseContext(), "Please connect to a hotspot",
Toast.LENGTH_SHORT).show();
}
});
}
else {
btnWifi.setVisibility(4);
warning.setText("This app may use your mobile data to update events and get their details.");
}
}
在上面的代码中，如果结果为假，(因此没有互联网连接，用户将被带到Android wi-fi面板，在那里他将被提示连接到wi-fi热点。
