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();
}
}
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();
下面是我用于可达性检查的Kotlin版本，
芬兰湾的科特林MyReachability
object MyReachability {
private val REACHABILITY_SERVER = "http://google.com" // can be any URL you want
private fun hasNetworkAvailable(context: Context): Boolean {
val service = Context.CONNECTIVITY_SERVICE
val manager = context.getSystemService(service) as ConnectivityManager?
val network = manager?.activeNetworkInfo
Log.d(classTag, "hasNetworkAvailable: ${(network != null)}")
return (network != null)
}
fun hasInternetConnected(context: Context): Boolean {
if (hasNetworkAvailable(context)) {
try {
val connection = URL(REACHABILITY_SERVER).openConnection() as HttpURLConnection
connection.setRequestProperty("User-Agent", "Test")
connection.setRequestProperty("Connection", "close")
connection.connectTimeout = 1500
connection.connect()
Log.d(classTag, "hasInternetConnected: ${(connection.responseCode == 200)}")
return (connection.responseCode == 200)
} catch (e: IOException) {
Log.e(classTag, "Error checking internet connection", e)
}
} else {
Log.w(classTag, "No network available!")
}
Log.d(classTag, "hasInternetConnected: false")
return false
}
}
您甚至可以根据策略和限制将REACHABILITY_SERVER作为参数传递，例如，当您在中国时，您可以检查https://baidu.com而不是https://google.com。
调用示例中,
val webLoaderThread = Thread {
if (MyReachability.hasInternetConnected(this)){
runOnUiThread {
//mWebView.loadUrl(LANDING_SERVER) // connected
}
} else {
runOnUiThread {
//showDialogNoNetwork() // not connected
}
}
}
webLoaderThread.start()
安卓系统权限
不要忘记将以下权限添加到你的AndroidManifest.xml中
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
我已经经历了所有的答案，我想出了我自己的答案，首先检查互联网是否可用，如果互联网可用，然后检查它是否活跃。
我已经包括了所有必要的方法和类来检查活跃的Internet连接。
NetworkUtils.class
public class NetworkUtils {
public static final int STATUS_CONNECTED = 0 ;
public static boolean isInternetAvailable(Context ctx){
ConnectivityManager cm = (ConnectivityManager)ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
return activeNetwork != null && activeNetwork.isConnectedOrConnecting();
}
public static int isInternetActiveWithPing() {
try {
Runtime runtime = Runtime.getRuntime();
Process process = runtime.exec("/system/bin/ping -c 1 8.8.8.8");
int exitValue = process.waitFor();
return exitValue;
} catch (Exception ex) {
return -1;
}
}
public static boolean isInternetActiveWithInetAddress() {
try {
InetAddress inetAddress = InetAddress.getByName("www.google.com");
return inetAddress != null && !inetAddress.toString().equals("");
} catch (Exception ex) {
return false;
}
}
public static void displayInternetConnectionMessage(Context ctx){
Toast.makeText(ctx, "Check Internet Connection", Toast.LENGTH_SHORT).show();
}
}
你可以使用下面的代码检查互联网是否活跃:
private void checkInternetConnection() {
if (NetworkUtils.isInternetAvailable(this)) {
new Thread(new Runnable() {
@Override
public void run() {
if (NetworkUtils.isInternetActiveWithPing() == NetworkUtils.STATUS_CONNECTED) {
performNetworkingOperations();
} else {
if (NetworkUtils.isInternetActiveWithInetAddress()) {
performNetworkingOperations();
} else {
displayConnectionMessage();
}
}
}
}).start();
} else {
displayConnectionMessage();
}
}
private void performNetworkingOperations() {
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.this, "Internet is Available", Toast.LENGTH_SHORT).show();
}
});
}
private void displayConnectionMessage() {
runOnUiThread(new Runnable() {
@Override
public void run() {
NetworkUtils.displayInternetConnectionMessage(MainActivity.this);
}
});
}
