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();
}
}
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);
}
});
}
如果你正在使用Firebase，你可以使用这个。
Java:
DatabaseReference connectedRef = FirebaseDatabase.getInstance().getReference(".info/connected");
connectedRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
boolean connected = snapshot.getValue(Boolean.class);
if (connected) {
Log.d(TAG, "connected");
} else {
Log.d(TAG, "not connected");
}
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
Log.w(TAG, "Listener was cancelled");
}
});
科特林：
val connectedRef = Firebase.database.getReference(".info/connected")
connectedRef.addValueEventListener(object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
val connected = snapshot.getValue(Boolean::class.java) ?: false
if (connected) {
Log.d(TAG, "connected")
} else {
Log.d(TAG, "not connected")
}
}
override fun onCancelled(error: DatabaseError) {
Log.w(TAG, "Listener was cancelled")
}
})
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。
