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();
}
}
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/
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")
}
})
正如Android文档建议的那样，之后
getActiveNetworkInfo()在Android 10中已弃用。使用
而不是针对Android 10 (API级别)的应用程序的NetworkCallbacks
29)更高。
下面是我们目前检查网络连接的方法:
val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
val activeNetwork: NetworkInfo? = cm.activeNetworkInfo
val isConnected: Boolean = activeNetwork?.isConnectedOrConnecting == true
使用NetworkCallbacks检查网络连接的新方法
步骤1:
private lateinit var connectivityManager:ConnectivityManager
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
...
connectivityManager = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
}
步骤2:创建回调:
private val callback = object : ConnectivityManager.NetworkCallback() {
override fun onAvailable(network: Network) {
super.onAvailable(network)
Timber.e("Network:onAvailable")
}
override fun onLost(network: Network) {
super.onLost(network)
Timber.e("Network:onLost")
}
}
步骤3:注册和取消注册回调:
private fun registerNetworkCallback() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
connectivityManager.registerDefaultNetworkCallback(callback)
} else {
// Old way to check network connection
}
}
override fun onStop() {
unRegisterNetworkCallback()
super.onStop()
}
private fun unRegisterNetworkCallback() {
connectivityManager.unregisterNetworkCallback(callback)
}
结帐更新详情如下链接:
https://developer.android.com/training/monitoring-device-state/connectivity-status-type
