实施ConnectivityManager和NetworkInfo时，应用程序停止

Question

For my app, I was trying to detect when the user is connected to the internet. This is one of the methods I've been using, although I've used some other that where basically the same, but using other methods of the objects used:

ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnected())
{
  return true;
}
  return false;
}

Even if this does not lead to any compilation error, when launching the app it stops abruptly and does not respond. I'd like to know why this happens and how to solve it or, if has no aparent solution, if there's another way of doing what I wanted.

I have tried deleting part of the code strategically and I have noticed that the part that gives problems is netInfo with both of ways it is being used, but I don`t know why.

Answer 1

在AndroidManifest文件中添加访问网络权限 ：

 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

Answer 2

First add users-permission in AndroidManifest.xml file like this

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

Second, this pics of code can give you a boolean . Network connection is available or not. so put it in a method and get return of those code like this..

public boolean getCheckedNetStatus(Context context) {
   try{
      ConnectivityManager connMgr = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
      NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
      if (networkInfo != null && networkInfo.isConnected()) {
         return true;
      } else {
         return false;
      }
   }catch(Exception e){
     Log.e("Net Check Err", e.toString());
     return false;
   }
}

Have try catch will protect your from unexpected crash your app...

Now Call it to conditionally execute your certain action like this

if(getCheckedNetStatus(yourActivity.this)){
    //Net is available 
    //So do your action
}else{
   //Net not available 
   //you can notify user that net not available 
   //So you (User) can't do this
}