"System services not available to Activities before onCreate()" Error message?

user_1231619 0
Viewed 49891

When the user hits an icon in my app, I want the app first to check if the device is connected to the internet and then do something depending on the result it receives (for know it's just popping up a dialog, informing whether the device is connected or not). So I wrote this code:

public class MainActivity extends Activity {

// SOME CONSTANTS WILL BE DEFINED HERE

AlertDialog.Builder builder = new AlertDialog.Builder(this);

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    findViewById(R.id.icoMyIcon).setOnClickListener(listener);
}


private OnClickListener listener = new OnClickListener() {

    public void onClick(View v) {
        if (isNetworkConnected()) {
            builder.setMessage("Internet connected!").setCancelable(false)
            .setPositiveButton("OK", null);
            builder.create().show();
        } else {
            builder.setMessage("Internet isn\'t connected!")
            .setCancelable(false)
            .setPositiveButton("OK", null);
            builder.create().show();
        }

    }
};


// Check if the device is connected to the Internet
private boolean isNetworkConnected() {
    ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo ni = cm.getActiveNetworkInfo();
    if (ni == null) {
        // There are no active networks.
        return false;
    } else
        return true;
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

}

When I'm trying to run this App on the emulator it keeps crushing and I'm getting this Error messages in LogCat:

07-24 22:59:45.034: E/AndroidRuntime(894): FATAL EXCEPTION: main
07-24 22:59:45.034: E/AndroidRuntime(894): java.lang.RuntimeException: Unable to 
    instantiate activity ComponentInfo{com.my.app/com.my.app.MainActivity}: 
    java.lang.IllegalStateException: System services not available to Activities before onCreate()
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.os.Handler.dispatchMessage(Handler.java:99)
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.os.Looper.loop(Looper.java:123)
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.app.ActivityThread.main(ActivityThread.java:4627)
07-24 22:59:45.034: E/AndroidRuntime(894):  at java.lang.reflect.Method.invokeNative(Native Method)
07-24 22:59:45.034: E/AndroidRuntime(894):  at java.lang.reflect.Method.invoke(Method.java:521)
07-24 22:59:45.034: E/AndroidRuntime(894):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
07-24 22:59:45.034: E/AndroidRuntime(894):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
07-24 22:59:45.034: E/AndroidRuntime(894):  at dalvik.system.NativeStart.main(Native Method)
07-24 22:59:45.034: E/AndroidRuntime(894): Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.app.Activity.getSystemService(Activity.java:3526)
07-24 22:59:45.034: E/AndroidRuntime(894):  at com.android.internal.app.AlertController$AlertParams.<init>(AlertController.java:743)
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.app.AlertDialog$Builder.<init>(AlertDialog.java:273)
07-24 22:59:45.034: E/AndroidRuntime(894):  at com.my.app.MainActivity.<init>(MainActivity.java:24)
07-24 22:59:45.034: E/AndroidRuntime(894):  at java.lang.Class.newInstanceImpl(Native Method)
07-24 22:59:45.034: E/AndroidRuntime(894):  at java.lang.Class.newInstance(Class.java:1429)
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
07-24 22:59:45.034: E/AndroidRuntime(894):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
07-24 22:59:45.034: E/AndroidRuntime(894):  ... 11 more

Why is it happening and how do I fix it? I'm a novice at this, so... please be gentle! :)

oncreate methods android
8 Answers

To call system services we have to use running activity. That means we need executed onCreate method that inherited to the super. So to identify that we have to use the current application context to call system service.

use 

ConnectivityManager cm = (ConnectivityManager) getBaseContext().getSystemService(Context.CONNECTIVITY_SERVICE);

or if we have context object that reference to Context, we can use it as below

ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
user_69173620

in my case, I got error message : “System services not available to Activities before onCreate()”

when I initialize class property using context like below

 class MainActivity : AppCompatActivity() {

        // this line below
        private val notificationManager: NotificationManagerCompat = NotificationManagerCompat.from(this) 

        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
        }

    }
user_91018760
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