AdMob banner ad not showing

Use below lines of code

AdView mAdView = (AdView) findViewById(R.id.adView);

AdRequest request = new AdRequest.Builder()
.addTestDevice(AdRequest.DEVICE_ID_EMULATOR)        // All emulators
.addTestDevice("AC98C820A50B4AD8A2106EDE96FB87D4")  // My Galaxy Nexus test phone
.build();


mAdView.loadAd(request );

instead of using this

AdRequest adRequest = new AdRequest.Builder().build();

because this line will be used when your application would be ready for publish on Google Play Store.

You can place your device's id in place of "AC98C820A50B4AD8A2106EDE96FB87D4". Code to get device id:

String android_id = Settings.Secure.getString(getContext().getContentResolver(),
            Settings.Secure.ANDROID_ID);

Please read these carefully:

https://developers.google.com/admob/android/targeting#test_ads

https://developers.google.com/admob/android/quick-start

See this

This problem is solved by uninstalling the app manually and reinstalling again without making any changes!!

Check if you have latest versions of adMob and GooglePlayServices lib.

In my case the ad didnt show up until I gave enough room for it.

Before it was like

<LinearLayout
        android:orientation="vertical"
        android:background="@color/primary"
        android:layout_width="match_parent"
        android:layout_height="90dip">
           <ImageView
                android:onClick="goBack"
                android:clickable="true"
                android:src="@drawable/ic_arrow_back_white_48dp"
                android:layout_width="50dip"
                android:layout_height="50dip"/>
           <com.google.android.gms.ads.AdView
                android:layout_gravity="center_horizontal"
                android:id="@+id/adView"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                ads:adSize="BANNER"
                ads:adUnitId="@string/dwn_bnr_ad"/>

Here the adview is having height of wrap_content, so it adjusts itself to achieve its height, but its parent (LinearLayout) has a strict height of 90dip which doesnt allow the adView to take enough space to display ads.

So what I did was just changed the height of the LinearLayout to wrap_content then things got fine