LinearLayout NullPointerException in Eclipse

Question

I am getting a NullPointerException on line 40 of this code. Below is the Google example of implementation of the new ad-mob ad service, which takes effect by august this year. This code is literally cut and pasted from thier documentation, yet I am getting the exception and can't resolve it.

Here is the class:

package com.example.com.stringtheory.newadmobtest;

import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdSize;
import com.google.android.gms.ads.AdView;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.widget.LinearLayout;

/**
 * A simple {@link Activity} that embeds an AdView.
 */
public class MainActivity extends Activity {
/** The view to show the ad. */
private AdView adView;

/* Your ad unit id. Replace with your actual ad unit id. */
private static final String AD_UNIT_ID = "ca-app-pub-6817177749834558/8445203226";

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

// Create an ad.
adView = new AdView(this);
adView.setAdSize(AdSize.BANNER);
adView.setAdUnitId(AD_UNIT_ID);

    // Add the AdView to the view hierarchy. The view will have no size
    // until the ad is loaded.
    LinearLayout layout = (LinearLayout) findViewById(R.id.linear);
    if (layout == null) 
        { Log.w("", "LinearLayout is null");

        }
    layout.addView(adView);

    // Create an ad request. Check logcat output for the hashed device ID to
    // get test ads on a physical device.
    AdRequest adRequest = new AdRequest.Builder()

        .build();

    // Start loading the ad in the background.
    adView.loadAd(adRequest);
  }

  @Override
  public void onResume() {
    super.onResume();
    if (adView != null) {
      adView.resume();
    }
  }

  @Override
  public void onPause() {
    if (adView != null) {
      adView.pause();
    }
    super.onPause();
  }

  /** Called before the activity is destroyed. */
  @Override
  public void onDestroy() {
    // Destroy the AdView.
    if (adView != null) {
      adView.destroy();
    }
    super.onDestroy();
  }
}

And here is the related XML:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.com.stringtheory.newadmobtest.MainActivity$PlaceholderFragment" >
    <LinearLayout
    android:id="@+id/linear"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginLeft="18dp"
    android:layout_marginTop="112dp"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />
</LinearLayout>

Any ideas on whats causing this?

PS - the specific line causing the issue reads:

    layout.addView(adView);

Answer 1

I fixed it. Here is the problem:

To start the test application, I had made a new project in eclipse. This comes with 2 layouts (activity_main and fragment_main).

I had seen the hello world text in the fragment_main layout, and for some reason I had added my linearLayout into that xml incorrectly.

While I was thinking I was pointing it to the correct layout, the system was seeing that the layout was, indeed, not existent where I thought it was. Simply overlooked it. Cooked me for about 2 hours on this little mistake.