Change your layout to below. Make sure you have only one @+id
for each variable you declare (the first time you use it).
<RelativeLayout
android:id="@+id/controlPanelLayout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin" >
<ImageView
android:id="@+id/playBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
/>
<ImageView
android:id="@+id/stopBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/playBtn"
android:layout_marginLeft="15dp"
android:src="@drawable/stop_simple" />
<ImageView
android:id="@+id/clearBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="15dp"
android:layout_toRightOf="@id/stopBtn"
android:src="@drawable/clear_simple" />
<ImageView
android:id="@+id/speakerBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/clearBtn"
android:layout_marginLeft="15dp"
android:src="@drawable/speaker_simple" />
<ImageView
android:id="@+id/settingsBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:src="@drawable/settings_simple" />
</RelativeLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="match_parent"
android:layout_above="@+id/adTalk"
android:layout_below="@id/controlPanelLayout"
android:layout_marginTop="10dp"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin" >
<EditText
android:id="@+id/textField"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:ems="10"
android:gravity="top"
android:inputType="textMultiLine"
android:linksClickable="true" >
<requestFocus />
</EditText>
</LinearLayout>
<com.google.ads.AdView
xmlns:googleads="http://schemas.android.com/apk/lib/com.google.ads"
android:id="@id/adTalk"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
googleads:adSize="BANNER"
android:layout_alignParentBottom="true"
android:layout_marginTop="5dp"
googleads:adUnitId="xxxxxxxxxxxx"
/>
</RelativeLayout>