Java 7 Meets Android - Beginning Java 7 - page 1183

Wave'sclicklistenerinvokes dukeAnimation.stop(); followedby dukeAn-
imation.start(); to stop and then start the animation. The stop() method is
called before start() to ensure that a subsequent click of the Wave button causes a
new animation to begin.
Along with Listing 12-3 's Java7MeetsAndroid.java source file,
Java7MeetsAndroid relies onthreeXMLresourcefilesandseveral PNGimages.
Listing 12-4 presents main.xml , which describes screen layout.

Listing 12-4. The main.xml file storing layout information that includes a pair of widgets

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/

apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center"
android:background="#ffffff">
<ImageView android:id="@+id/duke"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="10dip"/>
<Button android:id="@+id/wave"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/wave"/>
</LinearLayout>

Following the XML declaration, Listing 12-4 declares a LinearLayout element
that specifies a layout (a view group that arranges contained views on an Android
device'sscreeninsomemanner)forarrangingcontainedwidgets(includingnestedlay-
outs) either horizontally or vertically across the screen.
The <LinearLayout> tag specifies several attributes for controlling this linear
layout. These attributes include the following:
• orientation identifiesthelinearlayoutashorizontalorvertical-contained
widgets are laid out horizontally or vertically. The default orientation is hori-