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diff --git a/docs/html/resources/articles/ui-1.6.jd b/docs/html/resources/articles/ui-1.6.jd new file mode 100644 index 0000000..10cb524 --- /dev/null +++ b/docs/html/resources/articles/ui-1.6.jd @@ -0,0 +1,130 @@ +page.title=UI Framework Changes in Android 1.6 +@jd:body + +<p>Android 1.6 introduces numerous enhancements and bug fixes in the UI +framework. This article highlights two improvements in particular: more flexible +and robust RelativeLayout and easier click listeners. </p> + +<h3>More flexible, more robust RelativeLayout</h3> + +<p>RelativeLayout is the most versatile layout offered by the Android UI toolkit +and can be successfully used to reduce the number of views created by your +applications. This layout used to suffer from various bugs and limitations, +sometimes making it difficult to use without having some knowledge of its +implementation. To make your life easier, Android 1.6 comes with a revamped +RelativeLayout. </p> + +<p>This new implementation not only fixes all known bugs in +RelativeLayout but also addresses its major limitation: the +fact that views had to be declared in a particular order. Consider the following +XML layout:</p> + +<pre><?xml version="1.0" encoding="utf-8"?> + +<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" + android:layout_width="fill_parent" + android:layout_height="64dip" + android:padding="6dip"> + + <TextView + android:id="@+id/band" + android:layout_width="fill_parent" + android:layout_height="26dip" + + android:layout_below="@+id/track" + android:layout_alignLeft="@id/track" + android:layout_alignParentBottom="true" + + android:gravity="top" + android:text="The Airborne Toxic Event" /> + + <TextView + android:id="@id/track" + android:layout_marginLeft="6dip" + android:layout_width="fill_parent" + android:layout_height="26dip" + + android:layout_toRightOf="@+id/artwork" + + android:textAppearance="?android:attr/textAppearanceMedium" + android:gravity="bottom" + android:text="Sometime Around Midnight" /> + + <ImageView + android:id="@id/artwork" + android:layout_width="56dip" + android:layout_height="56dip" + android:layout_gravity="center_vertical" + + android:src="@drawable/artwork" /> + +</RelativeLayout></pre> + +<p>This code builds a very simple layout—an image on the left with two lines of +text stacked vertically. This XML layout is perfectly fine and contains no +errors. Unfortunately, Android 1.5's RelativeLayout is incapable of rendering it +correctly, as shown in the screenshot below.</p> + +<img src="images/ui-1.6_002.png" style="width: 320px; height: 480px;"> + +<p>The problem is that this layout uses forward references. For instance, the +"band" TextView is positioned below the "track" TextView but "track" is declared +after "band" and, in Android 1.5, RelativeLayout does not know how to handle +this case. Now look at the exact same layout running on Android 1.6:</p> + +<img src="images/ui-1.6.png" style="width: 320px; height: 480px;"> + +<p>As you can see Android 1.6 is now better able to handle forward reference. +The result on screen is exactly what you would expect when writing the +layout.</p> + +<h3>Easier click listeners</h3> + +<p>Setting up a click listener on a button is very common task, but +it requires quite a bit of boilerplate code:</p> + +<pre>findViewById(R.id.myButton).setOnClickListener(new View.OnClickListener() { + public void onClick(View v) { + // Do stuff + } +});</pre> + +<p>One way to reduce the amount of boilerplate is to share a single click +listener between several buttons. While this technique reduces the +number of classes, it still requires a fair amount of code and it still +requires giving each button an id in your XML layout file:</p> + +<pre>View.OnClickListener handler = View.OnClickListener() { + public void onClick(View v) { + switch (v.getId()) { + case R.id.myButton: // doStuff + break; + case R.id.myOtherButton: // doStuff + break; + } + } +} + +findViewById(R.id.myButton).setOnClickListener(handler); +findViewById(R.id.myOtherButton).setOnClickListener(handler);</pre> + +<p>With Android 1.6, none of this is necessary. All you have to do is +declare a public method in your Activity to handle the click +(the method <i>must</i> have one View argument):</p> + +<pre>class MyActivity extends Activity { + public void myClickHandler(View target) { + // Do stuff + } +}</pre> + +<p>And then reference this method from your XML layout:</p> + +<pre><Button android:onClick="myClickHandler" /></pre> + +<p>This new feature reduces both the amount of Java and XML you have to write, +leaving you more time to concentrate on your application.</p> + +<p>The Android team is committed to helping you write applications in the +easiest and most efficient way possible. We hope you find these improvements +useful and we're excited to see your applications on Android Market.</p> |