docs: Added Lint into Android Training and removed Layoutopt.

<ol>

  <li><a href="#Inspect">Inspect Your Layout</a></li>

  <li><a href="#Revise">Revise Your Layout</a></li>

  <li><a href="#Layoutopt">Use Layoutopt</a></li>

  <li><a href="#Lint">Use Lint</a></li>

</ol>

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android.widget.GridView}.</p>

<p>In this lesson you'll learn to use <a

href="{@docRoot}guide/developing/tools/hierarchy-viewer.html">Heirachy Viewer</a> and <a

href="{@docRoot}guide/developing/tools/hierarchy-viewer.html">Hierarchy Viewer</a> and <a

href="{@docRoot}guide/developing/tools/layoutopt.html">Layoutopt</a> to examine and optimize your

layout.</p>

<h2 id="Inspect">Inspect Your Layout</h2>

<p>The Android SDK tools include a tool called <a

href="{@docRoot}guide/developing/tools/hierarchy-viewer.html">Heirachy Viewer</a> that allows

href="{@docRoot}guide/developing/tools/hierarchy-viewer.html">Hierarchy Viewer</a> that allows

you to analyze your layout while your application is running. Using this tool helps you discover

bottlenecks in the layout performance.</p>

layout weight is necessary.</p>

<h2 id="Layoutopt">Use Layoutopt</h2>

<h2 id="Lint">Use Lint</h2>

<p>It is always good practice to run the <a href="http://tools.android.com/tips/lint">Lint</a> tool on your layout files to search for possible view hierarchy optimizations. Lint has replaced the Layoutopt tool and has much greater functionality. Some examples of Lint <a

href="http://tools.android.com/tips/lint-checks">rules</a> are:</p>

<ul>

<li>Use compound drawables - A {@link android.widget.LinearLayout} which contains an {@link android.widget.ImageView} and a {@link android.widget.TextView} can be more efficiently handled as a compound drawable.</li>

<li>Merge root frame - If a {@link android.widget.FrameLayout} is the root of a layout and does not provide background or padding etc, it can be replaced with a merge tag which is slightly more efficient.</li>

<li>Useless leaf - A layout that has no children or no background can often be removed (since it is invisible) for a flatter and more efficient layout hierarchy.</li>

<li>Useless parent - A layout with children that has no siblings, is not a {@link android.widget.ScrollView} or a root layout, and does not have a background, can be removed and have its children moved directly into the parent for a flatter and more efficient layout hierarchy.</li>

<li>Deep layouts - Layouts with too much nesting are bad for performance. Consider using flatter layouts such as {@link android.widget.RelativeLayout} or {@link android.widget.GridLayout} to improve performance. The default maximum depth is 10.</li>

</ul>

<p>Another benefit of Lint is that it is integrated into the Android Development Tools for Eclipse (ADT 16+). Lint automatically runs whenever you export an APK, edit and save an XML file or use the Layout Editor. To manually force Lint to run press the Lint button in the Eclipse toolbar.</p>

<img src="{@docRoot}images/training/lint_icon.png" alt="" />

<p>When used inside Eclipse, Lint has the ability to automatically fix some issues, provide suggestions for others and jump directly to the offending code for review. If you don’t use Eclipse for your development, Lint can also be run from the command line. More information about Lint is available at <a href="http://tools.android.com/tips/lint">tools.android.com</a>.</p>

<p>It is always good practice to also run the <a

href="{@docRoot}guide/developing/tools/layoutopt.html">layoutopt</a> tool on your final layout files

to search for places in your view hierarchy that may be optimized. Layoutopt is also in your SDK

{@code tools/} directory and takes a layout directory name or a space-separated list of layout files

that you'd like to inspect.</p>

<p>When you run {@code layoutopt} on a layout file, it prints a line number for each issue found, a

description of the issue, and for some types of issues it also suggests a resolution. For

example:</p>

<pre class="no-pretty-print classic">

$ layoutopt samples/

samples/compound.xml

   7:23 The root-level <FrameLayout/> can be replaced with <merge/>

   11:21 This LinearLayout layout or its FrameLayout parent is useless

samples/simple.xml

   7:7 The root-level <FrameLayout/> can be replaced with <merge/>

</pre>

<p>After you apply the suggested layout optimizations, run Hierarchy Viewer again to inspect the

performance changes.</p>