A bug in Android Data Binder

<span id="Label3"></p><p><p>Learning the usage of data binding with the official tutorials, which is really powerful, is a big step for Android toward MVVM and a small step toward the Web as Native's development approaches.</p></p><p><p>One way to bind is to use resource data directly, for Example:</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs perl">android:padding=<span class="hljs-string">"<span class="hljs-subst">@{large? <span class="hljs-variable">@dimen</span>/largePadding : <span class="hljs-variable">@dimen</span>/smallPadding}</span>"</span></code></pre></pre><p><p>Official tutorials:</p></p><p><p></p></p><p><p>The full version of the layout file is as Follows:</p></p><pre class="prettyprint"><code class=" hljs xml"><span class="hljs-tag"><span class="hljs-tag"><<span class="hljs-title">layout</span> <span class="hljs-attribute">xmlns:android</span>=<span class="hljs-value">"http://schemas.android.com/apk/res/android"</span>></span></span> <span class="hljs-tag"><span class="hljs-tag"><<span class="hljs-title">data</span> <span class="hljs-attribute">class</span>=<span class="hljs-value">"resourcebinding"</span>></span></span> <span class="hljs-tag"><span class="hljs-tag"><<span class="hljs-title">variable</span> <span class="hljs-attribute">name</span>=<span class="hljs-value">"large"</span> <span class="hljs-attribute">Type</span>=<span class="hljs-value">"boolean"</span> /></span></span> <span class="hljs-tag"><span class="hljs-tag"></<span class="hljs-title">Data</span>></span></span> <span class="hljs-tag"><span class="hljs-tag"><<span class="hljs-title">linearlayout</span><span class="hljs-attribute">android:layout_width</span>=<span class="hljs-value">"match_parent"</span><span class="hljs-attribute">android:layout_ Height</span>=<span class="hljs-value">"match_parent"</span>> </span></span> <span class="hljs-tag"><span class="hljs-tag"><<span class="hljs-title">TextView</span><span class="hljs-attribute">android:padding</span>=<span class="hljs-value">"@{large? @dimen/largepadding: @dimen/smallpadding} "</span><span class="hljs-attribute">android:background</span>=<span class="hljs-value">" @android: color/black "</span> <span class="hljs-attribute"> Android:textcolor</span>=<span class="hljs-value">"@android: color/white"</span><span class="hljs-attribute">android:layout_width</span>=<span class="hljs-value">"wrap_content"</span> <span class="hljs-attribute">android:layout_height</span>=<span class="hljs-value">"wrap_content"</span><span class="hljs-attribute">android:text</span>=<span class="hljs-value">"@string/hello_world" </span>/> </span></span> <span class="hljs-tag"><span class="hljs-tag"></<span class="hljs-title">linearlayout</span>></span></span><span class="hljs-tag"><span class="hljs-tag"></<span class="hljs-title">layout</span>></span></span></code></pre><p><p><code>largePadding</code>And <code>smallPadding</code> both are resource data that are defined in <code>dimens.xml</code> the File.</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs xml"><span class="hljs-tag"><<span class="hljs-title">dimen</span> <span class="hljs-attribute">name</span>=<span class="hljs-value">"largePadding"</span>></span>20dp<span class="hljs-tag"></<span class="hljs-title">dimen</span>></span><span class="hljs-tag"><<span class="hljs-title">dimen</span> <span class="hljs-attribute">name</span>=<span class="hljs-value">"smallPadding"</span>></span>5dp<span class="hljs-tag"></<span class="hljs-title">dimen</span>></span></code></pre></pre><p><p>In Java code, bind the large variable and assign the value to <code>ture</code> .</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs java"><span class="hljs-annotation">@Override</span><span class="hljs-keyword">protected</span><span class="hljs-keyword">void</span><span class="hljs-title">onCreate</span>(Bundle savedInstanceState) { <span class="hljs-keyword">super</span>.onCreate(savedInstanceState); ResourceBinding binding = DataBindingUtil.setContentView(<span class="hljs-keyword">this</span>, R.layout.activity_resource); binding.setLarge(<span class="hljs-keyword">true</span></code></pre></pre><p><p>theoretically, this should not be a problem, but when the Run works, there are errors, the error message is as Follows:</p></p><pre><pre>Cannot find the setter for attribute ' android:padding ' in Android.widget.TextView with parameter type Float.</pre></pre><p><p>Looks like a databinder <code>@dimen/largePadding</code> . to parse into a <code>float</code> type, you can try the type conversion:</p></p><pre class="prettyprint"><pre class="prettyprint"><code class=" hljs perl">android:padding=<span class="hljs-string">"<span class="hljs-subst">@{large? (<span class="hljs-keyword">int</span>)<span class="hljs-variable">@dimen</span>/largePadding : (<span class="hljs-keyword">int</span>)<span class="hljs-variable">@dimen</span>/smallPadding}</span>"</span></code></pre></pre><p><p>Compile through, Run the result is also correct, should be databinder out a bug, original resource binding also has so advanced usage, can directly carry on type conversion- <code>(int)@dimen/largePadding</code> .</p></p><p><p>Feel good magic, must read the source code, understand the DataBinder implementation Principle.</p></p> <p><p>A bug in Android Data Binder</p></p></span>