Android之butterknife(懒人库)

这个开源库可以让我们从大量的findViewById()和setOnclicktListener()解放出来，其对性能的影响微乎其微，其自定义注解的实现都是限定为RetentionPolicy.CLASS，也就是注解到编译出.class文件为止有效，在运行时不额外消耗性能。

我们先将butterknife库导入Android Studio中，导入到步骤如下：

点击Project Structure，选择你的app，然后点击Dependencies,再点击右边的加号

然后就出现了上面的界面，输入库名butterknife，点击OK,它就会自动添加了，不过要稍等一小会。然后打开project下的“build.gradle”，然后在"dependencies"下增加了“classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'”，然后在打开app文件夹下的“build.gradle”,添加“apply plugin: 'android-apt'”，“apt 'com.jakewharton:butterknife-compiler:8.1.0'”，然后点击“Sync Now”。

添加完,我们通过代码来演示一下到底如何用：

1.Activity中的绑定

<code class="hljs scala has-numbering"><span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">ExampleActivity</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Activity</span> {</span><span class="hljs-annotation">@Bind</span>(R.id.title) TextView title;<span class="hljs-annotation">@Bind</span>(R.id.subtitle) TextView subtitle;<span class="hljs-annotation">@Bind</span>(R.id.footer) TextView footer;<span class="hljs-annotation">@Override</span> public void onCreate(Bundle savedInstanceState) {<span class="hljs-keyword">super</span>.onCreate(savedInstanceState);setContentView(R.layout.simple_activity);ButterKnife.bind(<span class="hljs-keyword">this</span>);}
}</code>

这就相当于绑定了控件了。

2.资源绑定

通过预定义的注解（@BindBool, @BindColor, @BindDimen, @BindDrawable, @BindInt, @BindString）结合一个资源 ID以和表示该资源类型的相应的字段。

<code class="hljs scala has-numbering"><span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">ExampleActivity</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Activity</span> {</span><span class="hljs-annotation">@BindString</span>(R.string.title) String title;<span class="hljs-annotation">@BindDrawable</span>(R.drawable.graphic) Drawable graphic;<span class="hljs-annotation">@BindColor</span>(R.color.red) int red; <span class="hljs-annotation">@BindDimen</span>(R.dimen.spacer) Float spacer; <span class="hljs-comment">// ...</span>
}</code><div class="save_code tracking-ad" style="display: none;" data-mod="popu_249"><a target=_blank target="_blank"><img src="http://static.blog.csdn.net/images/save_snippets.png" alt="" /></a></div>

3.Fragment中的绑定

你还可以通过提供你自己的根视图来执行任意对象的绑定。

<code class="hljs java has-numbering"><span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">FancyFragment</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Fragment</span> {</span><span class="hljs-annotation">@Bind</span>(R.id.button1) Button button1;<span class="hljs-annotation">@Bind</span>(R.id.button2) Button button2;<span class="hljs-annotation">@Override</span> <span class="hljs-keyword">public</span> View <span class="hljs-title">onCreateView</span>(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {View view = inflater.inflate(R.layout.fancy_fragment, container, <span class="hljs-keyword">false</span>);ButterKnife.bind(<span class="hljs-keyword">this</span>, view);<span class="hljs-keyword">return</span> view;}
}</code>

4.监听器绑定Butter knife可以自动将侦听器配置为方法。

<code class="hljs java has-numbering"><span class="hljs-annotation">@OnClick</span>(R.id.submit)
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">submit</span>(View view) {}<span class="hljs-annotation">@OnClick</span>(R.id.submit)
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">submit</span>() {}
<span class="hljs-comment">//定义的指定类型将会被自动转换</span><span class="hljs-annotation">@OnClick</span>(R.id.submit)
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">sayHi</span>(Button button) {button.setText(<span class="hljs-string">"Hello!"</span>);
}</code>