Android APT（编译时代码生成）最佳实践

谁借莪１个温暖的怀抱￠ 2022-07-12 08:57 173阅读 0赞

越来越多第三方库使用apt技术，如[DBflow][]、[Dagger2][]、[ButterKnife][]、[ActivityRouter][]、[AptPreferences][]。在编译时根据Annotation生成了相关的代码，非常高大上但是也非常简单的技术，可以给开发带来了很大的便利。

## Annotation ##

如果想学习APT，那么就必须先了解Annotation的基础，这里附加我另外一篇文章的地址：[http://www.taoweiji.cn/2016/07/18/java-annotation][http_www.taoweiji.cn_2016_07_18_java-annotation]

## APT ##

APT(Annotation Processing Tool)是一种处理注释的工具,它对源代码文件进行检测找出其中的Annotation，使用Annotation进行额外的处理。  
Annotation处理器在处理Annotation时可以根据源文件中的Annotation生成额外的源文件和其它的文件(文件具体内容由Annotation处理器的编写者决定),APT还会编译生成的源文件和原来的源文件，将它们一起生成class文件。

### 创建Annotation Module ###

首先，我们需要新建一个名称为annotation的Java Library，主要放置一些项目中需要使用到的Annotation和关联代码。这里简单自定义了一个注解：

##### 配置build.gradle，主要是规定jdk版本 #####

### 创建Compiler Module ###

创建一个名为compiler的Java Library，这个类将会写代码生成的相关代码。核心就是在这里。

##### 配置build.gradle #####

<table style="box-sizing: border-box; border-spacing: 0px; border-collapse: collapse; background-color: transparent; width: 676px; max-width: 100%; margin-bottom: 20px; margin-top: 0px;"> 
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   <td style="box-sizing: border-box; padding: 8px; border-top: 1px solid rgb(221, 221, 221); border-right: 1px solid rgb(238, 238, 238) !important; border-bottom: 1px solid rgb(238, 238, 238) !important; border-left: 1px solid rgb(255, 255, 255); border-image: initial !important; line-height: 1.42857; vertical-align: top; color: rgb(102, 102, 102);"><pre style="box-sizing: border-box; overflow: auto; font-family: Menlo, Monaco, Consolas, &quot;Courier New&quot;, monospace; font-size: 13px; padding: 10px; margin-top: 0px; margin-bottom: 0px; line-height: 1.42857; color: rgb(51, 51, 51); word-break: break-all; word-wrap: break-word; background-color: rgb(245, 245, 245); border: none; border-radius: 4px;">
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        apply plugin: 'java'
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        sourceCompatibility = 1.7 
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        targetCompatibility = 1.7 
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        dependencies {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            compile fileTree(dir: 'libs', include: ['*.jar'])
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            compile 'com.google.auto.service:auto-service:1.0-rc2'
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            compile 'com.squareup:javapoet:1.7.0'
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            compile project(':annotation')
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        }
       
        
     </div></pre></td> 
  </tr> 
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</table>

1.  定义编译的jdk版本为1.7，这个很重要，不写会报错。
2.  AutoService 主要的作用是注解 processor 类，并对其生成 META-INF 的配置信息。
3.  JavaPoet 这个库的主要作用就是帮助我们通过类调用的形式来生成代码。
4.  依赖上面创建的annotation Module。
    
    #### 定义Processor类 ####
    
    生成代码相关的逻辑就放在这里。

<table style="box-sizing: border-box; border-spacing: 0px; border-collapse: collapse; background-color: transparent; width: 782px; max-width: 100%; margin-bottom: 20px; margin-top: 0px;"> 
 <tbody style="box-sizing: border-box;"> 
  <tr style="box-sizing: border-box;"> 
   <td style="box-sizing: border-box; padding: 8px; border-top: 1px solid rgb(221, 221, 221); border-right: 1px solid rgb(238, 238, 238) !important; border-bottom: 1px solid rgb(238, 238, 238) !important; border-left: 1px solid rgb(255, 255, 255); border-image: initial !important; line-height: 1.42857; vertical-align: top; color: rgb(102, 102, 102);"><pre style="box-sizing: border-box; overflow: auto; font-family: Menlo, Monaco, Consolas, &quot;Courier New&quot;, monospace; font-size: 13px; padding: 10px; margin-top: 0px; margin-bottom: 0px; line-height: 1.42857; color: rgb(51, 51, 51); word-break: break-all; word-wrap: break-word; background-color: rgb(245, 245, 245); border: none; border-radius: 4px;">
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        @AutoService(Processor.class)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        public class TestProcessor extends AbstractProcessor {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            @Override
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            public Set&lt;String&gt; getSupportedAnnotationTypes() {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                return Collections.singleton(Test.class.getCanonicalName());
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            @Override
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            public boolean process(Set&lt;? extends TypeElement&gt; annotations, RoundEnvironment roundEnv) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                return false;
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        }
       
        
     </div></pre></td> 
  </tr> 
 </tbody> 
</table>

##### 生成第一个类 #####

我们接下来要生成下面这个HelloWorld的代码：

修改上述TestProcessor的process方法

<table style="box-sizing: border-box; border-spacing: 0px; border-collapse: collapse; background-color: transparent; width: 751px; max-width: 100%; margin-bottom: 20px; margin-top: 0px;"> 
 <tbody style="box-sizing: border-box;"> 
  <tr style="box-sizing: border-box;"> 
   <td style="box-sizing: border-box; padding: 8px; border-top: 1px solid rgb(221, 221, 221); border-right: 1px solid rgb(238, 238, 238) !important; border-bottom: 1px solid rgb(238, 238, 238) !important; border-left: 1px solid rgb(255, 255, 255); border-image: initial !important; line-height: 1.42857; vertical-align: top; color: rgb(102, 102, 102);"><pre style="box-sizing: border-box; overflow: auto; font-family: Menlo, Monaco, Consolas, &quot;Courier New&quot;, monospace; font-size: 13px; padding: 10px; margin-top: 0px; margin-bottom: 0px; line-height: 1.42857; color: rgb(51, 51, 51); word-break: break-all; word-wrap: break-word; background-color: rgb(245, 245, 245); border: none; border-radius: 4px;">
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        @Override    
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        public boolean process(Set&lt;? extends TypeElement&gt; annotations, RoundEnvironment roundEnv) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           MethodSpec main = MethodSpec.methodBuilder("main")
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                   .addModifiers(Modifier.PUBLIC, Modifier.STATIC)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                   .returns(void.class)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                   .addParameter(String[].class, "args")
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                   .addStatement("$T.out.println($S)", System.class, "Hello, JavaPoet!")
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                   .build();
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld")
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                   .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                   .addMethod(main)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                   .build();
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           JavaFile javaFile = JavaFile.builder("com.example.helloworld", helloWorld)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                   .build();
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           try {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
               javaFile.writeTo(processingEnv.getFiler());
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           } catch (IOException e) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
               e.printStackTrace();
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           return false;
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        }
       
        
     </div></pre></td> 
  </tr> 
 </tbody> 
</table>

### 在app中使用 ###

##### 配置项目根目录的build.gradle #####

##### 配置app的build.gradle #####

<table style="box-sizing: border-box; border-spacing: 0px; border-collapse: collapse; background-color: transparent; width: 676px; max-width: 100%; margin-bottom: 20px; margin-top: 0px;"> 
 <tbody style="box-sizing: border-box;"> 
  <tr style="box-sizing: border-box;"> 
   <td style="box-sizing: border-box; padding: 8px; border-top: 1px solid rgb(221, 221, 221); border-right: 1px solid rgb(238, 238, 238) !important; border-bottom: 1px solid rgb(238, 238, 238) !important; border-left: 1px solid rgb(255, 255, 255); border-image: initial !important; line-height: 1.42857; vertical-align: top; color: rgb(102, 102, 102);"><pre style="box-sizing: border-box; overflow: auto; font-family: Menlo, Monaco, Consolas, &quot;Courier New&quot;, monospace; font-size: 13px; padding: 10px; margin-top: 0px; margin-bottom: 0px; line-height: 1.42857; color: rgb(51, 51, 51); word-break: break-all; word-wrap: break-word; background-color: rgb(245, 245, 245); border: none; border-radius: 4px;">
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        apply plugin: 'com.android.application'
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        apply plugin: 'com.neenbedankt.android-apt'
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        //...
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        dependencies {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            //..
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            compile project(':annotation')
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            apt project(':compiler')
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        }
       
        
     </div></pre></td> 
  </tr> 
 </tbody> 
</table>

##### 编译使用 #####

在随意一个类添加@Test注解

<table style="box-sizing: border-box; border-spacing: 0px; border-collapse: collapse; background-color: transparent; width: 676px; max-width: 100%; margin-bottom: 20px; margin-top: 0px;"> 
 <tbody style="box-sizing: border-box;"> 
  <tr style="box-sizing: border-box;"> 
   <td style="box-sizing: border-box; padding: 8px; border-top: 1px solid rgb(221, 221, 221); border-right: 1px solid rgb(238, 238, 238) !important; border-bottom: 1px solid rgb(238, 238, 238) !important; border-left: 1px solid rgb(255, 255, 255); border-image: initial !important; line-height: 1.42857; vertical-align: top; color: rgb(102, 102, 102);"><pre style="box-sizing: border-box; overflow: auto; font-family: Menlo, Monaco, Consolas, &quot;Courier New&quot;, monospace; font-size: 13px; padding: 10px; margin-top: 0px; margin-bottom: 0px; line-height: 1.42857; color: rgb(51, 51, 51); word-break: break-all; word-wrap: break-word; background-color: rgb(245, 245, 245); border: none; border-radius: 4px;">
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        @Test
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        public class MainActivity extends AppCompatActivity {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           @Override
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           protected void onCreate(Bundle savedInstanceState) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
               super.onCreate(savedInstanceState);
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
               setContentView(R.layout.activity_main);
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        }
       
        
     </div></pre></td> 
  </tr> 
 </tbody> 
</table>

点击Android Studio的ReBuild Project，可以在在app的 `build/generated/source/apt`目录下，即可看到生成的代码。

### 基于注解的View注入：DIActivity ###

到目前我们还没有使用注解，上面的@Test也没有实际用上，下面我们做一些更加实际的代码生成。实现基于注解的View，代替项目中的`findByView`。这里仅仅是学习怎么用APT，如果真的想用DI框架，推荐使用ButterKnife，功能全面。

1.  第一步，在annotation module创建@DIActivity、@DIView注解。

1.  创建DIProcessor方法

<table style="box-sizing: border-box; border-spacing: 0px; border-collapse: collapse; background-color: transparent; width: 1557px; max-width: 100%; margin-bottom: 20px; margin-top: 0px;"> 
 <tbody style="box-sizing: border-box;"> 
  <tr style="box-sizing: border-box;"> 
   <td style="box-sizing: border-box; padding: 8px; border-top: 1px solid rgb(221, 221, 221); border-right: 1px solid rgb(238, 238, 238) !important; border-bottom: 1px solid rgb(238, 238, 238) !important; border-left: 1px solid rgb(255, 255, 255); border-image: initial !important; line-height: 1.42857; vertical-align: top; color: rgb(102, 102, 102);"><pre style="box-sizing: border-box; overflow: auto; font-family: Menlo, Monaco, Consolas, &quot;Courier New&quot;, monospace; font-size: 13px; padding: 10px; margin-top: 0px; margin-bottom: 0px; line-height: 1.42857; color: rgb(51, 51, 51); word-break: break-all; word-wrap: break-word; background-color: rgb(245, 245, 245); border: none; border-radius: 4px;">
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        @AutoService(Processor.class)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        public class DIProcessor extends AbstractProcessor {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            private Elements elementUtils;
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            @Override
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            public Set&lt;String&gt; getSupportedAnnotationTypes() {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                // 规定需要处理的注解
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                return Collections.singleton(DIActivity.class.getCanonicalName());
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            @Override
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            public boolean process(Set&lt;? extends TypeElement&gt; annotations, RoundEnvironment roundEnv) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                System.out.println("DIProcessor");
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                Set&lt;? extends Element&gt; elements = roundEnv.getElementsAnnotatedWith(DIActivity.class);
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                for (Element element : elements) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    // 判断是否Class
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    TypeElement typeElement = (TypeElement) element;
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    List&lt;? extends Element&gt; members = elementUtils.getAllMembers(typeElement);
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    MethodSpec.Builder bindViewMethodSpecBuilder = MethodSpec.methodBuilder("bindView")
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                            .addModifiers(Modifier.PUBLIC, Modifier.STATIC)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                            .returns(TypeName.VOID)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                            .addParameter(ClassName.get(typeElement.asType()), "activity");
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    for (Element item : members) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                        DIView diView = item.getAnnotation(DIView.class);
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                        if (diView == null){
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                            continue;
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                        }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                        bindViewMethodSpecBuilder.addStatement(String.format("activity.%s = (%s) activity.findViewById(%s)",item.getSimpleName(),ClassName.get(item.asType()).toString(),diView.value()));
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    TypeSpec typeSpec = TypeSpec.classBuilder("DI" + element.getSimpleName())
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                            .superclass(TypeName.get(typeElement.asType()))
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                            .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                            .addMethod(bindViewMethodSpecBuilder.build())
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                            .build();
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    JavaFile javaFile = JavaFile.builder(getPackageName(typeElement), typeSpec).build();
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    try {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                        javaFile.writeTo(processingEnv.getFiler());
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    } catch (IOException e) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                        e.printStackTrace();
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                    }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                return true;
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            private String getPackageName(TypeElement type) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                return elementUtils.getPackageOf(type).getQualifiedName().toString();
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            @Override
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            public synchronized void init(ProcessingEnvironment processingEnv) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                super.init(processingEnv);
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                elementUtils = processingEnv.getElementUtils();
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            @Override
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            public SourceVersion getSupportedSourceVersion() {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                return SourceVersion.RELEASE_7;
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        }
       
        
     </div></pre></td> 
  </tr> 
 </tbody> 
</table>

1.  使用DIActivity

<table style="box-sizing: border-box; border-spacing: 0px; border-collapse: collapse; background-color: transparent; width: 676px; max-width: 100%; margin-bottom: 20px; margin-top: 0px;"> 
 <tbody style="box-sizing: border-box;"> 
  <tr style="box-sizing: border-box;"> 
   <td style="box-sizing: border-box; padding: 8px; border-top: 1px solid rgb(221, 221, 221); border-right: 1px solid rgb(238, 238, 238) !important; border-bottom: 1px solid rgb(238, 238, 238) !important; border-left: 1px solid rgb(255, 255, 255); border-image: initial !important; line-height: 1.42857; vertical-align: top; color: rgb(102, 102, 102);"><pre style="box-sizing: border-box; overflow: auto; font-family: Menlo, Monaco, Consolas, &quot;Courier New&quot;, monospace; font-size: 13px; padding: 10px; margin-top: 0px; margin-bottom: 0px; line-height: 1.42857; color: rgb(51, 51, 51); word-break: break-all; word-wrap: break-word; background-color: rgb(245, 245, 245); border: none; border-radius: 4px;">
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        @DIActivity
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        public class MainActivity extends Activity {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            @DIView(R.id.text)
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            TextView textView;
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;"></div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            @Override
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            protected void onCreate(Bundle savedInstanceState) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                super.onCreate(savedInstanceState);
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                setContentView(R.layout.activity_main);
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                DIMainActivity.bindView(this);
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
                textView.setText("Hello World!");
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
            }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        }
       
        
     </div></pre></td> 
  </tr> 
 </tbody> 
</table>

实际上就是通过apt生成以下代码

<table style="box-sizing: border-box; border-spacing: 0px; border-collapse: collapse; background-color: transparent; width: 680px; max-width: 100%; margin-bottom: 20px; margin-top: 0px;"> 
 <tbody style="box-sizing: border-box;"> 
  <tr style="box-sizing: border-box;"> 
   <td style="box-sizing: border-box; padding: 8px; border-top: 1px solid rgb(221, 221, 221); border-right: 1px solid rgb(238, 238, 238) !important; border-bottom: 1px solid rgb(238, 238, 238) !important; border-left: 1px solid rgb(255, 255, 255); border-image: initial !important; line-height: 1.42857; vertical-align: top; color: rgb(102, 102, 102);"><pre style="box-sizing: border-box; overflow: auto; font-family: Menlo, Monaco, Consolas, &quot;Courier New&quot;, monospace; font-size: 13px; padding: 10px; margin-top: 0px; margin-bottom: 0px; line-height: 1.42857; color: rgb(51, 51, 51); word-break: break-all; word-wrap: break-word; background-color: rgb(245, 245, 245); border: none; border-radius: 4px;">
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        public final class DIMainActivity extends MainActivity {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
         public static void bindView(MainActivity activity) {
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
           activity.textView = (android.widget.TextView) activity.findViewById(R.id.text);
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
         }
       
        
     </div>
       
        
     <div style="box-sizing: border-box; height: 20px;">
      
         
        }
       
        
     </div></pre></td> 
  </tr> 
 </tbody> 
</table>

### 常用方法 ###

##### 常用Element子类 #####

1.  TypeElement：类
2.  ExecutableElement：成员方法
3.  VariableElement：成员变量

##### 通过包名和类名获取TypeName #####

TypeName targetClassName = ClassName.get(“PackageName”, “ClassName”);

##### 通过Element获取TypeName #####

TypeName type = TypeName.get(element.asType());

##### 获取TypeElement的包名 #####

String packageName = processingEnv.getElementUtils().getPackageOf(type).getQualifiedName().toString();

##### 获取TypeElement的所有成员变量和成员方法 #####

List<? extends Element> members = processingEnv.getElementUtils().getAllMembers(typeElement);

### 总结 ###

推荐阅读dagger2、dbflow、ButterKnife等基于apt的开源项目代码。[JavaPoet][] 也有很多例子可以学习。

#### Example代码 ####

[https://github.com/taoweiji/DemoAPT][https_github.com_taoweiji_DemoAPT]

### 我们的开源项目推荐： ###

#### Android快速持久化框架：AptPreferences ####

AptPreferences是基于面向对象设计的快速持久化框架，目的是为了简化SharePreferences的使用，减少代码的编写。可以非常快速地保存基本类型和对象。AptPreferences是基于APT技术实现，在编译期间实现代码的生成，根据不同的用户区分持久化信息。

[https://github.com/joyrun/AptPreferences][AptPreferences]

#### ActivityRouter路由框架：通过注解实现URL打开Activity ####

基于apt技术，通过注解方式来实现URL打开Activity功能，并支持在WebView和外部浏览器使用，支持多级Activity跳转，支持Bundle、Uri参数注入并转换参数类型。

[https://github.com/joyrun/ActivityRouter][ActivityRouter]

[DBflow]: https://github.com/Raizlabs/DBFlow
[Dagger2]: https://github.com/google/dagger
[ButterKnife]: https://github.com/JakeWharton/butterknife
[ActivityRouter]: https://github.com/joyrun/ActivityRouter
[AptPreferences]: https://github.com/joyrun/AptPreferences
[http_www.taoweiji.cn_2016_07_18_java-annotation]: http://www.taoweiji.cn/2016/07/18/java-annotation
[JavaPoet]: https://github.com/square/javapoet
[https_github.com_taoweiji_DemoAPT]: https://github.com/taoweiji/DemoAPT