Android开发之手把手教你写ButterKnife框架 _Android开发

书史足自悦，安用勤与劬。这篇文章主要讲述Android开发之手把手教你写ButterKnife框架相关的知识，希望能为你提供帮助。

【Android开发之手把手教你写ButterKnife框架】欢迎转载，转载请标明出处：
http://blog.csdn.net/johnny901114/article/details/52664112
本文出自:【余志强的博客】

上一篇博客Android开发之手把手教你写ButterKnife框架（一）我们讲了ButterKnife是什么、ButterKnife的作用和功能介绍以及ButterKnife的实现原理。
本篇博客主要讲在android studio中如何使用apt。
一、新建个项目, 然后创建一个module名叫processor
新建module的时候一定要选择 java Library 否则在后面会找不到AbstractProcessor。
分别在app和processor 的文件夹下的build.gralde添加如下配置：

compileOptions { sourceCompatibility JavaVersion.VERSION_1_7 targetCompatibility JavaVersion.VERSION_1_7 }

二、然后在建一个module名叫annotation，主要用来保存项目用到的annotation.

import java.lang.annotation.Retention; import java.lang.annotation.Target; import static java.lang.annotation.ElementType.FIELD; import static java.lang.annotation.RetentionPolicy.CLASS; @Retention(CLASS) @Target(FIELD) public @interface BindView { int value(); }

三、新建MainActivity 字段上加上注解，如下：

public class MainActivity extends AppCompatActivity {@BindView(R.id.text_view) TextView textView; @BindView(R.id.view) TextView view; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } }

三、在processor module下新建一个ButterKnifeProcessor 继承AbstractProcessor.

@SupportedAnnotationTypes("com.chiclaim.processor.annotation.BindView") @SupportedSourceVersion(SourceVersion.RELEASE_7) public class ButterKnifeProcessor extends AbstractProcessor { @Override public boolean process(Set< ? extends TypeElement> annotations, RoundEnvironment roundEnv) { StringBuilder builder = new StringBuilder() .append("package com.chiclaim.processor.generated; \n\n") .append("public class GeneratedClass {\n\n") // open class .append("\tpublic String getMessage() {\n") // open method .append("\t\treturn \""); // for each javax.lang.model.element.Element annotated with the CustomAnnotation for (Element element : roundEnv.getElementsAnnotatedWith(BindView.class)) { String objectType = element.getSimpleName().toString(); // this is appending to the return statement builder.append(objectType).append(" says hello!\\n"); }builder.append("\"; \n") // end return .append("\t}\n") // close method .append("}\n"); // close classtry { // write the file JavaFileObject source = processingEnv.getFiler().createSourceFile("com.chiclaim.processor.generated.GeneratedClass"); Writer writer = source.openWriter(); writer.write(builder.toString()); writer.flush(); writer.close(); } catch (IOException e) { // Note: calling e.printStackTrace() will print IO errors // that occur from the file already existing after its first run, this is normal } return true; } }

@SupportedAnnotationTypes(…) 里面的参数是我们需要处理的注解
四、在processor module主目录下resources目录
然后新建META-INF目录，然后在META-INF下新建services 然后新建一个文件名为 javax.annotation.processing.Processor, 里面的内容就是刚刚新建的ButterKnifeProcessor的qualified name ：

com.chiclaim.butterknife.processor.ButterKnifeProcessor

当然也可以用新建这么多文件夹，只需要加入google AutoService，这样就会自动完成上面的操作。

@SupportedSourceVersion(SourceVersion.RELEASE_7) @AutoService(Processor.class) //AutoService自动生成文件(in processor.jar): META-INF/services/javax.annotation.processing.Processor public class ButterKnifeProcessor extends AbstractProcessor

五、添加android-apt支持
在全局的build.gradle添加添加apt支持，com.neenbedankt.gradle.plugins:android-apt:1.8,如下所示：

buildscript { repositories { jcenter() } dependencies { classpath ‘com.android.tools.build:gradle:2.2.0‘ classpath ‘com.neenbedankt.gradle.plugins:android-apt:1.8‘ // NOTE: Do not place your application dependencies here; they belong // in the individual module build.gradle files } }ext { sourceCompatibilityVersion = JavaVersion.VERSION_1_7 targetCompatibilityVersion = JavaVersion.VERSION_1_7 }allprojects { repositories { jcenter() } }task clean(type: Delete) { delete rootProject.buildDir }

分别在app module的build.gradle添加 apply plugin 如下所示：

apply plugin: ‘com.android.application‘ apply plugin: ‘com.neenbedankt.android-apt‘

六、添加module之间的依赖

dependencies { compile fileTree(include: [‘*.jar‘], dir: ‘libs‘) androidTestCompile(‘com.android.support.test.espresso:espresso-core:2.2.2‘, { exclude group: ‘com.android.support‘, module: ‘support-annotations‘ }) compile ‘com.android.support:appcompat-v7:24.2.1‘ testCompile ‘junit:junit:4.12‘ compile project(‘:annotation‘) compile project(‘:processor‘) compile project(‘:butterknife‘) } //把processor module生成的jar拷贝到app libs目录 task processorTask(type: Exec) { commandLine ‘cp‘, ‘../processor/build/libs/processor.jar‘, ‘libs/‘ } //build processor 生成processor.jar processorTask.dependsOn(‘:processor:build‘) preBuild.dependsOn(processorTask)

如下图所示：

文章图片

会在app module的build的目录下生成代码，如：

文章图片

public class GeneratedClass { public String getMessage() { return "button says hello!\nimageView says hello!\ntextView says hello!\nview says hello!\n"; } }

据此，在android studio 使用apt就介绍完毕了。
具体的可以查看github代码：https://github.com/chiclaim/study-butterknife
下一篇将介绍如何实现ButterKnife注入初始化View功能。