Android ButterKnife依赖注入框架使用教程
目录
- 简介
- APT整个流程
- ButterKnife的工作原理
简介
BuffterKnife 采用 注解+ APT技术
APT:Annotation Processor tool 注解处理器,是javac的一个工具,每个处理器都是继承于AbstractProcessor
注解处理器是运行在自己的java虚拟机中
APT如何生成字节码文件:
Annotation Processing 不能加入或删除java方法
APT整个流程
- 声明的注解等待生命周期为CLASS
- 继承AbstractProcessor类
- 再调用AbstractProcessor 的process方法
AbstractProcessor.java
// // Source code recreated from a .class file by IntelliJ IDEA // (powered by FernFlower decompiler) // package javax.annotation.processing; import java.util.Collections; import java.util.HashSet; import java.util.Objects; import java.util.Set; import javax.lang.model.SourceVersion; import javax.lang.model.element.AnnotationMirror; import javax.lang.model.element.Element; import javax.lang.model.element.ExecutableElement; import javax.lang.model.element.TypeElement; import javax.tools.Diagnostic.Kind; public abstract class AbstractProcessor implements Processor { protected ProcessingEnvironment processingEnv; private boolean initialized = false; protected AbstractProcessor() { } public Set<String> getSupportedOptions() { SupportedOptions so = (SupportedOptions)this.getClass().getAnnotation(SupportedOptions.class); return so == null ? Collections.emptySet() : arrayToSet(so.value(), false); } public Set<String> getSupportedAnnotationTypes() { // 返回所支持注解的类型 SupportedAnnotationTypes sat = (SupportedAnnotationTypes)this.getClass().getAnnotation(SupportedAnnotationTypes.class); boolean initialized = this.isInitialized(); if (sat == null) { if (initialized) { this.processingEnv.getMessager().printMessage(Kind.WARNING, "No SupportedAnnotationTypes annotation found on " + this.getClass().getName() + ", returning an empty set."); } return Collections.emptySet(); } else { boolean stripModulePrefixes = initialized && this.processingEnv.getSourceVersion().compareTo(SourceVersion.RELEASE_8) <= 0; return arrayToSet(sat.value(), stripModulePrefixes); } } public SourceVersion getSupportedSourceVersion() { //用来指定所使用的java版本 SupportedSourceVersion ssv = (SupportedSourceVersion)this.getClass().getAnnotation(SupportedSourceVersion.class); SourceVersion sv = null; if (ssv == null) { sv = SourceVersion.RELEASE_6; if (this.isInitialized()) { Messager var10000 = this.processingEnv.getMessager(); Kind var10001 = Kind.WARNING; String var10002 = this.getClass().getName(); var10000.printMessage(var10001, "No SupportedSourceVersion annotation found on " + var10002 + ", returning " + sv + "."); } } else { sv = ssv.value(); } return sv; } public synchronized void init(ProcessingEnvironment processingEnv) { // 初始化工作 if (this.initialized) { throw new IllegalStateException("Cannot call init more than once."); } else { Objects.requireNonNull(processingEnv, "Tool provided null ProcessingEnvironment"); this.processingEnv = processingEnv; this.initialized = true; } } public abstract boolean process(Set<? extends TypeElement> var1, RoundEnvironment var2); // process相对于main函数,即方法的入口,在process方法中可以完成扫描、评估、处理注解等等代码。process方法最后会生成所需要的java代码 public Iterable<? extends Completion> getCompletions(Element element, AnnotationMirror annotation, ExecutableElement member, String userText) { return Collections.emptyList(); } protected synchronized boolean isInitialized() { return this.initialized; } private static Set<String> arrayToSet(String[] array, boolean stripModulePrefixes) { assert array != null; Set<String> set = new HashSet(array.length); String[] var3 = array; int var4 = array.length; for(int var5 = 0; var5 < var4; ++var5) { String s = var3[var5]; if (stripModulePrefixes) { int index = s.indexOf(47); if (index != -1) { s = s.substring(index + 1); } } set.add(s); } return Collections.unmodifiableSet(set); } }
ProcessingEnvironment.java
// // Source code recreated from a .class file by IntelliJ IDEA // (powered by FernFlower decompiler) // package javax.annotation.processing; import java.util.Locale; import java.util.Map; import javax.lang.model.SourceVersion; import javax.lang.model.util.Elements; import javax.lang.model.util.Types; public interface ProcessingEnvironment { Map<String, String> getOptions(); Messager getMessager(); Filer getFiler(); //用于创建文件 Elements getElementUtils(); //用来处理Element的工具类,Element是指在注解处理过程中扫描的所有java源文件,可以把这个源文件想象成Element的全部,而源代码中每个独立的部分就可以认作为特定类型的Element Types getTypeUtils(); //TypeElement代表Element的类型, Types是用于获取源代码类型的信息 SourceVersion getSourceVersion(); Locale getLocale(); }
ButterKnife的工作原理
- 编译的时候扫描注解,并做相应的处理,生成java代码,生成Java代码是调用 javapoet 库生成的
- 调用ButterKnife.bind(this);方法的时候,将ID与对应的上下文绑定在一起
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