japt

新建两个JAVA library

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在japtlib 里面

package com.example.japtlib;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.SOURCE)
public @interface BindView {
   int value();
}

在compiler里面

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1. build.gradle 里面 ： compileOnly'com.google.auto.service:auto-service:1.0-rc4'
   // annotationProcessor'com.google.auto.service:auto-service:1.0-rc4'
   //javaPoet可以更方便的创建java文件
   implementation 'com.squareup:javapoet:1.9.0'

新建一个文件 在目录 compiler/src/main/resources/META-INF/services
com.example.compiler.BindViewProcessor (包名+注解器名称)

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3. 新建一个类

package com.example.compiler;

import com.example.japtlib.BindView;
import com.google.auto.service.AutoService;
import com.squareup.javapoet.ClassName;
import com.squareup.javapoet.JavaFile;
import com.squareup.javapoet.MethodSpec;
import com.squareup.javapoet.TypeSpec;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.Filer;
import javax.annotation.processing.Messager;
import javax.annotation.processing.ProcessingEnvironment;
import javax.annotation.processing.Processor;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Element;
import javax.lang.model.element.ElementKind;
import javax.lang.model.element.Modifier;
import javax.lang.model.element.TypeElement;
import javax.lang.model.element.VariableElement;
import javax.lang.model.util.ElementFilter;
import javax.lang.model.util.Elements;
import javax.tools.Diagnostic;

@AutoService(Processor.class)//自动注册
@SupportedAnnotationTypes("com.example.japtlib.BindView")//指名要处理的注解
@SupportedSourceVersion(SourceVersion.RELEASE_7)//知名支持的java版本
public class BindViewProcessor extends AbstractProcessor {

    private Messager messager;//打印日志的类
    private Filer filer;
    private Elements elementUtils;//元素节点工具

    @Override
    public synchronized void init(ProcessingEnvironment processingEnvironment) {
        super.init(processingEnvironment);
        filer = processingEnvironment.getFiler();
        messager = processingEnvironment.getMessager();
        elementUtils = processingEnvironment.getElementUtils();
        messager.printMessage(Diagnostic.Kind.NOTE, "=====init=====");
    }

    @Override
    public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
        for (TypeElement element : set) {
            messager.printMessage(Diagnostic.Kind.NOTE, "element-toString()"+(element.getQualifiedName().toString()));
            if (element.getQualifiedName().toString().equals(BindView.class.getCanonicalName())) {
                // main method
                MethodSpec main = MethodSpec.methodBuilder("main")
                        .addModifiers(Modifier.PUBLIC, Modifier.STATIC)
                        .returns(void.class)
                        .addParameter(String[].class, "args")
                        .addStatement("$T.out.println($S)", System.class, "Hello, JavaPoet!")
                        .addStatement("$T obj", ClassName.get("com.example.aptmodule","MainActivity"))
                        .build();
                // HelloWorld class
                TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld")
                        .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
                        .addMethod(main)
                        .build();

                try {
                    // build com.example.HelloWorld.java
                    JavaFile javaFile = JavaFile.builder("com.example", helloWorld)
                            .addFileComment(" This codes are generated automatically. Do not modify!")
                            .build();
                    // write to file
                    javaFile.writeTo(filer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return true;
    }

    @Override
    public Set<String> getSupportedAnnotationTypes() {
        return Collections.singleton(BindView.class.getCanonicalName());
    }

    @Override
    public SourceVersion getSupportedSourceVersion() {
        return SourceVersion.latestSupported();
    }

}

在app module里面
// 依赖注解处理器

 annotationProcessor project(':compiler')
    implementation project(':JAptLib')

使用：

@BindView(value = R.id.tv)
    TextView textView;