Android自定义注解生成文件

步骤一：新建注解的java module：

新module的gradle配置文件如下：

plugins {
    id 'java-library'
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
}

java {
    sourceCompatibility = JavaVersion.VERSION_1_8
    targetCompatibility = JavaVersion.VERSION_1_8
}

添加注解类：

import java.lang.annotation.ElementType;
import java.lang.annotation.Target;

@Target(ElementType.TYPE)
public @interface FragmentDestination {
    String pageUrl();

    boolean needLogin() default false;

    boolean asStarter() default false;
}

步骤二：新建注解处理器module：

同样也是新建java的module：

因为注解处理器是处理注解的，因此，这个module需要依赖与上面的那个注解module，gradle配置文件如下：

plugins {
    id 'java-library'
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation project(':libnavannotation')
    implementation 'com.alibaba:fastjson:1.2.59'
    implementation 'com.google.auto.service:auto-service:1.0-rc6'
    annotationProcessor 'com.google.auto.service:auto-service:1.0-rc6'
}

java {
    sourceCompatibility = JavaVersion.VERSION_1_8
    targetCompatibility = JavaVersion.VERSION_1_8
}

下面是最重要的编写注解处理器，

这个处理器的主要逻辑就是根据上一个注解module中声明的注解，来生成所需要的代码：

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.google.auto.service.AutoService;
import com.test.libnavannotation.ActivityDestination;
import com.test.libnavannotation.FragmentDestination;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.lang.annotation.Annotation;
import java.util.HashMap;
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.TypeElement;
import javax.tools.Diagnostic;
import javax.tools.FileObject;
import javax.tools.StandardLocation;

@AutoService(Processor.class)
@SupportedSourceVersion(SourceVersion.RELEASE_8)
@SupportedAnnotationTypes({"com.test.libnavannotation.ActivityDestination", "com.test.libnavannotation.FragmentDestination"})
public class NavProcessor extends AbstractProcessor {
    private Messager messager;
    private Filer filer;
    private static final String OUTPUT_FILE_NAME = "destination.json";

    @Override
    public synchronized void init(ProcessingEnvironment processingEnv) {
        super.init(processingEnv);
        //日志打印,在java环境下不能使用android.util.log.e()
        messager = processingEnv.getMessager();
        //文件处理工具
        filer = processingEnv.getFiler();
    }

    @Override
    public boolean process(Set