AOP（Aspect Oriented Programming）切面编程在处理一些与业务逻辑无关，但在很多地方又不得不添加相关逻辑代码，可以很好的解决相关问题，比如在Android中有些地方需要打LOG日志，或者在某些地方需要检查系统权限等，可以很好的解决这类问题。

而AOP中主要使用的就是AspectJ，AspectJ有自己相关的一套语法，大致和JAVA类似。官方简介

那么在AndroidStudio 中要怎么使用AOP呢？

首先需要新建一个module,方便引入相关的AspectJ配置，便于在其中编写与业务逻辑无关紧要，并且在代码中经常出现的常用代码， 之后在module下的build.gradle中 导入AspectJ的dependences

compile ‘org.aspectj:aspectjrt:1.8.9’
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并在build.gradle根下配置

repositories {mavenCentral()
}buildscript {repositories {mavenCentral()}dependencies {classpath 'com.android.tools.build:gradle:2.1.3'classpath 'org.aspectj:aspectjtools:1.8.9'classpath 'org.aspectj:aspectjweaver:1.8.9'}
}android.libraryVariants.all { variant ->LibraryPlugin plugin = project.plugins.getPlugin(LibraryPlugin)JavaCompile javaCompile = variant.javaCompilejavaCompile.doLast {String[] args = ["-showWeaveInfo","-1.5","-inpath", javaCompile.destinationDir.toString(),"-aspectpath", javaCompile.classpath.asPath,"-d", javaCompile.destinationDir.toString(),"-classpath", javaCompile.classpath.asPath,"-bootclasspath", plugin.project.android.bootClasspath.join(File.pathSeparator)]MessageHandler handler = new MessageHandler(true);new Main().run(args, handler)def log = project.loggerfor (IMessage message : handler.getMessages(null, true)) {switch (message.getKind()) {case IMessage.ABORT:case IMessage.ERROR:case IMessage.FAIL:log.error message.message, message.thrownbreak;case IMessage.WARNING:case IMessage.INFO:log.info message.message, message.thrownbreak;case IMessage.DEBUG:log.debug message.message, message.thrownbreak;}}}
}
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以上module的build.gradle 配置主要是搭建AspectJ运行环境

之后在app下的build.gradle添加module的依赖，并且添加如下配置

repositories {mavenCentral()
}
buildscript {repositories {mavenCentral()}dependencies {classpath 'org.aspectj:aspectjtools:1.8.9'}
}final def log = project.logger
final def variants = project.android.applicationVariants
variants.all { variant ->if (!variant.buildType.isDebuggable()) {log.debug("Skipping non-debuggable build type '${variant.buildType.name}'.")return;}JavaCompile javaCompile = variant.javaCompilejavaCompile.doLast {String[] args = ["-showWeaveInfo","-1.5","-inpath", javaCompile.destinationDir.toString(),"-aspectpath", javaCompile.classpath.asPath,"-d", javaCompile.destinationDir.toString(),"-classpath", javaCompile.classpath.asPath,"-bootclasspath", project.android.bootClasspath.join(File.pathSeparator)]log.debug "ajc args: " + Arrays.toString(args)MessageHandler handler = new MessageHandler(true);new Main().run(args, handler);for (IMessage message : handler.getMessages(null, true)) {switch (message.getKind()) {case IMessage.ABORT:case IMessage.ERROR:case IMessage.FAIL:log.error message.message, message.thrownbreak;case IMessage.WARNING:log.warn message.message, message.thrownbreak;case IMessage.INFO:log.info message.message, message.thrownbreak;case IMessage.DEBUG:log.debug message.message, message.thrownbreak;}}}
}
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以上配置主要是将app和module关联起来。

然后在module中创建TestAspectJ类， 具体代码如下：

package com.clayx.org.aspectj;import android.annotation.TargetApi;
import android.os.Build;
import android.util.Log;import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;/*** Created by Administrator on 2016/9/2.*/
@Aspect
public class TestAspectJ {private static final String METHOD_EXECUTION = "execution(* *..MainActivity+.onCreate(..))";private static final String METHOD_CALL = "call(* *..MainActivity+.test(..)) && args(name)";private String TAG = "Clayx";@Pointcut(METHOD_EXECUTION)public void methodExecution() {}@Pointcut(METHOD_CALL)public void methodCall(String name) {}@Around("methodExecution()")public void aroundMethodExecution(ProceedingJoinPoint joinPoint) throws Throwable {joinPoint.proceed();String result = "-----------------------------MethodExecution";Log.e(TAG, result);}@Around("methodCall(String)")public Object arouneMethodCall(ProceedingJoinPoint joinPoint){String name = (String) joinPoint.getArgs()[0];Log.e(TAG,name);return name;}}
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运行APP，打印出Log如下：

对于注解的使用，可以更好的和AspectJ结合使用，

注解类如下:

package com.clayx.org.aspectj.anno;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;/*** Created by Administrator on 2016/9/2.*/
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface TestAspectJ {}
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注解相关的AspectJ的实现类

package com.clayx.org.aspectj.anno;import android.content.Context;
import android.widget.Toast;import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;/*** Created by Administrator on 2016/9/2.*/@Aspect
public class TestAspect {@Pointcut("execution(@TestAspectJ private * *..*.*(..))")public void testAspect() {}@Around("testAspect()")public void testTestAspect(ProceedingJoinPoint joinPoint) {Toast.makeText((Context) joinPoint.getTarget(), "OK", Toast.LENGTH_SHORT).show();}}
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注解运行如下：