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Apt Note - 手动实现简易版Butterknife
早就发现了apt的强大,但是一直没有进行尝试,今天尝试使用apt和javapoet,实现一个简易版的Butterknife.
结构
anno 这个里面放的annotiation,写到单独的library中.依赖时使用compileOnly ,可以不包含到最终的app中,减少不必要的空间浪费.
api 这个里面放的是生成类的接口和bind需要用到的类.
compiler 这个是注解处理器.注解的获取和代码的生成都在这里完成.
三个库都使用 java Library.java的Library不能依赖Android的Library.
Anno
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.SOURCE)
public @interface BindView {
int value();
}Api
public interface IBind<T> {
void bind(T target);
}
------
public class VoidBind {
public static void bind(Object activity) {
try {
//反射对应的类,生成实例调用
Class clazz = Class.forName(activity.getClass().getCanonicalName() + "$VoidBind");
IBind instance = (IBind)clazz.newInstance();
//调用接口方法,为bind的view赋值
instance.bind(activity);
} catch (Exception e) {
e.printStackTrace();
}
}
}Compiler
VoidBindCompiler
@AutoService(Processor.class)
//要处理的annotiation集合
@SupportedAnnotationTypes( { "com.longforus.voidbindanno.BindView" })
@SupportedSourceVersion(SourceVersion.RELEASE_8)
public class VoidBindCompiler extends AbstractProcessor {
private ProcessingEnvironment mProcessingEnv;
private SimpleDateFormat mDateFormat;
@Override
public synchronized void init(ProcessingEnvironment processingEnv) {
super.init(processingEnv);
//后续要用到
mProcessingEnv = processingEnv;
mDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
}
@Override
public boolean process(Set<? extends TypeElement> annotations,RoundEnvironment roundEnv) {
//key为全类名 value为要处理的元素集合
Map<String,List<VariableElement>> map = new HashMap<>();
Set<? extends Element> annotatedWith = roundEnv.getElementsAnnotatedWith(BindView.class);
for (Element element : annotatedWith) {
VariableElement e = (VariableElement)element;
String fullClassName = getFullClassName(e);
//如果map中包含就返回,否则调用lambda,生成value并用K保存到map中
List<VariableElement> elements = map.computeIfAbsent(fullClassName,k -> new ArrayList<>());
elements.add(e);
}
for (Map.Entry<String,List<VariableElement>> entry : map.entrySet()) {
if (entry.getValue() == null || entry.getValue().isEmpty()) {
continue;
}
String fullName = entry.getKey();
int i = fullName.lastIndexOf(".");
//获取外围元素的类型,toString()其实就是全类名
TypeName enclosingTypeName = TypeName.get(entry.getValue().get(0).getEnclosingElement().asType());
//生成方法
MethodSpec.Builder methodBuild = MethodSpec.methodBuilder("bind").addAnnotation(Override.class).addModifiers(Modifier.PUBLIC).returns(void.class).addParameter(
enclosingTypeName,"target");
for (VariableElement element : entry.getValue()) {
methodBuild.addStatement(
String.format(Locale.CHINA,"target.%s=target.findViewById(%d)",element.getSimpleName().toString(),element.getAnnotation(BindView.class).value()));
}
String enclosingClassName = fullName.substring(i + 1,fullName.length());
//生成带泛型的接口类型名
ParameterizedTypeName superinterface = ParameterizedTypeName.get(ClassName.get(IBind.class),enclosingTypeName);
TypeSpec typeSpec = TypeSpec.classBuilder(enclosingClassName + "$VoidBind")
.addModifiers(Modifier.PUBLIC,Modifier.FINAL)
.addSuperinterface(superinterface)
.addMethod(methodBuild.build()).build();
String packageName = fullName.substring(0,i);
JavaFile javaFile = JavaFile.builder(packageName,typeSpec).addFileComment("This class generate by VoidBind.Don't modify it, - "+mDateFormat.format(new Date())).build();
try {
//写出到generated/source/kapt/debug/包名/目录下
javaFile.writeTo(mProcessingEnv.getFiler());
} catch (IOException e) {
e.printStackTrace();
}
}
return true;
}
private String getFullClassName(VariableElement e) {
//获取到持有e的外围元素,这里是Activity等
TypeElement enclosingElement = (TypeElement)e.getEnclosingElement();
//获取外围元素的包名
String packageName = mProcessingEnv.getElementUtils().getPackageOf(enclosingElement).getQualifiedName().toString();
return packageName + "." + enclosingElement.getSimpleName().toString();
}
}
gradle
apply plugin: 'java-library'
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation project(':VoidBindAnno')
//不能依赖android library
implementation project(':VoidBindApi')
implementation 'com.google.auto.service:auto-service:1.0-rc4'
implementation 'com.squareup:javapoet:1.11.0'
}
//指定编译的编码
tasks.withType(JavaCompile){
options.encoding = "UTF-8"
}
sourceCompatibility = "1.8"
targetCompatibility = "1.8"
使用
添加依赖
//注解
compileOnly project(':VoidBindAnno')
//工具
implementation project(':VoidBindApi')
//处理注解生成代码
kapt project(':VoidBindCompiler')进行注解
public class SecondActivity extends AppCompatActivity {
@BindView(R.id.button)
Button mButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
VoidBind.bind(this);
mButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(SecondActivity.this,"success",Toast.LENGTH_SHORT).show();
}
});
}
}如果在kotlin中使用,生成的代码提示被注解的var是private的.暂时还没想到怎么解决
生成的代码
// This class generate by VoidBind.Don't modify it, - 2018-05-09 14:57:29
package com.longforus.aptdemo;
import com.longforus.voidbindapi.IBind;
import java.lang.Override;
public final class SecondActivity$VoidBind implements IBind<SecondActivity> {
@Override
public void bind(SecondActivity target) {
target.mButton=target.findViewById(2131165219);
}
}
也算是打开了一种新的思路,工作中还没有发现适合实际应用的场景.笔记保存,方便查用.
-2018-5-9 15:09:57 升级为使用泛型接口,生成的代码不在强转