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使用annotationProcessor打造编译时的注解（一）
参数对象方法说明
public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
return false;
}
- 参数Set<? extends TypeElement> set：表示使用了支持处理注解的节点集合，此处只支持了BindView，所以此处set集合中只有一个元素
- RoundEnvironment roundEnvironment：表示当前或是之前的运行环境,可以通过该对象查找找到的注解
- return 返回true为表示后续处理器不会再处理(已经处理)
下面为process方法，相关的字段都已经注释好了
private Map<String, List<Element>> classMap = new HashMap<>();
@Override
public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
messager.printMessage(Diagnostic.Kind.NOTE, "process============");
for (TypeElement typeElement : set) {
messager.printMessage(Diagnostic.Kind.NOTE, "typeElement: " + typeElement.toString());
//typeElement就相当于com.cool.butterknife.annoation.BindView
//通过roundEnvironment来获取所有被BindView注解注解了的字段
Set<? extends Element> elementsAnnotatedWith = roundEnvironment.getElementsAnnotatedWith(typeElement);
for (Element element : elementsAnnotatedWith) {
//如果在MainActivity中有这段代码 @BindView(R.id.textView)TextView textView;
//此处的element就是TextView节点元素
//element.getEnclosingElement()为获取其父节点元素，即MainActivty
Element enclosingElement = element.getEnclosingElement();
TypeMirror classTypeMirror = enclosingElement.asType();
//className为MainActivty的全类名
String className = classTypeMirror.toString();
//上面只是拿MainActivty举个例子，但是真实的使用注解的可能还有SecondActivity等等，所有需要以类名为键保存里面所有使用了BindView注解的节点
List<Element> elements = classMap.get(className);
if (elements == null) {
elements = new ArrayList<>();
elements.add(element);
classMap.put(className, elements);
}else {
elements.add(element);
}
}
Set<Map.Entry<String, List<Element>>> entries = classMap.entrySet();
for (Map.Entry<String, List<Element>> entry : entries) {
String key = entry.getKey();
List<Element> value = entry.getValue();
//生成java代码
generateViewBinding(key,value);
}
}
return false;
}
generateViewBinding方法
首先看一下生成的2个类中的代码
public class MainActivity_ViewBinding implements Unbinder {
private MainActivity target;
@UiThread
public MainActivity_ViewBinding(final MainActivity target, View source) {
this.target = target;
target.textView = source.findViewById(2131165320);
target.textView2 = source.findViewById(2131165321);
}
public void unbind() {
MainActivity target = this.target;
this.target = null;
target.textView = null;
target.textView2 = null;
}
}
public class SecondActivity_ViewBinding implements Unbinder {
private SecondActivity target;
@UiThread
public SecondActivity_ViewBinding(final SecondActivity target, View source) {
this.target = target;
target.button = source.findViewById(2131165219);
}
public void unbind() {
SecondActivity target = this.target;
this.target = null;
target.button = null;
}
}
生成代码使用了 javapoet,没用过不懂的可以参考其github主页上的例子
private void generateViewBinding(String key, List<Element> values) {
//生成类元素节点 此处key为com.cool.butterknife.MainActivity或者com.cool.butterknife.SecondActivity
TypeElement classTypeElement = elementUtils.getTypeElement(key);
//生成参数 final MainActivity target
ParameterSpec targetParameterSpec = ParameterSpec
.builder(ClassName.get(classTypeElement), "target", Modifier.FINAL)
.build();
//生成参数 View source
ParameterSpec viewParameterSpec = ParameterSpec.builder(ClassName.get("android.view", "View"), "source")
.build();
MethodSpec constructor = null;
//生成构造函数
MethodSpec.Builder constructorMethodBuilder = MethodSpec.constructorBuilder()
.addParameter(targetParameterSpec)
.addParameter(viewParameterSpec)
.addAnnotation(ClassName.bestGuess("android.support.annotation.UiThread"))
.addModifiers(Modifier.PUBLIC);
// 构造函数中添加代码块
constructorMethodBuilder.addStatement("this.target = target");
for (Element element : values) {
BindView bindView = element.getAnnotation(BindView.class);
int id = bindView.value();
Name simpleName = element.getSimpleName();
constructorMethodBuilder.addStatement("target.$L = source.findViewById($L)", simpleName.toString(), id);
}
constructor = constructorMethodBuilder.build();
//生成unbind方法
MethodSpec.Builder unbindMethodSpec = MethodSpec.methodBuilder("unbind")
.addModifiers(Modifier.PUBLIC);
unbindMethodSpec.addStatement("$T target = this.target", ClassName.get(classTypeElement));
unbindMethodSpec.addStatement("this.target = null");
for (Element element : values) {
Name simpleName = element.getSimpleName();
unbindMethodSpec.addStatement("target.$L = null", simpleName.toString());
}
//生成MainActivity_ViewBinding类
TypeSpec typeSpec = TypeSpec.classBuilder(classTypeElement.getSimpleName() + "_ViewBinding")
.addField(ClassName.get(classTypeElement), "target", Modifier.PRIVATE)
.addMethod(constructor)
.addMethod(unbindMethodSpec.build())
.addSuperinterface(ClassName.bestGuess("com.cool.butterknife.core.Unbinder"))
.addModifiers(Modifier.PUBLIC)
.build();
//获取包名
String packageName = elementUtils.getPackageOf(classTypeElement).getQualifiedName().toString();
messager.printMessage(Diagnostic.Kind.NOTE, "packageName: " + packageName.toString());
JavaFile javaFile = JavaFile.builder(packageName, typeSpec)
.build();
try {
//写入java文件
javaFile.writeTo(filer);
} catch (IOException e) {
e.printStackTrace();
}
}
看完，你可能会有点身体不适，但是这个难点在于如何拼接类，有点繁琐，一不小心就容易出错，而且出错之后问题比较难找，唯有静下心来慢慢的看，一定要仔细。
到处，点击make就可以生成类了，接下来使用刚刚生成的类
/**
* Created by cool on 2018/7/3.
*/
public class Butterknife {
static final Map<Class<?>, Constructor<? extends Unbinder>> BINDINGS = new LinkedHashMap<>();
@NonNull
@UiThread
public static Unbinder bind(@NonNull Activity target) {
View sourceView = target.getWindow().getDecorView();
return createBinding(target, sourceView);
}
private static Unbinder createBinding(Activity target, View sourceView) {
Class<?> targetClass = target.getClass();
Constructor<? extends Unbinder> constructor = findBindingConstructorForClass(targetClass);
if (constructor == null) {
return Unbinder.EMPTY;
}
try {
return constructor.newInstance(target, sourceView);
} catch (IllegalAccessException e) {
throw new RuntimeException("Unable to invoke " + constructor, e);
} catch (InstantiationException e) {
throw new RuntimeException("Unable to invoke " + constructor, e);
} catch (InvocationTargetException e) {
Throwable cause = e.getCause();
if (cause instanceof RuntimeException) {
throw (RuntimeException) cause;
}
if (cause instanceof Error) {
throw (Error) cause;
}
throw new RuntimeException("Unable to create binding instance.", cause);
}
}
private static Constructor<? extends Unbinder> findBindingConstructorForClass(Class<?> targetClass) {
Constructor<? extends Unbinder> constructor = BINDINGS.get(targetClass);
if (constructor != null) {
return constructor;
}
String targetClassName = targetClass.getName();
try {
Class<?> viewBindingClass = Class.forName(targetClassName + "_ViewBinding");
constructor = (Constructor<? extends Unbinder>) viewBindingClass.getConstructor(targetClass, View.class);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
BINDINGS.put(targetClass, constructor);
return constructor;
}
}
呃呃，这个就不解释类，比较简单，接下来是使用
public class MainActivity extends AppCompatActivity {
@BindView(R.id.textView)
TextView textView;
@BindView(R.id.textView2)
TextView textView2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Butterknife.bind(this);
textView.setText("ButterKnife Test");
}
@OnClick(R.id.bt_click)
public void onClick(View view){
Toast.makeText(this,"点击",Toast.LENGTH_SHORT).show();
}
}
最后贴一下BindViewProcessor.java完整版
package com.cool.butterknife.compiler;
import com.cool.butterknife.annoation.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.ParameterSpec;
import com.squareup.javapoet.TypeSpec;
import java.io.IOException;
import java.util.ArrayList;
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.AnnotationMirror;
import javax.lang.model.element.AnnotationValue;
import javax.lang.model.element.Element;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.Modifier;
import javax.lang.model.element.Name;
import javax.lang.model.element.TypeElement;
import javax.lang.model.element.VariableElement;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.util.Elements;
import javax.tools.Diagnostic;
@AutoService(Processor.class)
@SupportedAnnotationTypes("com.cool.butterknife.annoation.BindView")
@SupportedSourceVersion(SourceVersion.RELEASE_7)
public class BindViewProcessor extends AbstractProcessor {
private Messager messager;
private Filer filer;
private Elements elementUtils;
private Map<String, List<Element>> classMap = new HashMap<>();
@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) {
messager.printMessage(Diagnostic.Kind.NOTE, "=======process============");
for (TypeElement typeElement : set) {
messager.printMessage(Diagnostic.Kind.NOTE, "typeElement: " + typeElement.toString());
//typeElement就相当于com.cool.butterknife.annoation.BindView
//通过roundEnvironment来获取所有被BindView注解注解了的字段
Set<? extends Element> elementsAnnotatedWith = roundEnvironment.getElementsAnnotatedWith(typeElement);
for (Element element : elementsAnnotatedWith) {
//如果在MainActivity中有这段代码 @BindView(R.id.textView)TextView textView;
//此处的element就是TextView节点元素
//element.getEnclosingElement()为获取其父节点元素，即MainActivty
Element enclosingElement = element.getEnclosingElement();
TypeMirror classTypeMirror = enclosingElement.asType();
//className为MainActivty的全类名
String className = classTypeMirror.toString();
//上面只是拿MainActivty举个例子，但是真实的使用注解的可能还有SecondActivity等等，所有需要以类名为键保存里面所有使用了BindView注解的节点
List<Element> elements = classMap.get(className);
if (elements == null) {
elements = new ArrayList<>();
elements.add(element);
classMap.put(className, elements);
} else {
elements.add(element);
}
}
Set<Map.Entry<String, List<Element>>> entries = classMap.entrySet();
for (Map.Entry<String, List<Element>> entry : entries) {
String key = entry.getKey();
List<Element> value = entry.getValue();
//生成java代码
generateViewBinding(key, value);
}
}
return false;
}
private void generateViewBinding(String key, List<Element> values) {
//生成类元素节点 此处key为com.cool.butterknife.MainActivity或者com.cool.butterknife.SecondActivity
TypeElement classTypeElement = elementUtils.getTypeElement(key);
//生成参数 final MainActivity target
ParameterSpec targetParameterSpec = ParameterSpec
.builder(ClassName.get(classTypeElement), "target", Modifier.FINAL)
.build();
//生成参数 View source
ParameterSpec viewParameterSpec = ParameterSpec.builder(ClassName.get("android.view", "View"), "source")
.build();
MethodSpec constructor = null;
//生成构造函数
MethodSpec.Builder constructorMethodBuilder = MethodSpec.constructorBuilder()
.addParameter(targetParameterSpec)
.addParameter(viewParameterSpec)
.addAnnotation(ClassName.bestGuess("android.support.annotation.UiThread"))
.addModifiers(Modifier.PUBLIC);
// 构造函数中添加代码块
constructorMethodBuilder.addStatement("this.target = target");
for (Element element : values) {
BindView bindView = element.getAnnotation(BindView.class);
int id = bindView.value();
Name simpleName = element.getSimpleName();
constructorMethodBuilder.addStatement("target.$L = source.findViewById($L)", simpleName.toString(), id);
}
constructor = constructorMethodBuilder.build();
//生成unbind方法
MethodSpec.Builder unbindMethodSpec = MethodSpec.methodBuilder("unbind")
.addModifiers(Modifier.PUBLIC);
unbindMethodSpec.addStatement("$T target = this.target", ClassName.get(classTypeElement));
unbindMethodSpec.addStatement("this.target = null");
for (Element element : values) {
Name simpleName = element.getSimpleName();
unbindMethodSpec.addStatement("target.$L = null", simpleName.toString());
}
//生成MainActivity_ViewBinding类
TypeSpec typeSpec = TypeSpec.classBuilder(classTypeElement.getSimpleName() + "_ViewBinding")
.addField(ClassName.get(classTypeElement), "target", Modifier.PRIVATE)
.addMethod(constructor)
.addMethod(unbindMethodSpec.build())
.addSuperinterface(ClassName.bestGuess("com.cool.butterknife.core.Unbinder"))
.addModifiers(Modifier.PUBLIC)
.build();
//获取包名
String packageName = elementUtils.getPackageOf(classTypeElement).getQualifiedName().toString();
messager.printMessage(Diagnostic.Kind.NOTE, "packageName: " + packageName.toString());
JavaFile javaFile = JavaFile.builder(packageName, typeSpec)
.build();
try {
//写入java文件
javaFile.writeTo(filer);
} catch (IOException e) {
e.printStackTrace();
}
}
}
onClick在写这篇文章时没做实现，到时实现放在第3篇吧
查看源码
使用annotationProcessor打造编译时的注解（三)
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