apt 与 JavaPoet 自动生成代码

@Override
public RecyclerView.ViewHolder onCreateInnerViewHolder(ViewGroup viewGroup, int viewType) {
    View convertView;
    convertView = (View) ONAViewTools.getONAView(viewType, mContext);
    return new RecycleViewItemHolder(convertView);
}

public static IONAView getONAView(int viewType, Context context) {
    .........
    return createONAView(viewType, context);
}

 public static IONAView createONAView(int viewType, Context context) {
        try {
            if (context != null) {
                switch (viewType) {
                    case EONAViewType._EnumONAMultPoster:
                        return new ONAMultPosterView(context);
                    case EONAViewType._EnumONAGalleryPoster:
                        return new ONAGalleryPosterView(context);
                        .......此处省略了很多条case:
                        return new ONASplitLineView(context);
                    case EONAViewType._EnumONAStarList:
                        return new ONAStarListView(context);
                    case EONAViewType._EnumONANewsItem:
                        return new ONANewsItemView(context);
                 }
            }
      }catch(Exception e){

       }
}

Element element = processingEviroment.getTypeUtils().asElement(typeMirror);

@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.TYPE)
public @interface ViewType {
    int value() default -1;
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile project(':viewtypebinder')
    compile 'com.squareup:javapoet:1.7.0'
}

sourceCompatibility = "1.7"
targetCompatibility = "1.7"

@SupportedAnnotationTypes("com.example.ViewType")
@SupportedOptions({"fileName","failedView"})
public class ViewTypeProcessor extends AbstractProcessor {

    private Messager mMessager;
    private static final String GENERATED_FILE_NAME = "fileName";
    private static final String FAILED_VIEW = "failedView";
    private String mFileName;

    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        System.out.println("process");
        Collection<? extends Element> annotatedElements = roundEnv.getElementsAnnotatedWith(ViewType.class);
        List<TypeElement> types = ElementFilter.typesIn(annotatedElements);
        if(types == null || types.isEmpty()){
            return false;
        }
        mFileName = processingEnv.getOptions().get(GENERATED_FILE_NAME);
        if(mFileName == null || mFileName.isEmpty()){
            mMessager.printMessage(Diagnostic.Kind.WARNING, "No option generatedFileName passed to annotation processor");
            return false;
        }
        //解析failedView参数 -------- ①
        ClassName failedView = null;
        String failedViewName = processingEnv.getOptions().get(FAILED_VIEW);
        try {
            if(failedViewName != null && !failedViewName.isEmpty()){
                failedView = ClassName.bestGuess(failedViewName);
            }
        }catch (IllegalArgumentException e){
            mMessager.printMessage(Diagnostic.Kind.ERROR, String.format(Locale.getDefault(), "Option is invalid: %s", failedViewName));
            throw  new AbortProcessViewTypeException(e);
        }
        TypeElement failedViewTypeElement = processingEnv.getElementUtils().getTypeElement(failedViewName);
        checkTypeVaild(failedViewTypeElement);

        ClassName className = null;
        try {
            className = ClassName.bestGuess(mFileName);
            System.out.println("Generate file name: " + mFileName);
        }catch (IllegalArgumentException e){
            mMessager.printMessage(Diagnostic.Kind.ERROR, String.format(Locale.getDefault(), "Option is invalid: %s", mFileName));
            RuntimeException processException = new AbortProcessViewTypeException();
            processException.initCause(e);
            throw processException;
        }
        ClassName View = ClassName.bestGuess("android.view.View");
        ClassName Context = ClassName.bestGuess("android.content.Context");
        //构建类
        TypeSpec.Builder typeBuilder = TypeSpec.classBuilder(className)
                .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
                .addJavadoc("This file is generated by apt, please do not modify!");
        ParameterSpec paramsContext = ParameterSpec.builder(Context, "context").build();
        ParameterSpec typeParamSpec = ParameterSpec.builder(TypeName.INT, "type").build();
        //构建方法 public static final createView(Context context, int type)
        MethodSpec.Builder methodBuilder = MethodSpec.methodBuilder("createView")
                .addModifiers(Modifier.FINAL, Modifier.PUBLIC, Modifier.STATIC)
                .returns(View)
                .addParameter(paramsContext)
                .addParameter(typeParamSpec);
        //如果指定了failedView，则如果创建View发生异常时，返回failedView
        if(failedView != null){
             methodBuilder.beginControlFlow("try");
        }
        //构建switch(type){
        //            }
        //代码块
        CodeBlock.Builder caseBlock = CodeBlock.builder().beginControlFlow("switch($N)", typeParamSpec);
        //循环遍历所有被注解元素，每项元素都会对应生成一条case 语句
        for (TypeElement type : types){
            ViewType viewType = type.getAnnotation(ViewType.class);
            if(viewType == null){
                continue;
            }
            checkTypeVaild(type);
            int value = viewType.value();
            ClassName viewName = ClassName.get(type);
            System.out.println("viewName = " +viewName.simpleName() + ", value = " + value);
            caseBlock.add("case $L:\n", value).indent().addStatement("return new $T($N)", viewName, paramsContext).unindent();
        }
        //没有匹配到的情况下，返回null
        caseBlock.add("default:\n").indent().addStatement("return null", View, paramsContext).unindent();
        caseBlock.endControlFlow();
        methodBuilder.addCode(caseBlock.build());
        if(failedView != null) {
            methodBuilder.nextControlFlow("catch($T t)", Throwable.class);
            methodBuilder.addStatement("return new $T($N)", failedView, paramsContext);
            methodBuilder.endControlFlow();
        }
        //构建文件
        JavaFile javaFile = JavaFile.builder(className.packageName(), typeBuilder.addMethod(methodBuilder.build()).build()).build();
        //写文件
        writeSourceFile(mFileName, javaFile.toString());
        return false;
    }

	TypeElement failedViewTypeElement = processingEnv.getElementUtils().getTypeElement(failedViewName);
	checkTypeVaild(failedViewTypeElement);

    private void checkTypeVaild(TypeElement type) {
        if(type.getKind() != ElementKind.CLASS){
            reportErrorWithAbort("The annotation @ViewType only applies to classes", type);
        }

        if(!ancestorIsView(type)){
           reportErrorWithAbort("The annotation @ViewType only applies to Views", type);
        }
        if(!isVisible(type)){
            reportErrorWithAbort("cannot resolve symbol " + type.getQualifiedName(), type);
        }
    }

    private boolean ancestorIsView(TypeElement type) {
        while (true){
            TypeMirror parentMirror = type.getSuperclass();
            if(parentMirror.getKind() == TypeKind.NONE){
                return false;
            }
            TypeElement parentElement = (TypeElement) processingEnv.getTypeUtils().asElement(parentMirror);
            if(parentElement.getQualifiedName().contentEquals("android.view.View")){
                return true;
            }
            type = parentElement;
        }
    }

    private boolean isVisible(TypeElement type){
        String myPackage = ClassName.bestGuess(mFileName).packageName();
        boolean isNestClass = type.getEnclosingElement().getKind() == ElementKind.CLASS;
        Set<Modifier> modifiers = type.getModifiers();
        if(isNestClass && !modifiers.contains(Modifier.STATIC)){
            return false;
        }
        if(modifiers.contains(Modifier.PUBLIC)){
            return true;
        }
        if(ClassName.get(type).packageName().contentEquals(myPackage)){
            return true;
        }
        return false;
    }

        JavaFile javaFile = JavaFile.builder(className.packageName(), typeBuilder.addMethod(methodBuilder.build()).build()).build();
        writeSourceFile(mFileName, javaFile.toString());

    private void writeSourceFile(String fileName, String s) {
        try {
            JavaFileObject fileObject = processingEnv.getFiler().createSourceFile(fileName);
            Writer writer =fileObject.openWriter();
            try {
                writer.write(s);
            }finally {
                try {
                    writer.close();
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
        }catch (IOException e){
            mMessager.printMessage(Diagnostic.Kind.WARNING, "could not write class " + fileName);
        }
    }

com.example.ViewTypeProcessor

@ViewType(MyViewTypes.MY_NAME_VIEW)
public class MyNameView extends TextView {
    public MyNameView(Context context) {
        this(context, null, 0);
    }

    public MyNameView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MyNameView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initView();
    }

    private void initView() {
        setText("吴涛");
        setTextColor(Color.BLACK);
        setTextSize(TypedValue.COMPLEX_UNIT_SP, 18);
        setGravity(Gravity.CENTER);
    }

}

public class FailedView extends View {

    public FailedView(Context context) {
        super(context);
    }

    public FailedView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public FailedView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }
}

apply plugin: 'com.android.application'
apply plugin: 'com.neenbedankt.android-apt'  //引入android-apt插件

android {
  .................

}

apt {
    arguments {
        fileName "com.example.wutao.autotypebinding.ViewTypeTools"  //注解处理器生成的java文件名
        failedView "com.example.wutao.autotypebinding.view.FailedView"      //指定异常View
    }
}

dependencies {
    ........
    ........
    provided project(":viewtypebinder") 
    apt project(':apt_compiler')
}

package com.example.wutao.autotypebinding;

import android.content.Context;
import android.view.View;
import com.example.wutao.autotypebinding.view.FailedView;
import com.example.wutao.autotypebinding.view.MyNameView;
import java.lang.Throwable;

/**
 * This file is generated by apt, please do not modify! */
public final class ViewTypeTools {
  public static final View createView(Context context, int type) {
    try {
      switch(type) {
        case 11:
          return new MyNameView(context);
        default:
          return null;
      }
    } catch(Throwable t) {
      return new FailedView(context);
    }
  }
}

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        View view = ViewTypeTools.createView(this, MyViewTypes.MY_NAME_VIEW);
        ViewGroup root = findViewById(R.id.root);
        root.addView(view);
    }
}

org.gradle.jvmargs=-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005
org.gradle.daemon=true