butterknife工具在项目中比较常用
分三个模块模块之间的UML关系图

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仿butterknife自定义BindView

一、创建三个library

1.compiler

 @AutoService(Processor.class)
public class ButterKnifeProcessor extends AbstractProcessor {

 /**
 * 用来指定支持的 AnnotationTypes
 *
 * @return
 */
@Override
public Set<String> getSupportedAnnotationTypes() {
    Set<String> types = new LinkedHashSet<>();
    for (Class<? extends Annotation> annotation : getSupportedAnnotations()) {
        types.add(annotation.getCanonicalName());
    }
    return types;
}

/**
 * 参考了 ButterKnife 的写法
 *
 * @return
 */
private Set<Class<? extends Annotation>> getSupportedAnnotations() {
    Set<Class<? extends Annotation>> annotations = new LinkedHashSet<>();
    annotations.add(BindView.class);
    return annotations;
}

/**
 * 用来指定支持的 SourceVersion
 *
 * @return
 */
@Override
public SourceVersion getSupportedSourceVersion() {
    return SourceVersion.latestSupported();
}

@Override
public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
    // 调试打印
    System.out.println("------------------------------------>");
    System.out.println("------------------------------------>");
    return false;
}
}

添加依赖

     compile 'com.google.auto.service:auto-service:1.0-rc3'
     compile 'com.squareup:javapoet:1.8.0'
    compile project(':annotations')
    compile files('libs/tools.jar')

如果我们在代码的任何地方有注解，都会来到 process 这个方法里面。

    @Override
    public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
    // 调试打印
    // System.out.println("------------------------------------>");
    // System.out.println("------------------------------------>");

    Set<? extends Element> bindViewElements = roundEnvironment.getElementsAnnotatedWith(BindView.class);

    // 解析 Element
    Map<Element, List<Element>> analysisElementMap = new LinkedHashMap<>();
    for (Element bindViewElement : bindViewElements) {
        Element enclosingElement = bindViewElement.getEnclosingElement();

        List<Element> elements = analysisElementMap.get(enclosingElement);
        if (elements == null) {
            elements = new ArrayList<>();
            analysisElementMap.put(enclosingElement, elements);
        }

        elements.add(bindViewElement);
    }

    // 生成 java 类
    for (Map.Entry<Element, List<Element>> entry : analysisElementMap.entrySet()) {
        Element enclosingElement = entry.getKey();
        List<Element> elements = entry.getValue();

        String classNameStr = enclosingElement.getSimpleName().toString();

        ClassName unbinderClassName = ClassName.get("com.butterknife", "Unbinder");
        // 组装类:  xxx_ViewBinding implements Unbinder
        TypeSpec.Builder typeSpecBuilder = TypeSpec.classBuilder(classNameStr + "_ViewBinding")
                .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
                .addSuperinterface(unbinderClassName);

        ClassName callSuperClassName = ClassName.get("android.support.annotation", "CallSuper");
        // 组装unbind 方法
        MethodSpec.Builder unbindMethodBuilder = MethodSpec.methodBuilder("unbind")
                .addAnnotation(Override.class)
                .addAnnotation(callSuperClassName)
                .addModifiers(Modifier.PUBLIC)
                .returns(TypeName.VOID);

        ClassName uiThreadClassName = ClassName.get("android.support.annotation", "UiThread");
        ClassName parameterClassName = ClassName.bestGuess(classNameStr);
        // 组装构造函数: public xxx_ViewBinding(xxx target)
        MethodSpec.Builder constructorBuilder = MethodSpec.constructorBuilder()
                .addAnnotation(uiThreadClassName)
                .addModifiers(Modifier.PUBLIC)
                .addParameter(parameterClassName, "target");

        // 添加 target.textView1 = Utils.findViewById(target,R.id.tv1);
        for (Element bindViewElement : elements) {
            String filedName = bindViewElement.getSimpleName().toString();
            ClassName utilClassName = ClassName.get("com.butterknife", "Utils");
            int resId = bindViewElement.getAnnotation(BindView.class).value();
            constructorBuilder.addStatement("target.$L = $T.findViewById(target,$L)",
                    filedName, utilClassName, resId);
        }

        typeSpecBuilder.addMethod(constructorBuilder.build());
        typeSpecBuilder.addMethod(unbindMethodBuilder.build());

        try {
            // 写入生成 java 类
            String packageName = mElementUtils.getPackageOf(enclosingElement).getQualifiedName().toString();
            JavaFile.builder(packageName, typeSpecBuilder.build())
                    .addFileComment("ButterKnife自动生成")
                    .build().writeTo(mFiler);
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("翻车了");
        }
    }

    return false;
}

2.annotations

创建BindView

 @Target(ElementType.FIELD)
 @Retention(RetentionPolicy.CLASS)
  public @interface BindView {
  int value();
  }

3.butterknife

创建Unbinder

public interface Unbinder {
@UiThread
void unbind();

Unbinder EMPTY = new Unbinder() {
    @Override
    public void unbind() {
    }
};}

创建Utils

 public class Utils {
public static final <T extends View> T findViewById(Activity activity, int viewId) {
    return (T) activity.findViewById(viewId);
}
}

创建 ButterKnife

public class ButterKnife {
private ButterKnife() {
    throw new AssertionError("No instances.");
}

public final static Unbinder bind(Activity activity) {
    String viewBindingClassName = activity.getClass().getName() + "_ViewBinding";
    try {
        Class<? extends Unbinder> viewBindingClass = (Class<? extends Unbinder>) Class.forName(viewBindingClassName);
        Constructor<? extends Unbinder> viewBindingConstructor = viewBindingClass.getDeclaredConstructor(activity.getClass());
        Unbinder unbinder = viewBindingConstructor.newInstance(activity);
        return unbinder;
    } catch (Exception e) {
        e.printStackTrace();
    }
    return Unbinder.EMPTY;
}
}

二、使用

1.module的builder

依赖

   compile project(':annotations')
   compile project(':butterknife')
   apt project(':compiler')

添加

   apply plugin: 'com.neenbedankt.android-apt'

2.工程的builder

   repositories {
    jcenter()
    mavenCentral()
  }
dependencies {
    classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
    // NOTE: Do not place your application dependencies here; they belong
    // in the individual module build.gradle files
}

3.使用

 public class MainActivity extends Activity {
@BindView(R.id.tv_text)
TextView textView1;
private Unbinder bind;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

        bind = ButterKnife.bind(this);
        textView1.setText("1111111111");
}
@Override
protected void onDestroy() {
    super.onDestroy();
    bind.unbind();
}
}