注解框架源码分析（XUtilsButterKnife）
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1.前言
频繁的findViewById是一件挺烦人的事，IOC注解框架应运而生，android中IOC框架就是注入控件和布局或者说是设置点击监听。
现在主流的有ButterKnife、xUtils、afinal等，IOC注解框架刚出来的时候，粗略看过源码后我是摒弃使用的，因为里面有反射、循环遍历寻找控件等操作，但是慢慢的接收了这种快捷方式，发现对实际性能影响并不大，不是在特别强迫症的情况下完全可行，特别是ButterKnife的出现，ButterKnife没有利用全反射，而是在同包下动态编译生成代码，性能几乎和自己findViewById性能是一样的！
2.源码分析
下面我们来实际分析xUtils和ButterKnife的源码：
2.1 xUtils 使用
xUtils源码地址：https://github.com/wyouflf/xUtils3
xUtils 包含了orm, http(s), image, view注解，下面我们重点讲解View注解（IOC注入）：
public class MainActivity extends AppCompatActivity
@ViewInject(R.id.test_tv)
private TextView test_tv;
@ViewInject(R.id.test_btn)
private Button test_btn;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
x.view().inject(this);
test_tv.setText("测试文本");
test_btn.setText("测试按钮");
/**
* 1. 方法必须私有限定,
* 2. 方法参数形式必须和type对应的Listener接口一致.
* 3. 注解参数value支持数组: value=id1, id2, id3
* 4. 其它参数说明见@link org.xutils.view.annotation.Event类的说明.
**/
@Event(value = R.id.test_btn,
type = View.OnClickListener.class/*可选参数, 默认是View.OnClickListener.class*/)
private void iconIvClick(View view)
test_tv.setText("点击了按钮，修改测试文本");
Toast.makeText(this, "点击了按钮，修改测试文本", Toast.LENGTH_LONG).show();
2.2 xUtils源码分析
我们挑一些关键的源码分析，先分析x.view().inject(this);这句代码做了什么：
点击进入查看是一个接口ViewInjector，看不到实现代码，我就Ctrl+鼠标左键查看实现类：
找到实现类ViewInjectorImpl中inject(Activity activity)方法代码：
@Override
public void inject(Activity activity)
//获取Activity的ContentView的注解
Class<?> handlerType = activity.getClass();
try
// 找到ContentView这个注解，在activity类上面获取
ContentView contentView = findContentView(handlerType);
if (contentView != null)
int viewId = contentView.value();
if (viewId > 0)
// 如果有注解获取layoutId的值，利用反射调用activity的setContentView方法注入视图
Method setContentViewMethod = handlerType.getMethod("setContentView", int.class);
setContentViewMethod.invoke(activity, viewId);
catch (Throwable ex)
LogUtil.e(ex.getMessage(), ex);
// 处理 findViewById和setOnclickListener的注解
injectObject(activity, handlerType, new ViewFinder(activity));
根据源码可知，先判断是否有ContentView这个注解，在activity类上面获取，有则setContentView(R.layout.xxxx)，然后再处理 findViewById和setOnclickListener的注解（injectObject方法）：
@SuppressWarnings("ConstantConditions")
private static void injectObject(Object handler, Class<?> handlerType, ViewFinder finder)
if (handlerType == null || IGNORED.contains(handlerType))
return;
// 从父类到子类递归
injectObject(handler, handlerType.getSuperclass(), finder);
// inject view
Field[] fields = handlerType.getDeclaredFields();
if (fields != null && fields.length > 0)
for (Field field : fields)
Class<?> fieldType = field.getType();
if (
/* 不注入静态字段 */ Modifier.isStatic(field.getModifiers()) ||
/* 不注入final字段 */ Modifier.isFinal(field.getModifiers()) ||
/* 不注入基本类型字段 */ fieldType.isPrimitive() ||
/* 不注入数组类型字段 */ fieldType.isArray())
continue;
ViewInject viewInject = field.getAnnotation(ViewInject.class);
if (viewInject != null)
try
View view = finder.findViewById(viewInject.value(), viewInject.parentId());
if (view != null)
field.setAccessible(true);
field.set(handler, view);
else
throw new RuntimeException("Invalid @ViewInject for "
+ handlerType.getSimpleName() + "." + field.getName());
catch (Throwable ex)
LogUtil.e(ex.getMessage(), ex);
// end inject view
// inject event
Method[] methods = handlerType.getDeclaredMethods();
if (methods != null && methods.length > 0)
for (Method method : methods)
if (Modifier.isStatic(method.getModifiers())
|| !Modifier.isPrivate(method.getModifiers()))
continue;
//检查当前方法是否是event注解的方法
Event event = method.getAnnotation(Event.class);
if (event != null)
try
// id参数
int[] values = event.value();
int[] parentIds = event.parentId();
int parentIdsLen = parentIds == null ? 0 : parentIds.length;
//循环所有id，生成ViewInfo并添加代理反射
for (int i = 0; i < values.length; i++)
int value = values[i];
if (value > 0)
ViewInfo info = new ViewInfo();
info.value = value;
info.parentId = parentIdsLen > i ? parentIds[i] : 0;
method.setAccessible(true);
// EventListenerManager 动态代理执行相应的方法
EventListenerManager.addEventMethod(finder, info, event, handler, method);
catch (Throwable ex)
LogUtil.e(ex.getMessage(), ex);
// end inject event
源码中利用类的反射循环获取属性的注解值然后通过findViewById之后，动态的注入到控件属性里面；事件注入也是类似首先findViewById然后利用动态代理去反射执行方法，动态代理代码如下：
public static void addEventMethod(
//根据页面或view holder生成的ViewFinder
ViewFinder finder,
//根据当前注解ID生成的ViewInfo
ViewInfo info,
//注解对象
Event event,
//页面或view holder对象
Object handler,
//当前注解方法
Method method)
try
View view = finder.findViewByInfo(info);
if (view != null)
// 注解中定义的接口，比如Event注解默认的接口为View.OnClickListener
Class<?> listenerType = event.type();
// 默认为空，注解接口对应的Set方法，比如setOnClickListener方法
String listenerSetter = event.setter();
if (TextUtils.isEmpty(listenerSetter))
listenerSetter = "set" + listenerType.getSimpleName();
String methodName = event.method();
boolean addNewMethod = false;
/*
根据View的ID和当前的接口类型获取已经缓存的接口实例对象，
比如根据View.id和View.OnClickListener.class两个键获取这个View的OnClickListener对象
*/
Object listener = listenerCache.get(info, listenerType);
DynamicHandler dynamicHandler = null;
/*
如果接口实例对象不为空
获取接口对象对应的动态代理对象
如果动态代理对象的handler和当前handler相同
则为动态代理对象添加代理方法
*/
if (listener != null)
dynamicHandler = (DynamicHandler) Proxy.getInvocationHandler(listener);
addNewMethod = handler.equals(dynamicHandler.getHandler());
if (addNewMethod)
dynamicHandler.addMethod(methodName, method);
// 如果还没有注册此代理
if (!addNewMethod)
dynamicHandler = new DynamicHandler(handler);
dynamicHandler.addMethod(methodName, method);
// 生成的代理对象实例，比如View.OnClickListener的实例对象
listener = Proxy.newProxyInstance(
listenerType.getClassLoader(),
new Class<?>[]listenerType,
dynamicHandler);
listenerCache.put(info, listenerType, listener);
Method setEventListenerMethod = view.getClass().getMethod(listenerSetter, listenerType);
setEventListenerMethod.invoke(view, listener);
catch (Throwable ex)
LogUtil.e(ex.getMessage(), ex);
在实例化DynamicHandler的时候穿递的是Activity/Fragment。然后调用EventListenerManager.addEventMethod(finder, info, event, handler, method);法的时候，将method（当前注解方法）传递进去了。完整类名有，方法名字有。动态代理的实现如下：
public static class DynamicHandler implements InvocationHandler
// 存放代理对象，比如Fragment或view holder
private WeakReference<Object> handlerRef;
// 存放代理方法
private final HashMap<String, Method> methodMap = new HashMap<String, Method>(1);
private static long lastClickTime = 0;
public DynamicHandler(Object handler)
this.handlerRef = new WeakReference<Object>(handler);
public void addMethod(String name, Method method)
methodMap.put(name, method);
public Object getHandler()
return handlerRef.get();
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
Object handler = handlerRef.get();
if (handler != null)
String eventMethod = method.getName();
if ("toString".equals(eventMethod))
return DynamicHandler.class.getSimpleName();
method = methodMap.get(eventMethod);
if (method == null && methodMap.size() == 1)
for (Map.Entry<String, Method> entry : methodMap.entrySet())
if (TextUtils.isEmpty(entry.getKey()))
method = entry.getValue();
break;
if (method != null)
if (AVOID_QUICK_EVENT_SET.contains(eventMethod))
long timeSpan = System.currentTimeMillis() - lastClickTime;
if (timeSpan < QUICK_EVENT_TIME_SPAN)
LogUtil.d("onClick cancelled: " + timeSpan);
return null;
lastClickTime = System.currentTimeMillis();
try
return method.invoke(handler, args);
catch (Throwable ex)
throw new RuntimeException("invoke method error:" +
handler.getClass().getName() + "#" + method.getName(), ex);
else
LogUtil.w("method not impl: " + eventMethod + "(" + handler.getClass().getSimpleName() + ")");
return null;
2.3 ButterKnife的使用
ButterKnife源码https://github.com/JakeWharton/butterknife
相比起xutils来，ButterKnife更受欢迎，第一在性能方面xutils完全是利用的反射，butterknife是轻量级的反射使用的注解都是编译时注解，而且它还提供了一个Android Studio的插件不需要我们去写任何的代码，作者JakeWharton很出名的写过很多大型的第三方框架。
ButterKnife的代码自动生成的Android Studio插件： android-butterknife-zelezny
后期我会模仿这个插件编写一个自己的IOC注解框架的AndroidStudio插件。
public class MainActivity extends AppCompatActivity
@BindView(R.id.test_tv)
TextView test_tv;
@BindView(R.id.test_btn)
Button test_btn;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
test_tv.setText("测试文本");
test_btn.setText("测试按钮");
@OnClick(R.id.test_tv, R.id.test_btn)
public void onViewClicked(View view)
switch (view.getId())
case R.id.test_tv:
break;
case R.id.test_btn:
test_tv.setText("点击了按钮，修改测试文本");
Toast.makeText(this, "点击了按钮，修改测试文本", Toast.LENGTH_LONG).show();
break;
上面是ButterKnifeZelezny这个插件自动生成的代码，只需要自己实现业务逻辑代码就够了，基本 @BindView、@OnClick等注解自动生成非常好用的插件。
2.4 ButterKnife源码分析
源码入口从ButterKnife.bind(this)这里查起：
/**
* BindView annotated fields and methods in the specified @link Activity. The current content
* view is used as the view root.
*
* @param target Target activity for view binding.
*/
@NonNull @UiThread
public static Unbinder bind(@NonNull Activity target)
View sourceView = target.getWindow().getDecorView();
return createBinding(target, sourceView);
bind(activity)最后调用了createBinding(target, sourceView)，其实bind(view)和bind(dialog)等方法都会调用createBinding(target, sourceView)，源码如下：
/**
* BindView annotated fields and methods in the specified @link View. The view and its children
* are used as the view root.
*
* @param target Target view for view binding.
*/
@NonNull @UiThread
public static Unbinder bind(@NonNull View target)
return createBinding(target, target);
/**
* BindView annotated fields and methods in the specified @link Dialog. The current content
* view is used as the view root.
*
* @param target Target dialog for view binding.
*/
@NonNull @UiThread
public static Unbinder bind(@NonNull Dialog target)
View sourceView = target.getWindow().getDecorView();
return createBinding(target, sourceView);
/**
* BindView annotated fields and methods in the specified @code target using the @code source
* @link Activity as the view root.
*
* @param target Target class for view binding.
* @param source Activity on which IDs will be looked up.
*/
@NonNull @UiThread
public static Unbinder bind(@NonNull Object target, @NonNull Activity source)
View sourceView = source.getWindow().getDecorView();
return createBinding(target, sourceView);
/**
* BindView annotated fields and methods in the specified @code target using the @code source
* @link View as the view root.
*
* @param target Target class for view binding.
* @param source View root on which IDs will be looked up.
*/
@NonNull @UiThread
public static Unbinder bind(@NonNull Object target, @NonNull View source)
return createBinding(target, source);
/**
* BindView annotated fields and methods in the specified @code target using the @code source
* @link Dialog as the view root.
*
* @param target Target class for view binding.
* @param source Dialog on which IDs will be looked up.
*/
@NonNull @UiThread
public static Unbinder bind(@NonNull Object target, @NonNull Dialog source)
View sourceView = source.getWindow().getDecorView();
return createBinding(target, sourceView);
就是最终会用目标对象target和绑定的View进行处理，下面分析createBinding(target, sourceView)的源码：
private static Unbinder createBinding(@NonNull Object target, @NonNull View source)
Class<?> targetClass = target.getClass();
if (debug) Log.d(TAG, "Looking up binding for " + targetClass.getName());
Constructor<? extends Unbinder> constructor = findBindingConstructorForClass(targetClass);
if (constructor == null)
return Unbinder.EMPTY;
//noinspection TryWithIdenticalCatches Resolves to API 19+ only type.
try
return constructor.newInstance(target, source);
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);
源码中通过findBindingConstructorForClass(targetClass)获取构造方法，然后调用constructor.newInstance(target, source)通过反射调用构造方法，下面先分析findBindingConstructorForClass(targetClass)：
@Nullable @CheckResult @UiThread
private static Constructor<? extends Unbinder> findBindingConstructorForClass(Class<?> cls)
//1.先从BINDINGS这个Map中获取缓存的Constructor
Constructor<? extends Unbinder> bindingCtor = BINDINGS.get(cls);
//2.如果有缓存那么就直接返回Constructor
if (bindingCtor != null)
if (debug) Log.d(TAG, "HIT: Cached in binding map.");
return bindingCtor;
//3.反射获取目标类对象，判断是否是android和java包下的框架类，框架类终止查询构造方法操作，返回空不再进行处理
String clsName = cls.getName();
if (clsName.startsWith("android.") || clsName.startsWith("java."))
if (debug) Log.d(TAG, "MISS: Reached framework class. Abandoning search.");
return null;
try
//4.通过反射加载(clsName + "_ViewBinding")名字的类
Class<?> bindingClass = cls.getClassLoader().loadClass(clsName + "_ViewBinding");
//noinspection unchecked
//bindingClass 中查询参数为(cls, View.class)的构造函数，cls为最初的目标类
bindingCtor = (Constructor<? extends Unbinder>) bindingClass.getConstructor(cls, View.class);
if (debug) Log.d(TAG, "HIT: Loaded binding class and constructor.");
catch (ClassNotFoundException e)
if (debug) Log.d(TAG, "Not found. Trying superclass " + cls.getSuperclass().getName());
//报错后查询cls的父类，看是否在父类中有实现这个构造方法
bindingCtor = findBindingConstructorForClass(cls.getSuperclass());
catch (NoSuchMethodException e)
throw new RuntimeException("Unable to find binding constructor for " + clsName, e);
//将反射查询出的结果缓存在BINDINGS中
BINDINGS.put(cls, bindingCtor);
return bindingCtor;
根据源码分析得知（源码中我加了注释） Class<?> bindingClass = cls.getClassLoader().loadClass(clsName + "_ViewBinding")也就是target类名+_ViewBinding，然后bindingClass.getConstructor(cls, View.class)获取这个类对应参数的构造方法，按照源码执行顺序最后要执行的也是这个方法。
我的target类是MainActivity，那么实现类是MainActivity_ViewBinding这个类，不过这个类是在编译运行时才会生成的，Ctrl+N 搜索类如下图
如果搜不到我们可以在项目目录..\\app\\build中找到，编译后在目录..\\app\\build\\intermediates\\classes\\debug\\你的包名（com\\xxx\\xxx）
那么下面查看MainActivity_ViewBinding的代码：
public class MainActivity_ViewBinding implements Unbinder
private MainActivity target;
private View view2131165311;
private View view2131165310;
@UiThread
public MainActivity_ViewBinding(MainActivity target)
this(target, target.getWindow().getDecorView());
@UiThread
public MainActivity_ViewBinding(final MainActivity target, View source)
this.target = target;
View view = Utils.findRequiredView(source, 2131165311, "field 'test_tv' and method 'onViewClicked'");
target.test_tv = (TextView)Utils.castView(view, 2131165311, "field 'test_tv'", TextView.class);
this.view2131165311 = view;
view.setOnClickListener(new DebouncingOnClickListener()
public void doClick(View p0)
target.onViewClicked(p0以上是关于注解框架源码分析（XUtilsButterKnife）的主要内容，如果未能解决你的问题，请参考以下文章