深入理解ButterKnife源码并掌握原理（四）

到此我们整个的流程算分析完了。

最后我们看下对外提供的API

bind 方法

那么还差一步，什么时候都要我们生成的java文件呢？答案是：
ButterKnife.bind(this);方法。
我们看一下ButterKnife对外提供的API

/*** 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 @UiThreadpublic static Unbinder bind(@NonNull Activity target) {View sourceView = target.getWindow().getDecorView();return createBinding(target, sourceView);}/*** 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 @UiThreadpublic 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 @UiThreadpublic 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 @UiThreadpublic 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 @UiThreadpublic 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 @UiThreadpublic static Unbinder bind(@NonNull Object target, @NonNull Dialog source) {View sourceView = source.getWindow().getDecorView();return createBinding(target, sourceView);}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);}}

我们看到bind的一系列方法都会调用createBinding方法

   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);}}

Class<\?> （？是转义字符csdn要不支持）targetClass = target.getClass();获取类的实例，最后获取构造函数，最后constructor.newInstance方法来调用该类的构造函数。
而该类的构造函数是通过findBindingConstructorForClass方法，我可没来看下此方法：

   @Nullable @CheckResult @UiThreadprivate static Constructor<? extends Unbinder> findBindingConstructorForClass(Class<?> cls) {//缓存中查找，找到直接返回Constructor<? extends Unbinder> bindingCtor = BINDINGS.get(cls);if (bindingCtor != null) {if (debug) Log.d(TAG, "HIT: Cached in binding map.");return bindingCtor;}//检查合法性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 {//构造一个class，可以看类名就是我们生成的。Class<?> bindingClass = Class.forName(clsName + "_ViewBinding");//noinspection unchecked// 获取我们的构造函数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());bindingCtor = findBindingConstructorForClass(cls.getSuperclass());} catch (NoSuchMethodException e) {throw new RuntimeException("Unable to find binding constructor for " + clsName, e);}//加入到缓存中BINDINGS.put(cls, bindingCtor);return bindingCtor;}

可以看到用到了简单的缓存。

unbind 方法

在新版的8.4.0中去除了 unbind方法。

ButterKnife.unbind(this);

采用了接口的形式。让生成的类来实现，比如：

 public final class SimpleAdapter$ViewHolder_ViewBinding implements Unbinder {@UiThreadpublic SimpleAdapter$ViewHolder_ViewBinding(SimpleAdapter.ViewHolder target, View source) {//...}//...@Overridepublic void unbind() {/...}｝

那如何unbind呢？？
ButterKnife.bind(this)返回值是一个我们生成的java文件类的实例对象。返回的是一个Unbinder 正和此意。
so，你可以这么用：

  private  Unbinder unbinder;     @Override protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.simple_activity);unbinder=ButterKnife.bind(this);｝@Overrideprotected void onDestroy() {super.onDestroy();unbinder.unbind();}

到此我们就算完了。

下一篇我们讲自己来实现类似butterknife的demo，这样我们才能正在的会学，会用。
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深入理解ButterKnife源码并掌握原理（五)