零、前言

我最喜欢的框架，没有之一：
编译期生成代码的方式，对运行时没有任何副作用。
加上AndroidStudio快捷键，简直好用之至。

添加依赖：

implementation 'com.jakewharton:butterknife:8.8.1'
annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'

混淆

## butterknife start
-keep class butterknife.** { *; }
-dontwarn butterknife.internal.**
-keep class **$$ViewBinder { *; }-keepclasseswithmembernames class * {@butterknife.* <fields>;
}-keepclasseswithmembernames class * {@butterknife.* <methods>;
}
## butterknife end

一、Activity中使用

1.基础使用：

public class MainActivity extends AppCompatActivity {@BindView(R.id.id_tv)TextView mIdTv;//绑定视图@BindView(R.id.id_btn)Button mIdBtn;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);//1.绑定ActivityButterKnife.bind(this);}@OnClick(R.id.id_btn)//单机事件public void onViewClicked() {Log.e(TAG, "onViewClicked: ");}@OnLongClick(R.id.id_btn)//长按事件public boolean onViewLongClicked() {Log.e(TAG, "onViewLongClicked: ");//和原生一样，返回true，抬起时不触发单机return true;}
}

多事件：

@OnClick({R.id.id_btn, R.id.imageView})
public void onViewClicked(View view) {switch (view.getId()) {case R.id.id_btn:break;case R.id.imageView:break;}
}

二、Fragment中使用:

public class MyFragment extends Fragment {@BindView(R.id.imageView)ImageView mImageView;Unbinder unbinder;@Nullable@Overridepublic View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {View view = inflater.inflate(R.layout.fg_test, container, false);//绑定Viewunbinder = ButterKnife.bind(this, view);return view;}@Overridepublic void onDestroyView() {super.onDestroyView();unbinder.unbind();}//销毁时解绑View@OnClick(R.id.imageView)public void onViewClicked() {Toast.makeText(getContext(), "hello", Toast.LENGTH_LONG).show();}
}

附：使用Fragment

FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(R.id.id_fl,new MyFragment());
ft.commit();

还有其他很多注解，感觉都没用太大用，下面看一下源码是怎么工作的

三、源码浅析：

1、首先来看这句话都进行了哪些事：ButterKnife.bind(this);

---B0:butterknife.ButterKnife#bind(android.app.Activity)

bind有6个重载的方法：这里使用的是一参Activity的bind方法

  @NonNull @UiThreadpublic static Unbinder bind(@NonNull Activity target) {//获取Activity对应窗口上的最顶端布局View sourceView = target.getWindow().getDecorView();//调用createBinding方法，见--B1return createBinding(target, sourceView);}

--B1:butterknife.ButterKnife#createBinding

这算一个非常核心的方法，6个bind()方法都是调用它

private static Unbinder createBinding(@NonNull Object target, @NonNull View source) {//获取target的classClass<?> targetClass = target.getClass();if (debug) Log.d(TAG, "Looking up binding for " + targetClass.getName());//获取绑定Class的构造函数，见--B2Constructor<? extends Unbinder> constructor = findBindingConstructorForClass(targetClass);//如果构造函数是空的，返回EMPTY的Unbinder枚举if (constructor == null) {return Unbinder.EMPTY;}//noinspection TryWithIdenticalCatches Resolves to API 19+ only type.try {//返回使用构造函数创建MainActivity_ViewBinding实例：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);}}

--B2:butterknife.ButterKnife#findBindingConstructorForClass

通过字节码文件获取类的构造函数

 @Nullable @CheckResult @UiThreadprivate static Constructor<? extends Unbinder> findBindingConstructorForClass(Class<?> cls) {//BINDINGS的声明：可见是一个LinkedHashMap，以class为键，构造函数为值。//static final Map<Class<?>, Constructor<? extends Unbinder>> BINDINGS = new LinkedHashMap<>();//从map中拿传入的cls的构造函数Constructor<? extends Unbinder> bindingCtor = BINDINGS.get(cls);//如果不为空if (bindingCtor != null) {if (debug) Log.d(TAG, "HIT: Cached in binding map.");//就返回拿到的构造函数return bindingCtor;}//否则，获取字节码文件的名字:如：com.toly1994.butterknifetest.MainActivityString clsName = cls.getName();//如果名字的字符串，是以android.或java.开头的if (clsName.startsWith("android.") || clsName.startsWith("java.")) {if (debug) Log.d(TAG, "MISS: Reached framework class. Abandoning search.");//返回空return null;}try {//加载com.toly1994.butterknifetest.MainActivity_ViewBinding类生成Clazz对象bindingClass：见：--B3Class<?> bindingClass = cls.getClassLoader().loadClass(clsName + "_ViewBinding");//noinspection unchecked//获取自动生成的MainActivity_ViewBinding中的两参构造函数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);}//将cls和获取到的构造函数放入mapBINDINGS.put(cls, bindingCtor);return bindingCtor;}

--B3:见鬼，哪来的什么MainActivity_ViewBinding让我加载?

Butter Knife会自动创建这个类，我们来看看它的庐山真面目

MainActivity_ViewBinding.png

可见bind方法，主要是把XxxActivity创建一个XxxActivity_ViewBinding,并创建一个XxxActivity_ViewBinding对象

2、现在焦点就在MainActivity_ViewBinding的身上

com.toly1994.butterknifetest.MainActivity_ViewBinding

// Generated code from Butter Knife. Do not modify!public class MainActivity_ViewBinding implements Unbinder {
//持有一个MainActivity的引用private MainActivity target;
//持有一个View的引用private View view2131165244;//一参构造：调用两参构造@UiThreadpublic MainActivity_ViewBinding(MainActivity target) {this(target, target.getWindow().getDecorView());}//两参构造：@UiThreadpublic MainActivity_ViewBinding(final MainActivity target, View source) {//target赋值this.target = target;View view;//将target对象中的mIdTv赋值为：findRequiredViewAsType(视图，id,字段介绍，类名)方法：见--B4target.mIdTv = Utils.findRequiredViewAsType(source, R.id.id_tv, "field 'mIdTv'", TextView.class);//findRequiredView找到按钮，见：--B4-1view = Utils.findRequiredView(source, R.id.id_btn, "field 'mIdBtn' and method 'onViewClicked'");//view强转后为target对象中的mIdBtn赋值target.mIdBtn = Utils.castView(view, R.id.id_btn, "field 'mIdBtn'", Button.class);view2131165244 = view;//为按钮设置监听：见--B5view.setOnClickListener(new DebouncingOnClickListener() {@Overridepublic void doClick(View p0) {//这里是调用的target也就是Activity中的onViewClicked方法//应该知道为什么可以简便的写点击事件了吧target.onViewClicked();}});}@Override@CallSuper//解绑:置空操作public void unbind() {MainActivity target = this.target;if (target == null) throw new IllegalStateException("Bindings already cleared.");this.target = null;target.mIdTv = null;target.mIdBtn = null;view2131165244.setOnClickListener(null);view2131165244 = null;}
}

--B4:butterknife.internal.Utils#findRequiredViewAsType

根据类型查询需要的View
这个who只是在抛异常的时候告诉你，是谁异常

  public static <T> T findRequiredViewAsType(View source, @IdRes int id, String who,Class<T> cls) {//findRequiredView(视图，id,字段介绍)：见--B4-1View view = findRequiredView(source, id, who);//castView(视图，id,字段, Class)：见--B4-2return castView(view, id, who, cls);}

--B4-1:findRequiredView(视图，id,字段介绍)

看到findViewById有没有小激动

  public static View findRequiredView(View source, @IdRes int id, String who) {//真正的findViewById操作View view = source.findViewById(id);if (view != null) {//如果视图不为空就返回找到的视图return view;}//视图为空，就抛出一个IllegalStateException异常：String name = getResourceEntryName(source, id);throw new IllegalStateException("Required view '"+ name+ "' with ID "+ id+ " for "+ who+ " was not found. If this view is optional add '@Nullable' (fields) or '@Optional'"

--B4-2：castView(视图，id,字段, Class)

public static <T> T castView(View view, @IdRes int id, String who, Class<T> cls) {try {//将View强转为T类型，T类型是Class<T>中的泛型，即findRequiredViewAsType中传入的类型return cls.cast(view);} catch (ClassCastException e) {String name = getResourceEntryName(view, id);throw new IllegalStateException("View '"+ name+ "' with ID "+ id+ " for "+ who+ " was of the wrong type. See cause for more info.", e);}
}

cast()方法是Clazz的一个公共方法：由下可见它反会一个由传入值强转成的T类型对象

    @SuppressWarnings("unchecked")public T cast(Object obj) {if (obj != null && !isInstance(obj))throw new ClassCastException(cannotCastMsg(obj));return (T) obj;}

--B5:这是butterknife源码中的一个类：

继承自：View.OnClickListener

public abstract class DebouncingOnClickListener implements View.OnClickListener {
//是否可用static boolean enabled = true;//可以再次使用private static final Runnable ENABLE_AGAIN = new Runnable() {@Override public void run() {enabled = true;}};@Override public final void onClick(View v) {//如果可用if (enabled) {//设置为不可用enabled = false;//v.post(ENABLE_AGAIN);doClick(v);//模板方法}}public abstract void doClick(View v);
}

后记、

1.声明：

[1]本文由张风捷特烈原创,转载请注明
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