O3-開源框架使用之Butterknife 8.8.1及原始碼淺析

ButterKnife 開源 · 發表 2018-09-18 19:54:54

摘要：零、前言我最喜歡的框架，沒有之一：編譯期生成程式碼的方式，對執行時沒有任何副作用。加上AndroidStudio快捷鍵，簡直好用之至。新增依賴： implementation 'com.jakewharton:butterknife:8.8.1' a...

零、前言

我最喜歡的框架，沒有之一：

編譯期生成程式碼的方式，對執行時沒有任何副作用。

加上AndroidStudio快捷鍵，簡直好用之至。

新增依賴：

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.基礎使用：

public class MainActivity extends AppCompatActivity {

@BindView(R.id.id_tv)
TextView mIdTv;//繫結檢視
@BindView(R.id.id_btn)
Button mIdBtn;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//1.繫結Activity
ButterKnife.bind(this);
}

@OnClick(R.id.id_btn)//單機事件
public void onViewClicked() {
Log.e(TAG, "onViewClicked: ");
}

@OnLongClick(R.id.id_btn)//長按事件
public boolean onViewLongClicked() {
Log.e(TAG, "onViewLongClicked: ");

//和原生一樣，返回true，抬起時不觸發單機
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
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fg_test, container, false);
//繫結View
unbinder = ButterKnife.bind(this, view);
return view;
}

@Override
public void onDestroyView() {
super.onDestroyView();
unbinder.unbind();
}

//銷燬時解綁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();

還有其他很多註解，感覺都沒用太大用，下面看一下原始碼是怎麼工作的

三、原始碼淺析：

1、首先來看這句話都進行了哪些事：ButterKnife.bind(this);

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

bind有6個過載的方法：這裡使用的是一參Activity的bind方法

@NonNull @UiThread
public static Unbinder bind(@NonNull Activity target) {
//獲取Activity對應視窗上的最頂端佈局
View sourceView = target.getWindow().getDecorView();
//呼叫createBinding方法，見--B1
return createBinding(target, sourceView);
}

--B1:butterknife.ButterKnife#createBinding

這算一個非常核心的方法，6個bind()方法都是呼叫它

private static Unbinder createBinding(@NonNull Object target, @NonNull View source) {
//獲取target的class
Class<?> targetClass = target.getClass();
if (debug) Log.d(TAG, "Looking up binding for " + targetClass.getName());
//獲取繫結Class的建構函式，見--B2
Constructor<? extends Unbinder> constructor = findBindingConstructorForClass(targetClass);
//如果建構函式是空的，返回EMPTY的Unbinder列舉
if (constructor == null) {
return Unbinder.EMPTY;
}

//noinspection TryWithIdenticalCatches Resolves to API 19+ only type.
try {
//返回使用建構函式建立MainActivity_ViewBinding例項：
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

通過位元組碼檔案獲取類的建構函式

@Nullable @CheckResult @UiThread
private static Constructor<? extends Unbinder> findBindingConstructorForClass(Class<?> cls) {

//BINDINGS的宣告：可見是一個LinkedHashMap，以class為鍵，建構函式為值。
//static final Map<Class<?>, Constructor<? extends Unbinder>> BINDINGS = new LinkedHashMap<>();
//從map中拿傳入的cls的建構函式
Constructor<? extends Unbinder> bindingCtor = BINDINGS.get(cls);
//如果不為空
if (bindingCtor != null) {
if (debug) Log.d(TAG, "HIT: Cached in binding map.");
//就返回拿到的建構函式
return bindingCtor;
}
//否則，獲取位元組碼檔案的名字:如：com.toly1994.butterknifetest.MainActivity
String clsName = cls.getName();
//如果名字的字串，是以android.或java.開頭的
if (clsName.startsWith("android.") || clsName.startsWith("java.")) {
if (debug) Log.d(TAG, "MISS: Reached framework class. Abandoning search.");
//返回空
return null;
}
try {
//載入com.toly1994.butterknifetest.MainActivity_ViewBinding類生成Clazz物件bindingClass：見：--B3
Class<?> bindingClass = cls.getClassLoader().loadClass(clsName + "_ViewBinding");
//noinspection unchecked
//獲取自動生成的MainActivity_ViewBinding中的兩參建構函式
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);
}
//將cls和獲取到的建構函式放入map
BINDINGS.put(cls, bindingCtor);
return bindingCtor;
}

--B3:見鬼，哪來的什麼MainActivity_ViewBinding讓我載入?

Butter Knife會自動建立這個類，我們來看看它的廬山真面目

MainActivity_ViewBinding.png

可見bind方法，主要是把XxxActivity建立一個XxxActivity_ViewBinding,並建立一個XxxActivity_ViewBinding物件

2、現在焦點就在MainActivity_ViewBinding的身上

com.toly1994.butterknifetest.MainActivity_ViewBinding

// Generated code from Butter Knife. Do not modify!

public class MainActivity_ViewBinding implements Unbinder {
//持有一個MainActivity的引用
private MainActivity target;
//持有一個View的引用
private View view2131165244;

//一參構造：呼叫兩參構造
@UiThread
public MainActivity_ViewBinding(MainActivity target) {
this(target, target.getWindow().getDecorView());
}

//兩參構造：
@UiThread
public MainActivity_ViewBinding(final MainActivity target, View source) {
 //target賦值
this.target = target;
View view;
//將target物件中的mIdTv賦值為：findRequiredViewAsType(檢視，id,欄位介紹，類名)方法：見--B4
target.mIdTv = Utils.findRequiredViewAsType(source, R.id.id_tv, "field 'mIdTv'", TextView.class);
//findRequiredView找到按鈕，見：--B4-1
view = Utils.findRequiredView(source, R.id.id_btn, "field 'mIdBtn' and method 'onViewClicked'");
//view強轉後為target物件中的mIdBtn賦值
target.mIdBtn = Utils.castView(view, R.id.id_btn, "field 'mIdBtn'", Button.class);
view2131165244 = view;
//為按鈕設定監聽：見--B5
view.setOnClickListener(new DebouncingOnClickListener() {
@Override
public void doClick(View p0) {
//這裡是呼叫的target也就是Activity中的onViewClicked方法
//應該知道為什麼可以簡便的寫點選事件了吧
target.onViewClicked();
}
});
}

@Override
@CallSuper
//解綁: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

根據型別查詢需要的View

這個who只是在拋異常的時候告訴你，是誰異常

public static <T> T findRequiredViewAsType(View source, @IdRes int id, String who,
Class<T> cls) {
//findRequiredView(檢視，id,欄位介紹)：見--B4-1
View view = findRequiredView(source, id, who);
//castView(檢視，id,欄位, Class)：見--B4-2
return castView(view, id, who, cls);
}

--B4-1:findRequiredView(檢視，id,欄位介紹)

看到findViewById有沒有小激動

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) {
//如果檢視不為空就返回找到的檢視
return view;
}
//檢視為空，就丟擲一個IllegalStateException異常：
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(檢視，id,欄位, Class)

public static <T> T castView(View view, @IdRes int id, String who, Class<T> cls) {
try {
//將View強轉為T型別，T型別是Class<T>中的泛型，即findRequiredViewAsType中傳入的型別
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的一個公共方法：由下可見它反會一個由傳入值強轉成的T型別物件

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

--B5:這是butterknife原始碼中的一個類：

繼承自：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) {
//設定為不可用
enabled = false;
//
v.post(ENABLE_AGAIN);
doClick(v);//模板方法
}
}

public abstract void doClick(View v);
}

後記、

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