1，配置
工程 gradle
buildscript {
repositories {
mavenCentral()
google()
}
dependencies {
classpath 'com.jakewharton:butterknife-gradle-plugin:10.1.0'
}
}
在 module 中添加
apply plugin: 'com.android.library'
apply plugin: 'com.jakewharton.butterknife'
依赖中添加
implementation 'com.jakewharton:butterknife:10.1.0'
annotationProcessor 'com.jakewharton:butterknife-compiler:10.1.0'
// 如果是 Kotlin，请用 annotationProcessor 替换掉 kapt
tip：在使用中请注意使用 R2 而不是 R
github 地址： https://github.com/JakeWharton/butterknife
2，绑定 View
注意在 onCreate 调用 ButterKnife.bind
class ExampleActivity extends Activity {
@BindView(R.id.title) TextView title;
@BindView(R.id.subtitle) TextView subtitle;
@BindView(R.id.footer) TextView footer;
@Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.simple_activity);
ButterKnife.bind(this);
// TODO Use fields...
}
}
3，Resource 绑定
class ExampleActivity extends Activity {
@BindString(R.string.title) String title;
@BindDrawable(R.drawable.graphic) Drawable graphic;
@BindColor(R.color.red) int red; // int or ColorStateList field
@BindDimen(R.dimen.spacer) Float spacer; // int (for pixel size) or float (for exact value) field
// ...
}
4，Non-Activity 绑定
只要 bind 了View Root，你也可以在任意object中进行绑定，如 Fragment
public class FancyFragment extends Fragment {
@BindView(R.id.button1) Button button1;
@BindView(R.id.button2) Button button2;
@Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fancy_fragment, container, false);
ButterKnife.bind(this, view);
// TODO Use fields...
return view;
}
}
或者listView 的adapter
public class MyAdapter extends BaseAdapter {
@Override public View getView(int position, View view, ViewGroup parent) {
ViewHolder holder;
if (view != null) {
holder = (ViewHolder) view.getTag();
} else {
view = inflater.inflate(R.layout.whatever, parent, false);
holder = new ViewHolder(view);
view.setTag(holder);
}
holder.name.setText("John Doe");
// etc...
return view;
}
static class ViewHolder {
@BindView(R.id.title) TextView name;
@BindView(R.id.job_title) TextView jobTitle;
public ViewHolder(View view) {
ButterKnife.bind(this, view);
}
}
}
5，View 列表
@BindViews({ R.id.first_name, R.id.middle_name, R.id.last_name })
List<EditText> nameViews;
还提供了 run 和 set 方法来修改列表属性
static final butterknife.Action<View> DISABLE = new butterknife.Action<View>() {
@Override public void apply(View view, int index) {
view.setEnabled(false);
}
};
static final butterknife.Setter<View, Boolean> ENABLED = new butterknife.Setter<View, Boolean>() {
@Override public void set(View view, Boolean value, int index) {
view.setEnabled(value);
}
};
ViewCollections.run(nameViews, DISABLE);
ViewCollections.set(nameViews, ENABLED, false);
6，Listener 绑定
@OnClick(R.id.submit)
public void submit(View view) {
// TODO submit data to server...
}
// 参数可以省略掉
@OnClick(R.id.submit)
public void submit() {
// TODO submit data to server...
}
// 如果是指定类型也会cast到相应的类型
@OnClick(R.id.submit)
public void sayHi(Button button) {
button.setText("Hello!");
}
// 也可以binding到多个View上
@OnClick({ R.id.door1, R.id.door2, R.id.door3 })
public void pickDoor(DoorView door) {
if (door.hasPrizeBehind()) {
Toast.makeText(this, "You win!", LENGTH_SHORT).show();
} else {
Toast.makeText(this, "Try again", LENGTH_SHORT).show();
}
}
// 在自定义View中不需要指定View ID
public class FancyButton extends Button {
@OnClick
public void onClick() {
// TODO do something!
}
}
7，unbind
对于不同生命周期的bind，需要的退出的时候 unbind
public class FancyFragment extends Fragment {
@BindView(R.id.button1) Button button1;
@BindView(R.id.button2) Button button2;
private Unbinder unbinder;
@Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fancy_fragment, container, false);
unbinder = ButterKnife.bind(this, view);
// TODO Use fields...
return view;
}
@Override public void onDestroyView() {
super.onDestroyView();
unbinder.unbind();
}
}
8，可选bind
在bind listener的时候，如果 View 找不到我们可以在变量中添加 @Nullable，或者在方法上添加 @Optional
@Nullable @BindView(R.id.might_not_be_there) TextView mightNotBeThere;
@Optional @OnClick(R.id.maybe_missing) void onMaybeMissingClicked() {
// TODO ...
}
9，多个Listener
有的View 的Listener 会有多个回调函数，这个时候我们可以使用 callback 来指定相应的回调
@OnItemSelected(R.id.list_view)
void onItemSelected(int position) {
// TODO ...
}
@OnItemSelected(value = R.id.maybe_missing, callback = NOTHING_SELECTED)
void onNothingSelected() {
// TODO ...
}
10，原理
通过编译时注解，使用 javapoet 库生成相应的java文件
在我们调用 ButterKnife.bind(view) 方法的时候，根据类的全限定类型，来执行相应的代码
@NonNull @UiThread
public static Unbinder bind(@NonNull View target) {
return bind(target, target);
}
@NonNull @UiThread
public static Unbinder bind(@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);
}
}
@Nullable @CheckResult @UiThread
private static Constructor<? extends Unbinder> findBindingConstructorForClass(Class<?> cls) {
Constructor<? extends Unbinder> bindingCtor = BINDINGS.get(cls);
if (bindingCtor != null || BINDINGS.containsKey(cls)) {
if (debug) Log.d(TAG, "HIT: Cached in binding map.");
return bindingCtor;
}
String clsName = cls.getName();
if (clsName.startsWith("android.") || clsName.startsWith("java.")
|| clsName.startsWith("androidx.")) {
if (debug) Log.d(TAG, "MISS: Reached framework class. Abandoning search.");
return null;
}
try {
Class<?> bindingClass = cls.getClassLoader().loadClass(clsName + "_ViewBinding");
//noinspection unchecked
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);
}
BINDINGS.put(cls, bindingCtor);
return bindingCtor;
}
通过代码我们看到，这些方法都是执行的 UIThread 的，并且一般都是以 "_ViewBinding" 结尾，生成的文件我们可以在 build/generated/source/debug 下面看到
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