使用反射结合动态代理实现一个View注解绑定库，支持View和事件绑定，代码简洁，使用简单，扩展性强。
支持的功能
@ContentView 绑定layout 替代setContentView() @BindView 绑定View 替代findViewById() @OnClick 绑定点击事件 替代setOnClickListener() @OnLongClick 绑定长按事件 替代setOnLongClickListener()
代码
注解类
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@Target (ElementType.TYPE) @Retention (RetentionPolicy.RUNTIME) public @interface ContentView { int value(); } |
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@Target (ElementType.FIELD) @Retention (RetentionPolicy.RUNTIME) public @interface BindView { int value(); } |
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@Target (ElementType.ANNOTATION_TYPE) @Retention (RetentionPolicy.RUNTIME) public @interface OnEvent { //订阅方式 String setCommonListener(); //事件源对象 Class<?> commonListener(); } |
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@Target (ElementType.METHOD) @Retention (RetentionPolicy.RUNTIME) @OnEvent (setCommonListener = "setOnClickListener" , commonListener = View.OnClickListener. class ) public @interface OnClick { int value(); } |
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@Target (ElementType.METHOD) @Retention (RetentionPolicy.RUNTIME) @OnEvent (setCommonListener = "setOnLongClickListener" , commonListener = View.OnLongClickListener. class ) public @interface OnLongClick { int value(); } |
实现类
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public class MsInjector { public static void inject(Object object) { injectContentView(object); injectView(object); injectEvent(object); } private static void injectContentView(Object object) { Class<?> clazz = object.getClass(); //获取到ContentView注解 ContentView contentView = clazz.getAnnotation(ContentView. class ); if (contentView == null ) { return ; } //获取到注解的值，也就是layoutResID int layoutResID = contentView.value(); try { //反射出setContentView方法并调用 Method method = clazz.getMethod( "setContentView" , int . class ); method.invoke(object, layoutResID); } catch (Exception e) { e.printStackTrace(); } } private static void injectView(Object object) { Class<?> clazz = object.getClass(); //获取到所有字段并遍历 Field[] fields = clazz.getDeclaredFields(); for (Field field : fields) { field.setAccessible( true ); //获取字段上的BindView注解 BindView bindView = field.getAnnotation(BindView. class ); if (bindView == null ) { continue ; } //获取到viewId int viewId = bindView.value(); try { //通过反射调用findViewById得到view实例对象 Method method = clazz.getMethod( "findViewById" , int . class ); Object view = method.invoke(object, viewId); //赋值给注解标注的对应字段 field.set(object, view); } catch (Exception e) { e.printStackTrace(); } } } private static void injectEvent(Object object) { Class<?> clazz = object.getClass(); //获取到当前页年所有方法并遍历 Method[] declaredMethods = clazz.getDeclaredMethods(); for (Method declaredMethod : declaredMethods) { declaredMethod.setAccessible( true ); //获取方法上的所有注解并遍历 Annotation[] annotations = declaredMethod.getDeclaredAnnotations(); for (Annotation annotation : annotations) { //获取注解本身 Class<? extends Annotation> annotationType = annotation.annotationType(); //获取注解上的OnEvent注解 OnEvent onEvent = annotationType.getAnnotation(OnEvent. class ); if (onEvent == null ) { continue ; } //拿到注解中的元素 String setCommonListener = onEvent.setCommonListener(); Class<?> commonListener = onEvent.commonListener(); try { //由于上边没有明确获取是哪个注解，所以这里需要使用反射获取viewId Method valueMethod = annotationType.getDeclaredMethod( "value" ); valueMethod.setAccessible( true ); int viewId = ( int ) valueMethod.invoke(annotation); //通过反射findViewById获取到对应的view Method findViewByIdMethod = clazz.getMethod( "findViewById" , int . class ); Object view = findViewByIdMethod.invoke(object, viewId); //通过反射获取到view中对应的setCommonListener方法 Method viewMethod = view.getClass().getMethod(setCommonListener, commonListener); //使用动态代理监听回调 Object proxy = Proxy.newProxyInstance( clazz.getClassLoader(), new Class[]{commonListener}, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { //最终执行被标注的方法 return declaredMethod.invoke(object, null ); } } ); //调用view的setCommonListener方法 viewMethod.invoke(view, proxy); } catch (Exception e) { e.printStackTrace(); } } } } } 复制代码 |
使用
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@ContentView (R.layout.activity_main) public class MainActivity extends AppCompatActivity { @BindView (R.id.button1) private Button button1; @BindView (R.id.button2) Button button2; @Override protected void onCreate(Bundle savedInstanceState) { super .onCreate(savedInstanceState); MsInjector.inject( this ); } @OnClick (R.id.button1) public void clickButton1() { Toast.makeText( this , "click button1" , Toast.LENGTH_SHORT).show(); } @OnClick (R.id.button2) public void clickButton2() { Toast.makeText( this , "click button2" , Toast.LENGTH_SHORT).show(); } @OnLongClick (R.id.button1) public boolean longClickButton1() { Toast.makeText( this , "long click button1" , Toast.LENGTH_SHORT).show(); return false ; } @OnLongClick (R.id.button2) public boolean longClickButton2() { Toast.makeText( this , "long click button2" , Toast.LENGTH_SHORT).show(); return false ; } } |
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原文链接：https://juejin.cn/post/7095708497542807560
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