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
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@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
