台州seo网站排名,杭州公司网站制作,可不可以用p2p做视频网站,建设营销型网站哪家好1. 日常遇到的冗余的接口方法实现
日常开发中#xff0c;经常会要实现接口#xff0c;但是很多场景中#xff0c;只需要用到其中一两个方法#xff0c;例如 ActivityLifecycleCallbacks#xff0c;它有很多个接口需要实现#xff0c;但是很多时候我们只需要用到其中的一…1. 日常遇到的冗余的接口方法实现
日常开发中经常会要实现接口但是很多场景中只需要用到其中一两个方法例如 ActivityLifecycleCallbacks它有很多个接口需要实现但是很多时候我们只需要用到其中的一两个 val myActivityLifecycleCallbacks object : Application.ActivityLifecycleCallbacks {/*** 例如我们只需要监听 Activity 的创建和销毁那么 onActivityStarted onActivityResumed onActivityPaused* onActivityStoppedonActivityStoppedonActivitySaveInstanceState 这 6 个方法是完全没必要是做实现的* 即使是空实现*/override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {TODO(Not yet implemented)}override fun onActivityStarted(activity: Activity) {TODO(Not yet implemented)}override fun onActivityResumed(activity: Activity) {TODO(Not yet implemented)}override fun onActivityPaused(activity: Activity) {TODO(Not yet implemented)}override fun onActivityStopped(activity: Activity) {TODO(Not yet implemented)}override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {TODO(Not yet implemented)}override fun onActivityDestroyed(activity: Activity) {TODO(Not yet implemented)}}如果有多个不同业务需要实现这个接口就这样很容易产生代码冗余。有没有一种优雅的方式只需要实现自己需要的方法而不再需要去关注其他方法有的那就是利用 Java 的动态代理和 kotlin 的委托模式
2. 利用 Java 的动态代理和 Kotlin 的委托模式
首先需要实现一个通用的动态代理新建一个 Kotlin 文件 DelegateObject.kt这里通过 inline 和 reified 关键字获取到泛型的 class 信息
import java.lang.reflect.InvocationHandler
import java.lang.reflect.Proxyinline fun reified T noOpDelegate() : T {val javaClass T::class.javareturn Proxy.newProxyInstance(javaClass.classLoader, arrayOf(javaClass), no_op_invocationHandler) as T
}val no_op_invocationHandler InvocationHandler { _, _, _ - }这样就可以获取到任意一个接口的一个对象只是没有具体的实现。接着再利用 Kotlin 的 by 关键字实现对象委托 val myActivityLifecycleCallbacks object : Application.ActivityLifecycleCallbacks by noOpDelegate() {}由于 Kotlin 委托模式的原理实际上在编译期间也是会生成 ActivityLifecycleCallbacks 的所有方法先来看看转译后的实现 private final Application.ActivityLifecycleCallbacks myActivityLifecycleCallbacks (Application.ActivityLifecycleCallbacks)(new Application.ActivityLifecycleCallbacks() {// $FF: synthetic fieldprivate final Application.ActivityLifecycleCallbacks $$delegate_0;{int $i$f$noOpDelegate false;Class javaClass$iv Application.ActivityLifecycleCallbacks.class;Object var10001 Proxy.newProxyInstance(javaClass$iv.getClassLoader(), new Class[]{javaClass$iv}, DelegateObjectKt.getNo_op_invocationHandler());if (var10001 null) {throw new NullPointerException(null cannot be cast to non-null type android.app.Application.ActivityLifecycleCallbacks);} else {this.$$delegate_0 (Application.ActivityLifecycleCallbacks)var10001;}}public void onActivityCreated(NonNull NotNull Activity activity, Nullable org.jetbrains.annotations.Nullable Bundle savedInstanceState) {Intrinsics.checkNotNullParameter(activity, activity);this.$$delegate_0.onActivityCreated(activity, savedInstanceState);}public void onActivityDestroyed(NonNull NotNull Activity activity) {Intrinsics.checkNotNullParameter(activity, activity);this.$$delegate_0.onActivityDestroyed(activity);}public void onActivityPaused(NonNull NotNull Activity activity) {Intrinsics.checkNotNullParameter(activity, activity);this.$$delegate_0.onActivityPaused(activity);}public void onActivityResumed(NonNull NotNull Activity activity) {Intrinsics.checkNotNullParameter(activity, activity);this.$$delegate_0.onActivityResumed(activity);}public void onActivitySaveInstanceState(NonNull NotNull Activity activity, NonNull NotNull Bundle outState) {Intrinsics.checkNotNullParameter(activity, activity);Intrinsics.checkNotNullParameter(outState, outState);this.$$delegate_0.onActivitySaveInstanceState(activity, outState);}public void onActivityStarted(NonNull NotNull Activity activity) {Intrinsics.checkNotNullParameter(activity, activity);this.$$delegate_0.onActivityStarted(activity);}public void onActivityStopped(NonNull NotNull Activity activity) {Intrinsics.checkNotNullParameter(activity, activity);this.$$delegate_0.onActivityStopped(activity);}});现在已经将 ActivityLifecycleCallbacks 的匿名内部类对象委托给了 noOpDelegate 生成的代理对象。这样需要用到具体哪个方法时只需要再次重写即可例如文章最开始的例子可以变为 val myActivityLifecycleCallbacks object : Application.ActivityLifecycleCallbacks by noOpDelegate() {override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {TODO(Not yet implemented)}override fun onActivityDestroyed(activity: Activity) {TODO(Not yet implemented)}}经过精简的代码可以使代码更加简洁可以更好的聚焦业务实现
