Android开发Viewbinding委托实例详解

private class FragmentViewBindingProperty<in F : Fragment, out T : ViewBinding>(
    private val viewNeedInitialization: Boolean,
    viewBinder: (F) -> T,
    onViewDestroyed: (T) -> Unit,
) : LifecycleViewBindingProperty<F, T>(viewBinder, onViewDestroyed) {
    private var fragmentLifecycleCallbacks: FragmentManager.FragmentLifecycleCallbacks? = null
    private var fragmentManager: Reference<FragmentManager>? = null
    // 赋值操作
    override fun getValue(thisRef: F, property: KProperty<*>): T {
        val viewBinding = super.getValue(thisRef, property)
        reGISterFragmentLifecycleCallbacksIfNeeded(thisRef)
        return viewBinding
    }
    private fun registerFragmentLifecycleCallbacksIfNeeded(fragment: Fragment) {
        if (fragmentLifecycleCallbacks != null) return
        val fragmentManager = fragment.parentFragmentManager.also { fm ->
            this.fragmentManager = WeakReference(fm)
        }
        fragmentLifecycleCallbacks = ClearOnDestroy(fragment).also { callbacks ->
            fragmentManager.registerFragmentLifecycleCallbacks(callbacks, false)
        }
    }
    override fun isViewInitialized(thisRef: F): Boolean {
        if (!viewNeedInitialization) return true
        if (thisRef !is DialogFragment) {
            return thisRef.view != null
        } else {
            return super.isViewInitialized(thisRef)
        }
    }
    override fun clear() {
        super.clear()
        fragmentManager?.get()?.let { fragmentManager ->
            fragmentLifecycleCallbacks?.let(fragmentManager::unregisterFragmentLifecycleCallbacks)
        }
        fragmentManager = null
        fragmentLifecycleCallbacks = null
    }
    override fun getLifecycleOwner(thisRef: F): LifecycleOwner {
        try {
            return thisRef.viewLifecycleOwner
        } catch (ignored: IllegalStateException) {
            error("Fragment doesn't have view associated with it or the view has been destroyed")
        }
    }
    // 有意思的代码
    private inner class ClearOnDestroy(
        fragment: Fragment
    ) : FragmentManager.FragmentLifecycleCallbacks() {
        private var fragment: Reference<Fragment> = WeakReference(fragment)
        override fun onFragmentDestroyed(fm: FragmentManager, f: Fragment) {
            // Fix for destroying view for case with issue of navigation
            if (fragment.get() === f) {
                postClear()
            }
        }
    }
}

    //非反射写法
    private val viewBinding by viewBinding(ViewProfileBinding::bind)
    //反射写法
    private val viewBinding: ItemProfileBinding by viewBinding()

-keep,allowoptimization class * implements androidx.viewbinding.ViewBinding {
    public static *** bind(android.view.View);
    public static *** inflate(...);
}