Simulate activity startup mode in compose

About startup mode

We all know that activity There are many startup modes in the system ：standard、singleTop、singleInstance、singleTask Four kinds of . But in compose Because it is a single activity So there is no such thing as a startup mode , So in this article I use some NavHostController Some of api To achieve the effect in startup mode .

standard

The default effect is standard The effect of

singleTop

compose We can determine whether the top page is what we want to launch singleTop Page to process .

If the top page is singleTop The top page is refreshed directly .

Judging code ：

/** *  Determine whether the top page is the page we want to route  */
fun sameAsTopPage(controller: NavHostController,dstRoute: String):Boolean{
    
    val distination = controller.currentDestination?.route ?: ""
    return distination == dstRoute
}

singleTask

The way we do it , It will first determine whether there is a target page in the current routing stack , If it exists, it will go back to the target page , The middle page will be destroyed automatically

fun toSingleInstance(controller: NavHostController, route: String){
    
    val findRoute = controller.findDestination(route)
    if (findRoute == null){
    
        controller.navigate(route)
    }else{
    
        controller.popBackStack()
        controller.navigate(route)
    }
}

singleSinstance

At present, we don't have a good way to implement the singleton mode , So there is no implementation here .

however compose The scenario of the single example in does not seem to exist , So it doesn't matter .