Possible to jump straight to second view in ViewAnimator

问题

I have a ViewAnimator (ViewSwitcher to be precise) with fade in/out animations associated to it and two Views which I transition between using the ViewAnimator.showNext() and ViewAnimator.showPrevious() methods.

There is a requirement in my app where sometimes I need to start straight from the second View, without showing a fade animation in going from the first View to the second. Anyone know if there is a straightforward way to accomplish this without having to mess around with the in/out animations associated to my ViewAnimator?

Note: I have tried calling ViewAnimator.setDisplayedChild(1) but that also animates the transition.

回答1:

I looked around and waited for a response but I'm guessing it's not possible. So, in the absence of a better solution, set your ViewAnimator's in/out animations to null when you want to jump straight to a particular child View of your ViewAnimator, as follows:

myViewAnimator.setInAnimation(null);
myViewAnimator.setOutAnimation(null);
myViewAnimator.setDisplayedChild(childIndex);

If anyone knows a better way - rather than playing with the ViewAnimator's in/out animations - please share!

回答2:

Unfortunately, there is no built-in function to do that, but you can add this function, which does the job:

public static void setDisplayedChildNoAnim(ViewAnimator viewAnimator, int whichChild) {
    Animation inAnimation = viewAnimator.getInAnimation();
    Animation outAnimation = viewAnimator.getOutAnimation();
    viewAnimator.setInAnimation(null);
    viewAnimator.setOutAnimation(null);
    viewAnimator.setDisplayedChild(whichChild);
    viewAnimator.setInAnimation(inAnimation);
    viewAnimator.setOutAnimation(outAnimation);
}

回答3:

Here's a more comprehensive way, which let you choose either an id or a view, and with/without animation:

fun ViewAnimator.setViewToSwitchTo(viewToSwitchTo: View, animate: Boolean = true): Boolean {
    if (currentView === viewToSwitchTo)
        return false
    for (i in 0 until childCount) {
        if (getChildAt(i) !== viewToSwitchTo)
            continue
        if (animate)
            displayedChild = i
        else {
            val outAnimation = this.outAnimation
            val inAnimation = this.inAnimation
            this.inAnimation = null
            this.outAnimation = null
            displayedChild = i
            this.inAnimation = inAnimation
            this.outAnimation = outAnimation
        }
        return true
    }
    return false
}

fun ViewAnimator.setViewToSwitchTo(@IdRes viewIdToSwitchTo: Int, animate: Boolean = true): Boolean {
    if (currentView.id == viewIdToSwitchTo)
        return false
    for (i in 0 until childCount) {
        if (getChildAt(i).id != viewIdToSwitchTo)
            continue
        if (animate)
            displayedChild = i
        else {
            val outAnimation = this.outAnimation
            val inAnimation = this.inAnimation
            this.inAnimation = null
            this.outAnimation = null
            displayedChild = i
            this.inAnimation = inAnimation
            this.outAnimation = outAnimation
        }
        return true
    }
    return false
}

Example of usage:

viewSwitcher.setViewToSwitchTo(someView,false)

来源：https://stackoverflow.com/questions/11231933/possible-to-jump-straight-to-second-view-in-viewanimator