How to know when fragment actually visible in viewpager

问题

I am using 4 fragments inside a ViewPager ,as ViewPager load the previous and next fragment in advance ,and no lifecycle method is called when navigating between fragments. So is there any way to detect when Fragment is actually visible. Thanks in Advance.

回答1:

Of course. Assuming that viewPager is your instance of the ViewPager, use: viewPager.getCurrentItem().

Within your Fragment you can check if its instance is visible to the user like so:

@Override
public void setUserVisibleHint(boolean visible) {
    super.setUserVisibleHint(visible);
    if (visible) {
        Log.i("Tag", "Reload fragment");
    }
}

Always make sure that you search for answers throughly before asking your question. For instance, the first place you should check would be: https://developer.android.com/reference/android/support/v4/view/ViewPager.html

回答2:

as per @Matt's answer setUserVisibleHint is deprecated so here is alternative way for this.

    @Override
    public void setMenuVisibility(boolean isvisible) {
        super.setMenuVisibility(isvisible);
        if (isvisible){
            Log.d("Viewpager", "fragment is visible ");
        }else {
            Log.d("Viewpager", "fragment is not visible ");
        }
    }

回答3:

Did you try the isVisible method in the fragment?

回答4:

You can use viewPager.getCurrrentItem() to get the currently selected index, and from that you should be able to extrapolate which fragment is shown. However what you probably want is to use addOnPageChangeListener() to add an OnPageChangeListener. This will let you keep track of what page is selected, as it's selected by implementing the onPageSelected(int selected) method.

来源：https://stackoverflow.com/questions/48893014/how-to-know-when-fragment-actually-visible-in-viewpager

标签

android

android-viewpager

fragment