Kotlin - How to add OnPageChangeListener in ViewPager

user_1380032 0
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I am new in kotlin, How can I add OnPageChangeListener in a ViewPager.

viewPager?.addOnPageChangeListener // Now how can I add listener to it.
android-viewpager kotlin android
4 Answers

For ViewPager2 you can do it using OnPageChangeCallBack,

viewPager2?.registerOnPageChangeCallback(object : ViewPager2.OnPageChangeCallback() {
        override fun onPageSelected(position: Int) {
            super.onPageSelected(position)
        }

        override fun onPageScrollStateChanged(state: Int) {
            super.onPageScrollStateChanged(state)
        }

        override fun onPageScrolled(position: Int,
                                    positionOffset: Float,
                                    positionOffsetPixels: Int) {
            super.onPageScrolled(position, positionOffset, positionOffsetPixels)
        }
    })
user_68451310

Since most of the times we need to override only one of three ViewPager.OnPageChangeListener's methods (usually onPageSelected), this might be useful to reduce the code:

viewPager?.addOnPageChangeListener(object : ViewPager.SimpleOnPageChangeListener() {

    //override only methods you need, not all of them

    override fun onPageSelected(position: Int) {

    }
})
user_22192370
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