组合ViewModels和ViewPagers

看起来你在用 ViewModel 沟通 onTouchEvent(ev: MotionEvent?) 从你的 适配器 & 查看寻呼机

1. 使一个接口具有方法 onSwipeDown() & onSwipeUp() (或为ViewModel创建任意N个方法)

2. 视图模型

3. 将此接口实现到 视图模型 (它将公开ViewModel中的接口方法)

4. 将ViewModel传递给适配器和视图寻呼机的位置。

瞧!您已经制作了适配器&独立于ViewModel的直接引用的视图寻呼机。

来自Jeel Vankhede的答案被标记为一个解决方案并付诸实施。为供将来参考,解决方案代码将粘贴在下面,以显示ViewPager和适配器如何成功独立于ViewModel的细节:

查看寻呼机: 注意,我们现在有了一个接口对象。滑动ViewPager时,如果没有接口对象,则会引发异常。

//Overriding default touch events and swapping x/y coordinates prior to handling
class VerticalTimerViewPager(context: Context, attributeSet: AttributeSet): ViewPager(context, attributeSet){

    var timerViewPagerEventListener: TimerViewPagerEvent? = null

    init {
        setPageTransformer(true, VerticalPageTransformer())
    }

    override fun onInterceptTouchEvent(ev: MotionEvent?): Boolean {
        ev ?: return false
        val intercepted =  super.onInterceptTouchEvent(swapXYOnMotionEvent(ev))
            swapXYOnMotionEvent(ev)
        return intercepted
    }

    override fun onTouchEvent(ev: MotionEvent?): Boolean {
        timerViewPagerEventListener ?: throwInterfaceExeption()
        when(ev?.action){
            MotionEvent.ACTION_DOWN ->  timerViewPagerEventListener?.onViewPagerSwipeDown()
            MotionEvent.ACTION_UP ->    timerViewPagerEventListener?.onViewPagerSwipeUp()
        }
        return super.onTouchEvent(swapXYOnMotionEvent(ev ?: return false))
    }

    private fun throwInterfaceExeption():Boolean {
        throw RuntimeException("${this.javaClass.simpleName}: Parent Activity must implement TimerViewPagerEvent interface" )
    }

    private fun swapXYOnMotionEvent(motionEvent: MotionEvent): MotionEvent{
        with(motionEvent){
            val newX = (y/height)*width
            val newY = (x/width) * height
            setLocation(newX, newY)
        }
        return motionEvent
    }

    interface TimerViewPagerEvent{
        fun onViewPagerSwipeUp()
        fun onViewPagerSwipeDown()
    }
}

现在获取对象列表(本例中为计时器)

class TimerSlidePagerAdapter(fragmentManager: FragmentManager, private val timers: List<TimerEntity>?):
        FragmentStatePagerAdapter(fragmentManager){

    override fun getItem(position: Int): Fragment {
        if (count > 0) {
            return makeTimerFragment(position)
        }
        return NoDataFragment()
    }

    override fun getCount(): Int = timers?.size ?: 0

    //Internal Functions
    private fun makeTimerFragment(position: Int): Fragment {
        timers ?: return NoDataFragment()
        val timeInMS = timers[position].timeInMS
        return if (timeInMS > 0) {
            TimerFragment.newInstance(timeInMS)
        } else {
            NoDataFragment()
        }
    }
}

活动实施:

    private fun setupPagerAdapter() {
        val pagerAdapter = TimerSlidePagerAdapter(
                fragmentManager = supportFragmentManager,
                timers = viewModel?.timers?.value)

        with(pager){
            adapter = pagerAdapter
            timerViewPagerEventListener = this@MainActivity
        }
    }

private fun observeTimers(){
    viewModel.timers.observe(this, Observer {timerList->
        timerList ?: Log.e(this.javaClass.simpleName, "List of timers is null")
                .also {return@Observer}
        setupPagerAdapter()
    })
}