java - 旋转屏幕后， View 寻呼机保留旧 fragment

Question

我有一个 View 寻呼机，有 4 个 fragment 。 (我使用 FragmentStatePagerAdapter)

每个 fragment 都有一个“FrameLayout/容器”，我在其中添加和替换许多 fragment 。

一切正常，但是当我更改屏幕方向时，该行的第一个 fragment 将恢复到实际 fragment 上。然后两者同时出现。

我用一张图片来说明所发生的情况:

First Fragment

Second Fragment

[当我旋转屏幕时]

/image/kxaVn.png 

我的主要 Activity 代码

class MainActivity : AppCompatActivity() {


val numPages = 4
var pager: ViewPager? = null
private val TITLES = arrayOf("Feed", "Catalogo","Guia","Rendimento")
var menuImages:Array<ImageView>?=null
var menuTexts:Array<TextView>?=null

var fragments = arrayListOf<Fragment>()


private var fragmentCreated1: FeedContainerFragment? = null
private var fragmentCreated2: CatalogContainerFragment? = null
private var fragmentCreated3: GuideContainerFragment? = null
private var fragmentCreated4: TestContainerFragment? = null



override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_default)


     fragments.add(FeedContainerFragment())
     fragments.add(CatalogContainerFragment())
     fragments.add(GuideContainerFragment())
     fragments.add(TestContainerFragment())


    menuImages= arrayOf(findViewById(R.id.icon_feed) as ImageView,
                        findViewById(R.id.icon_catalogue) as ImageView,
                        findViewById(R.id.icon_guide) as ImageView,
                        findViewById(R.id.icon_form) as ImageView)

    menuTexts= arrayOf(findViewById(R.id.text_feed) as TextView,
                    findViewById(R.id.text_catalogue) as TextView,
                    findViewById(R.id.text_guide) as TextView,
                    findViewById(R.id.text_form) as TextView)




    menuImages?.get(0)?.setColorFilter(ContextCompat.getColor(baseContext,R.color.colorAccent))
    menuTexts?.get(0)?.setTextColor(ContextCompat.getColor(baseContext,R.color.colorAccent))


    //view pager

    pager = findViewById(R.id.pager) as ViewPager
    val pagerAdapter = ScreenSlidePagerAdapter(supportFragmentManager)


    pager?.adapter = pagerAdapter
    pager?.offscreenPageLimit = 4


    pager?.addOnPageChangeListener(object : ViewPager.OnPageChangeListener {
        override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {

        }

        override fun onPageSelected(position: Int) {
            pager?.adapter?.notifyDataSetChanged()
            repaintMenuDefaultColor()

            menuImages?.get(position)?.setColorFilter(ContextCompat.getColor(baseContext,R.color.colorAccent))
            menuTexts?.get(position)?.setTextColor(ContextCompat.getColor(baseContext,R.color.colorAccent))

        }

        override fun onPageScrollStateChanged(state: Int) {

        }
    })


    //Navigation Menus
    MenuUtils.generateMaterialMenu(this)
    MenuUtils.generateBottomMenu(this, this.pager!!)


}

private inner class ScreenSlidePagerAdapter(fm: FragmentManager) : FragmentStatePagerAdapter(fm) {
    override fun getCount(): Int {
        return numPages
    }

    override fun getItem(position: Int): Fragment {
        when(position) {
            0->return FeedContainerFragment()
            1->return CatalogContainerFragment()
            2->return GuideContainerFragment()
            3->return TestContainerFragment()

            else->return FeedContainerFragment()
        }

    }


    override fun getPageTitle(position: Int): CharSequence {
        return TITLES[position]
    }

    override fun getItemPosition(obj: Any?): Int {

        if (obj is Refreshable) {
            return POSITION_NONE
        }
        return super.getItemPosition(obj)
    }



    override fun instantiateItem(container:ViewGroup, position:Int):Any {
        val createdFragment = super.instantiateItem(container, position) as Fragment
        when (position) {
            0 -> fragmentCreated1 = createdFragment as FeedContainerFragment
            1 -> fragmentCreated2 = createdFragment as CatalogContainerFragment
            2 -> fragmentCreated3 = createdFragment as GuideContainerFragment
            3 -> fragmentCreated4 = createdFragment as TestContainerFragment

        }


        return createdFragment
    }

}


override fun onBackPressed() {
    if (fragmentManager.backStackEntryCount > 0) {
        fragmentManager.popBackStack()
    } else {
        super.onBackPressed()
    }
}


fun repaintMenuDefaultColor(){
    this.menuImages?.map {
        it.setColorFilter(ContextCompat.getColor(baseContext,R.color.menu_icon))
    }

    this.menuTexts?.map {
        it.setTextColor(ContextCompat.getColor(baseContext,R.color.menu_text))
    }


}

}

欢迎任何帮助!

编辑:实际上，发生的情况是 ViewPager 将实际 fragment 保留为“幽灵”，然后恢复该行的第一个 fragment 。

有没有办法清洁屏幕并删除“幽灵”？

编辑2:找到解决方案。在将 fragment 添加到每个“容器”上之前，我需要验证 fragment 实例是否已存在 问题不在 ViewPager 或 Adapter 上。每次我改变方向时都会包含一个新的 fragment 。

所以，只需将验证放在下面即可:

     if(savedInstanceState == null) {
        activity
                .supportFragmentManager
                .beginTransaction()
                .add(R.id.containerGuide, YourFragment())
                .commit()
    }

Answer 1

旋转屏幕时，将重新创建 Activity 和 Fragments，以便从位置 0 开始..

1. 重建 viewpager 时保存 Fragment 位置只需选择您需要的 Fragment。
2. 查看此链接 https://developer.android.com/guide/topics/resources/runtime-changes.html
3. 禁用屏幕旋转。