Question

我正在创建一个使用底部导航的项目。我正在使用片段进行标签调用

val transaction = supportFragmentManager.beginTransaction()
transaction.add(R.id.frame_layout, Fragment1.newInstance(),Fragment1.newInstance().TAG)
transaction.addToBackStack(null).commit()

bottomNavigationView.setOnNavigationItemSelectedListener(object : BottomNavigationView.OnNavigationItemSelectedListener {

        override fun onNavigationItemSelected(item: MenuItem): Boolean {

            if(item.itemId == lastSelectedItemId){
                return true
            }

            var menuTag:String ?= null
            var selectedFragment: Fragment? = null
            lastSelectedItemId = item.itemId

            when (item.itemId) {
                R.id.tab1 -> {
                    selectedFragment = Fragment1.newInstance()
                    menuTag = selectedFragment.TAG
                }
                R.id.tab2 -> {
                    selectedFragment = Fragment2.newInstance()
                    menuTag = selectedFragment.TAG
                }
                R.id.tab3 -> {
                    selectedFragment = Fragment3.newInstance()
                    menuTag = selectedFragment.TAG
                }
                R.id.tab4 ->{
                    selectedFragment = Fragment4.newInstance()
                    menuTag = selectedFragment.TAG
                }
            }

            val transaction = supportFragmentManager.beginTransaction()
            transaction.replace(R.id.frame_layout, selectedFragment,menuTag)
            transaction.addToBackStack(menuTag).commit()
            return true
        }
    })

但片段总是重新加载我累了一些方法

替换（）。addToBackStack（空）
替换（）。addToBackStack（标签）
添加，隐藏，显示

addToBackStack（） - 使用这个，当我点击android默认的底部后退按钮时，它弄乱了我的片段布局。与return @ OnNavigationItemSelectedListener相同

我跟随了许多与此问题相关的论坛，但在我的情况下，没有任何工作。

我的第四个片段是

class Fragment4 : Fragment() {

var listOfMoreMenus = ArrayList<MoreLinksObject>()
var adapter: MoreLinksAdapter?=null
public var TAG: String = "more"
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
}

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                          savedInstanceState: Bundle?): View? {
    val moreView = inflater.inflate(R.layout.fragment_more, container, false)
    val listView = moreView.findViewById(R.id.moreLinks) as ListView

    listOfMoreMenus.add(MoreLinksObject("test1","link1")) 
    listOfMoreMenus.add(MoreLinksObject("test2","link2")) 
    listOfMoreMenus.add(MoreLinksObject("test3","link3")) 
    listView.setNestedScrollingEnabled(true)
    adapter = MoreLinksAdapter(getActivity()!!,listOfMoreMenus)
    listView.adapter = adapter
    return moreView

}

companion object {
    fun newInstance(): Fragment4 {
        return Fragment4()
    }
}


inner class MoreLinksAdapter: BaseAdapter {

    var  listOfMoreMenus= ArrayList<MoreLinksObject>()
    var context: Context?=null
    constructor(context:Context, listOfMoreMenus: ArrayList<MoreLinksObject>):super(){
        this.listOfMoreMenus=listOfMoreMenus
        this.context=context

    }

    override fun getItem(position: Int): Any {
        return listOfMoreMenus[position]
    }

    override fun getItemId(position: Int): Long {
        return position.toLong()
    }

    override fun getCount(): Int {
        return  listOfMoreMenus.size
    }

    override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View {
        val MoreLinkObj =  listOfMoreMenus[position]
        var inflator = context!!.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
        var myView = inflator.inflate(R.layout.more_menu, null)
        val moreMenuName = myView.findViewById(R.id.moreMenuName) as TextView
        moreMenuName.text =  MoreLinkObj.name!!
        return myView
    }

}
}

Answer 1

嗯，每次选择一个选项时，您都会提供每个片段的新实例，每次调用newInstance()。你有两个选择：

1）片段数组

在创建片段并将其重新使用时，将片段保存在全局数组中

2）标记

在片段中添加一个标签，然后用它来查找相同的片段。

因为您已经设置了最适合您的标签：

val FRAGMENT_1_TAG =  "FRAGMENT_1_TAG"
val FRAGMENT_2_TAG =  "FRAGMENT_2_TAG"
val FRAGMENT_3_TAG =  "FRAGMENT_3_TAG"
val FRAGMENT_4_TAG =  "FRAGMENT_4_TAG"

when (item.itemId) {
                R.id.tab1 -> {
                title = "Fragment1"
                selectedFragment = supportFragmentManager.findFragmentByTag(FRAGMENT_1_TAG);
                if (selectedFragment == null) {
                    selectedFragment = Fragment1.newInstance()
                }
                menuTag = FRAGMENT_1_TAG
                }
                R.id.tab2 -> {
                title = "Fragment2"
                selectedFragment = supportFragmentManager.findFragmentByTag(FRAGMENT_2_TAG);
                if (selectedFragment == null) {
                    selectedFragment = Fragment2.newInstance()
                }
                    menuTag = FRAGMENT_2_TAG
                }
                R.id.tab3 -> {
                title = "Fragment3"
                selectedFragment = supportFragmentManager.findFragmentByTag(FRAGMENT_3_TAG);
                if (selectedFragment == null) {
                    selectedFragment = Fragment3.newInstance()
                }
                    menuTag = FRAGMENT_3_TAG
                }
                R.id.tab4 ->{
                title = "Fragment4"
                selectedFragment = supportFragmentManager.findFragmentByTag(FRAGMENT_4_TAG);
                if (selectedFragment == null) {
                    selectedFragment = Fragment4.newInstance()
                }
                    menuTag = FRAGMENT_4_TAG
                }
            }

修改

要清除列表视图，您可以在添加新内容之前清除它，因此每次调用onCreateView时，您的列表都将从头开始初始化：

listOfMoreMenus.clear() listOfMoreMenus.add(MoreLinksObject("test1","link1")) listOfMoreMenus.add(MoreLinksObject("test2","link2")) listOfMoreMenus.add(MoreLinksObject("test3","link3"))

至于更改标题，如果您的工具栏属于活动，您可以在每次更改片段时设置标题。（见上文）。如果它属于片段，则需要在onCreateView方法中更改它，以便每次更改片段时都会更改它。

Android - 底部导航标签调用的片段每次都在重新加载

1 个答案: