Fragment 懒加载介绍
日常项目中无可或缺的会用到ViewPager嵌套Fragment的操作,以及Fragment中再嵌套Fragment的这种复杂嵌套的操作.由于ViewPager的缓存机制就会加载多个Fragmen页面导致加载速度变慢,这个时候我们就用到了Fragment 懒加载操作了
效果.png
示例效果实现是基于 ViewPager+FragmentStatePagerAdapter+Fragment
image.png
方案:
- ViewPager + FragmentStatePagerAdapter+Fragment 实现页面搭建
- 基于Fragment setUserVisibleHint() +onResume()+onPause() 处理懒加载
懒加载效果
效果.gif
实现:
1. ViewPager的FragmentStatePagerAdapter()
package com.wu.material.adapter
import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentManager
import androidx.fragment.app.FragmentStatePagerAdapter
/**
*
* 作者:吴奎庆
*
* 时间:2021/11/13
*
* 用途:
*/
class FragmentAdapter(fragmentList:ArrayList<Fragment>,fm: FragmentManager): FragmentStatePagerAdapter (fm){
var fragmentList=ArrayList<Fragment>()
init {
this.fragmentList=fragmentList
}
override fun getItem(position: Int): Fragment {
return fragmentList.get(position)
}
override fun getCount(): Int {
return fragmentList.size
}
}
2. 懒加载Fragment的处理
2.1 懒加载Fragment的基类
package com.wu.material.fragment
import android.content.Context
import android.os.Bundle
import android.util.Log
import android.view.View
import androidx.fragment.app.Fragment
/**
* @author wkq
*
* @date 2022年01月30日 14:09
*
*@des ViewPager+Fragment懒加载
*
*/
// Fragment 完整生命周期：
// onAttach -> onCreate -> onCreatedView -> onActivityCreated ->
// onStart -> onResume ->
// onPause -> onStop ->
// onDestroyView -> onDestroy -> onDetach
abstract class ViewPagerLazyLoadingFragment : Fragment() {
/**
* 当前页面是否可见
*/
private var isVisibleToUser = false
private var isResume = false
override fun onHiddenChanged(hidden: Boolean) {
super.onHiddenChanged(hidden)
Log.e("LazyLoadingFragment :", "onHiddenChanged()" + hidden)
}
/**
* 懒加载执行的方法
*/
abstract fun lazyLoad()
override fun onAttach(context: Context) {
super.onAttach(context)
Log.e("LazyLoadingFragment :", "onAttach()")
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
Log.e("LazyLoadingFragment :", "onCreate()")
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
Log.e("LazyLoadingFragment :", "onViewCreated()")
}
override fun onStart() {
super.onStart()
Log.e("LazyLoadingFragment :", "onStart()")
}
override fun onResume() {
super.onResume()
isResume = true
if (isVisibleToUser) {
lazyLoad()
}
Log.e("LazyLoadingFragment :", "onResume()")
}
/**
* 是否用户可见
*/
override fun setUserVisibleHint(isVisibleToUser: Boolean) {
super.setUserVisibleHint(isVisibleToUser)
this.isVisibleToUser = isVisibleToUser
if (isVisibleToUser && isResume) {
lazyLoad()
}
Log.e("LazyLoadingFragment :", "setUserVisibleHint()" + isVisibleToUser)
}
override fun onPause() {
super.onPause()
isResume = false
Log.e("LazyLoadingFragment :", "onPause()")
}
override fun onStop() {
super.onStop()
Log.e("LazyLoadingFragment :", "onStop()")
}
override fun onDestroyView() {
super.onDestroyView()
Log.e("LazyLoadingFragment :", "onDestroyView()")
}
override fun onDestroy() {
super.onDestroy()
isResume = false
isVisibleToUser = false
Log.e("LazyLoadingFragment :", "onDestroy()")
}
override fun onDetach() {
super.onDetach()
Log.e("LazyLoadingFragment :", "onDetach()")
}
}
2.2 懒加载的Fragment
package com.wu.material.fragment
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Toast
import com.wu.material.R
/**
* @author wkq
*
* @date 2022年01月30日 14:09
*
*@des 懒加载测试页面
*
*/
class DemoLazyLoadFragment : ViewPagerLazyLoadingFragment() {
companion object {
fun newInstance(): DemoLazyLoadFragment {
val args = Bundle()
val fragment = DemoLazyLoadFragment()
fragment.arguments = args
return fragment
}
}
override fun lazyLoad() {
Log.e("DemoLazyLoadFragment :","加载数据")
Toast.makeText(activity,"懒加载加载数据", Toast.LENGTH_SHORT).show()
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.page_1, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
}
}
3. 主要实现
package com.wu.material.activity
import android.content.Context
import android.graphics.Color
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.databinding.DataBindingUtil
import androidx.fragment.app.Fragment
import com.wu.material.R
import com.wu.material.adapter.FragmentAdapter
import com.wu.material.databinding.ActivityLazyLoadingBinding
import com.wu.material.fragment.*
import com.wu.material.widget.CustomTitleView
import net.lucode.hackware.magicindicator.ViewPagerHelper
import net.lucode.hackware.magicindicator.buildins.commonnavigator.CommonNavigator
import net.lucode.hackware.magicindicator.buildins.commonnavigator.abs.CommonNavigatorAdapter
import net.lucode.hackware.magicindicator.buildins.commonnavigator.abs.IPagerIndicator
import net.lucode.hackware.magicindicator.buildins.commonnavigator.abs.IPagerTitleView
import net.lucode.hackware.magicindicator.buildins.commonnavigator.indicators.LinePagerIndicator
/**
* @author wkq
*
* @date 2022年03月16日 9:04
*
*@des
*
*/
class LazyLoadingFragmentActivity : AppCompatActivity() {
var binding: ActivityLazyLoadingBinding? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = DataBindingUtil.setContentView<ActivityLazyLoadingBinding>(this, R.layout.activity_lazy_loading)
initVp()
initMagicIndicator()
}
private fun initMagicIndicator() {
var mTitles = arrayOf("当前", "历史", "曾经", "未来")
binding!!.magicIndicator.setBackgroundColor(Color.WHITE)
val commonNavigator = CommonNavigator(this)
commonNavigator.scrollPivotX = 0.35f
commonNavigator.adapter = object : CommonNavigatorAdapter() {
override fun getCount(): Int {
return if (mTitles == null) 0 else mTitles.size
}
override fun getTitleView(context: Context, index: Int): IPagerTitleView {
val simplePagerTitleView = CustomTitleView(context)
simplePagerTitleView.setText(mTitles.get(index))
simplePagerTitleView.normalColor = Color.parseColor("#666666")
simplePagerTitleView.selectedColor = Color.parseColor("#222222")
simplePagerTitleView.setOnClickListener { binding!!.vpContent.setCurrentItem(index) }
return simplePagerTitleView
}
override fun getIndicator(context: Context): IPagerIndicator {
val indicator = LinePagerIndicator(context)
indicator.mode = LinePagerIndicator.MODE_EXACTLY
indicator.setColors(Color.parseColor("#3399FF"))
indicator.setRoundRadius(5f)
return indicator
}
}
binding!!.vpContent.offscreenPageLimit
binding!!.magicIndicator.navigator = commonNavigator
ViewPagerHelper.bind(binding!!.magicIndicator, binding!!.vpContent)
}
private fun initVp() {
var fragmentList = ArrayList<Fragment>()
fragmentList.add(DemoLazyLoadFragment.newInstance())
fragmentList.add(DemoFragment2.newInstance())
fragmentList.add(DemoFragment3.newInstance())
fragmentList.add(DemoFragment4.newInstance())
var fragmentAdapter = FragmentAdapter(fragmentList, this.supportFragmentManager)
this.binding!!.vpContent.adapter = fragmentAdapter
}
}
总结
由ViewPager +FragmentStateAdapter+Fragment 实现复杂页面的嵌效果,基于Fragment的setUserVisibleHint()方法简单的实现了Fragment的懒加载效果
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