Android横竖屏切换configChanges=“screenSize|orientation“避免activity销毁重建，Kotlin

Android横竖屏切换configChanges="screenSize|orientation"避免activity销毁重建，Kotlin

如果不在Androidmanifest.xml设置activity的：

android:configChanges="screenSize|orientation"

那么，每次横竖屏切换activity都会重新走onCreate() ... onDestory()生命周期，即销毁重建。如果设置了上面的配置后，每次横竖屏切换，activity只是回调：

    override fun onConfigurationChanged(newConfig: Configuration) {
        super.onConfigurationChanged(newConfig)
      
    }

而不再走或触发activity的创建-消耗重的生命周期。

import android.content.res.Configuration
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.GridLayoutManager
import androidx.recyclerview.widget.RecyclerView
import java.util.UUID

const val ITEM_COUNT = 300

class MainActivity : AppCompatActivity() {
    private var mAdapter: MyAdapter? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        Log.d("fly", "onCreate")

        setContentView(R.layout.activity_main)

        val rv = findViewById<RecyclerView>(R.id.rv)
        val layoutManager = GridLayoutManager(this, 3)
        rv.layoutManager = layoutManager

        mAdapter = MyAdapter()
        rv.adapter = mAdapter
    }

    override fun onDestroy() {
        super.onDestroy()
        Log.d("fly", "onDestroy")
    }

    class MyAdapter : RecyclerView.Adapter<MyVH> {
        private var mList = mutableListOf<MyItem>()

        constructor() {
            val list = mutableListOf<MyItem>()
            for (i in 0 until ITEM_COUNT) {
                val item = MyItem(i)
                item.data = 0L
                item.change = false
                list.add(item)
            }
            mList = list
        }

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyVH {
            val view = LayoutInflater.from(parent.context).inflate(android.R.layout.simple_list_item_2, parent, false)
            return MyVH(view)
        }

        override fun getItemCount(): Int {
            return mList.size
        }

        override fun onBindViewHolder(holder: MyVH, position: Int) {
            holder.text1.text = "pos=${mList[position].pos}"
            holder.text2.text = "data=${mList[position].data}"
        }
    }

    class MyVH(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val text1: TextView = itemView.findViewById(android.R.id.text1)
        val text2: TextView = itemView.findViewById(android.R.id.text2)
    }

    class MyItem {
        var pos = 0
        var data = 0L
        var contentId = UUID.randomUUID()
        var change = false

        constructor(pos: Int) {
            this.pos = pos
        }

        constructor() : this(0) {
        }
    }

    override fun onConfigurationChanged(newConfig: Configuration) {
        super.onConfigurationChanged(newConfig)
        Log.d("fly", "onConfigurationChanged")
    }
}

启动后，滑动到pos=30：

横竖屏切换，可以看到，Android自动在切换后把位置滚动到pos=30，无须recycleview再做滚动计算和调整：

日志：

Android重写onConfigurationChanged规避横竖屏切换时候重新进入onCreate生命周期-CSDN博客文章浏览阅读2.1k次。Android重写onConfigurationChanged规避横竖屏切换时候重新进入onCreate生命周期Android系统内在的机制，当activity在横竖屏切换时候，会强制重新开始进入activity的生命周期onCreate，在有些特殊的场景，开发者不希望重新进入onCreate生命周期，那么，可以通过重写Android的onConfigurationChanged规避。_onconfigurationchangedhttps://blog.csdn.net/zhangphil/article/details/50607742