Android Glide preload RecyclerView切入后台不可见再切换可见只加载当前视野可见区域item图片,Kotlin
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /><uses-permission android:name="android.permission.READ_MEDIA_IMAGES" />
build.gradle文件:
plugins {id("org.jetbrains.kotlin.kapt")
}implementation("com.github.bumptech.glide:glide:4.16.0")
kapt("com.github.bumptech.glide:compiler:4.16.0")
如果手机图片很多,假设已经将全部图片装入宫格的列表,在快速上下滑动过程中,由于glide会累积每一个图片的加载任务,如果图片比较大,上下滑动时间又很长,那么累积任务会很严重,导致异常发生,实现在RecyclerView切入后台(或不可见)时候,然后再次切换回来,只加载当前RecyclerView可见区域的item,非可见区域的图片加载任务,全部清除掉。
注意这里是利用onRestart生命周期模拟当RecyclerView不可见又切换回来的场景,这里可以换成其他场景,只要捕捉到RecyclerView已经消失在视野可见区域,比如利用fragment或者activity的可见性判断等等。
import android.content.Context
import android.graphics.Bitmap
import android.os.Bundle
import android.provider.MediaStore
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.appcompat.widget.AppCompatImageView
import androidx.recyclerview.widget.GridLayoutManager
import androidx.recyclerview.widget.RecyclerView
import androidx.recyclerview.widget.RecyclerView.OnScrollListener
import com.bumptech.glide.load.DataSource
import com.bumptech.glide.load.engine.GlideException
import com.bumptech.glide.request.RequestListener
import com.bumptech.glide.request.target.Target
import java.lang.ref.WeakReferenceconst val PHOTO_SIZE = 150const val EMPTY = 0
const val LOAD = 1class MainActivity : AppCompatActivity() {private val TAG = "Glide FLY"private var mItems = ArrayList<MyData>()private var mLayoutManager: GridLayoutManager? = nullprivate var mAdapter: MyAdapter? = nullprivate var mVisibleItemPosition: IntArray? = nulloverride fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContentView(R.layout.activity_main)init()mItems = readAllImage(applicationContext)mAdapter?.onChange(mItems)}override fun onResume() {super.onResume()Log.d(TAG, "onResume")}//当按了home键后,再次调出app,会进入onRestartoverride fun onRestart() {super.onRestart()Log.d(TAG, "onRestart")loadOnlyVisibleItem()}private fun loadOnlyVisibleItem() {Log.d(TAG, "可见区域 ${mVisibleItemPosition!![0]}->${mVisibleItemPosition!![1]}")for (i in mVisibleItemPosition!![0]..mVisibleItemPosition!![1]) {Log.d(TAG, "可见区域 ${mItems[i].pos} -- ${mItems[i].path}")}for (i in 0 until mItems.size) {if (i !in mVisibleItemPosition!![0]..mVisibleItemPosition!![1]) {if (mItems[i].status == LOAD) {mItems[i].targetRef?.get()?.let {GlideApp.with(this).clear(it)}mItems[i].status = EMPTY}}}}private fun getVisibleItemPosition(): IntArray {val first = mLayoutManager?.findFirstVisibleItemPosition()val last = mLayoutManager?.findLastVisibleItemPosition()return intArrayOf(first!!, last!!)}private fun init() {val spanCount = 8val rv = findViewById<RecyclerView>(R.id.recycler_view)mLayoutManager = GridLayoutManager(this, spanCount)rv.layoutManager = mLayoutManagerrv.addOnScrollListener(object : OnScrollListener() {override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {super.onScrolled(recyclerView, dx, dy)mVisibleItemPosition = getVisibleItemPosition()}})mAdapter = MyAdapter(this)rv.adapter = mAdapter}private fun readAllImage(context: Context): ArrayList<MyData> {val photos = ArrayList<MyData>()//读取手机图片val cursor = context.contentResolver.query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,null,null,null,null)while (cursor!!.moveToNext()) {//图片路径 urival path = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA))//图片名称//val name = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DISPLAY_NAME))//图片大小//val size = cursor.getLong(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.SIZE))photos.add(MyData(path))}cursor.close()return photos}
}class MyAdapter(private val context: Context) : RecyclerView.Adapter<MyVH>() {private var items = ArrayList<MyData>()fun onChange(items: ArrayList<MyData>) {this.items = itemsnotifyDataSetChanged()}override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyVH {val v = LayoutInflater.from(context).inflate(R.layout.item, parent, false)val params = v.layoutParamsparams.width = PHOTO_SIZEparams.height = PHOTO_SIZEreturn MyVH(v)}override fun onBindViewHolder(holder: MyVH, position: Int) {load(holder, position)holder.text.text = "$position"}override fun getItemCount(): Int {return items.size}private fun load(holder: MyVH, position: Int) {items[position].pos = positionitems[position].status = LOADval target: Target<*> = GlideApp.with(holder.itemView.context).asBitmap().load(items[position].path).centerCrop().addListener(object : RequestListener<Bitmap> {override fun onLoadFailed(e: GlideException?,model: Any?,target: Target<Bitmap>,isFirstResource: Boolean): Boolean {items[position].status = EMPTYreturn false}override fun onResourceReady(resource: Bitmap,model: Any,target: Target<Bitmap>?,dataSource: DataSource,isFirstResource: Boolean): Boolean {holder.image.setImageBitmap(resource)items[position].status = EMPTY// 特别注意此处返回是true,而不能是false。// 因为如果返回false,当按home键把app切入后台后,再按app图标调出app切换到前台可见,反复切换,// 会造成Bitmap未回收的崩溃。return true}}).preload(PHOTO_SIZE,PHOTO_SIZE)items[position].targetRef = WeakReference(target)}
}class MyVH(itemView: View) : RecyclerView.ViewHolder(itemView) {var image: AppCompatImageViewvar text: TextViewinit {image = itemView.findViewById(R.id.image)text = itemView.findViewById(R.id.text)}
}class MyData(var path: String) {var targetRef: WeakReference<Target<*>>? = nullvar status = EMPTYvar pos = 0
}
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity"><androidx.recyclerview.widget.RecyclerViewandroid:id="@+id/recycler_view"android:layout_width="match_parent"android:layout_height="match_parent" /></RelativeLayout>
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="wrap_content"android:layout_height="wrap_content"android:padding="1px"><androidx.appcompat.widget.AppCompatImageViewandroid:id="@+id/image"android:layout_width="wrap_content"android:layout_height="wrap_content"android:scaleType="centerCrop"android:src="@drawable/ic_launcher_background" /><TextViewandroid:id="@+id/text"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_centerInParent="true"android:background="@android:color/holo_green_light"android:paddingLeft="1dp"android:paddingRight="1dp"android:text="-.-"android:textColor="@android:color/holo_red_dark"android:textSize="5dp" />
</RelativeLayout>
import android.content.Context
import android.util.Log
import com.bumptech.glide.GlideBuilder
import com.bumptech.glide.annotation.GlideModule
import com.bumptech.glide.module.AppGlideModule@GlideModule
class MyModule : AppGlideModule() {override fun applyOptions(context: Context, builder: GlideBuilder) {builder.setLogLevel(Log.DEBUG)}override fun isManifestParsingEnabled(): Boolean {return false}
}
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