Android Gldie复用只取之前decode过的缓存resource，Kotlin-CSDN博客

Android Gldie复用只取之前decode过的缓存resourceKotlin

import android.graphics.Bitmap
import android.os.Bundle
import android.util.Log
import android.widget.ImageView
import androidx.appcompat.app.AppCompatActivity
import androidx.lifecycle.lifecycleScope
import com.bumptech.glide.load.DataSource
import com.bumptech.glide.load.engine.GlideException
import com.bumptech.glide.load.resource.bitmap.CenterCrop
import com.bumptech.glide.request.RequestListener
import com.bumptech.glide.request.target.Target
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.channels.Channel
import kotlinx.coroutines.flow.receiveAsFlow
import kotlinx.coroutines.launch


class MainActivity : AppCompatActivity() {
    private val TAG = "Glide/${this::class.simpleName}"

    companion object {
        const val FAIL = -1
        const val SUCCESS = 1
        const val SIZE = 400
    }

    private val mCrop = CenterCrop()
    private val resId = R.mipmap.pic2
    private var mImageView: ImageView? = null

    private val mChannel = Channel<Int>()

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

        val imageView = findViewById<ImageView>(R.id.image)
        mImageView = findViewById(R.id.image2)

        GlideApp.with(this)
            .asBitmap()
            .load(resId)
            .transform(mCrop)
            .override(SIZE, SIZE)
            .addListener(object : RequestListener<Bitmap> {
                override fun onLoadFailed(
                    e: GlideException?,
                    model: Any?,
                    target: Target<Bitmap>,
                    isFirstResource: Boolean
                ): Boolean {
                    Log.d(TAG, "onLoadFailed")
                    signal(FAIL)
                    return false
                }

                override fun onResourceReady(
                    resource: Bitmap,
                    model: Any,
                    target: Target<Bitmap>?,
                    dataSource: DataSource,
                    isFirstResource: Boolean
                ): Boolean {
                    Log.d(TAG, "onResourceReady")
                    signal(SUCCESS)
                    return false
                }
            }).into(imageView)

        waitReceive()
    }

    fun signal(s: Int) {
        lifecycleScope.launch(Dispatchers.IO) {
            mChannel.send(s)
        }
    }

    private fun waitReceive() {
        lifecycleScope.launch(Dispatchers.IO) {
            mChannel.receiveAsFlow().collect {
                Log.d(TAG, "collect $it")

                if (it == SUCCESS) {
                    fetchCacheBitmap()
                }
            }
        }
    }

    private fun fetchCacheBitmap() {
        val bitmap = runCatching {
            GlideApp.with(this@MainActivity)
                .asBitmap()
                .load(resId)
                .transform(mCrop)
                .onlyRetrieveFromCache(true) //从内存或者glide decode好的resource里面取不去原始decode
                .override(SIZE, SIZE)
                .addListener(object : RequestListener<Bitmap> {
                    override fun onLoadFailed(
                        e: GlideException?,
                        model: Any?,
                        target: Target<Bitmap>,
                        isFirstResource: Boolean
                    ): Boolean {
                        Log.d(TAG, "cache onLoadFailed")
                        return false
                    }

                    override fun onResourceReady(
                        resource: Bitmap,
                        model: Any,
                        target: Target<Bitmap>?,
                        dataSource: DataSource,
                        isFirstResource: Boolean
                    ): Boolean {
                        Log.d(TAG, "cache onResourceReady")
                        return false
                    }
                }).submit()
                .get() //不要在这里加timeout值
        }.onFailure {
            Log.d(TAG, "取Glide缓存失败:${it.message}")
        }.onSuccess {
            Log.d(TAG, "取Glide缓存成功:${it.byteCount}")
        }.getOrNull()

        Log.d(TAG, "getOrNull=${bitmap?.byteCount}")

        if (bitmap != null) {
            lifecycleScope.launch(Dispatchers.Main) {
                //之前的缓存资源取到了。
                //使用之前的缓存设置到新的ImageView里面。
                mImageView?.setImageBitmap(bitmap)
            }
        }
    }
}

可以看到第一次因为是全新的加载没有缓存glide只能干脏活把原始的图片文件decode成resource花费200+毫秒而之后只从缓存包括磁盘的resource半成品中取仅仅花费20+毫秒时间开销是原先的约1/10加载速度相当于快了约10倍。

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