緩存的使用之OkHttp + DiskLruCache

本文以單張圖片為素材，實(shí)現(xiàn)OkHttp + DiskLruCache的使用

1、DiskLruCache工具類

/**
 * 圖片的磁盤緩存工具類
 */
class DiskLruCacheUtils {

    companion object{

        lateinit var mDiskLruCache: DiskLruCache

        /**
        * 初始化磁盤緩存
        */
        fun initDisk(context : Context){
            try {
                val cacheDir = getDiskCacheDir(context, "bitmap")
                if (!cacheDir.exists()) {
                    cacheDir.mkdirs()
                }
                mDiskLruCache = DiskLruCache.open(cacheDir, getAppVersion(context), 1, 10 * 1024 * 1024)
            } catch (e: IOException) {
                e.printStackTrace()
            }
        }

        /**
         * 獲取磁盤緩存路徑地址
         */
        fun getDiskCacheDir(context: Context, uniqueName: String): File {
            val cachePath: String = if (Environment.MEDIA_MOUNTED == Environment.getExternalStorageState()
                || !Environment.isExternalStorageRemovable()
            ) {
                context.externalCacheDir!!.path
            } else {
                context.cacheDir.path
            }
            return File(cachePath + File.separator + uniqueName)
        }

        /**
         * 獲取系統(tǒng)版本號
         */
        private fun getAppVersion(context: Context): Int {
            try {
                val info = context.packageManager.getPackageInfo(context.packageName, 0)
                return info.versionCode
            } catch (e: PackageManager.NameNotFoundException) {
                e.printStackTrace()
            }
            return 1
        }

        /**
         * 將圖片地址進(jìn)行MD5編碼
         */
        fun hashKeyForDisk(key: String): String? {
            return try {
                val mDigest: MessageDigest = MessageDigest.getInstance("MD5")
                mDigest.update(key.toByteArray())
                bytesToHexString(mDigest.digest())
            } catch (e: NoSuchAlgorithmException) {
                key.hashCode().toString()
            }
        }

        private fun bytesToHexString(bytes: ByteArray): String? {
            val sb = StringBuilder()
            for (i in bytes.indices) {
                val hex = Integer.toHexString(0xFF and bytes[i].toInt())
                if (hex.length == 1) {
                    sb.append('0')
                }
                sb.append(hex)
            }
            return sb.toString()
        }

        /**
         * 下載圖片并寫入磁盤緩存
         */
        fun downloadUrlToStream(urlString: String, outputStream: OutputStream): Boolean {
            var urlConnection: HttpURLConnection? = null
            var out: BufferedOutputStream? = null
            var `in`: BufferedInputStream? = null
            try {
                val url = URL(urlString)
                urlConnection = url.openConnection() as HttpURLConnection
                `in` = BufferedInputStream(urlConnection.inputStream, 8 * 1024)
                out = BufferedOutputStream(outputStream, 8 * 1024)
                var b: Int
                while (`in`.read().also { b = it } != -1) {
                    out.write(b)
                }
                return true
            } catch (e: IOException) {
                e.printStackTrace()
            } finally {
                urlConnection?.disconnect()
                try {
                    out?.close()
                    `in`?.close()
                } catch (e: IOException) {
                    e.printStackTrace()
                }
            }
            return false
        }

        /**
         * 把byte字節(jié)寫入緩存DiskLruCache
         */
        @Throws(java.lang.Exception::class)
        fun writeToDiskLruCache(url: String, buf: ByteArray) {
            Log.d("TAG", "$url : 開始寫入緩存...")

            //DiskLruCache緩存需要一個(gè)key，我先把url轉(zhuǎn)換成md5字符串，
            //然后以md5字符串作為key鍵
            val key: String? = hashKeyForDisk(url)
            val editor: DiskLruCache.Editor = mDiskLruCache.edit(key)
            val os: OutputStream = editor.newOutputStream(0)
            os.write(buf)
            os.flush()
            editor.commit()
            mDiskLruCache.flush()
            Log.d("TAG", "$url : 寫入緩存完成.")
        }

    }
}

2、OkHttp + DiskLruCache的使用

  • 首先讀磁盤，如果有緩存則直接顯示；
  • 如果磁盤中沒有緩存，則需要通過OkHttp 下載圖片，下載成功后將圖片緩存進(jìn)磁盤，同時(shí)完成圖片的顯示；
/**
 * OkHttp + DiskLruCache
 */
class OkhttpDiskLruCacheActivity : AppCompatActivity() {

    lateinit var imageView : ImageView
    private val oriUrl : String = "https://t7.baidu.com/it/u=2168645659,3174029352&fm=193&f=GIF"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_okhttp_disk_lru_cache)
        imageView = findViewById(R.id.image_id)
        loadImage()
    }

    private fun loadImage(){
        //先讀取磁盤緩存
        try {
            val key = DiskLruCacheUtils.hashKeyForDisk(oriUrl)
            val snapShot = mDiskLruCache[key]
            if (snapShot != null) {
                val `is` = snapShot.getInputStream(0)
                val bitmap = BitmapFactory.decodeStream(`is`)
                imageView.setImageBitmap(bitmap)
            }
            else{
                downloadBitmapFromNetwork(imageView,oriUrl)
            }
        } catch (e: IOException) {
            e.printStackTrace()
        }
    }

    private fun downloadBitmapFromNetwork(image: ImageView, image_url: String) {
        Log.d("TAG", "從網(wǎng)絡(luò)中加載圖片資源 ...  @ $image_url")

        //初始化OkHttpClient
        val client = OkHttpClient()

        //創(chuàng)建OkHttpClient針對某個(gè)url的數(shù)據(jù)請求
        val request: Request = Request.Builder().url(image_url).build()
        val call: Call = client.newCall(request)

        //請求加入隊(duì)列
        call.enqueue(object : Callback {
            override fun onFailure(call: Call?, e: IOException?) {
                //此處處理請求失敗的業(yè)務(wù)邏輯
            }

            @Throws(IOException::class)
            override fun onResponse(call: Call?, response: Response) {
                //如果response響應(yīng)成功則繼續(xù)，否則返回
                if (!response.isSuccessful()) return

                //我寫的這個(gè)例子是請求一個(gè)圖片
                //response的body是圖片的byte字節(jié)
                val bytes: ByteArray = response.body()!!.bytes()

                //已經(jīng)獲得圖片數(shù)據(jù)，記到要寫入硬盤緩存
                //出于性能考慮，此處可以放到后臺或者放到一個(gè)線程里面處理
                //簡單期間，我就在這兒直接寫緩存了。
                try {
                    DiskLruCacheUtils.writeToDiskLruCache(image_url, bytes)
                } catch (e: Exception) {
                    e.printStackTrace()
                }

                //把byte字節(jié)組裝成圖片
                val bmp = BitmapFactory.decodeByteArray(bytes, 0, bytes.size)

                //回調(diào)是運(yùn)行在非ui主線程，
                //數(shù)據(jù)請求成功后，在主線程中更新
                runOnUiThread { //網(wǎng)絡(luò)圖片請求成功，更新到主線程的ImageView
                    image.setImageBitmap(bmp)
                }
            }
        })
    }
}

3、第2步可以改為以下方式

/**
 * OkHttp + DiskLruCache
 */
class OkhttpCacheActivity : AppCompatActivity() {

    lateinit var mOkHttpClient : OkHttpClient
    private val oriUrl : String = "https://t7.baidu.com/it/u=2168645659,3174029352&fm=193&f=GIF"


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

        val image: ImageView = findViewById(R.id.image_id)

        val mCache = Cache(DiskLruCacheUtils.getDiskCacheDir(this,"Neo"), 8 * 1024 * 1024)
        val mBuilder = OkHttpClient.Builder()

        mOkHttpClient = mBuilder
            .connectTimeout(10, TimeUnit.SECONDS) //連接超時(shí)閾值
            .writeTimeout(10, TimeUnit.SECONDS) //寫超時(shí)閾值
            .readTimeout(10, TimeUnit.SECONDS) //讀超時(shí)閾值
            .retryOnConnectionFailure(true) //當(dāng)失敗后重試
            .cache(mCache)
            .build()

        val mRequest: Request = Request.Builder().url(oriUrl).build()

        mOkHttpClient.newCall(mRequest).enqueue(object : Callback {
            override fun onFailure(call: Call?, e: IOException?) {}

            @Throws(IOException::class)
            override fun onResponse(call: Call?, response: Response) {
                if (response.isSuccessful) {
                    val bytes: ByteArray? = response.body()?.bytes()
                    val bmp = bytes?.let { BitmapFactory.decodeByteArray(bytes, 0, it.size) }
                    runOnUiThread { image.setImageBitmap(bmp) }
                }
            }
        })
    }

    override fun onDestroy() {
        super.onDestroy()
        //取消所有Okhttp的網(wǎng)絡(luò)請求
        mOkHttpClient.dispatcher().cancelAll();
    }
}
?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請聯(lián)系作者
【社區(qū)內(nèi)容提示】社區(qū)部分內(nèi)容疑似由AI輔助生成，瀏覽時(shí)請結(jié)合常識與多方信息審慎甄別。
平臺聲明：文章內(nèi)容（如有圖片或視頻亦包括在內(nèi)）由作者上傳并發(fā)布，文章內(nèi)容僅代表作者本人觀點(diǎn)，簡書系信息發(fā)布平臺，僅提供信息存儲服務(wù)。

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容