kotlin-PRDownloader下载器开源库

因为项目需要做一个下载的功能，虽然目前有众多的下载器，但是简单好用，而且支持断点的下载器，先推荐下这个吧，PRDownloader

GitHub地址镇楼：
https://github.com/MindorksOpenSource/PRDownloader

里面有很详细的说明，不过都是英语的，我用谷歌翻译大概功能如下：
1 PRDownloader可用于下载任何类型的文件，例如图像，视频，pdf，apk等。
2 该文件下载器库支持在下载文件时暂停和继续。
3 支持大文件下载。
4 该下载器库具有一个简单的界面来发出下载请求。
5 我们可以使用给定的下载ID检查下载状态。
6 PRDownloader在下载文件时为onProgress，onCancel，onStart，onError等
提供回调。
7 支持适当的请求取消。
8 可以并行发出许多请求。
9 所有类型的定制都是可能的。

添加依赖：

implementation 'com.mindorks.android:prdownloader:0.6.0'

添加网络申请的权限：

<uses-permission android:name="android.permission.INTERNET" />

使用方法如下，里面都备注好了！！

class MainActivity : AppCompatActivity(), EasyPermissions.PermissionCallbacks {
    private var dirPath: String? = null
    lateinit var savePic: Button
    val REQUEST_CODE_SAVE_IMG = 10
    val TAG = "MainActivity"
    lateinit var mContext: Context
    val URL13 =
        "https://img-blog.csdn.net/20170418112008577?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvd" +
                "GlhbmRpd3V5YQ==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center"

    lateinit var mBtnDown: Button
    lateinit var buttonCancelOne: Button
    lateinit var mTvProgressing: TextView
    lateinit var mPbDownloading: ProgressBar
    var downloadIdOne = 0

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        mContext = this
        setContentView(R.layout.activity_main)
        dirPath = com.example.prdownloader.Utils.Utils().getRootDirPath(applicationContext)
        //下载按钮
        mBtnDown = findViewById(R.id.buttonOne)
        //取消下载按钮
        buttonCancelOne = findViewById(R.id.buttonCancelOne)
        //保存图片按钮
        savePic = findViewById(R.id.btn_savePic)
        //进度展示文字显示
        mTvProgressing = findViewById(R.id.textViewProgressOne)
        //进度下载进度条显示
        mPbDownloading = findViewById(R.id.progressBarOne)
        onClickListnerOne()
    }

    private fun onClickListnerOne() {
        mBtnDown.setOnClickListener {
            //此处判断运行的状态，如果在运行中时，点击暂停
            if (Status.RUNNING == PRDownloader.getStatus(downloadIdOne)) {
                PRDownloader.pause(downloadIdOne)
                return@setOnClickListener
            }
            //设置控件的激活状态，false为未激活状态，任何点击效果都没用
            mBtnDown.isEnabled = false
            //进度条启动无限循环动画（进入不确定模式）
            mPbDownloading.isIndeterminate = true
            //绘制进度条在不确定模式中的样式
            mPbDownloading.indeterminateDrawable.setColorFilter(
                Color.BLUE, android.graphics.PorterDuff.Mode.SRC_IN
            )

            //此处判断运行的状态，如果在中止时，点击重启
            if (Status.PAUSED == PRDownloader.getStatus(downloadIdOne)) {
                PRDownloader.resume(downloadIdOne)
                return@setOnClickListener
            }
            //改变downloadIdOne状态
            downloadIdOne = PRDownloader.download(URL13, dirPath, "facebook.apk")
                .build()
                //监听启动或者重启状态
                .setOnStartOrResumeListener(object : OnStartOrResumeListener {
                    override fun onStartOrResume() {
                        mPbDownloading.isIndeterminate = false
                        mBtnDown.isEnabled = true
//                        buttonOne.text=R.string.pause.toString()
                        mBtnDown.setText(R.string.pause)
                        buttonCancelOne.isEnabled = true
                    }
                })
                //在暂停时调用
                .setOnPauseListener(object : OnPauseListener {
                    override fun onPause() {
//                        buttonOne.text=R.string.resume.toString()
                        mBtnDown.setText(R.string.resume)
                    }
                })
                //监听取消后
                .setOnCancelListener(object : OnCancelListener {
                    override fun onCancel() {
//                        buttonOne.text=R.string.start.toString()
                        mBtnDown.setText(R.string.start)
                        buttonCancelOne.isEnabled = false
                        mPbDownloading.progress = 0
                        mTvProgressing.text = ""
                        downloadIdOne = 0
                        mPbDownloading.isIndeterminate = false
                    }
                })
                //进度条监听，
                .setOnProgressListener(object : OnProgressListener {
                    override fun onProgress(progress: Progress) {
                        var progressPercent = progress.currentBytes * 100 / progress.totalBytes
                        mPbDownloading.progress = progressPercent.toInt()
                        mTvProgressing.text = com.example.prdownloader.Utils.Utils()
                            .getProgressDisplayLine(progress.currentBytes, progress.totalBytes)
                        mPbDownloading.isIndeterminate = false
                    }
                })
                .start(object : OnDownloadListener {
                    //下载完成时调用
                    override fun onDownloadComplete() {
                        mBtnDown.isEnabled = false
                        buttonCancelOne.isEnabled = false
//                        buttonOne.text=R.string.completed.toString()
                        mBtnDown.setText(R.string.completed)
                    }

                    //下载出现错误时调用
                    override fun onError(error: Error?) {
//                        buttonOne.text=R.string.start.toString()
                        mBtnDown.setText(R.string.start)
                        Toast.makeText(
                            applicationContext,
                            getString(R.string.some_error_occurred) + "" + 1,
                            Toast.LENGTH_SHORT
                        ).show()
                        mTvProgressing.text = ""
                        mPbDownloading.progress = 0
                        downloadIdOne = 0
                        buttonCancelOne.isEnabled = false
                        mPbDownloading.isIndeterminate = false
                        mBtnDown.isEnabled = true
                    }
                })
        }
        buttonCancelOne.setOnClickListener {
            PRDownloader.cancel(downloadIdOne)
        }
        btn_savePic.setOnClickListener {
            requestPermission()
        }
    }

    fun requestPermission() {
        if (Build.VERSION.SDK_INT >= 23) {
            //读取sd卡的权限
            val mPermissionList = arrayOf<String>(
                Manifest.permission.READ_EXTERNAL_STORAGE,
                Manifest.permission.WRITE_EXTERNAL_STORAGE
            )
            if (EasyPermissions.hasPermissions(mContext, mPermissionList.toString())) {
                //已经同意过
                saveImage()
            } else {
                //未同意过，或者说是拒绝了，再次申请权限
                EasyPermissions.requestPermissions(
                    this,
                    "保存图片需要读取sd卡的权限", REQUEST_CODE_SAVE_IMG,
                    mPermissionList.toString()
                )
            }
        } else {
            saveImage()
        }
    }

    //保存图片
    fun saveImage() {
        val bitmap = BitmapFactory.decodeResource(resources, R.mipmap.fj)
        var isSaveSuccess = ImgUtils().saveImageToGallery(mContext, bitmap)
        if (isSaveSuccess) {
            Toast.makeText(mContext, "保存图片成功", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(mContext, "保存图片失败，请稍后重试", Toast.LENGTH_SHORT).show();
        }
    }

    //授权结果分发下去
    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        EasyPermissions.onRequestPermissionsResult(requestCode, permissions, grantResults, this)
    }

    //拒绝授权
    override fun onPermissionsDenied(requestCode: Int, perms: MutableList<String>) {
        Log.i(TAG, "onPermissionsDenied:" + requestCode + ":" + perms.size)
        if (EasyPermissions.somePermissionPermanentlyDenied(this, perms)) {
            //打开系统设置，手动授权
            AppSettingsDialog.Builder(this).build().show()
        }
    }

    //同意授权
    override fun onPermissionsGranted(requestCode: Int, perms: MutableList<String>) {
        TODO("Not yet implemented")
        Log.i(TAG, "onPermissionsGranted:" + requestCode + ":" + perms.size)
        saveImage()
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == AppSettingsDialog.DEFAULT_SETTINGS_REQ_CODE) {
            //拒绝授权后，从系统设置了授权后，返回APP进行相应的操作
            Log.i(TAG, "onPermissionsDenied:------>自定义设置授权后返回APP")
            saveImage()
        }
    }
}

然后还有一个工具类：

class Utils {
    fun  getRootDirPath(context: Context):String{
        if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())){
            val file=ContextCompat.getExternalFilesDirs(context.applicationContext,null)[0]
            var uri= Uri.fromFile(file)
            context.sendBroadcast(Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE,uri))
            return file.absolutePath
        }else{
            return context.applicationContext.filesDir.absolutePath
        }
    }
    fun getProgressDisplayLine(currentBytes:Long,totalBytes:Long):String{
        return getBytesToMBString(currentBytes)+"/"+getBytesToMBString(totalBytes)
    }
    fun getBytesToMBString(bytes:Long):String{
        return String.format(Locale.ENGLISH,"%.2fMb",bytes/(1024.00*1024.00))
    }
}

左乔治，右佩琦，法力无边，编写完成！！！希望这个可以帮助到大家的说啦