kotlin--Flow文件下载

    implementation 'androidx.navigation:navigation-fragment-ktx:2.3.5'
    implementation 'androidx.navigation:navigation-ui-ktx:2.3.5'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    //依赖协程核心库 ，提供Android UI调度器
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.5.1"
    //依赖当前平台所对应的平台库 (必须)
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.5.1'
    implementation 'com.squareup.retrofit2:retrofit:2.9.0'

        dataBinding {
            enabled = true
        }

package com.aruba.flowapplyapplication.download

import java.io.File

/**
 * 下载状态
 * Created by aruba on 2021/9/19.
 */
sealed class DownloadStatus {
    data class Progress(val progress: Int) : DownloadStatus()
    data class Err(val t: Throwable) : DownloadStatus()
    data class Done(val file: File) : DownloadStatus()
}

package com.aruba.flowapplyapplication.download

import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.flow
import okhttp3.OkHttpClient
import okhttp3.Request
import java.io.File
import com.dongnaoedu.flowpractice.utils.copyTo
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.flow.catch
import kotlinx.coroutines.flow.flowOn
import okhttp3.Dispatcher
import java.io.IOException

/**
 * Created by aruba on 2021/9/19.
 */
object DownloadManager {
    fun download(url: String, file: File): Flow<DownloadStatus> {
        return flow {
            val request = Request.Builder().url(url).get().build();
            val response = OkHttpClient.Builder().build().newCall(request).execute()
            if (response.isSuccessful) {
                response.body()!!.let { body ->
                    //文件大小
                    val totalLength = body.contentLength().toDouble()
                    //写文件
                    file.outputStream().run {
                        val input = body.byteStream()
                        input.copyTo(this) { currentLength ->
                            //当前下载进度
                            val process = currentLength / totalLength * 100
                            emit(DownloadStatus.Progress(process.toInt()))
                        }
                    }

                    emit(DownloadStatus.Done(file))
                }
            } else {
                throw IOException(response.toString())
            }
        }.catch {
            file.delete()
            emit(DownloadStatus.Err(it))
        }.flowOn(Dispatchers.IO)
    }
}

package com.dongnaoedu.flowpractice.utils

import java.io.InputStream
import java.io.OutputStream

inline fun InputStream.copyTo(out: OutputStream, bufferSize: Int = DEFAULT_BUFFER_SIZE, progress: (Long)-> Unit): Long {
    var bytesCopied: Long = 0
    val buffer = ByteArray(bufferSize)
    var bytes = read(buffer)
    while (bytes >= 0) {
        out.write(buffer, 0, bytes)
        bytesCopied += bytes
        bytes = read(buffer)

        progress(bytesCopied)
    }
    return bytesCopied
}

package com.aruba.flowapplyapplication.viewmodel

import android.app.Application
import android.content.Context
import android.util.Log
import android.view.View
import android.widget.Toast
import androidx.lifecycle.*
import com.aruba.flowapplyapplication.download.DownloadManager
import com.aruba.flowapplyapplication.download.DownloadStatus
import com.aruba.flowapplyapplication.download.DownloadStatus.Progress
import kotlinx.coroutines.MainScope
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.launch
import java.io.File

/**
 * Created by aruba on 2021/9/19.
 */
class DownloadViewModel(val context: Application) : AndroidViewModel(context) {
    private var progressData = MutableLiveData<Int>()
    val progress = progressData

    private val url: String = "http://10.254.219.178:8080/test.rar"

    fun downloadClick(v: View) {
        viewModelScope.launch {
            progressData.value = 0
            val file = File(context.getExternalFilesDir(null), "test.rar")
            DownloadManager.download(url, file).collect {
                when (it) {
                    is Progress -> {
                        Log.i("progress", "progress: $it.progress")
                        progressData.value = it.progress
                    }
                    is DownloadStatus.Done -> {
                        progressData.value = 100
                        Toast.makeText(context, "下载完成", Toast.LENGTH_SHORT).show()
                    }
                    is DownloadStatus.Err ->
                        Toast.makeText(context, it.toString(), Toast.LENGTH_SHORT).show()
                }
            }
        }
    }
}

package com.aruba.flowapplyapplication

import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.lifecycle.ViewModelProvider
import androidx.lifecycle.lifecycleScope
import com.aruba.flowapplyapplication.databinding.FragmentFlowDownBinding
import com.aruba.flowapplyapplication.viewmodel.DownloadViewModel

class FlowDownloadFragment : Fragment() {

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val fragmentFlowDownBinding = DataBindingUtil.inflate<FragmentFlowDownBinding>(
            layoutInflater,
            R.layout.fragment_flow_down,
            container,
            false
        )

        val downloadViewModel = ViewModelProvider(
            this,
            ViewModelProvider.AndroidViewModelFactory(requireActivity().application)
        ).get(DownloadViewModel::class.java)
        fragmentFlowDownBinding.downloadViewModel = downloadViewModel
        fragmentFlowDownBinding.lifecycleOwner = this;

        return fragmentFlowDownBinding.root
    }

}