Android下载进度条demo

布局文件

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ui.center.CenterFragment">

    <TextView
        android:id="@+id/text_center"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:layout_marginStart="8dp"
        android:gravity="center"
        android:layout_marginEnd="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ProgressBar
        android:id="@+id/mPgb"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:max="100"
        style="@style/Widget.AppCompat.ProgressBar.Horizontal"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

UI文件

class CenterViewModel : ViewModel() {
    private val _text = MutableLiveData<String>().apply {
        value = "this is the center"

    }
    val text: LiveData<String> = _text
}

class CenterFragment : Fragment() {
    lateinit var mPgb: ProgressBar
    lateinit var textView: TextView
    private lateinit var centerViewModel: CenterViewModel
    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        centerViewModel = ViewModelProvider(this).get(CenterViewModel::class.java)
        val root = inflater.inflate(R.layout.fragment_center, container, false)
        textView = root.findViewById(R.id.text_center)
        centerViewModel.text.observe(viewLifecycleOwner, {
            textView.text = it
        })
        mPgb = root.findViewById(R.id.mPgb)
        textView.setOnClickListener {
            initDownload()
        }
        return root
    }


    private fun initDownload() {
        val okHttpClient: OkHttpClient = OkHttpClient.Builder().build()
        val request: Request = Request.Builder()
            .url("https://8629e1d8ab66424c0245ed79d86fed17.dlied1.cdntips.net/dlied1.qq.com/qqweb/QQlite/qqlite_4.0.1.1060_537064365.apk")
            .get()
            .build()
        okHttpClient.newCall(request).enqueue(object : Callback {
            override fun onFailure(call: Call, e: IOException) {
                Log.e("tag", "onFailure: " + e.message);
            }
            override fun onResponse(call: Call, response: Response) {
                val responseBody = response.body() // 获取到请求体
                val inputStream = responseBody?.byteStream() // 转换成字节流
                val path: String = "" + Environment.getExternalStorageDirectory() + "/" + "qq.apk"
                saveFile(
                    inputStream,
                    path, responseBody?.contentLength()
                )
            }
        })
    }

    private fun saveFile(inputStream: InputStream?, s: String?, l: Long?) {
        var count: Long = 0
        try {
            // 获取到输出流，写入到的地址
            val outputStream = FileOutputStream(File(s!!))
            var length = -1
            val bytes = ByteArray(1024 * 10)
            while (inputStream!!.read(bytes).also { length = it } != -1) {
                // 写入文件
                outputStream.write(bytes, 0, length)
                count += length.toLong()
                val finalCount = count
                activity?.runOnUiThread {
                    // 设置进度条最大值
                    mPgb.setMax(l!!.toInt())
                    // 设置进度
                    mPgb.setProgress(finalCount.toInt())
                    val num = "" + (100 * finalCount / l) + "%"
                    // 设置进度文本 （100 * 当前进度 / 总进度）
                    textView.text = num
                }
            }
            inputStream.close() // 关闭输入流
            outputStream.close() // 关闭输出流
            activity?.runOnUiThread { // 如果写入的进度值完毕，Toast
                Toast.makeText(activity, "下载完成", Toast.LENGTH_SHORT).show()
            }
        } catch (e: Exception) {
            e.printStackTrace()
        }
    }
}

效果图