在 Android 应用程序中使用 AsyncTask 在 for 循环期间更新 ProgressBar

Question

我正在尝试做一个应用程序，我想在其中使用 AsyncTask 更新 for 循环中的 ProgressBar。最好是向您展示我正在尝试做的伪代码

button.setOnClickListener{
    for(int i=0; i<5000; i++)
    {
        doSomeHeavyStuff();
        UpdateProgressBarAsyncTask(i).execute()
    }
}

这是我目前所拥有的

主要活动：

    class MainActivity : AppCompatActivity() {

    var progress:ProgressBar? = null


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

        progress = findViewById(R.id.progress)
        val buttonStart = findViewById<TextView>(R.id.button)
        var maxNumber = 5000
        buttonStart.setOnClickListener{
            for(i in 0 until maxNumber)
            {
                HeavyStuff()
                ProgressTask(i,progress!!,maxNumber,this).execute()
            }
        }


    }

internal class ProgressTask (var actual:Int, var progress: ProgressBar, var max: Int, var context: Activity): AsyncTask <Void, Int, Int>()
    {
        override fun onPreExecute() {
            super.onPreExecute()
            progress.visibility = View.VISIBLE
            progress.max = max
        }

        override fun onProgressUpdate(vararg values: Int?) {
            super.onProgressUpdate(*values)
            progress.setProgress(values[0]!!)
        }

        override fun doInBackground(vararg params: Void?): Int? {
            publishProgress(actual)
            return null
        }

        override fun onPostExecute(result: Int?) {
            super.onPostExecute(result)
            progress.visibility = View.INVISIBLE
            Toast.makeText(context, "Finished!", Toast.LENGTH_SHORT).show()
        }
    }

XML:

<ProgressBar
        android:id="@+id/progress"
        style="@android:style/Widget.ProgressBar.Horizontal"
        android:layout_width="300dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="24dp"
        android:layout_marginLeft="24dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="24dp"
        android:layout_marginRight="24dp"
        android:layout_marginBottom="24dp"
        android:visibility="invisible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

我在这里错过了什么吗？现在它在 HeavyStuff() 完成后显示 ProgressBar，因此它不会在 for 循环期间显示。我在这里错过了什么？

你们能帮我解决这个问题吗？

谢谢

Answer 1

其实我觉得doBackground函数里面需要有重物和For循环（主线程调用重物会卡住UI导致ANR） , 请看下面的代码:

const val max = 50000

class MainActivity : AppCompatActivity() {

    var progress: ProgressBar? = null

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

        progress = findViewById(R.id.progress)
        buttonStart.setOnClickListener {
            ProgressTask(progress!!, max, this).execute()
        }
    }

    internal class ProgressTask(
        var progress: ProgressBar,
        var max: Int,
        var context: Activity
    ) : AsyncTask<Void, Int, Int>() {
        override fun onPreExecute() {
            super.onPreExecute()
            progress.visibility = View.VISIBLE
            progress.max = max
        }

        override fun onProgressUpdate(vararg values: Int?) {
            super.onProgressUpdate(*values)
            progress.setProgress(values[0]!!)
        }

        override fun doInBackground(vararg params: Void?): Int? {
            for (i in 0 until max) {
                doHeavyStuff()
                publishProgress(i)
            }
            return null
        }

        override fun onPostExecute(result: Int?) {
            super.onPostExecute(result)
            progress.visibility = View.INVISIBLE
            Toast.makeText(context, "Finished!", Toast.LENGTH_SHORT).show()
        }
    }
}

Answer 2

我会采用这种方法来避免内存泄漏：

private lateinit var mTextView: WeakReference<TextView>
private lateinit var mProgressBar: WeakReference<ProgressBar>

private const val MAX = 50000

class ProgressTask(
    pb: ProgressBar,

var max: Int
) : AsyncTask<Void, Int, Int>() {

init {
    mProgressBar = WeakReference(pb)
}

override fun onPreExecute() {
    super.onPreExecute()
    mProgressBar.get()?.visibility = View.VISIBLE
    mProgressBar.get()?.max = MAX
}

override fun onProgressUpdate(vararg values: Int?) {
    super.onProgressUpdate(*values)
    mProgressBar.get()?.progress = values[0]!!
}

override fun doInBackground(vararg p0: Void?): Int {
    for (i in 0 until MAX) {
        doHeavyStuff()
        publishProgress(i)
    }
    return 1
}

override fun onPostExecute(result: Int?) {
    super.onPostExecute(result)
    mProgressBar.get()?.visibility = View.GONE
}

}

在 Android 应用程序中使用 AsyncTask 在 for 循环期间更新 ProgressBar

Update ProgressBar during a for loop using AsyncTask in Android app

android

for-loop

kotlin

android-asynctask

progress-bar