如何在 addView 一些 textview 后使 Android linearlayout 刷新？

Question

My res xml has a linearlayout and a button

    <LinearLayout
        android:id="@+id/linearLayout"
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:layout_marginStart="32dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="32dp"
        android:gravity="center_horizontal"
        android:orientation="horizontal"

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="TextView" />
    </LinearLayout>

    <Button
        android:id="@+id/btn_add_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="84dp"
        android:text="Button" />

click the button some char array added to linearLayout one by one

    val chars = "Hello".toCharArray() 

    btn_add_text.setOnClickListener {
        linearLayout.removeAllViews()
        chars.forEachIndexed { index, char ->
            val tv = Textview(this)
            tv.textSize = 36f
            tv.text = char
            tv.id = index
            linearLayout.addView(tv)
            linearLayout.invalidate()
    }

After forEachIndexed loop has finished linearLayout refreshed and can see [H][e][l][l][o] five textviews. But I want to make linearLayout refresh after each linearLayout.addView(tv).

Answer 1

As far as I know if you want a view to redraw you call invalidate and if you want to update the viewbounds you need to call requestLayout as well.

Answer 2

If you want to see step by step you can try this:

val handler = Handler()
btn_add_text.setOnClickListener {
linearLayout.removeAllViews()
chars.forEachIndexed { index, char ->
      val tv = TextView(context!!)
      tv.textSize = 24f
      tv.text = char.toString()
      tv.id = index
      handler.postDelayed(Runnable {
          linearLayout.addView(tv)
      },500 * index.toLong())
    }
}

Answer 3

I think linearlayout is refreshing so fast, you are not able to see intermediate refreshes, what you can do is, use a worker thread and make it sleep for 500 ms between each iteration, and post data to main thread via handler, your each change of charachter will be visible.