子线程中更新UI的几种方式

一、主线程申请成功后子线程申请

val textView:TextView = findViewById<TextView>(R.id.textView)
textView.setOnClickListener{
    textView.text = "Main"
    thread{
        textView.text = "${Thread.currentThread().name}"
    }
}

二、在子线程中创建ViewRootImpl

thread{
    Looper.prepare()
    val button = Button(this)
    windowManager.addView(button,WindowManager.LayoutParams())
    button.setOnClickListener{
        button.text="${Thread.currentThread().name}"
    }
    Looper.loop()
}

三、利用硬件加速机制绕开requestLayout()
在硬件加速支持下，如果控件只是执行了invalidate()，而没有触发requestLayout()，是不会触发ViewRootImpl#checkThread()的

ViewGroup.png

四、SurfaceView
Android中有一个控件SurfaceView，可以通过holder获得Canvas对象，可以直接在子线程中更新UI

val surface :SurfaceView! =findViewById<SurfaceView>(R.id.surface)
surface.holder.addCallback(object :SurfaceHolder.Callback {
    override fun surfacedreated(holder:SurfaceHolder){
        thread {
            while(!destroved){
                val canvas :Canvas! = holder.lockCanvas()
                val random = Random()
                val r:Int =random.nextInt( bound: 255)
                val g:Int =random.nextInt( bound: 255)
                val b:Int = random.nextInt( bound: 255)
                canvas.drawColor(Color.rgb(r，g，b))
                holder.unlockCanvasAndPost(canvas)
                SystemClock.sleep( ms:500)
             } 
         }
    }

    override fun surfaceDestroyed(holder: SurfaceHolder?){
        destroved = true
    }

    override fun surfaceChanged(
        holder: SurfaceHolder?,
        format: Int
        width: Int
        height: Int
    ){

    }
}