Android自定义视图

自定义视图

自定义视图组件 | Android 开发者 | Android Developers (google.cn)

创建视图类 | Android 开发者 | Android Developers (google.cn)

系统如何绘制View

下图是布局树

视图的每一次刷新都是完整地遍历布局树的过程，这个过程比较耗时

Android系统显示原理简介 - 简书 (jianshu.com)

要在16ms内画完每一个界面

class MyView @JvmOverloads constructor(
    context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : View(context, attrs, defStyleAttr) {
    // xml加载完毕时调用
    override fun onFinishInflate() {
        super.onFinishInflate()
        Log.d("yu","onFinishInflate：")
    }
	
    override fun onAttachedToWindow() {
        super.onAttachedToWindow()
        Log.d("yu", "onAttachedToWindow: ")
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        Log.d("yu", "onMeasure: ")
    }

    override fun onLayout(changed: Boolean, left: Int, top: Int, right: Int, bottom: Int) {
        super.onLayout(changed, left, top, right, bottom)
        Log.d("yu", "onLayout: ")
    }

    override fun onDraw(canvas: Canvas?) {
        super.onDraw(canvas)
        Log.d("yu", "onDraw: ")
    }

    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
        super.onSizeChanged(w, h, oldw, oldh)
        Log.d("yu", "onSizeChanged: ")
    }

    override fun onDetachedFromWindow() {
        super.onDetachedFromWindow()
        Log.d("yu", "onDetachedFromWindow: ")
    }
}

启动输出

onFinishInflate：   
onAttachedToWindow:
onMeasure:         
onMeasure:         
onSizeChanged:     
onLayout:          
onDraw:

• DashPathEffect：将Path的线段虚线化，intervals为虚线的ON和OFF的数组，数组中元素数目需要 >= 2； 而phase则为绘制时的偏移量。

Android自定义view之利用PathEffect实现动态效果 - 掘金 (juejin.cn)