【Android】Observe and Execute Code on View Size Measured

Issue

When an android view was just created, its size is zero

If we want to do some work depend on its size at this time, it does not work

So we need a callback to get notify from view, when it is measured

Solution

In earlier android versions, we can achieve this by using :

addOnLayoutChangeListener isLaidOut isLayoutRequested

• addOnLayoutChangeListener can observe layout changes
• isLaidOut means view have size that greater than 0
• isLayoutRequested means layout will change later, it’s not the final value we want

In latest kotlin android extension library, we have a fast way to do these steps

there is a extend function of View called doOnLayout , just write code like this

view.doOnLayout {
  println(it.measuredWidth)
  println(it.measuredHeight)
}

Sumary

It’s a simple extend function, but greatly changed android ui programming

You need not to write some code like view.post() or view.postDelayed() any more

原文地址：https://blog.csdn.net/u013718730/article/details/142934902

免责声明：本站文章内容转载自网络资源，如本站内容侵犯了原著者的合法权益，可联系本站删除。更多内容请关注自学内容网（zxcms.com）！