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Android 一张图理解getWidth和getMeasuredWidth

2013-09-06 10:37 513 查看
The Android
Documentation says that there is two sizes for a view, the measured dimensions and thedrawing
dimensions. The measured dimension is the one computed in the measure pass (the onMeasuremethod),
while the drawing dimensions are the actual size on screen. Particularly, the documentation says that:

These values may, but do not have to, be different from the measured width and height.

So, my question is: what could make the drawing dimension be different of the measured dimension? If the onMeasure(int,int) method
respects the layout requirements (given as the parameterswidthMeasureSpec and heightMeasureSpec,
how could the SDK decides that the view should have a different drawing size?

Additionally, how/where in the Android Source Code the
measured width/height is used to compute the drawing width/height? I tryed to look into the View
source code, but I can't figure out how the measuredWidth/Height is used to compute the final width/height. Maybe it has something to do with the padding, but I'm not sure.



android android-layout view size dimensions
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this question
asked Dec 28 '11 at 15:08





lgfischer

9016

I think that these measures can be different in case if a scroll is added to the view. – Yury Dec
28 '11 at 16:32
Maybe, but I developed a custom ViewGroup, and this is happening in my code. I am not dealing with scroll until the point where this
behavior occurs. So I think that there should be more than scroll involved into this. – lgfischer Dec
28 '11 at 18:34


1 Answer

activeoldestvotes

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As the name suggests the measuredWidth/height is used during measuring and layoutting phase.

Let me give an example,

A widget is asked to measure itself, The widget says that it wants to be 200px by 200px. This is measuredWidth/height.

During the layout phase, i.e. in onLayout method. The method can use the measuredWidth/height of its children or assign a new width/width by calling layout method of the view.

lets say the onLayout method calls childview.layout(0,0,150,150) now the width/height of the view is different than the measured width/height.

I would suggest not to use the measuredWidth/height outside onLayout method.

to summarize .

onMeasure -> sets up measuredWidth/height

onLayout -> sets up the width/height of the widget.

additionallly

public
void View.layout(int l, int t, int r, int b)


seems to be place where the assignment of position and size happens.

The Android
Documentation says that there is two sizes for a view, the measured dimensions and thedrawing
dimensions. The measured dimension is the one computed in the measure pass (the onMeasuremethod),
while the drawing dimensions are the actual size on screen. Particularly, the documentation says that:

These values may, but do not have to, be different from the measured width and height.

So, my question is: what could make the drawing dimension be different of the measured dimension? If the onMeasure(int,int) method
respects the layout requirements (given as the parameterswidthMeasureSpec and heightMeasureSpec,
how could the SDK decides that the view should have a different drawing size?

Additionally, how/where in the Android Source Code the
measured width/height is used to compute the drawing width/height? I tryed to look into the View
source code, but I can't figure out how the measuredWidth/Height is used to compute the final width/height. Maybe it has something to do with the padding, but I'm not sure.



android android-layout view size dimensions
share|improve
this question
asked Dec 28 '11 at 15:08





lgfischer

9016

I think that these measures can be different in case if a scroll is added to the view. – Yury Dec
28 '11 at 16:32
Maybe, but I developed a custom ViewGroup, and this is happening in my code. I am not dealing with scroll until the point where this
behavior occurs. So I think that there should be more than scroll involved into this. – lgfischer Dec
28 '11 at 18:34


1 Answer

activeoldestvotes

up
vote12down
voteaccepted
As the name suggests the measuredWidth/height is used during measuring and layoutting phase.

Let me give an example,

A widget is asked to measure itself, The widget says that it wants to be 200px by 200px. This is measuredWidth/height.

During the layout phase, i.e. in onLayout method. The method can use the measuredWidth/height of its children or assign a new width/width by calling layout method of the view.

lets say the onLayout method calls childview.layout(0,0,150,150) now the width/height of the view is different than the measured width/height.

I would suggest not to use the measuredWidth/height outside onLayout method.

to summarize .

onMeasure -> sets up measuredWidth/height

onLayout -> sets up the width/height of the widget.

additionallly

public
void View.layout(int l, int t, int r, int b)


seems to be place where the assignment of position and size happens.

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Android getWidth和getMeasuredWidth的正解

泡在网上的日子 发表于2013-03-07 20:11， 第 285 次阅读

摘要 一。也许很多童鞋对getWidth()和 getMeasuredWidth()的用法有很多的不解，这两者之间有什麼样的不同呢，网上也有各种不同的版本，但大多数都大同小异，从这个地方 Ctrl+C,到另一个地方Ctrl+V,没有把问题说透，也有一部分文章误导了大家对这两个方法的认识，

一。也许很多童鞋对getWidth()和 getMeasuredWidth()的用法有很多的不解，这两者之间有什麼样的不同呢，网上也有各种不同的版本，但大多数都大同小异，从这个地方 Ctrl+C,到另一个地方Ctrl+V,没有把问题说透，也有一部分文章误导了大家对这两个方法的认识，我也是深受其害。这裡先纠正下面的一个版本的说 法，Baidu上一搜一大堆的，可惜这种说法是错的，所以希望大家就不要再盲目的转载到你的空间裡：

getWidth得到是某个view的实际尺寸.

getMeasuredWidth是得到某view想要在parent view里面占的大小.

想必你也见过这样的解释，听起来这样的解释也似云裡雾裡，没有把问题点透。

二。好了，错误的版本就不过多说了，下面对这两个方法做一下正解，首先大家应先知道以下几点：

1. 在一个类初始化时，即在构造函数当中我们是得不到View的实际大小的。感兴趣的朋友可以试一下，getWidth()和getMeasuredWidth()得到的结果都是0.但是我们可以从onDraw()方法裡面得到控件的大小。

2. 这两个方法所得到的结果的单位是像素即pixel.

对两个方法做介绍：

getWidth(): 得到的是view在父Layout中佈局好后的宽度值，如果没有父佈局，那麼默认的父佈局是整个屏幕。也许不好理解。通过一个例子来说明一下。

例1 ：

这裡是在LinearLayout裡添加一个TextView控件，如果此时要得到对TextView获取getWidth()，那麼是在TextView添加到Layout后再去获取值，并不单单的是对TextView本身宽度的获取。

getMeasuredWidth()：先看一下API裡面怎麼说的

The width of this view as measured in the most recent call to measure(). This should be used during measurement and layout calculations only.

得到的是在最近一次调用measure()方法测量后得到的view的宽度，它仅仅用在测量和layout的计算中。

所以此方法得到的是view的内容佔据的实际宽度。

你如果想从一个最简单的例子中的到它们的不同，下面将对上面的例子做一下修改：

总结（正解）：

getWidth(): View在设定好佈局后整个View的宽度。

getMeasuredWidth(): 对View上的内容进行测量后得到的View内容佔据的宽度，前提是你必须在父佈局的onLayout()方法或者此View的onDraw()方法裡调 用measure(0,0);(measure 参数的值你可以自己定义)，否则你得到的结果和getWidth()得到的结果一样。

也许我组织的不是很好，大家有什麼不清楚的地方再给我留言。关於这两个方法的区别就是看你有没有用measure()方法，当然measure（）的位置也是很重要的。


Android 一张图理解getWidth和getMeasuredWidth



(2012-04-16 10:52:35)


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杂谈

分类： Android



view.getMeasuredHeight()可能隐藏在上头.可能在下头.如果view没有超出屏幕的时候view.getMeasuredHeight() 有可能小于 view.getHeight()

getWidth():
View在設定好佈局後整個View的寬度。

getMeasuredWidth(): 對View上的內容進行測量後得到的View內容佔據的寬度

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