Is a RelativeLayout more expensive than a LinearLayout?

冷暖自知 提交于 2019-11-26 11:11:40

In a talk at Google I/O 2013 (Writing Custom Views for Android), Romain Guy clarified the misunderstanding that caused everyone to start using RelativeLayouts for everything. A RelativeLayout always has to do two measure passes. Overall it is negligible as long as your view hierarchy is simple. But if your hierarchy is complex, doing an extra measure pass could potentially be fairly costly. Also if you nest RelativeLayouts, you get an exponential measurement algorithm.

https://www.youtube.com/watch?v=NYtB6mlu7vA&t=1m41s

https://www.youtube.com/watch?v=NYtB6mlu7vA&t=38m04s

Lie Ryan

Unless you're laying out lots of Views (e.g. in a ListView), the performance of choosing between LinearLayout or RelativeLayout is negligible. Pick whichever is most convenient to use for the job, and worry about performance only when you need to.

And here's what the official docs about Creating Efficient Layouts says about performance of RelativeLayout and LinearLayout:

Sticking to the basic features is unfortunately not the most efficient way to create user interfaces. A common example is the abuse of LinearLayout, which leads to a proliferation of views in the view hierarchy. Every view — or worse, every layout manager — that you add to your application comes at a cost: initialization, layout and drawing become slower. The layout pass can be especially expensive when you nest several LinearLayout that use the weight parameter, which requires the child to be measured twice.

Nicholas Liu

Relativelayout is more effective than Linearlayout.

From here:

It is a common misconception that using the basic layout structures leads to the most efficient layouts. However, each widget and layout you add to your application requires initialization, layout, and drawing. For example, using nested instances of LinearLayout can lead to an excessively deep view hierarchy. Furthermore, nesting several instances of LinearLayout that use the layout_weight parameter can be especially expensive as each child needs to be measured twice. This is particularly important when the layout is inflated repeatedly, such as when used in a ListView or GridView.

2018 UPDATE: In the N release of Android, the ConstraintLayout class provides similar functionality to RelativeLayout, but at a significantly lower cost. It is very powerful layout manager and it should be used whenever it is necessary to build a complex GUI.

You can try

<LinearLayout>
       <ViewPager/><!--Loading images from net, it is very good as a testing case.-->
       <ViewPagerIndicator/>
       <TextView/> <!--Show some info about page-->
</LinearLayout>

<RelativeLayout>           
       <ViewPager/><!--Loading images from net, it is very good as a testing case.-->
       <ViewPagerIndicator below="id of ViewPager"/>
       <TextView below="id of ViewPagerIndicator"/> <!--Show some info about page-->
</RelativeLayout>

You will find that there're a lot of different, if your Pages loading some images from internet. In this case the LinearLayout is 100% better than RelativeLayout ever.

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