问题
I am learning about Android UI and am unclear why people use nine-patch, when you could use vector graphics, because those are scalable without any pixel degradation. I am a beginner in Android, so I hope I am not missing anything here, but it seems like it would be easier to build vector graphics and use those. You would not need the special editor to build them.
Can anyone explain the advantages to using nine-patch over vector? (Don't just explain advantages of nine-patch, as that is already done on StackO., but rather the advantages that vector does not have). Because it seems like Android recommends nine-patch. Thanks.
回答1:
In vector graphics all side are scale or stretch when we set it to any background whereas in 9-patch we can define which sides can scale or strech so at runtime only those side scale which we set it to scale in 9-patch tool.
from this -> The advantage of using 9-patch images is that when using it as a background, for instance, the image won't stretch and loose proportions in different screen sizes. the center 'patch' will remain as is and the 'borders' patches will be stretched to fit the screen/view size.
let say you have this image.
and a button with fill parent width. if you set this image to button background it will scale completely and your image gets blur (mean t will expand to button width)and it will not look good. so what 9 - path tool do that you define that online scale some part of image let say if width is fill parent. dont scale whole image . let say we set that after t (in image). scale whole area, so t will not get blur. so this will make good your button.hope you got my point..:)
after making your image 9 patch and setting to button background. your button look like this.
instead of t(in image). whole area expand and fill the buttons width.
回答2:
Imagine a button with rounded corners. How do you scale it? If you scale it only horizontally, you will have elliptic corners, which would be ugly.
This is what 9-patch is for.
回答3:
i hate 9patches. i am quite attentive when doing my artwork. i don't even use photoshop. i go with illustrator. i do everything right when exporting my artwork, i used to do my 9 patches with insane zoom on, maybe check afther that in photoshop for misplaced pixels... ** sad trumpet ** when put on a view, if i used some subtle round corners like 6px or 10px and a stroke everything looks awful at mdpi.
So I solved my problems by marrying the two. I wrote my own 9patch which uses vectors. :)
Everything looks like it's been touched by baby Jesus. Perfect corners, strokes and, best of all, you can use one asset for all the screen sizes, densities while, of course, no more transparent borders, wicked errors because 9patch won't stretch inward, so on and so forth.
I use vectors for icons too. While there sometimes are issues with various effects, these are minimal and easily avoided if you do some reading on how to avoid them.
Best of luck to all you guys!
This is a very basic example.
You can do whatever strikes your fancy. Because of the performance impact of svg's on an app, when first run [or when the user changes appearance options, i like to save the newly generated bitmaps as pngs, if possible.
You don't get any more "best of both worlds" than this.
回答4:
You can define content are on a 9-patch image which means (for example) text will always be placed in that specific area, I think you cannot do this in Vector image. Android has built-in support for 9-path but for vectors you have to use a library.
回答5:
9-patch rendering is easy to implement and efficient. If you have an image that can be scaled by stretching horizontal or vertical lines (e.g. buttons or rectangular icons), then use a 9-patch. If you have some icons that don't scale well, then create multiple versions at different resolutions and use Android's resource management to handle it. Both of these approaches are much easier and more efficient than vector graphics.
If you have large images or scenes to render, and you don't want to take up a ton of space with bitmaps, thats when you start thinking about vector graphics.
来源：https://stackoverflow.com/questions/23670363/nine-patch-versus-vector-graphics