将 ImageView ScaleType 设置为“center"；没有按我的预期工作 [英] Setting ImageView ScaleType to "center" is not working as I expect it

问题描述

我的 ImageView 有以下布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:descendantFocusability="blocksDescendants">
    <ImageView
        android:id="@+id/imageview_icon"
        android:layout_width="48dp"
        android:layout_height="48dp"
        android:scaleType="fitCenter" />
    (...)
</LinearLayout>

那些 48dp 分别等于 ldpi、mdpi 和 hdpi 中的 36px、48px 和 72px.ImageView 中将使用的所有图像基本上都是图标，我在网上找到了我想要的应用程序(免费许可).但不幸的是，它没有提供大于 48px 的图像，并且使用不同的图像是不可能的.所以我需要一个新的解决方案...

Those 48dp equal to 36px, 48px and 72px in ldpi, mdpi and hdpi respectively. All the images that will be used in this ImageView are basically icons and I've found on the web what I want for my app (free license). But unfortunately, it doesn't come with images bigger than 48px and using different images is out of the question. So I need a new solution...

现在我在 ldpi 和 mdpi 文件夹中分别有 36px 和 48px 的图像.但是我遇到了 hdpi 的问题.对于在 hdpi 上运行的设备，我想要的是让他们使用 mdpi 图像(可用的更大的图像)并按原样使用它，而无需缩放.基本上，hdpi 的 ImageView 是 72px，所以我希望 48px 的图像位于 72px 的中间，没有缩放.为此，我只是尝试将上面 ImageView 中的 scaleType 更改为 center，但无论如何图像都会被缩放.

For now I have 36px and 48px images in the ldpi and mdpi folders, respectively. But I'm having trouble with hdpi. What I want for devices running on hdpi is for them to use the mdpi image (the bigger one available) and use it as it is, without scaling. Basically, the ImageView for hdpi is 72px, so I want the 48px image to be inside the 72px, in the center, without scaling. For that, I simply tried to change scaleType in the ImageView above to just center, but the image gets scaled anyway.

我在这里的最终问题是，解决上述问题的正确方法是什么?如何让 ldpi 和 mdpi 图像以各自的密度使用，但让运行 hdpi 的设备拾取可​​用的最大图像(即mdpi 的)并防止任何缩放，只是将图像放在 ImageView 的中心?

My ultimate question in here is, what's the proper way to fix the problem described above? How can I have ldpi and mdpi images being used in their respective densities, but have devices running hdpi pick up the biggest image available (which is the mdpi ones) and prevent any scaling, just fitting the image in the center of the ImageView?

我自己回答了这个问题，但这可能是其他来到这里的人正在寻找的答案.但我确实提供了一些关于真正发生的事情和潜在问题的见解.如果可以，请查看并提供解决方法/修复.我敢你:)

I answered this question myself, but it might to be the answer others coming here are looking for. But I do provide some insight on what's really happening and the underlying problem. Please take a look and provide a workaround/fix if you can. I dare you :)

推荐答案

这个问题原来是一个非问题，我向任何找到它的人道歉，希望当它获胜时，接受的答案将是他们正在寻找的答案不是.

This question turns out to be a non-question and I apologize to anyone that founds it, hoping the accepted answer will be what they are looking for when it won't be.

为了清楚起见，scaleType=centerInside 正在按预期工作.也就是说，如果您的图像小于 ImageView 本身，则该图像不会缩放到 ImageView 的边界，它将保持在中心并且未缩放.

To make it clear, scaleType=centerInside is working as expected. That is, if you have an image smaller than the ImageView itself, than that image won't be scaled to the bounds of the ImageView, it will remain in the center and unscaled.

但要使上述内容按预期工作，drawable 必须放在 nodpi 文件夹中.我知道这并不总是可以接受的.因此，当必须将该可绘制对象放入其中一个密度文件夹而不是 nodpi 文件夹时，scaleType 属性仅在特定情况下有效.

But for the above to work as expected, the drawable must be placed in the nodpi folder. I understand that this is not always acceptable. So, when that drawable must be placed into one of the density folders instead of the nodpi folder, the scaleType attribute will only work in specific situations.

何时生效:

• 您正在使用 Xdpi 密度的设备/模拟器上运行应用程序，并且Xdpi 密度文件夹中有一个drawable(这里 X 表示，l、m、h 甚至 xh).
• 您正在运行应用设备/模拟器，例如，具有 hdpi 密度，但在hdpi 文件夹，系统从nodpi 文件夹(并不总是知道它会选择哪个文件夹来自).

• You are running the app on a device/emulator with Xdpi density and there is a drawable in the Xdpi density folder (here X means, l, m, h or even xh).
• You are running the app device/emulator, for instance, with hdpi density, but there isn't a drawable in the hdpi folder and the system picks the alternative drawable from the nodpi folder (it's not always known which folder it will pick from).

当它不起作用时:

• 您正在运行应用设备/模拟器，例如，使用 hdpi密度，但 hdpi 文件夹中没有可绘制对象，并且系统从任何其他密度中选择替代可绘制对象文件夹(不是 nodpi 文件夹)，drawable 将缩放到ImageView 边界和 scaleType 属性不会做任何东西.

• You are running the app device/emulator, for instance, with hdpi density, but there isn't a drawable in the hdpi folder and the system picks the alternative drawable from any other of the density folders (not the nodpi folder), the drawable will be scaled to the ImageView bounds and the scaleType attribute will not do anything.

总之，我的问题没有正确"答案，这实际上取决于您要达到的目标.回答 my 问题虽然，我只需要做两件事:a) 将 ImageView scaleType 设置为 centerInsideb) 将 mdpi 文件夹中的所有可绘制对象复制到 hdpi 文件夹中(如上所述，scaleType=centerInside 将使其工作).

In conclusion, there's no "right" answer to my question, it really depends on what you are trying to achieve. The answer my question though, I just need to do 2 things: a) Set the ImageView scaleType to centerInside and b) Duplicate all drawables from the mdpi folder into the hdpi folder (as explained above, the scaleType=centerInside will make it work).

当然，复制drawables不是最佳的，但我找不到任何其他解决方案，到目前为止，也没有其他人可以......所以，我暂时将这个标记为已接受.

Of course, duplicating drawables is not optimal, but I can't find any other solution and so far, no one else could either... So, in the time being, I'll mark this one as accepted.

那么最佳答案/解决方案是什么?
在我看来，如果设备/模拟器在 hdpi 中运行并且 hdpi 文件夹中没有匹配的可绘制对象，则应该从 中选择可绘制对象mdpi 文件夹而不缩放它，允许 scaleType 属性来做这件事.或者，如果系统在相应的密度文件夹中找不到匹配的可绘制对象，可能会强制系统转到 nodpi 文件夹，这也可能是一个解决方案.

What would be the optimal answer/solution then?
In my opinion, if the device/emulator is running in hdpi and there isn't a matching drawable in the hdpi folder it should be pick the drawable from the mdpi folder without scaling it, allowing the scaleType attribute to do it's thing. Or maybe force the system to go to the nodpi folder if it doesn't find a matching drawable in the respective density folder, that could a solution too.

因此，如果任何人都可以为此问题提供解决方法/解决方案，那将是真正正确的答案.如果真的发生这种情况，我会更改接受状态.

So, if anyone can ever provide a workaround/fix to this issue, that would be the real correct answer. If it ever comes to that, I'll change the accepted status.

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