使用后台时，Android ViewPager性能问题

I've got an Activity made by XML, I've set it's background to a background image I have in my drawable folder.

我有一个由XML制作的活动，我将它的背景设置为我在可绘制文件夹中的背景图像。

In the same activity I've created a ViewPager to allow swiping back and forth between views. All the views inside the ViewPager contain one image.

在相同的活动中，我创建了一个ViewPager来允许在视图之间来回切换。ViewPager中的所有视图都包含一个映像。

Whenever I swipe left or right, the transition is very slow.

无论我何时向左或向右滑动，过渡都非常缓慢。

I tried removing the background image by setting it to white (#fff) and all the lag was gone. It worked perfect! The problem is that I do need that background for the application.

我尝试将背景图像设置为白色(#fff)，所有的延迟都消失了。完美的工作!问题是我确实需要这个应用程序的背景。

Is there any way to optimize a background image or something so swiping will go smoothly again? Currently it's too frustrating to use because of the lag.

有什么方法可以优化背景图像或其他东西，这样的滑动将会再次顺利进行?目前，由于延迟，使用它太令人沮丧了。

I also tried cropping the image to a small size and then just stretched it over the screen, but I didn't notice any performance improvements. Also it's not the images fault that are located in the ViewPager, when I tested it with TextViews instead there was the same lag.

我还试着将图像裁剪成较小的尺寸，然后将它拉伸到屏幕上，但我没有注意到任何性能改进。同样，位于ViewPager中的不是图像错误，当我使用textview测试它时，也存在同样的延迟。

3 个解决方案

#1

I figured it out myself after some searching, I will leave the answer here for anyone else who encounters this problem.

我在搜索之后自己算出来了，我把答案留给遇到这个问题的人。

Apparently android has a lot of trouble rendering a background when the image is stretched. At least on the Galaxy Tab 10.1 running Android 3.2 it does.

显然，当图像被拉伸时，android在渲染背景时会遇到很多麻烦。至少在运行Android 3.2的Galaxy Tab 10.1上是这样的。

The background image I was using was a picture of a wooden floor, because it's a pattern of the same planks repeating itself I managed to crop the image down from 1440 x 1050 to about 350x500. When using this image as background while stretched out over the entire screen there was a huge performance drop. When displaying as a single image in the top left corner however, it worked just fine.

我使用的背景图片是一张木地板的图片，因为它是同一块木板的图案重复出现，我成功地将图片从1440 x 1050裁剪到350x500。当把这张图片作为背景，在整个屏幕上展开时，会有一个巨大的性能下降。当在左上角显示单个图像时，它工作得很好。

Using the method described here I managed to repeat the image over the entire screen instead of stretching it. Surprisingly enough, I noticed absolutely no extra stress and the transitions went very smooth.

使用这里描述的方法，我设法在整个屏幕上重复图像，而不是拉伸它。令人惊讶的是，我注意到没有额外的压力，而且过渡非常顺利。

So here it is, hope this will help others out there with the same performance issues!

所以在这里，希望这能帮助其他人解决同样的性能问题!

#2

Another solution in the later years: You have to put your drawables into appropriate folders. I had my background.png in drawable folder and it lagged because it struggles with the streching. I could not use repeatable because I dont have that kind of pattern on my phone.

在以后的几年里，另一个解决方案是:你必须将你的可绘制文件放入适当的文件夹中。我有我的背景。png在drawable文件夹中，它滞后了，因为它与streching斗争。我不能使用可重复，因为我的手机没有这种模式。

But when i put my drawable background in drawable-xhdpi, worked without any lag at all. So for future reference its also possbile that this might solve your problem. Ref this question which solves itself: ViewPager really slow on Samsung S4

但是，当我把可绘制的背景放在drawable-xhdpi中时，它完全没有任何延迟。因此，为了将来的参考，它也有可能解决你的问题。请参考这个问题:ViewPager在三星S4上的速度确实很慢

#3

This trick helps me a lot when swiping with pager. It is based on hardware acceleration.

这个技巧在我使用寻呼机时帮助很大。它基于硬件加速。

       viewPager.setOnPageChangeListener(new OnPageChangeListener() {
                @Override
                public void onPageScrollStateChanged(int scrollState) {
                    if (scrollState != ViewPager.SCROLL_STATE_IDLE) {
                        final int childCount = viewPager.getChildCount();
                        for (int i = 0; i < childCount; i++)
                            viewPager.getChildAt(i).setLayerType(View.LAYER_TYPE_NONE, null);
                    }
                }

          ....
});

Hope it will help.

希望它会有所帮助。

#1