How to cycle through a list of images without the images taking time to load in dart?-CodePudding

In my app I have an InkWell on an image that I want to turn into a different image when you click on it. I have set up a list where the onTap simply cycles through the list onto the next image. The problem is, when you click it, it takes about half a second for the next image to load. I would like to be able to show the images instantaneously when clicking it.

int index = 0;

@override
  Widget build(BuildContext context) {
    List images = [
      Image.asset('assets/image0.jpg'),
      Image.asset('assets/image1.jpg'),
      Image.asset('assets/image2.jpg'),
      Image.asset('assets/image3.jpg'),
    ];
    return InkWell(
      onTap: () {
        setState(() {
          index  ;
        });
      },
      child: images[index],
    );
  }

This is my current code

CodePudding user response：

One way to ensure that the images are displayed instantly when you click on the InkWell is to pre-load the images before they are displayed. You can do this by using the precacheImage function provided by Flutter's Image class.

Here's an example of how you can pre-load the images and display them instantaneously when you click on the InkWell:

int index = 0;

@override
void initState() {
  super.initState();
  // Pre-load the images
  List<String> imagePaths = [    'assets/image0.jpg',    'assets/image1.jpg',    'assets/image2.jpg',    'assets/image3.jpg',  ];
  for (String path in imagePaths) {
    precacheImage(AssetImage(path), context);
  }
}

@override
Widget build(BuildContext context) {
  List<Image> images = [    Image.asset('assets/image0.jpg'),    Image.asset('assets/image1.jpg'),    Image.asset('assets/image2.jpg'),    Image.asset('assets/image3.jpg'),  ];
  return InkWell(
    onTap: () {
      setState(() {
        index  ;
      });
    },
    child: images[index % images.length],
  );
}

The precacheImage function asynchronously loads the image and stores it in a cache, so that it can be displayed quickly when needed. By calling precacheImage for each of the images in the list before the app is displayed, you can ensure that the images are already loaded and ready to be displayed when you click on the InkWell.

You may also want to consider using a PageView widget instead of an InkWell to display the images. The PageView widget allows you to swipe between pages (in this case, images), and it has built-in support for pre-loading the next page. This can give a smoother and more seamless experience when flipping through the images.

CodePudding user response：

it takes about half a second for the next image to load

This is probably because your List of images is within your build method, so every setState it rebuilds.

Move your List outside of the build method:

 int index = 0;
  List images = [
    Image.asset('assets/image0.jpg'),
    Image.asset('assets/image1.jpg'),
    Image.asset('assets/image2.jpg'),
    Image.asset('assets/image3.jpg'),
  ];

  @override
  Widget build(BuildContext context) {
    
    return InkWell(
      onTap: () {
        setState(() {
          index  ;
        });
      },
      child: images[index],
    );
  }