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b319938ecd
This updates the framework to provide higher level wrappers around ui.instantiateImageCodecWithSize(). Functionally, this doesn't change anything (other than deprecating the older loadBuffer() method in favor of loadImage()), but it sets the stage for a simpler change that will allow us to provide a more flexible way to load sized images. #118543
71 lines
2.4 KiB
Dart
71 lines
2.4 KiB
Dart
// Copyright 2014 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'dart:convert';
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import 'dart:ui' as ui show Codec;
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import 'dart:ui';
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import 'package:flutter/foundation.dart';
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import 'package:flutter/material.dart';
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/// An animated GIF image with 3 1x1 pixel frames (a red, green, and blue
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/// frames). The GIF animates forever, and each frame has a 100ms delay.
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const String kAnimatedGif = 'R0lGODlhAQABAKEDAAAA//8AAAD/AP///yH/C05FVFNDQVBFMi'
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'4wAwEAAAAh+QQACgD/ACwAAAAAAQABAAACAkwBACH5BAAKAP8A'
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'LAAAAAABAAEAAAICVAEAIfkEAAoA/wAsAAAAAAEAAQAAAgJEAQ'
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'A7';
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/// A 50x50 blue square png
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const String kBlueSquare = 'iVBORw0KGgoAAAANSUhEUgAAADIAAAAyCAYAAAAeP4ixAAAASEl'
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'EQVR42u3PMQ0AMAgAsGFjL/4tYQU08JLWQSN/9TsgRERERERERE'
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'REREREREREREREREREREREREREREREREREREREREQ2BgNuaUcSj'
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'uqqAAAAAElFTkSuQmCC';
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/// A 10x10 grid of animated looping placeholder gifts that fade into a
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/// blue square.
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class AnimatedPlaceholderPage extends StatelessWidget {
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const AnimatedPlaceholderPage({super.key});
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@override
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Widget build(BuildContext context) {
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return GridView.builder(
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itemCount: 100,
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gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 10),
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itemBuilder: (BuildContext context, int index) {
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return FadeInImage(
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placeholder: const DelayedBase64Image(Duration.zero, kAnimatedGif),
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image: DelayedBase64Image(Duration(milliseconds: 100 * index), kBlueSquare),
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);
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},
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);
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}
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}
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int _key = 0;
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/// An image provider that is always unique from other DelayedBase64Images and
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/// simulates a delay in loading.
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class DelayedBase64Image extends ImageProvider<int> {
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const DelayedBase64Image(this.delay, this.data);
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final String data;
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final Duration delay;
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@override
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Future<int> obtainKey(ImageConfiguration configuration) {
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return SynchronousFuture<int>(_key++);
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}
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@override
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ImageStreamCompleter loadImage(int key, ImageDecoderCallback decode) {
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return MultiFrameImageStreamCompleter(
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codec: Future<ui.Codec>.delayed(
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delay,
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() async => decode(await ImmutableBuffer.fromUint8List(base64.decode(data))),
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),
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scale: 1.0,
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);
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}
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}
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