Flutter自定义Widget—可加载原生图片资源的Image
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上一篇博客讲解了Flutter如何调用原生图片资源,本次再进一步,将其封装成Flutter Widget,方便使用。
继承ImageProvider,实现我们的逻辑。
import 'dart:io';
import 'dart:typed_data';
import 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';
import 'dart:ui' as ui;
import 'package:flutter_app/util/methodChannelUtil.dart';
/// 自定义ImageProvider用于读取原生图片
class NativeImageProvider extends ImageProvider<NativeImageProvider> {
/// 需要从原生中去加载的图片名称,比如: ic_launcher,不用带后缀
final String imageName;
final double scale;
const NativeImageProvider(this.imageName, {this.scale: 1.0});
@override
ImageStreamCompleter load(NativeImageProvider key, DecoderCallback decode) {
return MultiFrameImageStreamCompleter(
codec: _loadAsync(key),
scale: key.scale,
debugLabel: key.imageName,
informationCollector: () {
return <DiagnosticsNode>[
DiagnosticsProperty<ImageProvider>('Image provider', this),
DiagnosticsProperty<NativeImageProvider>('Image key', key),
];
},
);
}
Future<ui.Codec> _loadAsync(NativeImageProvider key) async {
String path = await getNativeImage(imageName);
print(">>>>>>>>>>>>>>>>$path<<<<<<<<<<<<<<<<<<<");
var file = File(path);
return await _loadAsyncFromFile(key, file);
}
Future<ui.Codec> _loadAsyncFromFile(
NativeImageProvider key, File file) async {
assert(key == this);
final Uint8List bytes = await file.readAsBytes();
if (bytes.lengthInBytes == 0) {
throw new Exception("File was empty");
}
return await ui.instantiateImageCodec(bytes);
}
/// 获取原生图片文件路径
Future<String> getNativeImage(String imageName) async {
String path = "";
try {
path = await MethodChannelUtil.nativeChannel
.invokeMethod("image", {'name': '$imageName'});
} on PlatformException catch (e) {
print(e.message);
}
return path;
}
@override
Future<NativeImageProvider> obtainKey(ImageConfiguration configuration) {
return SynchronousFuture<NativeImageProvider>(this);
}
@override
int get hashCode => ui.hashValues(imageName, scale);
@override
bool operator ==(Object other) {
if (other.runtimeType != runtimeType)
return false;
return other is NativeImageProvider
&& other.imageName == imageName
&& other.scale == scale;
}
}
使用
Image(image: NativeImageProvider("ic_launcher"),)
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