Flutter基础-Adding assets and images

Specifying assets

pubspec.yaml

flutter:
  assets:
    - assets/my_icon.png
    - assets/background.png

flutter:
  assets:
    - assets/

Asset bundling

Asset variants

.../pubspec.yaml
  .../graphics/my_icon.png
  .../graphics/background.png
  .../graphics/dark/background.png
  ...etc.

flutter:
  assets:
    - graphics/background.png

flutter:
  assets:
    - graphics/

Loading assets

AssetBudle

Loading text assets

Each Flutter app has a rootBundle object for easy access to the main asset bundle. It is possible to load assets directly using the rootBundle global static from package:flutter/services.dart.

import 'dart:async' show Future;
import 'package:flutter/services.dart' show rootBundle;

Future<String> loadAsset() async {
  return await rootBundle.loadString('assets/config.json');
}

Loading images

Declaring resolution-aware image assets

.../image.png
  .../Mx/image.png
  .../Nx/image.png
  ...etc.

.../my_icon.png
  .../2.0x/my_icon.png
  .../3.0x/my_icon.png

Loading images

Widget build(BuildContext context) {
  // ...
  return DecoratedBox(
    decoration: BoxDecoration(
      image: DecorationImage(
        image: AssetImage('graphics/background.png'),
        // ...
      ),
      // ...
    ),
  );
  // ...
}

Asset images in package in package dependencies

.../pubspec.yaml
  .../icons/heart.png
  .../icons/1.5x/heart.png
  .../icons/2.0x/heart.png
  ...etc.

AssetImage('icons/heart.png', package: 'my_icons')

Bunding of package assets

.../lib/backgrounds/background1.png
  .../lib/backgrounds/background2.png
  .../lib/backgrounds/background3.png

flutter:
  assets:
    - packages/fancy_backgrounds/backgrounds/background1.png

Sharing assets with the underlying platform

Android

flutter:
  assets:
    - icons/heart.png

.../pubspec.yaml
  .../icons/heart.png
  ...etc.

AssetManager assetManager = registrar.context().getAssets();
String key = registrar.lookupKeyForAsset("icons/heart.png");
AssetFileDescriptor fd = assetManager.openFd(key);

IOS

NSString* key = [registrar lookupKeyForAsset:@"icons/heart.png"];
NSString* path = [[NSBundle mainBundle] pathForResource:key ofType:nil];

Platform assets

Updating the app icon

Android

iOS

Updating the launch screen