1.Image

显示图片的小部件

文档

构造方法

1.展示ImageProvider的图像

Image({Key key, @required ImageProvider image, String semanticLabel, bool excludeFromSemantics: false, double width, double height, Color color, BlendMode colorBlendMode, BoxFit fit, AlignmentGeometry alignment: Alignment.center, ImageRepeat repeat: ImageRepeat.noRepeat, Rect centerSlice, bool matchTextDirection: false, bool gaplessPlayback: false, FilterQuality filterQuality: FilterQuality.low })

2.展示资源文件中的图片

Image.asset(String name, { Key key, AssetBundle bundle, String semanticLabel, bool excludeFromSemantics: false, double scale, double width, double height, Color color, BlendMode colorBlendMode, BoxFit fit, AlignmentGeometry alignment: Alignment.center, ImageRepeat repeat: ImageRepeat.noRepeat, Rect centerSlice, bool matchTextDirection: false, bool gaplessPlayback: false, String package, FilterQuality filterQuality: FilterQuality.low })

3.展示本地文件中的图片

Image.file(File file, { Key key, double scale: 1.0, String semanticLabel, bool excludeFromSemantics: false, double width, double height, Color color, BlendMode colorBlendMode, BoxFit fit, AlignmentGeometry alignment: Alignment.center, ImageRepeat repeat: ImageRepeat.noRepeat, Rect centerSlice, bool matchTextDirection: false, bool gaplessPlayback: false, FilterQuality filterQuality: FilterQuality.low })

4.展示内存中的图片

Image.memory(Uint8List bytes, { Key key, double scale: 1.0, String semanticLabel, bool excludeFromSemantics: false, double width, double height, Color color, BlendMode colorBlendMode, BoxFit fit, AlignmentGeometry alignment: Alignment.center, ImageRepeat repeat: ImageRepeat.noRepeat, Rect centerSlice, bool matchTextDirection: false, bool gaplessPlayback: false, FilterQuality filterQuality: FilterQuality.low })

5.展示网络图片

Image.network(String src, { Key key, double scale: 1.0, String semanticLabel, bool excludeFromSemantics: false, double width, double height, Color color, BlendMode colorBlendMode, BoxFit fit, AlignmentGeometry alignment: Alignment.center, ImageRepeat repeat: ImageRepeat.noRepeat, Rect centerSlice, bool matchTextDirection: false, bool gaplessPlayback: false, FilterQuality filterQuality: FilterQuality.low, Map<String, String> headers })

属性

alignment → AlignmentGeometry：图像对齐方式

centerSlice → Rect：.9图片相关

color → Color：如果为非null，则使用colorBlendMode将此颜色与每个图像像素混合。

colorBlendMode → BlendMode：将颜色与图像混合

excludeFromSemantics → bool：//

filterQuality → FilterQuality：用于设置图像的FilterQuality

fit → BoxFit：图片填充方式

gaplessPlayback → bool：当图像变更时是否显示旧的图像

height → double：高度

width → double：宽度

image → ImageProvider：要显示的图像

matchTextDirection → bool：是否在TextDirection的方向上绘制图像

repeat → ImageRepeat：图像平铺方式

semanticLabel → String：图像的语意描述

示例1：

Image(
          alignment:Alignment.center,
//          centerSlice: Rect.fromLTRB(2.0, 2.0, 2.0, 2.0),
//          color: Colors.white,
          colorBlendMode: BlendMode.color,
          excludeFromSemantics: false,
          filterQuality: FilterQuality.high,
          fit: BoxFit.scaleDown,
          gaplessPlayback: true,
          width: 300.0,
          height: 300.0,
          image: ExactAssetImage('res/images/timg.jpg'),
          matchTextDirection: true,
          repeat: ImageRepeat.noRepeat,
          semanticLabel: "123",
      );

示例2：（加载资源文件图片）

Image.asset('res/images/timg.jpg',alignment:Alignment.center,
//          centerSlice: Rect.fromLTRB(2.0, 2.0, 2.0, 2.0),
      color: Colors.white,
      colorBlendMode: BlendMode.color,
      excludeFromSemantics: false,
      filterQuality: FilterQuality.high,
      fit: BoxFit.scaleDown,
      gaplessPlayback: true,
      width: 300.0,
      height: 300.0,
      matchTextDirection: true,
      repeat: ImageRepeat.noRepeat,
      semanticLabel: "123",
    );

步骤：

1.创建资源文件夹

2.复制图片到图片文件夹中

3.pubspec.yaml中添加图片路径（注意格式）

4.Image中使用图片

示例3：（展示本地文件中的图片）

Image.file(File('/sdcard/timg.jpg'),alignment:Alignment.center,
//          centerSlice: Rect.fromLTRB(2.0, 2.0, 2.0, 2.0),
      color: Colors.white,
      colorBlendMode: BlendMode.color,
      excludeFromSemantics: false,
      filterQuality: FilterQuality.high,
      fit: BoxFit.scaleDown,
      gaplessPlayback: true,
      width: 300.0,
      height: 300.0,
      matchTextDirection: true,
      repeat: ImageRepeat.noRepeat,
      semanticLabel: "123",
    );

步骤

1.sd卡根目录放置图片（timg.jpg）

2.添加访问sd卡权限

AndroidManifest.xml

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

dart中

PermissionStatus permissionStatus = await PermissionHandler().checkPermissionStatus(PermissionGroup.storage);
    if(permissionStatus.value == PermissionStatus.granted){
      //已经授权
      tag = true;
    }else{
      //获取权限
      Map<PermissionGroup, PermissionStatus> permissions = await PermissionHandler().requestPermissions([PermissionGroup.storage]) as Map<PermissionGroup, PermissionStatus>;
      if(permissions.containsKey(PermissionGroup.storage)){
        tag = true;
      }
    }

2.添加图片部件（这里仅展示android示例）

示例4：（展示网络图片）

Image.network('https://ss0.bdstatic.com/70cFuHSh_Q1YnxGkpoWK1HF6hhy/it/u=2880582101,4095911409&fm=26&gp=0.jpg',alignment:Alignment.center,
//          centerSlice: Rect.fromLTRB(2.0, 2.0, 2.0, 2.0),
//      color: Colors.white,
      colorBlendMode: BlendMode.color,
      excludeFromSemantics: false,
      filterQuality: FilterQuality.high,
      fit: BoxFit.scaleDown,
      gaplessPlayback: true,
      width: 300.0,
      height: 300.0,
      matchTextDirection: true,
      repeat: ImageRepeat.noRepeat,
      semanticLabel: "123",
    );

2.Icon

一个图形图标小部件，使用IconData中描述的字体

文档

属性

color → Color：图标颜色

icon → IconData：图标描述

semanticLabel → String：图标语义

size → double：图标大小

textDirection → TextDirection：图标文本方向

示例

Icon(
      Icons.home,
      color:Colors.red,
      semanticLabel: '测试',
      size: 100.0,
      textDirection: TextDirection.rtl,
    );

3.RawImage

一个直接显示dart：ui.Image的小部件。很少直接使用

文档

4.AssetBundle

应用程序使用的资源集合

资产包包含可由应用程序使用的资源，例如图像和字符串。对这些资源的访问是异步的

文档

示例

Widget build(BuildContext context) {
    Future<String> result = DefaultAssetBundle.of(context).loadString("res/string/test.txt");
    return FutureBuilder(
      future: result,
      builder: (BuildContext context, AsyncSnapshot<String> snapshot){
        return Text(snapshot.data.toString());
      },
    );
  }

步骤

1.添加文本文件

2.pubspec.yaml中添加文件路径

3.代码中load文件

Flutter布局基础-基础部件（一）Assets, images, and icon