Flutter - Layout a Grid

问题:

I am trying to layout a 4x4 grid of tiles in flutter. I managed to do it with columns and rows. But now I found the GridView component. Could anyone provide an example on how to do it using it?

I can't really wrap my head around the docs. I don't seem to get the results I want.

回答1:

A simple example loading images into the tiles.

import 'package:flutter/material.dart';

void main() {
  runApp( MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(

      color: Colors.white30,
      child: GridView.count(
          crossAxisCount: 4,
          childAspectRatio: 1.0,
          padding: const EdgeInsets.all(4.0),
          mainAxisSpacing: 4.0,
          crossAxisSpacing: 4.0,
          children: <String>[
            'http://www.for-example.org/img/main/forexamplelogo.png',
            'http://www.for-example.org/img/main/forexamplelogo.png',
            'http://www.for-example.org/img/main/forexamplelogo.png',
            'http://www.for-example.org/img/main/forexamplelogo.png',
            'http://www.for-example.org/img/main/forexamplelogo.png',
            'http://www.for-example.org/img/main/forexamplelogo.png',
            'http://www.for-example.org/img/main/forexamplelogo.png',
            'http://www.for-example.org/img/main/forexamplelogo.png',
            'http://www.for-example.org/img/main/forexamplelogo.png',
            'http://www.for-example.org/img/main/forexamplelogo.png',
            'http://www.for-example.org/img/main/forexamplelogo.png',
          ].map((String url) {
            return GridTile(
                child: Image.network(url, fit: BoxFit.cover));
          }).toList()),
    );
  }
}

The Flutter Gallery app contains a real world example, which can be found here.

回答2:

GridView is used for implementing material grid lists. If you know you have a fixed number of items and it's not very many (16 is fine), you can use GridView.count. However, you should note that a GridView is scrollable, and if that isn't what you want, you may be better off with just rows and columns.

import 'dart:collection';
import 'package:flutter/scheduler.dart';
import 'package:flutter/material.dart';
import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter/foundation.dart';

void main() {
  runApp(new MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.orange,
      ),
      home: new MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget{
  @override
  Widget build(BuildContext context){
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Grid Demo'),
      ),
      body: new GridView.count(
        crossAxisCount: 4,
        children: new List<Widget>.generate(16, (index) {
          return new GridTile(
            child: new Card(
              color: Colors.blue.shade200,
              child: new Center(
                child: new Text('tile $index'),
              )
            ),
          );
        }),
      ),
    );
  }
}

回答3:

Use whichever suits your need.

1. GridView.count(...)

   GridView.count(
     crossAxisCount: 2,
     children: <Widget>[
       FlutterLogo(),
       FlutterLogo(),
       FlutterLogo(),
       FlutterLogo(),
     ],
   )
   

2. GridView.builder(...)

   GridView.builder(
     gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
     itemBuilder: (_, index) => FlutterLogo(),
     itemCount: 4,
   )
   

3. GridView(...)

   GridView(
     gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
     children: <Widget>[
       FlutterLogo(),
       FlutterLogo(),
       FlutterLogo(),
       FlutterLogo(),
     ],
   )
   

4. GridView.custom(...)

   GridView.custom(
     gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
     childrenDelegate: SliverChildListDelegate(
       [
         FlutterLogo(),
         FlutterLogo(),
         FlutterLogo(),
         FlutterLogo(),
       ],
     ),
   )
   

5. GridView.extent(...)

   GridView.extent(
     maxCrossAxisExtent: 400,
     children: <Widget>[
       FlutterLogo(),
       FlutterLogo(),
       FlutterLogo(),
       FlutterLogo(),
     ],
   )
   

Output (same for all):

回答4:

Please visit this repo.

Widget _gridView() {
    return GridView.count(
      crossAxisCount: 4,
      padding: EdgeInsets.all(4.0),
      childAspectRatio: 8.0 / 9.0,
      children: itemList
          .map(
            (Item) => ItemList(item: Item),
          )
          .toList(),
    );
  }

Below screenshot contains crossAxisCount: 2

回答5:

There are few named constructors in GridView for different scenarios,

Constructors

1. GridView
2. GridView.builder
3. GridView.count
4. GridView.custom
5. GridView.extent

Below is a example of GridView constructor:

import 'package:flutter/material.dart';

void main() => runApp(
  MaterialApp(
    home: ExampleGrid(),
  ),
);

class ExampleGrid extends StatelessWidget {
  List<String> images = [
    "https://uae.microless.com/cdn/no_image.jpg",
    "https://images-na.ssl-images-amazon.com/images/I/81aF3Ob-2KL._UX679_.jpg",
    "https://www.boostmobile.com/content/dam/boostmobile/en/products/phones/apple/iphone-7/silver/device-front.png.transform/pdpCarousel/image.jpg",
    "https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSgUgs8_kmuhScsx-J01d8fA1mhlCR5-1jyvMYxqCB8h3LCqcgl9Q",
    "https://ae01.alicdn.com/kf/HTB11tA5aiAKL1JjSZFoq6ygCFXaw/Unlocked-Samsung-GALAXY-S2-I9100-Mobile-Phone-Android-Wi-Fi-GPS-8-0MP-camera-Core-4.jpg_640x640.jpg",
    "https://media.ed.edmunds-media.com/gmc/sierra-3500hd/2018/td/2018_gmc_sierra-3500hd_f34_td_411183_1600.jpg",
    "https://hips.hearstapps.com/amv-prod-cad-assets.s3.amazonaws.com/images/16q1/665019/2016-chevrolet-silverado-2500hd-high-country-diesel-test-review-car-and-driver-photo-665520-s-original.jpg",
    "https://www.galeanasvandykedodge.net/assets/stock/ColorMatched_01/White/640/cc_2018DOV170002_01_640/cc_2018DOV170002_01_640_PSC.jpg",
    "https://media.onthemarket.com/properties/6191869/797156548/composite.jpg",
    "https://media.onthemarket.com/properties/6191840/797152761/composite.jpg",
  ];
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: GridView(
        physics: BouncingScrollPhysics(), // if you want IOS bouncing effect, otherwise remove this line
        gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),//change the number as you want
        children: images.map((url) {
          return Card(child: Image.network(url));
        }).toList(),
      ),
    );
  }
}

If you want your GridView items to be dynamic according to the content, you can few lines to do that but the simplest way to use StaggeredGridView package. I have provided an answer with example here.

Below is an example for a GridView.count:

import 'package:flutter/material.dart';

void main() => runApp(
      MaterialApp(
        home: ExampleGrid(),
      ),
    );

class ExampleGrid extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: GridView.count(
        crossAxisCount: 4,
        children: List.generate(40, (index) {
          return Card(
            child: Image.network("https://robohash.org/$index"),
          ); //robohash.org api provide you different images for any number you are giving
        }),
      ),
    );
  }
}

Screenshot for above snippet:

Example for a SliverGridView:

import 'package:flutter/material.dart';

void main() => runApp(
      MaterialApp(
        home: ExampleGrid(),
      ),
    );

class ExampleGrid extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: CustomScrollView(
        primary: false,
        slivers: <Widget>[
          SliverPadding(
            padding: const EdgeInsets.all(20.0),
            sliver: SliverGrid.count(
              crossAxisSpacing: 10.0,
              crossAxisCount: 2,
              children: List.generate(20, (index) {
                return Card(child: Image.network("https://robohash.org/$index"));
              }),
            ),
          ),
        ],
      )
    );
  }
}