【发布时间】：2018-07-04 12:52:31
【问题描述】：
这是我应用的 main.dart 文件：
import 'package:flutter/material.dart';
main() {
runApp(
new MaterialApp(
title: 'Flutter Database Test',
theme: ThemeData(
textTheme: TextTheme(
display1: TextStyle(fontSize: 24.0, color: Colors.white),
display2: TextStyle(fontSize: 24.0, color: Colors.grey),
display3: TextStyle(fontSize: 18.0, color: Colors.black),
),
),
home: new MyHomePage(),
),
);
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
List<Color> color = [
Colors.white,
Colors.black,
Colors.pink,
Colors.blue,
Colors.red,
Colors.yellow,
Colors.orange,
Colors.green,
Colors.cyan,
Colors.purple,
Colors.brown,
Colors.indigo,
Colors.teal,
Colors.grey,
];
Color _pencolor = Colors.white;
Color _canvasclr = Colors.black;
bool ispen = true;
Color bc = Colors.black54;
List<Offset> points = List<Offset>();
GlobalKey<ScaffoldState> _skey = GlobalKey<ScaffoldState>();
int cchanged = change[1];
static var change = [1, 2, 0];
@override
Widget build(BuildContext context) {
MyPainter _painter = MyPainter(color: cchanged, canvasp: points, changed: color.indexOf(_pencolor));
_painter.addListener(() {
print('hello');
});
return new Scaffold(
resizeToAvoidBottomPadding: true,
key: _skey,
appBar: AppBar(
backgroundColor: bc,
elevation: 0.0,
title: Text(
'Draw',
style: Theme.of(context).textTheme.display1,
),
centerTitle: true,
actions: <Widget>[
IconButton(
icon: Icon(Icons.content_paste),
onPressed: () {
_skey.currentState.showSnackBar(SnackBar(
backgroundColor: Colors.transparent,
content: Center(
child: Text(
'Choose Canvas Color',
textScaleFactor: 0.7,
style: Theme.of(context).textTheme.display3,
))));
ispen = false;
}),
IconButton(
icon: Icon(Icons.edit),
onPressed: () {
_skey.currentState.showSnackBar(SnackBar(
content: Center(
child:
Text('Choose Pen Color', textScaleFactor: 0.7, style: Theme.of(context).textTheme.display3)),
backgroundColor: Colors.transparent,
));
ispen = true;
})
],
),
drawer: Drawer(
child: ListView(
children: <Widget>[
ListTile(
title: Text('Create Canvas'),
leading: Icon(Icons.add),
onTap: () {
//TODO
},
),
ListTile(
title: Text('Connect to Canvas'),
leading: Icon(Icons.compare_arrows),
onTap: () {
//TODO
},
)
],
),
),
body: Container(
color: bc,
child: Column(
children: <Widget>[
Expanded(
child: Padding(
padding: const EdgeInsets.only(left: 8.0, right: 8.0, top: 10.0),
child: ClipRRect(
child: Container(
color: _canvasclr,
child: GestureDetector(
onPanStart: (DragStartDetails d) {
points.add(Offset(d.globalPosition.dx, d.globalPosition.dy - 100));
cchanged = change[2];
print('${d.globalPosition},$points');
setState(() {});
},
onPanUpdate: (DragUpdateDetails d) {
points.add(Offset(d.globalPosition.dx, d.globalPosition.dy - 100));
print('${d.globalPosition}');
cchanged = change[0];
setState(() {});
},
child: CustomPaint(
isComplex: true,
willChange: false,
child: Container(),
painter: _painter,
),
),
),
borderRadius: BorderRadius.circular(25.0),
),
),
),
Container(
height: 75.0,
child: ListView.builder(
scrollDirection: Axis.horizontal,
shrinkWrap: true,
itemCount: color.length,
itemBuilder: (BuildContext context, int index) {
return InkWell(
splashColor: Colors.white,
onTap: () {
ispen ? _pencolor = color[index] : _canvasclr = color[index];
setState(() {});
},
child: Padding(
padding: const EdgeInsets.all(12.0),
child: CircleAvatar(
backgroundColor: color[index],
),
),
);
},
),
),
],
),
),
);
}
}
class MyPainter extends CustomPainter {
final int color;
final List<Offset> canvasp;
Paint p = Paint();
List<Paint> _paint = [
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.white,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.black,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.pink,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.blue,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.red,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.yellow,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.orange,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.green,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.cyan,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.purple,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.brown,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.indigo,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.teal,
Paint()
..strokeCap = StrokeCap.round
..strokeJoin = StrokeJoin.round
..strokeWidth = 2.0
..color = Colors.grey,
];
final int changed;
MyPainter({
this.color,
this.canvasp,
this.changed,
});
@override
void paint(Canvas canvas, Size size) {
print('painting ....... $canvasp');
for (int i = 0; i < canvasp.length; i++) {
canvas.drawCircle(canvasp[i], 10.0, _paint[color]);
}
}
@override
bool shouldRepaint(MyPainter oldDelegate) {
return oldDelegate.canvasp.length != canvasp.length;
}
}
此实现显示了我正在尝试构建以在画布上绘制的应用。
但是，当我触摸屏幕时，我无法绘制它。相反，它仅在我更改墨水池中的颜色时才会重新绘制 - 而不是在书写时或在 GestureDetector 中接收到事件时。
我们将不胜感激以更改我现有代码的形式给出答案。
【问题讨论】：
-
这次我已经为您完成了，但通常最好在发布之前格式化您的代码（VS Code 和 IntelliJ 有一个热键）。
标签： android flutter repaint flutter-layout