I need to move container at constant speed, my code moves it to the required location but not at constant speed it moves at different speeds each time.
double xVal = currentXLocationOfTheContainer;
double yVal = currentYLocationOfTheContainer;
static double xDistance = requiedXLocationOfTheContainer - currentXLocationOfTheContainer;
static double yDistance = requiedXLocationOfTheContainer - currentYLocationOfTheContainer;
Timer.periodic(const Duration(milliseconds: 10), (timer) {
setState(() {
xVal = xVal xDistance/100;
yVal = yVal yDistance/100;
});
});
CodePudding user response:
the formula is V = Distance/Duration
so for constant speed we need constant Distance in constant time.
for Example 2000 pixel per second
Or 2 pixel per Millisecond
Fist way : const distance.
double xVal = currentXLocationOfTheContainer;
double yVal = currentYLocationOfTheContainer;
static double xDistance = requiedXLocationOfTheContainer - currentXLocationOfTheContainer;
static double yDistance = requiedXLocationOfTheContainer - currentYLocationOfTheContainer;
Timer.periodic(const Duration(milliseconds: 10), (timer) {
setState(() {
xVal = xVal (xDistance > 0 ? 20 : -20);
yVal = yVal (yDistance > 0 ? 20 : -20);
});
});
note:speed in above code is 2 * sqrt(2) = 2.8284
pixel per millisecond
second way : const time.
for real Distance we use https://en.wikipedia.org/wiki/Pythagorean_theorem
import 'dart:math';
double xVal = currentXLocationOfTheContainer;
double yVal = currentYLocationOfTheContainer;
static double xDistance = requiedXLocationOfTheContainer - currentXLocationOfTheContainer;
static double yDistance = requiedXLocationOfTheContainer - currentYLocationOfTheContainer;
var realDisatanse = sqrt((xDistance*xDistance) (yDistance*yDistance));
var speedPerMillisecond = 2;
var time = realDisatanse / speedPerMillisecond;
Timer.periodic(const Duration(milliseconds: time), (timer) {
setState(() {
xVal = xVal xDistance;
yVal = yVal yDistance;
});
});
note:speed in above code is 2
pixel per millisecond
CodePudding user response:
You can use AnimatedPositioned widget which has default curve = Curves.linear
Animation as per documentation: https://flutter.github.io/assets-for-api-docs/assets/animation/curve_linear.mp4
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return const MaterialApp(
home: HomePage(),
);
}
}
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
@override
State<HomePage> createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
final targetX = 200;
final targetY = 200;
int currentX = 0;
int currentY = 0;
@override
void initState() {
super.initState();
Future.delayed(const Duration(seconds: 3), () {
if (mounted) {
setState(() {
currentX = targetX;
currentY = targetY;
});
}
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: const Text('AnimatedPositionedExample')),
body: Stack(
children: [
AnimatedPositioned(
child: Container(color: Colors.lime, height: 50, width: 50),
left: currentX.toDouble(),
top: currentY.toDouble(),
duration: const Duration(seconds: 1),
curve: Curves.linear,
)
],
),
);
}
}