一个非常简单的问题:如何为Flutter相机插件实现点按对焦功能?
我已经在全球范围内搜索了各种解决方案,但没有发现任何有用信息。
有人有想法吗?
一个非常简单的问题:如何为Flutter相机插件实现点按对焦功能?
我已经在全球范围内搜索了各种解决方案,但没有发现任何有用信息。
有人有想法吗?
你需要使用相机控制器方法手动设置焦点:
controller.setFocusPoint(offset)
import 'package:camera/camera.dart';
import 'package:flutter/material.dart';
late List<CameraDescription> cameras;
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
cameras = await availableCameras();
runApp(const MaterialApp(home: CameraApp()));
}
class CameraApp extends StatefulWidget {
const CameraApp({Key? key}) : super(key: key);
@override
_CameraAppState createState() => _CameraAppState();
}
class _CameraAppState extends State<CameraApp> {
late CameraController controller;
bool showFocusCircle = false;
double x = 0;
double y = 0;
@override
void initState() {
super.initState();
controller = CameraController(cameras[0], ResolutionPreset.max);
controller.initialize().then((_) {
if (!mounted) {
return;
}
setState(() {});
});
}
@override
void dispose() {
controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
if (!controller.value.isInitialized) {
return Container();
}
return GestureDetector(
onTapUp: (details) {
_onTap(details);
},
child: Stack(
children: [
Center(
child: CameraPreview(controller)
),
if(showFocusCircle) Positioned(
top: y-20,
left: x-20,
child: Container(
height: 40,
width: 40,
decoration: BoxDecoration(
shape: BoxShape.circle,
border: Border.all(color: Colors.white,width: 1.5)
),
))
],
)
);
}
Future<void> _onTap(TapUpDetails details) async {
if(controller.value.isInitialized) {
showFocusCircle = true;
x = details.localPosition.dx;
y = details.localPosition.dy;
double fullWidth = MediaQuery.of(context).size.width;
double cameraHeight = fullWidth * controller.value.aspectRatio;
double xp = x / fullWidth;
double yp = y / cameraHeight;
Offset point = Offset(xp,yp);
print("point : $point");
// Manually focus
await controller.setFocusPoint(point);
// Manually set light exposure
//controller.setExposurePoint(point);
setState(() {
Future.delayed(const Duration(seconds: 2)).whenComplete(() {
setState(() {
showFocusCircle = false;
});
});
});
}
}
}
请注意为x、y点值添加边界,以避免在轻触超出相机预览范围时导致崩溃:
if (point != null &&
(point.dx < 0 || point.dx > 1 || point.dy < 0 || point.dy > 1)) {
throw ArgumentError(
'The values of point should be anywhere between (0,0) and (1,1).');
}
Positioned
小部件是Stack
小部件的直接子元素。我曾经遇到同样的问题,在几次搜索后找到了解决方案。Stack
小部件的文档以了解更多信息。Stack
小部件之后,我在我的代码中遇到了快门按钮的位置问题。我通过简单地使用另一个Positioned
小部件来容纳按钮来解决了这个问题。class _CameraPageState extends State<CameraPage> {
late CameraController controller;
XFile? pictureFile;
// for tap to focus
bool showFocusCircle = false;
double x = 0;
double y = 0;
@override
void initState() {
super.initState();
controller = CameraController(
widget.cameras![0],
ResolutionPreset.max,
);
controller.initialize().then((_) {
if (!mounted) {
return;
}
setState(() {});
});
}
@override
void dispose() {
controller.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
if (!controller.value.isInitialized) {
return const SizedBox(
child: Center(
child: CircularProgressIndicator(),
),
);
}
return GestureDetector(
onTapUp: (details) {
_onTap(details);
},
child: Stack(
children: [
Padding(
padding: const EdgeInsets.all(4.0),
child: Center(
child: Container(
height: 700,
width: 700,
margin: const EdgeInsets.only(bottom: 70),
child: CameraPreview(controller),
),
),
),
Positioned(
left: MediaQuery.of(context).size.width / 2 - 40,
bottom: 40,
child: Padding(
padding: const EdgeInsets.all(8.0),
child: ElevatedButton(
onPressed: () async {
pictureFile = await controller.takePicture();
// Preview Picture in another page
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => ImagePreview(pictureFile!),
),
);
setState(() {});
},
child: const Text(' '),
),
),
),
if (showFocusCircle)
Positioned(
top: y - 20,
left: x - 20,
child: Container(
height: 40,
width: 40,
decoration: BoxDecoration(
shape: BoxShape.circle,
border: Border.all(color: Colors.white, width: 1.5)),
),
)
],
),
);
}
Future<void> _onTap(TapUpDetails details) async {
if (controller.value.isInitialized) {
showFocusCircle = true;
x = details.localPosition.dx;
y = details.localPosition.dy;
print(x);
print(y);
double fullWidth = MediaQuery.of(context).size.width;
double cameraHeight = fullWidth * controller.value.aspectRatio;
double xp = x / fullWidth;
double yp = y / cameraHeight;
Offset point = Offset(xp, yp);
print("point : $point");
// Manually focus
await controller.setFocusPoint(point);
// Manually set light exposure
controller.setExposurePoint(point);
setState(() {
Future.delayed(const Duration(seconds: 2)).whenComplete(() {
setState(() {
showFocusCircle = false;
});
});
});
}
}
这就是它的样子。