我如何在颤抖中获取文本小部件的大小 [英] How can I get the size of the Text Widget in flutter
问题描述
我为文本
的内容背景绘制了一个形状。
我希望背景自动缩放文本,即使 softWrap
是真实的。
所以,我需要在 Widget build(BuildContext context)
之前获取我的Text Widget的宽度和高度。
实际上,我正在使用flutter模拟类似于iOS消息的聊天气泡效果。这是iOS版本的教程。
我找到了另一种方法而不使用上下文
:
最终约束= BoxConstraints(
maxWidth:800.0,//计算出的最大宽度
minHeight:0.0,
minWidth:0.0,
);
RenderParagraph renderParagraph = RenderParagraph(
TextSpan(
text:text,
style:TextStyle(
fontSize:fontSize,
),
),
textDirection:ui.TextDirection.ltr,
maxLines:1,
);
renderParagraph.layout(constraints);
double textlen = renderParagraph.getMinIntrinsicWidth(fontSize).ceilToDouble();
I've painted a shape for the background of my content of Text
.
I want the background autoscale the Text, even the softWrap
being true.
So, I need to get the width and height of my Text Widget before Widget build(BuildContext context)
.
Actually, I am simulating the chat bubble effect like iOS message using flutter. Here is the iOS version tutorial. Creating a Chat Bubble .
The core code below:
let label = UILabel()
label.numberOfLines = 0
label.font = UIFont.systemFont(ofSize: 18)
label.textColor = .white
label.text = text
let constraintRect = CGSize(width: 0.66 * view.frame.width,
height: .greatestFiniteMagnitude)
let boundingBox = text.boundingRect(with: constraintRect,
options: .usesLineFragmentOrigin,
attributes: [.font: label.font],
context: nil)
label.frame.size = CGSize(width: ceil(boundingBox.width),
height: ceil(boundingBox.height))
let bubbleSize = CGSize(width: label.frame.width + 28,
height: label.frame.height + 20)
let width = bubbleSize.width
let height = bubbleSize.height
=========================================
SOLUTION
Here is my solution.
bubble.dart:
// Define a CustomPainter to paint the bubble background.
class BubblePainter extends CustomPainter {
@override
void paint(Canvas canvas, Size size) {
final Paint paint = Paint()
..color = Color(0xff188aff)
..style = PaintingStyle.fill;
final Path bubble = Path()
..moveTo(size.width - 22.0, size.height)
..lineTo(17.0, size.height)
..cubicTo(
7.61, size.height, 0.0, size.height - 7.61, 0.0, size.height - 17.0)
..lineTo(0.0, 17.0)
..cubicTo(0.0, 7.61, 7.61, 0.0, 17.0, 0.0)
..lineTo(size.width - 21, 0.0)
..cubicTo(size.width - 11.61, 0.0, size.width - 4.0, 7.61,
size.width - 4.0, 17.0)
..lineTo(size.width - 4.0, size.height - 11.0)
..cubicTo(size.width - 4.0, size.height - 1.0, size.width, size.height,
size.width, size.height)
..lineTo(size.width + 0.05, size.height - 0.01)
..cubicTo(size.width - 4.07, size.height + 0.43, size.width - 8.16,
size.height - 1.06, size.width - 11.04, size.height - 4.04)
..cubicTo(size.width - 16.0, size.height, size.width - 19.0, size.height,
size.width - 22.0, size.height)
..close();
canvas.drawPath(bubble, paint);
}
@override
bool shouldRepaint(BubblePainter oldPainter) => true;
}
// This is my custom RenderObject.
class BubbleMessage extends SingleChildRenderObjectWidget {
BubbleMessage({
Key key,
this.painter,
Widget child,
}) : super(key: key, child: child);
final CustomPainter painter;
@override
RenderCustomPaint createRenderObject(BuildContext context) {
return RenderCustomPaint(
painter: painter,
);
}
@override
void updateRenderObject(
BuildContext context, RenderCustomPaint renderObject) {
renderObject..painter = painter;
}
}
Use the BubbleMessage
Widget like this:
import 'bubble.dart'
...code ...
BubbleMessage(
painter: BubblePainter(),
child: Container(
constraints: BoxConstraints(
maxWidth: 250.0,
minWidth: 50.0,
),
padding: EdgeInsets.symmetric(horizontal: 15.0, vertical: 6.0),
child: Text(
'your text variable',
softWrap: true,
style: TextStyle(
fontSize: 16.0,
),
),
),
),
...code ...
The bubble effect:
I found another method without using the context
:
final constraints = BoxConstraints(
maxWidth: 800.0, // maxwidth calculated
minHeight: 0.0,
minWidth: 0.0,
);
RenderParagraph renderParagraph = RenderParagraph(
TextSpan(
text: text,
style: TextStyle(
fontSize: fontSize,
),
),
textDirection: ui.TextDirection.ltr,
maxLines: 1,
);
renderParagraph.layout(constraints);
double textlen = renderParagraph.getMinIntrinsicWidth(fontSize).ceilToDouble();
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