如何在行小部件中放置CustomPaint？

Question

我是新手。 我想连续放置一个进度条（用custompainter制作），但是我不知道该怎么做。我希望该行的所有元素都对齐，垂直居中，并且它们之间的间距相等。

我的代码是：

import requests
overpass_query = """
[out:json][timeout:600];
{{geocodeArea:Niedersachsen}}->.searchArea;
(
  node[place=city](area.searchArea);  
  node[place=town](area.searchArea);  

);
out;
"""
overpass_url = "http://overpass-api.de/api/interpreter"
response = requests.get(overpass_url, params={'data': overpass_query})
data = response.json()

/home/enno/events/docker/etl/venv/bin/python /home/enno/events/docker/etl/test2.py
Traceback (most recent call last):
  File "/home/enno/events/docker/etl/test2.py", line 16, in <module>
    data = response.json()
  File "/home/enno/events/docker/etl/venv/lib/python3.6/site-packages/requests/models.py", line 897, in json
    return complexjson.loads(self.text, **kwargs)
  File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

Process finished with exit code 1

和：

Widget build(BuildContext context) {
return MaterialApp(
    home: Scaffold(
  body: Container(alignment: Alignment.center, child: Row(
    mainAxisAlignment: MainAxisAlignment.spaceEvenly,
    children: <Widget>[
      Text('text1'),
      Text('text2'),
      CustomPaint(painter: progressBar(),),
      Text('text3'),
      Text('text4')
    ],
  ),) 
));

Answer 1

在当前代码中，CustommPaint的大小为0。CustomPaint的documentation提到了其大小的获取方式，因此您需要为孩子提供size或提供其size属性（例如size：Size（ 50，14））。同样在绘画方法中，您应该使用Size参数，以便仅在可用的空间中绘制，而不会越过边界（就像您当前所做的那样）：

canvas.drawRRect(RRect.fromRectAndRadius(Rect.fromLTWH(0, 0, size.width, size.height), corner), paint);