代码勘误

[SeniorDoctorHui]

p20中的s01中的clock_manage.dart中有以下代码:

void collectDigit({int target = 0, double offsetRate = 0}) {
    if (target > 10 && count > numParticles) {
      return;
    }

    double space = _radius * 2;
    double offSetX = (digits[target][0].length * 2 * (_radius + 1) + space) *
        offsetRate;

    for (int i = 0; i < digits[target].length; i++) {
      for (int j = 0; j < digits[target][j].length; j++) {
        if (digits[target][i][j] == 1) {
          double rX = j * 2 * (_radius + 1) + (_radius + 1); //第(i，j)个点圆心横坐标
          double rY = i * 2 * (_radius + 1) + (_radius + 1); //第(i，j)个点圆心纵坐标
          particles[count] = Particle(x: rX + offSetX,        //**这里第一次会发生越界,因为particles数组长度为0,从而导致程序发生异常**
              y: rY, size: _radius, color: Colors.blue,
              active: true);
          count++;
        }
      }
    }
  }

可以修改如下

if(particles.length <= count){
            //没有则增加
            particles.add(Particle(x: rX + offSetX,
                y: rY, size: _radius, color: Colors.blue,
                active: true));
          }else{
            particles[count] = Particle(x: rX + offSetX,
                y: rY, size: _radius, color: Colors.blue,
                active: true);
          }