RubyMotion:打开新屏幕后失去超级视图

Question

我使用的是ProMotion、Teacup和MMDrawerController的组合。当我加载应用程序时，一切都很好，但是当我尝试从一个屏幕切换到另一个屏幕时，我在Teacup上得到了一个错误，因为superview是零。Teacup错误是：*** Terminating app due to uncaught exception 'NoMethodError', reason: 'calculations.rb:15:in calculate:': undefined method 'bounds' for nil:NilClass (NoMethodError)。因为view.superview是空的，所以会抛出它。

我是初学者，但我觉得Teacup错误只是我设置所有东西的方式(或者可能与MMDrawerController不兼容)的一个更大问题的症状。

所以，这个应用程序加载到WeekScreen，在WeekScreen上，我添加了一个带按钮的导航栏，返回到WeekScreen。当我点击那个按钮时，我会得到错误。(我在这里简化了代码-我真的没有一个带有按钮的页面应用程序可以返回到同一个屏幕)

screens/root_screen.rb

class RootScreen < MMDrawerController
  include PM::ScreenModule

  title 'Schedule'

  def self.new(args = {})
    alloc.init.tap do |root_screen|
      root_screen.on_create(args)
    end
  end

  def centerViewController=(centerViewController)
    super
    self.title = centerViewController.title
  end

  def on_create(args={})
    super

    self.leftDrawerViewController   = Screen::MenuScreen.new(nav_bar: false)
    self.rightDrawerViewController  = nil
    self.centerViewController = week_screen

    leftDrawerButton = MMDrawerBarButtonItem.alloc.initWithTarget self, action:"show_menu:"
    navigationItem.setLeftBarButtonItem leftDrawerButton, animated:true
  end

  def will_appear
    self.title = centerViewController.title
  end

  def show_menu(sender)
    toggleDrawerSide MMDrawerSideLeft, animated:true, completion: nil
  end

  def week_screen
    @week_screen ||= Screen::WeekScreen.new
  end
end

screens/week_screen.rb

module Screen
  class WeekScreen < PM::Screen

    title ''
    stylesheet :week_styles
    include Teacup::TableViewDelegate

    @@cell_identifier = nil
    @selected_date = nil

    def will_appear
      super

      # mm_drawerController.title = title
      view.subviews.each &:removeFromSuperview

      layout(view, :main_view) do |main_view|
        week_table

        subview(UIView, :program_nav) do
          @week_btn = subview(UIButton.buttonWithType(UIButtonTypeRoundedRect), :week_btn)
        end

        @week_btn.when_tapped do
          open WeekScreen.new(nav_bar: true)
        end
      end
    end

    # a bunch of table stuff removed here to keep this clean-ish
  end
end

styles/week_styles.rb

Teacup::Stylesheet.new :week_styles do
  style :main_view,
    frame: [[0,30], ["100%", "100% - 30]]

  style :program_nav,
    frame: [[0, "100% - 78"], ["100%", 78]],
    backgroundColor: "#f1f2f2".to_color,
    autoresizingMask: (UIViewAutoresizingFlexibleLeftMargin |
                   UIViewAutoresizingFlexibleRightMargin |
                   UIViewAutoresizingFlexibleTopMargin)

  style :week_btn,
    center_x: '50%',
    center_y: '50%',
    width: 36,
    height: 36,
    backgroundImage: UIImage.imageNamed("week-view-btn")
end

Answer 1

尝试将对on_create的调用移到on_load内部。屏幕的view属性是init.tap块中的nil。