Firemonkey：为继承样式名的FMXObject触发级联样式刷新

Alright, let's tackle this FMX style refresh scenario you're working with. You've got a TLabel called BaseStyleLabel (with StyleName set to 'BaseStyle') using styles like 'BaseStyle1', 'BaseStyle2', etc., plus a dependent TLabel named MyTextLabel—and you want all these components to update their styles automatically when BaseStyleLabel's StyleLookup changes.

Here are two solid approaches to make this work:

1. Quick & Direct: Manual Refresh via StyleLookupChanged Event #

The simplest way is to hook into the OnStyleLookupChanged event of your BaseStyleLabel, then explicitly refresh all related components when the style changes.

Step-by-Step Implementation: #

• First, assign the OnStyleLookupChanged event to your BaseStyleLabel (either in the form designer or code).
• Add this event handler to refresh both the base label and all dependent labels:

procedure TYourForm.BaseStyleLabelStyleLookupChanged(Sender: TObject);
var
  I: Integer;
  CurrentComponent: TComponent;
begin
  // Refresh the base style label first
  (Sender as TLabel).ApplyStyleLookup;
  (Sender as TLabel).Repaint;

  // Refresh all dependent MyTextLabel components (adjust the condition to match your setup)
  for I := 0 to ComponentCount - 1 do
  begin
    CurrentComponent := Components[I];
    if (CurrentComponent is TLabel) and (CurrentComponent.Name = 'MyTextLabel') then
    begin
      (CurrentComponent as TLabel).ApplyStyleLookup;
      (CurrentComponent as TLabel).Repaint;
    end;
  end;
end;

Key Notes: #

• ApplyStyleLookup tells the component to reload its style from the resource based on the current StyleLookup value.
• Repaint forces the component to redraw immediately—without this, the style change might not show up right away.
• If your dependent components are nested inside containers (like TPanel or TScrollBox), you'll need a recursive function to traverse all child components instead of just the form's direct components.

2. Scalable: Use a Style Manager Class #

If you have more than a couple dependent components, a dedicated style manager keeps your code clean and maintainable. This class will handle listening for style changes and refreshing all registered components automatically.

Style Manager Code: #

type
  TStyleManager = class
  private
    FBaseStyleComp: TControl;
    FRegisteredComponents: TList<TControl>;
    procedure OnBaseStyleLookupChanged(Sender: TObject);
  public
    constructor Create(BaseStyleComponent: TControl);
    destructor Destroy; override;
    procedure RegisterDependentComponent(Comp: TControl);
    procedure UnregisterDependentComponent(Comp: TControl);
    procedure SwitchStyle(const NewStyleName: string);
  end;

constructor TStyleManager.Create(BaseStyleComponent: TControl);
begin
  inherited Create;
  FBaseStyleComp := BaseStyleComponent;
  FRegisteredComponents := TList<TControl>.Create;
  // Hook into the base component's style change event
  FBaseStyleComp.OnStyleLookupChanged := OnBaseStyleLookupChanged;
end;

destructor TStyleManager.Destroy;
begin
  FRegisteredComponents.Free;
  inherited;
end;

procedure TStyleManager.OnBaseStyleLookupChanged(Sender: TObject);
var
  Comp: TControl;
begin
  // Refresh the base component
  FBaseStyleComp.ApplyStyleLookup;
  FBaseStyleComp.Repaint;

  // Refresh all registered dependent components
  for Comp in FRegisteredComponents do
  begin
    Comp.ApplyStyleLookup;
    Comp.Repaint;
  end;
end;

procedure TStyleManager.RegisterDependentComponent(Comp: TControl);
begin
  if not FRegisteredComponents.Contains(Comp) then
    FRegisteredComponents.Add(Comp);
end;

procedure TStyleManager.UnregisterDependentComponent(Comp: TControl);
begin
  FRegisteredComponents.Remove(Comp);
end;

procedure TStyleManager.SwitchStyle(const NewStyleName: string);
begin
  FBaseStyleComp.StyleLookup := NewStyleName;
end;

How to Use It: #

// Initialize the manager in your form's OnCreate event
procedure TYourForm.FormCreate(Sender: TObject);
var
  StyleMgr: TStyleManager;
begin
  StyleMgr := TStyleManager.Create(BaseStyleLabel);
  // Register your dependent component(s)
  StyleMgr.RegisterDependentComponent(MyTextLabel);
  // Store StyleMgr as a form field if you need to switch styles later
end;

// To switch styles anywhere in your code:
StyleMgr.SwitchStyle('BaseStyle3');

This approach is great if you plan to add more dependent components later—just call RegisterDependentComponent for each new one, and the manager handles the rest.

内容的提问来源于stack exchange，提问作者soddoff Baldrick