1、設定遊戲啟動的預設視窗模式

設定預設模式可通過修改配置檔案的方式，配置檔名DefaultGameUserSettings.ini，位於Config目錄下，如果沒有該檔案可新建一個，配置項如下

[/Script/Engine.GameUserSettings]
 bUseVSync=False
 ResolutionSizeX=1280
 ResolutionSizeY=720
 LastUserConfirmedResolutionSizeX=1280
 LastUserConfirmedResolutionSizeY=720
 WindowPosX=-1
 WindowPosY=-1
 bUseDesktopResolutionForFullscreen=True
 FullscreenMode=2
 LastConfirmedFullscreenMode=2
 

UENUM(BlueprintType)
namespace EWindowMode
{
enum Type
{
/** The window is in true fullscreen mode */
Fullscreen,
/** The window has no border and takes up the entire area of the screen */
WindowedFullscreen,
/** The window has a border and may not take up the entire screen area */
Windowed,
};
}

修改ResolutionSizeX和ResolutionSizeY，可設定視窗解析度

2、執行中切換視窗模式

遊戲執行中可通過UGameUserSettings類實現視窗模式切換

void SetFullScreenMode(bool bFull)
{
    if (bFull)
	{
		UGameUserSettings::GetGameUserSettings()->SetFullscreenMode(EWindowMode::WindowedFullscreen);//或者EWindowMode::Fullscreen
	}
	else
	{
		UGameUserSettings::GetGameUserSettings()->SetFullscreenMode(EWindowMode::Windowed);
	}
	UGameUserSettings::GetGameUserSettings()->ApplyResolutionSettings(false);
}
 

以上程式碼在UE4.16中測試通過