UE4中UMG CheckBox Group实现

学习UE4的时候，发现UMG居然没有CheckBoxGroup，CheckBox分组需要自己管理。相比于Unity3D来说，UE4在UI方面确实欠缺很多，为此，下面就给大家介绍下实现一个CheckBox Group的方法，没接触过的都可以看看。

实现效果如下： 

编辑界面如下： 

代码实现如下：

CheckBoxGroup.h

// Fill out your copyright notice in the Description page of Project Settings.
#pragma once
#include "CoreMinimal.h"
#include "Components/NamedSlot.h"
#include "Components/CanvasPanel.h"
#include "Components/CheckBox.h"
#include "CheckBoxGroup.generated.h"
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnCheckBoxGroupStateChangedEvent, const TArray<UCheckBox*>&, childChangedArray);
UCLASS()
class UCheckBoxGroup : public UNamedSlot
｛
    GENERATED_BODY()
public:
    UCheckBoxGroup();
protected:
    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "CheckBox Group")
    bool _allowSwitchOff;
    UPROPERTY(BlueprintAssignable, Category = "CheckBox Group")
    FOnCheckBoxGroupStateChangedEvent _onStateChangedEvent;
    UPanelWidget* _groupRoot;
    FScriptDelegate _onStateChangedScriptDelegate;
    UCheckBox* _lastCheckedChild;
protected:
    virtual void OnWidgetRebuilt() override;
    bool InitGroup();
    bool InitChild(UCheckBox* child);
    UFUNCTION(Category = "CheckBox Group")
    void OnStateChanged(bool bIsChecked);
public:
    UFUNCTION(BlueprintCallable, Category = "CheckBox Group")
    TArray<UCheckBox*> CheckChildsState();
    /*
    UFUNCTION(BlueprintCallable, Category = "CheckBox Group")
    bool SetChildState(int nID, bool status);
    */
    UFUNCTION(BlueprintCallable, Category = "CheckBox Group")
    bool AddGroupChild(UCheckBox* child);
    UFUNCTION(BlueprintCallable, Category = "CheckBox Group")
    bool RemoveGroupChild(UCheckBox* child);
｝;

CheckBoxGroup.cpp

// Fill out your copyright notice in the Description page of Project Settings.
#include "CheckBoxGroup.h"
UCheckBoxGroup::UCheckBoxGroup()
｛
    _allowSwitchOff = false;
    _groupRoot = nullptr;
    _lastCheckedChild = nullptr;
    _onStateChangedScriptDelegate.BindUFunction(this, TEXT("OnStateChanged"));
    //
    _allowSwitchOff = false;
｝
void UCheckBoxGroup::OnWidgetRebuilt()
｛
    _groupRoot = Cast<UPanelWidget>(GetChildAt(0));
    if (nullptr != _groupRoot)
    ｛
        InitGroup();
    ｝
    else
    ｛
        //UE_LOG(PeterLog, Error, TEXT("UCheckBoxGroup isn`t have group root!"));
    ｝
｝
bool UCheckBoxGroup::InitGroup()
｛
    if (nullptr == _groupRoot)
    ｛
        return false;
    ｝
    int childCnt = _groupRoot->GetChildrenCount();
    for (int i = 0; i < childCnt; ++i)
    ｛
        InitChild(Cast<UCheckBox>(_groupRoot->GetChildAt(i)));
    ｝
    return true;
｝
bool UCheckBoxGroup::InitChild(UCheckBox* child)
｛
    if (nullptr == child)
    ｛//
        return false;
    ｝
    child->OnCheckStateChanged.Add(_onStateChangedScriptDelegate);
    return true;
｝
void UCheckBoxGroup::OnStateChanged(bool bIsChecked)
｛
    TArray<UCheckBox*> childChangedArray = CheckChildsState();
    if (0 != childChangedArray.Num())
    ｛
        _onStateChangedEvent.Broadcast(childChangedArray);
    ｝
｝
TArray<UCheckBox*> UCheckBoxGroup::CheckChildsState()
｛
    TArray<UCheckBox*> childChangedArray;
    if (nullptr == _groupRoot)
    ｛
        return childChangedArray;
    ｝
    int childCnt = _groupRoot->GetChildrenCount();
    UCheckBox* childWidget = nullptr;
    UCheckBox* newLastCheckedChild = nullptr;
    UCheckBox* firstCheckedChild = nullptr;
    bool hasLastChecked = false;
    bool hasOtherChecked = false;
    for (int i = 0; i < childCnt; ++i)
    ｛
        childWidget = Cast<UCheckBox>(_groupRoot->GetChildAt(i));
        if (nullptr != childWidget)
        ｛
            if (nullptr == firstCheckedChild)
            ｛//保存第一个
                firstCheckedChild = childWidget;
            ｝
            if (childWidget->IsChecked())
            ｛
                if (childWidget != _lastCheckedChild)
                ｛
                    if (!hasOtherChecked)
                    ｛
                        newLastCheckedChild = childWidget;
                        hasOtherChecked = true;
                    ｝
                    else
                    ｛//uncheck childWidget,只保留一个选择项
                        childWidget->SetCheckedState(ECheckBoxState::Unchecked);
                    ｝
                    childChangedArray.Add(childWidget);
                ｝
                else
                ｛
                    hasLastChecked = true;
                ｝
            ｝
        ｝
    ｝
    if (hasOtherChecked)
    ｛//uncheck _lastChild
        if (hasLastChecked && nullptr != _lastCheckedChild)
        ｛
            _lastCheckedChild->SetCheckedState(ECheckBoxState::Unchecked);
            childChangedArray.Add(_lastCheckedChild);//原有选择项被改变
        ｝
        _lastCheckedChild = newLastCheckedChild;
    ｝
    else
    ｛
        if (!_allowSwitchOff)
        ｛
            if (nullptr != _lastCheckedChild)
            ｛
                if (!hasLastChecked)
                ｛
                    _lastCheckedChild->SetCheckedState(ECheckBoxState::Checked);//还原，保留选择项
                ｝
            ｝
            else
            ｛//选择第一个作为默认的选择项
                if (nullptr != firstCheckedChild)//选择第一个
                ｛
                    _lastCheckedChild = firstCheckedChild;
                    _lastCheckedChild->SetCheckedState(ECheckBoxState::Checked);
                    childChangedArray.Add(_lastCheckedChild);
                ｝
            ｝
        ｝
        else
        ｛
            if (nullptr != _lastCheckedChild && 0 == childChangedArray.Num())
            ｛//没有一个被选择且改变的情况，肯定是最后一个被uncheck了
                childChangedArray.Add(_lastCheckedChild);
            ｝
        ｝
    ｝
    return childChangedArray;
｝
/*
bool UCheckBoxGroup::SetChildState(int nID, bool status)
｛
    if (nullptr == _groupRoot)
    ｛
        return false;
    ｝
    TArray<UCheckBox*> childChangedArray;
    int childCnt = _groupRoot->GetChildrenCount();
    UCheckBox* childWidget = nullptr;
    UCheckBox* findCheckedChild = nullptr;
    //查找子物体
    for (int i = 0; i < childCnt; ++i)
    ｛
        childWidget = Cast<UCheckBox>(_groupRoot->GetChildAt(i));
        if (nullptr != childWidget && nID == childWidget->ID)
        ｛
            findCheckedChild = childWidget;
            break;
        ｝
    ｝
    if (nullptr == findCheckedChild)
    ｛//未找到该子物体
        return false;
    ｝
    if (findCheckedChild->IsChecked() != status)
    ｛//判断值
        findCheckedChild->SetCheckedState(status ? ECheckBoxState::Checked : ECheckBoxState::Unchecked);
        childChangedArray.Add(findCheckedChild);
    ｝
    if (status)
    ｛
        _lastCheckedChild = findCheckedChild;
        for (int i = 0; i < childCnt; ++i)
        ｛
            childWidget = Cast<UCheckBox>(_groupRoot->GetChildAt(i));
            if (nullptr != childWidget)
            ｛
                if (childWidget != findCheckedChild && childWidget->IsChecked())
                ｛
                    childWidget->SetCheckedState(ECheckBoxState::Unchecked);
                    childChangedArray.Add(childWidget);
                ｝
            ｝
        ｝
    ｝
    else
    ｛
        TArray<UCheckBox*> changedArray = CheckChildsState();
        //移除合并时可能重复的项
        int findIndex = childChangedArray.Find(findCheckedChild);
        if (INDEX_NONE != findIndex)
        ｛
            findIndex = changedArray.Find(findCheckedChild);
            if (INDEX_NONE != findIndex)
            ｛
                changedArray.RemoveAt(findIndex);
            ｝
        ｝
        //合并
        childChangedArray.Append(changedArray);
    ｝
    if (0 != childChangedArray.Num())
    ｛//广播改变
        _onStateChangedEvent.Broadcast(childChangedArray);
    ｝
    return true;
｝
*/
bool UCheckBoxGroup::AddGroupChild(UCheckBox* child)
｛
    if (nullptr == _groupRoot || nullptr == child)
    ｛
        return false;
    ｝
    _groupRoot->AddChild(child);
    bool bInit = InitChild(child);
    if (!bInit)
    ｛
        _groupRoot->RemoveChild(child);
        return false;
    ｝
    return true;
｝
bool UCheckBoxGroup::RemoveGroupChild(UCheckBox* child)
｛
    if (nullptr == _groupRoot || nullptr == child)
    ｛
        return false;
    ｝
    return _groupRoot->RemoveChild(child);
｝