使用QGraphicsView實現氣泡聊天窗口+排雷

經過多方調查，用Qt實現氣泡聊天窗口的方式有如下幾個：

• 使用QWebEngineView控件內嵌html+CSS
• 使用QTextEdit內嵌html
• 使用QGraphicsView實現
• 使用QWidget自己繪制氣泡樣式實現

作為一名C++程序員，對CSS+html這套結構的不熟悉導致無法使用前兩個方案，而第三個方案又不夠高效，所以最終我選擇了最后一個方案。
最終效果：

存在問題：無法選擇文字及跨選（但理論上可以通過重寫鼠標相關事件，達到模擬選擇的效果）

左側和右側的消息分別是封裝的兩個Item，而這兩個Item又從同一個基類繼承而來。
氣泡通過重寫void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);函數，在里面根據文字的寬高計算氣泡的位置並畫上去，然后再把字寫上去。
並且當窗口大小發生變化時，需要重新計算文字尺寸，進行繪制。

#pragma once

#include <QGraphicsRectItem>

//聊天元素所有item的基類
class ChatBaseItem : public QGraphicsRectItem
{
public:
    ChatBaseItem();
    virtual ~ChatBaseItem();

public:
    virtual int Resize(int width);      //傳入值為viewport寬，返回值為item高
};

#include "chatbaseitem.h"

ChatBaseItem::ChatBaseItem()
    : QGraphicsRectItem()
{
}

ChatBaseItem::~ChatBaseItem()
{
}

int ChatBaseItem::Resize(int width)
{
    return 0;
}

左側聊天氣泡Item

#pragma once

#include "chatbaseitem.h"
#include <QDateTime>

class OtherMsgItem : public ChatBaseItem
{

public:
    OtherMsgItem(QPixmap icon, QString name, QString msg, QDateTime datetime = QDateTime());
    virtual ~OtherMsgItem();

    virtual int Resize(int width);  //返回整個item的高度

protected:
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
    virtual QRectF boundingRect() const;

private:
    QGraphicsPixmapItem icon_item_;
    QGraphicsSimpleTextItem name_item_;
    QString text_;
    QSize text_size_;     //文字尺寸
    QDateTime datetime_;
};

#include <QPainter>
#include <QMargins>
#include <QTextOption>

#include "othermsgitem.h"

const int kMsgFontSize = 14;
const int kNameFontSize = 13;

const QPoint kNamePos = QPoint(64, 0);
const QPoint kIconPos = QPoint(20, 8);
const QPoint kBorderPos = QPoint(kNamePos.x(), kNamePos.y()+18);
const QMargins kMargins = QMargins(12,11,12,11);        //文字距邊框的距離
const QPoint kTextPos = QPoint(kBorderPos.x()+ kMargins.left(), kBorderPos.y() + kMargins.top());
const int kMarginRight = 40;                           //邊框距窗口右側的距離

OtherMsgItem::OtherMsgItem(QPixmap icon, QString name, QString msg, QDateTime datetime /*= QDateTime()*/)
    : ChatBaseItem()
    , datetime_(datetime)
{
    icon_item_.setPixmap(icon);
    icon_item_.setPos(kIconPos);

    text_ = msg;

    QFont font("Microsoft YaHei");
    font.setPixelSize(kNameFontSize);
    
    name_item_.setText(name);
    name_item_.setPos(kNamePos);
    name_item_.setFont(font);
    name_item_.setBrush(QColor(153, 153, 153));

    icon_item_.setParentItem(this);

    name_item_.setParentItem(this);
}

OtherMsgItem::~OtherMsgItem()
{
}

int OtherMsgItem::Resize(int width)
{
    //每行最大可容納文字的寬度
    int row_width = width - kTextPos.x() - kMarginRight-kMargins.right();
    
    //計算文字總共需要多寬
    QFont font("Microsoft YaHei");
    font.setPixelSize(kMsgFontSize);
    QFontMetrics font_matrics(font);
    int text_total_width = font_matrics.width(text_);
    int text_row_height = font_matrics.lineSpacing();

    if(row_width<text_total_width)
    {
        int row = text_total_width / row_width;
        ++row;

        int text_total_height = row* text_row_height;

        text_size_.setWidth(row_width);
        text_size_.setHeight(text_total_height);
    }
    else
    {
        text_size_.setWidth(text_total_width);
        text_size_.setHeight(text_row_height);
    }
    return text_size_.height()+kMargins.top()+kMargins.bottom()+kBorderPos.y();
}

void OtherMsgItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    QSize rnd(17,17);
    QRectF border(kBorderPos.x(), kBorderPos.y(), text_size_.width()+kMargins.left()+ kMargins.right(),text_size_.height() + kMargins.top() + kMargins.bottom());
    //氣泡加邊
    painter->setPen(QPen(QColor(229, 229, 229), 1, Qt::SolidLine));
    painter->drawRoundedRect(border.x(), border.y(), border.width(), border.height(), rnd.width(), rnd.height());

    //氣泡
    painter->setBrush(QBrush(Qt::white));
    painter->setPen(Qt::NoPen);
    painter->drawRoundedRect(border.x()+1, border.y()+1, border.width()-2, border.height()-2, rnd.width(), rnd.height());

    //三角，用矩形實現
    QRect rect1(border.x()+1, border.y()+1, 20, 20);
    painter->setPen(Qt::NoPen);
    painter->setBrush(QBrush(Qt::white));
    painter->drawRect(rect1);

    //三角加邊
    QPen pen;
    pen.setColor(QColor(229, 229, 229));
    painter->setPen(pen);
    painter->drawLine(border.x() , border.y() , border.x() +20, border.y() );
    painter->drawLine(border.x() , border.y() , border.x() , border.y() +20);

    QPen penText;
    penText.setColor(QColor(51, 51, 51));
    painter->setPen(penText);
    QTextOption option1(Qt::AlignLeft);
    option1.setWrapMode(QTextOption::WrapAtWordBoundaryOrAnywhere);
    QFont font("Microsoft YaHei");
    font.setPixelSize(kMsgFontSize);
    painter->setFont(font);

    QRectF text_rect(kTextPos.x(), kTextPos.y(), text_size_.width(), text_size_.height());
    painter->drawText(text_rect, text_, option1);
}

QRectF OtherMsgItem::boundingRect() const
{
    QRectF border(kBorderPos.x(), kBorderPos.y(), text_size_.width() + kMargins.left() + kMargins.right(), text_size_.height() + kMargins.top() + kMargins.bottom());
    return QRectF(0,0,border.width(),border.height());
}

右側氣泡和左側氣泡不同，計算位置時，左端點需要根據窗口寬度事實計算。

#pragma once

#include "chatbaseitem.h"
#include <QDateTime>

class SelfMsgItem : public ChatBaseItem
{
public:
    SelfMsgItem(QPixmap icon, QString msg, QDateTime datetime = QDateTime());
    virtual ~SelfMsgItem();

    virtual int Resize(int width);  //返回整個item的高度

protected:
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
    virtual QRectF boundingRect() const;

private:
    QGraphicsPixmapItem icon_item_;
    QString text_;
    QSize text_size_;     //文字尺寸
    QDateTime datetime_;
    int port_width_;
};

#include <QPen>
#include <QPainter>
#include "selfmsgitem.h"

const int kMsgFontSize = 14;
const int kNameFontSize = 13;

const int kIconY = 0;
const int kBorderY = 10;
const int kIconWidth = 34;
const QMargins kIconMargins = QMargins(10,0,20,0);
const QMargins kMargins = QMargins(12, 11, 12, 11);        //文字距邊框的距離
const int kMarginLeft = 40;                                //邊框距窗口左側的距離

SelfMsgItem::SelfMsgItem(QPixmap icon, QString msg, QDateTime datetime /*= QDateTime()*/)
    : ChatBaseItem()
    , datetime_(datetime)
    , text_(msg)
{
    icon_item_.setPixmap(icon);
    icon_item_.setY(kIconY);
    icon_item_.setParentItem(this);
}

SelfMsgItem::~SelfMsgItem()
{
}

int SelfMsgItem::Resize(int width)
{
    port_width_ = width;
    //每行最大可容納文字的寬度
    int row_width = width - kMarginLeft - kMargins.left() - kMargins.right() - kIconWidth - kIconMargins.left() - kIconMargins.right();

    //計算文字總共需要多寬
    QFont font("Microsoft YaHei");
    font.setPixelSize(kMsgFontSize);
    QFontMetrics font_matrics(font);
    int text_total_width = font_matrics.width(text_);
    int text_row_height = font_matrics.lineSpacing();

    if (row_width < text_total_width)
    {
        int row = text_total_width / row_width;

        int text_total_height = (row+1)* text_row_height;   //row從零開始，需要補加1

        text_size_.setWidth(row_width);
        text_size_.setHeight(text_total_height);
    }
    else
    {
        text_size_.setWidth(text_total_width);
        text_size_.setHeight(text_row_height);
    }
    return text_size_.height() + kMargins.top() + kMargins.bottom() + kBorderY;
}

void SelfMsgItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    QSize rnd(17, 17);
    //氣泡聊天框左端點需要根據控件寬度計算
    QRectF border(port_width_- kIconMargins.left()-kIconMargins.right()-kIconWidth-text_size_.width()-kMargins.left()-kMargins.right()
        , kBorderY
        , text_size_.width() + kMargins.left() + kMargins.right()
        , text_size_.height() + kMargins.top() + kMargins.bottom());
    icon_item_.setX(border.x()+ border.width() + 10);

    //氣泡
    painter->setBrush(QBrush(QColor(149,182,57)));
    painter->setPen(Qt::NoPen);
    painter->drawRoundedRect(border.x(), border.y(), border.width(), border.height(), rnd.width(), rnd.height());

    //三角，用矩形實現
    QRect rect1(border.x() + border.width() - 20, border.y(), 20, 20);
    painter->setPen(Qt::NoPen);
    painter->setBrush(QBrush(QColor(149, 182, 57)));
    painter->drawRect(rect1);

    QPen penText;
    penText.setColor(QColor(255, 255, 255));
    painter->setPen(penText);
    QTextOption option1(Qt::AlignLeft);
    option1.setWrapMode(QTextOption::WrapAtWordBoundaryOrAnywhere);
    QFont font("Microsoft YaHei");
    font.setPixelSize(kMsgFontSize);
    painter->setFont(font);

    QRectF text_rect(border.x()+kMargins.left(), border.y() + kMargins.top(), text_size_.width(), text_size_.height());
    painter->drawText(text_rect, text_, option1);
}

QRectF SelfMsgItem::boundingRect() const
{
    QRectF border(port_width_ - kIconMargins.left() - kIconMargins.right() - kIconWidth - text_size_.width() - kMargins.left() - kMargins.right()
        , kBorderY
        , text_size_.width() + kMargins.left() + kMargins.right()
        , text_size_.height() + kMargins.top() + kMargins.bottom());
    return QRectF(0, 0, border.width(), border.height());
}

接下是view調用

#pragma once

#include <QGraphicsView>
#include <QDateTime>
#include <QMap>

class ChatBaseItem;
class ChatView : public QGraphicsView
{
    Q_OBJECT

public:
    ChatView(QWidget *parent);
    ~ChatView();

    void Resize(int width);

    void ClearAll();
    void AppendSelfMessage(QPixmap icon, QString msg, QDateTime datetime);
    void AppendOtherMessage(QPixmap icon,QString name, QString msg, QDateTime datetime);
protected:
    virtual void mousePressEvent(QMouseEvent *e);

private:
    void CheckTime(QDateTime datetime);               //檢查是否需要插入時間，傳入值為當前消息時間
    void AppendTime(QDateTime datetime, QString time);
    QMap<QDateTime, ChatBaseItem*> items_;
};

#include <QDebug>
#include <QTextEdit>
#include <QScrollBar>
#include <QGraphicsScene>
#include "chatview.h"
#include "chatbaseitem.h"
#include "selfmsgitem.h"
#include "othermsgitem.h"
#include "chattimeitem.h"
#include "src/vapplication.h"

const int kMarkRole = Qt::UserRole;
const int kRoleOtherMsg = kMarkRole + 1;
const int kRoleSelfMsg = kRoleOtherMsg + 1;
const int kRoleTime = kRoleSelfMsg + 1;

ChatView::ChatView(QWidget *parent)
    : QGraphicsView(parent)
{
    setScene(new QGraphicsScene());
    this->setAlignment(Qt::AlignLeft | Qt::AlignTop);

    setStyleSheet("background: rgb(245,245,245) ;border:0px");
    this->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    this->verticalScrollBar()->setStyleSheet(theStyleSheet["scrollbar"]);
}

ChatView::~ChatView()
{
    ClearAll();
}

void ChatView::Resize(int width)
{
    int height = 20;
    for (ChatBaseItem* item : items_)
    {
        item->setPos(0, height);
        height = height + item->Resize(width);
        height += 20;
    }

    this->scene()->setSceneRect(QRectF(0, 0, width, height));
}

void ChatView::ClearAll()
{
    for (auto it = items_.begin(); it != items_.end();)
    {
        ChatBaseItem* item = it.value();
        it = items_.erase(it);
        delete item;
    }
}

void ChatView::AppendSelfMessage(QPixmap icon, QString msg, QDateTime datetime)
{
    ChatBaseItem* item = new SelfMsgItem(icon, msg, datetime);
    item->setData(kMarkRole,kRoleSelfMsg);
    CheckTime(datetime);
    scene()->addItem(item);
    items_.insert(datetime, item);

    Resize(this->viewport()->width());
    update();

    //滾動到底部
    QScrollBar *vScrollBar = verticalScrollBar();
    vScrollBar->setValue(vScrollBar->maximum());
}

void ChatView::AppendOtherMessage(QPixmap icon, QString name, QString msg, QDateTime datetime)
{
    ChatBaseItem* item = new OtherMsgItem(icon, name, msg, datetime);
    item->setData(kMarkRole, kRoleOtherMsg);
    CheckTime(datetime);
    scene()->addItem(item);
    items_.insert(datetime, item);

    Resize(this->viewport()->width());
    update();
    QScrollBar *vScrollBar = verticalScrollBar();
    vScrollBar->setValue(vScrollBar->maximum());
}

void ChatView::mousePressEvent(QMouseEvent *e)
{
    //截獲鼠標點擊事件
}

void ChatView::CheckTime(QDateTime datetime)
{
    if (items_.size() == 0|| datetime.secsTo(items_.lastKey())>60 * 5/*5分鍾*/)
    {
        //第一條消息前插入時間
        QDateTime dt = datetime.addMSecs(-1);
        AppendTime(dt,dt.toString("hh:mm:ss"));
    }
}

void ChatView::AppendTime(QDateTime datetime, QString time)
{
    ChatBaseItem* item = new ChatTimeItem(time);
    item->setData(kMarkRole, kRoleTime);
    scene()->addItem(item);
    items_.insert(datetime, item);

    Resize(this->viewport()->width());
    update();
}

在子類化Item時，一定要注意重寫virtual QRectF boundingRect() const;方法，返回實際item的尺寸，讓scene知道，並且要加入const，不然當消息左上角超出窗口范圍時，會出現無法觸發paint的問題。