Qt 5.8.0 下实现触摸屏热插拔功能的探索与实践（3）

以下是基于提供的 QLinuxFbIntegration 源码，完整添加触摸屏热插拔逻辑的最终版本（仅增量修改，保留原有所有逻辑，核心实现定时检测设备节点、清理旧驱动、重建输入处理器）：

第一步：修改头文件（qlinuxfbintegration.h）

先补充热插拔所需的成员声明（需添加到 QLinuxFbIntegration 类定义中）：

cpp 复制代码

// 在 qlinuxfbintegration.h 的 QLinuxFbIntegration 类中添加以下内容
#include <QTimer>
#include <QMutex>
#include <QFile>

class QLinuxFbIntegration : public QPlatformIntegration
{
    Q_OBJECT  // 必须添加，支持信号槽和定时器
private:
    // 原有成员保留...
    QScopedPointer<QPlatformNativeInterface> m_nativeInterface;
    QScopedPointer<QFbVtHandler> m_vtHandler;
    QLinuxFbScreen *m_primaryScreen = nullptr;
    QScopedPointer<QPlatformFontDatabase> m_fontDb;
    QScopedPointer<QPlatformServices> m_services;
    QPlatformInputContext *m_inputContext = nullptr;

    // ========== 新增热插拔核心成员 ==========
    QTimer *m_touchMonitorTimer = nullptr;  // 触摸屏检测定时器
    QMutex m_inputHandlerMutex;             // 输入处理器清理锁
    QString m_touchDeviceNode;              // 触摸屏设备节点（如/dev/input/event0）
    bool m_lastTouchDeviceExist = false;    // 上一次设备状态

    // 清理旧的输入处理器（核心：避免内存泄漏和重复驱动）
    void cleanupInputHandlers();

private slots:
    // 定时检测触摸屏设备状态
    void checkTouchDeviceStatus();

public:
    // 原有构造/析构/成员函数保留...
    QLinuxFbIntegration(const QStringList &paramList);
    ~QLinuxFbIntegration() override;
    void initialize() override;

    // 新增：手动触发输入设备重初始化（供检测逻辑/应用层调用）
    void recreateInputHandlers();

    // 新增：设置触摸屏设备节点（可从环境变量/应用层配置）
    void setTouchDeviceNode(const QString &node) { m_touchDeviceNode = node; }
};

第二步：修改实现文件（qlinuxfbintegration.cpp）

完整替换原有实现，添加热插拔逻辑（核心修改处已标注）：

cpp

运行

cpp 复制代码

/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the plugins of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qlinuxfbintegration.h"
#include "qlinuxfbscreen.h"

#include <QtFontDatabaseSupport/private/qgenericunixfontdatabase_p.h>
#include <QtServiceSupport/private/qgenericunixservices_p.h>
#include <QtEventDispatcherSupport/private/qgenericunixeventdispatcher_p.h>

#include <QtFbSupport/private/qfbvthandler_p.h>
#include <QtFbSupport/private/qfbbackingstore_p.h>
#include <QtFbSupport/private/qfbwindow_p.h>
#include <QtFbSupport/private/qfbcursor_p.h>

#include <QtGui/private/qguiapplication_p.h>
#include <qpa/qplatforminputcontextfactory_p.h>

#if QT_CONFIG(libinput)
#include <QtInputSupport/private/qlibinputhandler_p.h>
#endif

#if QT_CONFIG(evdev) && !defined(Q_OS_ANDROID)
#include <QtInputSupport/private/qevdevmousemanager_p.h>
#include <QtInputSupport/private/qevdevkeyboardmanager_p.h>
#include <QtInputSupport/private/qevdevtouchmanager_p.h>
#endif

#if QT_CONFIG(tslib) && !defined(Q_OS_ANDROID)
#include <QtInputSupport/private/qtslib_p.h>
#endif

// ========== 新增头文件 ==========
#include <QTimer>
#include <QMutex>
#include <QFile>
#include <QDebug>

QT_BEGIN_NAMESPACE

QLinuxFbIntegration::QLinuxFbIntegration(const QStringList &paramList)
    : m_fontDb(new QGenericUnixFontDatabase),
      m_services(new QGenericUnixServices)
{
    m_primaryScreen = new QLinuxFbScreen(paramList);
    
    // ========== 初始化触摸屏设备节点（优先从环境变量读取） ==========
    m_touchDeviceNode = qgetenv("QT_QPA_EVDEV_TOUCHSCREEN_DEVICE");
    if (m_touchDeviceNode.isEmpty())
        m_touchDeviceNode = "/dev/input/event0"; // 默认节点
}

QLinuxFbIntegration::~QLinuxFbIntegration()
{
    // ========== 新增：停止定时器并清理 ==========
    if (m_touchMonitorTimer) {
        m_touchMonitorTimer->stop();
        m_touchMonitorTimer->deleteLater();
    }
    
    destroyScreen(m_primaryScreen);
}

void QLinuxFbIntegration::initialize()
{
    if (m_primaryScreen->initialize())
        screenAdded(m_primaryScreen);
    else
        qWarning("linuxfb: Failed to initialize screen");

    m_inputContext = QPlatformInputContextFactory::create();

    m_nativeInterface.reset(new QPlatformNativeInterface);

    m_vtHandler.reset(new QFbVtHandler);

    if (!qEnvironmentVariableIntValue("QT_QPA_FB_DISABLE_INPUT"))
        createInputHandlers();

    // ========== 新增：启动触摸屏热插拔检测 ==========
    if (!m_touchDeviceNode.isEmpty() && !qEnvironmentVariableIntValue("QT_QPA_FB_DISABLE_INPUT")) {
        m_touchMonitorTimer = new QTimer(this);
        m_touchMonitorTimer->setInterval(3000); // 3秒检测一次（可配置）
        connect(m_touchMonitorTimer, &QTimer::timeout, this, &QLinuxFbIntegration::checkTouchDeviceStatus);
        m_touchMonitorTimer->start();
        
        // 初始化设备状态
        m_lastTouchDeviceExist = QFile::exists(m_touchDeviceNode);
        qInfo("linuxfb: Touch monitor started for device: %s", qPrintable(m_touchDeviceNode));
    }
}

bool QLinuxFbIntegration::hasCapability(QPlatformIntegration::Capability cap) const
{
    switch (cap) {
    case ThreadedPixmaps: return true;
    case WindowManagement: return false;
    default: return QPlatformIntegration::hasCapability(cap);
    }
}

QPlatformBackingStore *QLinuxFbIntegration::createPlatformBackingStore(QWindow *window) const
{
    return new QFbBackingStore(window);
}

QPlatformWindow *QLinuxFbIntegration::createPlatformWindow(QWindow *window) const
{
    return new QFbWindow(window);
}

QAbstractEventDispatcher *QLinuxFbIntegration::createEventDispatcher() const
{
    return createUnixEventDispatcher();
}

QList<QPlatformScreen *> QLinuxFbIntegration::screens() const
{
    QList<QPlatformScreen *> list;
    list.append(m_primaryScreen);
    return list;
}

QPlatformFontDatabase *QLinuxFbIntegration::fontDatabase() const
{
    return m_fontDb.data();
}

QPlatformServices *QLinuxFbIntegration::services() const
{
    return m_services.data();
}

void QLinuxFbIntegration::createInputHandlers()
{
#if QT_CONFIG(libinput)
    if (!qEnvironmentVariableIntValue("QT_QPA_FB_NO_LIBINPUT")) {
        new QLibInputHandler(QLatin1String("libinput"), QString());
        return;
    }
#endif

    bool useTslib = false;
#if QT_CONFIG(tslib)
    useTslib = qEnvironmentVariableIntValue("QT_QPA_FB_TSLIB");
    if (useTslib)
        new QTsLibMouseHandler(QLatin1String("TsLib"), QString());
#endif

#if QT_CONFIG(evdev) && !defined(Q_OS_ANDROID)
    new QEvdevKeyboardManager(QLatin1String("EvdevKeyboard"), QString(), this);
    new QEvdevMouseManager(QLatin1String("EvdevMouse"), QString(), this);
    if (!useTslib) {
        // ========== 优化：从环境变量读取触摸参数（如旋转/反转） ==========
        QString touchSpec = qgetenv("QT_QPA_EVDEV_TOUCHSCREEN_PARAMS");
        new QEvdevTouchManager(QLatin1String("EvdevTouch"), touchSpec, this);
        qInfo("linuxfb: EvdevTouchManager created with spec: %s", qPrintable(touchSpec));
    }
#endif
}

// ========== 新增：清理旧的输入处理器（核心） ==========
void QLinuxFbIntegration::cleanupInputHandlers()
{
    QMutexLocker locker(&m_inputHandlerMutex);

#if QT_CONFIG(libinput)
    // 清理 libinput 处理器
    QList<QLibInputHandler*> libinputHandlers = findChildren<QLibInputHandler*>();
    for (auto *handler : libinputHandlers) {
        handler->deleteLater();
        qDebug("linuxfb: Cleaned up QLibInputHandler");
    }
#endif

#if QT_CONFIG(tslib) && !defined(Q_OS_ANDROID)
    // 清理 tslib 处理器
    QList<QTsLibMouseHandler*> tslibHandlers = findChildren<QTsLibMouseHandler*>();
    for (auto *handler : tslibHandlers) {
        handler->deleteLater();
        qDebug("linuxfb: Cleaned up QTsLibMouseHandler");
    }
#endif

#if QT_CONFIG(evdev) && !defined(Q_OS_ANDROID)
    // 清理 evdev 键盘/鼠标/触摸处理器
    QList<QEvdevKeyboardManager*> keyboardMgrs = findChildren<QEvdevKeyboardManager*>();
    for (auto *mgr : keyboardMgrs) {
        mgr->deleteLater();
        qDebug("linuxfb: Cleaned up QEvdevKeyboardManager");
    }

    QList<QEvdevMouseManager*> mouseMgrs = findChildren<QEvdevMouseManager*>();
    for (auto *mgr : mouseMgrs) {
        mgr->deleteLater();
        qDebug("linuxfb: Cleaned up QEvdevMouseManager");
    }

    QList<QEvdevTouchManager*> touchMgrs = findChildren<QEvdevTouchManager*>();
    for (auto *mgr : touchMgrs) {
        mgr->deleteLater();
        qDebug("linuxfb: Cleaned up QEvdevTouchManager");
    }
#endif
}

// ========== 新增：重新初始化输入设备 ==========
void QLinuxFbIntegration::recreateInputHandlers()
{
    QMutexLocker locker(&m_inputHandlerMutex);

    // 1. 先清理旧处理器（避免重复驱动）
    cleanupInputHandlers();
    
    // 2. 延迟重建（确保旧驱动完全销毁）
    QTimer::singleShot(100, this, &QLinuxFbIntegration::createInputHandlers);
    
    qInfo("linuxfb: Recreated input handlers for touch device");
}

// ========== 新增：检测触摸屏设备状态 ==========
void QLinuxFbIntegration::checkTouchDeviceStatus()
{
    if (m_touchDeviceNode.isEmpty())
        return;

    // 1. 检测当前设备节点是否存在（Linux下拔出会删除该文件）
    bool currentExist = QFile::exists(m_touchDeviceNode);

    // 2. 设备从离线→在线：触发重连
    if (!m_lastTouchDeviceExist && currentExist) {
        qWarning("linuxfb: Touch device reconnected: %s", qPrintable(m_touchDeviceNode));
        recreateInputHandlers();
    }

    // 3. 设备从在线→离线：仅日志提示
    if (m_lastTouchDeviceExist && !currentExist) {
        qWarning("linuxfb: Touch device disconnected: %s", qPrintable(m_touchDeviceNode));
    }

    // 4. 更新状态
    m_lastTouchDeviceExist = currentExist;
}

QPlatformNativeInterface *QLinuxFbIntegration::nativeInterface() const
{
    return m_nativeInterface.data();
}

QT_END_NAMESPACE

核心实现说明

新增功能	实现逻辑
设备节点检测	通过 `QFile::exists(m_touchDeviceNode)` 检测 `/dev/input/eventX` 是否存在（Linux 下设备拔出会删除该文件）
定时检测	3 秒一次触发 `checkTouchDeviceStatus()`，低开销且能及时感知设备插拔
旧驱动清理	`cleanupInputHandlers()` 遍历并销毁所有输入处理器（键盘 / 鼠标 / 触摸），避免内存泄漏和重复驱动冲突
驱动重建	设备插入时调用 `recreateInputHandlers()` → 先清理旧驱动 → 重新调用 `createInputHandlers()` 初始化新驱动
参数配置	从环境变量 `QT_QPA_EVDEV_TOUCHSCREEN_PARAMS` 读取触摸参数（如 `rotate=90:invertx`），灵活适配不同硬件

第三步：编译与运行配置

1. 编译 QtInputSupport 模块（若修改了 Qt 源码）

bash 复制代码

cd /qt-everywhere-opensource-src-5.8.0/qtbase/src/plugins/platforms/linuxfb
qmake
make -j4
sudo make install

2. 应用启动配置（关键）

启动应用时指定触摸屏设备节点和参数：

bash 复制代码

# 指定触摸屏设备节点（根据实际硬件调整）
export QT_QPA_EVDEV_TOUCHSCREEN_DEVICE=/dev/input/event0
# 可选：触摸屏参数（旋转90度、反转X轴）
export QT_QPA_EVDEV_TOUCHSCREEN_PARAMS="rotate=90:invertx"
# 禁用libinput（确保使用evdev驱动）
export QT_QPA_FB_NO_LIBINPUT=1
# 启动应用（指定linuxfb平台）
./your_app -platform linuxfb

第四步：验证热插拔效果

启动应用 ：日志会打印 linuxfb: Touch monitor started for device: /dev/input/event0；
拔出触摸屏 ：日志打印 linuxfb: Touch device disconnected: /dev/input/event0；
插入触摸屏 ：日志打印 linuxfb: Touch device reconnected: /dev/input/event0 → Cleaned up QEvdevTouchManager → EvdevTouchManager created；
操作触摸屏：应用能正常响应触控事件（点击、滑动）。

关键优化点

线程安全 ：通过 QMutex 保护驱动的创建 / 销毁，避免多线程竞争；
延迟重建 ：QTimer::singleShot(100) 确保旧驱动完全销毁后再重建，避免冲突；
环境变量适配：设备节点和触摸参数通过环境变量配置，无需修改代码即可适配不同硬件；
低开销检测：3 秒一次的定时器检测，对系统资源占用可忽略不计；
兼容原有逻辑：完全保留 libinput/tslib/evdev 的原有优先级，仅增量添加热插拔逻辑。

该修改方案是 Qt 5.8.0 下实现触摸屏热插拔的最优解，无需重新编译整个 Qt，仅修改 linuxfb 平台集成代码即可，且完全兼容原有输入驱动逻辑。