qt实现窗口背景透明

方法一：

    MainWindow w;
    //方法一：主界面透明，界面里面的控件不透明
    w.setWindowFlags(Qt::FramelessWindowHint);//设置无窗口框架边界
    w.setAttribute(Qt::WA_TranslucentBackground);//设置背景透明
    w.show();

编辑界面：

运行效果：

 方法二：

w.setWindowOpacity(0.5);//直接设置整个窗口（包含里面的控件）0完全透明，1不透明

运行效果是整个界面包括里面的控件都是透明度50%：

 注意：

如果用方法一的话，一定要设置成无边框模式，否则界面会显示黑色，如下图：

 具体代码如下： main.cpp：

#include "mainwindow.h"

#include <QApplication>

#include <QLabel>

#include <QDesktopWidget>

int main(int argc, char *argv[])

{

    QApplication a(argc, argv);

    MainWindow w;

    //方法一：主界面透明，界面里面的控件不透明

    w.setWindowFlags(Qt::FramelessWindowHint);//设置无窗口框架边界

    w.setAttribute(Qt::WA_TranslucentBackground);//设置背景透明

    //方法二：

//    w.setWindowOpacity(0.5);//直接设置整个窗口（包含里面的控件）0完全透明，1不透明

    //方法三：

    //w.setStyleSheet("background-color:transparent;");//主界面背景变黑

    w.show();

    return a.exec();

}

mainwindow.h：

#ifndef MAINWINDOW_H

#define MAINWINDOW_H

#include <QMainWindow>

QT_BEGIN_NAMESPACE

namespace Ui { class MainWindow; }

QT_END_NAMESPACE

class MainWindow : public QMainWindow

{

    Q_OBJECT

public:

    MainWindow(QWidget *parent = nullptr);

    ~MainWindow();

private:

    Ui::MainWindow *ui;

};

#endif // MAINWINDOW_H

mainwindow.cpp：

#include "mainwindow.h"

#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)

    : QMainWindow(parent)

    , ui(new Ui::MainWindow)

{

    ui->setupUi(this);

}

MainWindow::~MainWindow()

{

    delete ui;

}

mainwindow.ui:

<?xml version="1.0" encoding="UTF-8"?>

<ui version="4.0">

 <class>MainWindow</class>

 <widget class="QMainWindow" name="MainWindow">

  <property name="geometry">

   <rect>

    <x>0</x>

    <y>0</y>

    <width>800</width>

    <height>600</height>

   </rect>

  </property>

  <property name="windowTitle">

   <string>MainWindow</string>

  </property>

  <widget class="QWidget" name="centralwidget">

   <widget class="QLabel" name="label">

    <property name="geometry">

     <rect>

      <x>10</x>

      <y>20</y>

      <width>261</width>

      <height>211</height>

     </rect>

    </property>

    <property name="styleSheet">

     <string notr="true">background:rgb(0, 255, 0)</string>

    </property>

    <property name="text">

     <string>TextLabel</string>

    </property>

   </widget>

  </widget>

  <widget class="QMenuBar" name="menubar">

   <property name="geometry">

    <rect>

     <x>0</x>

     <y>0</y>

     <width>800</width>

     <height>26</height>

    </rect>

   </property>

  </widget>

  <widget class="QStatusBar" name="statusbar"/>

 </widget>

 <resources/>

 <connections/>

</ui>

工程的.pro文件：

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++11

# The following define makes your compiler emit warnings if you use

# any Qt feature that has been marked deprecated (the exact warnings

# depend on your compiler). Please consult the documentation of the

# deprecated API in order to know how to port your code away from it.

DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if it uses deprecated APIs.

# In order to do so, uncomment the following line.

# You can also select to disable deprecated APIs only up to a certain version of Qt.

#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \

    main.cpp \

    mainwindow.cpp

HEADERS += \

    mainwindow.h

FORMS += \

    mainwindow.ui

# Default rules for deployment.

qnx: target.path = /tmp/$${TARGET}/bin

else: unix:!android: target.path = /opt/$${TARGET}/bin

!isEmpty(target.path): INSTALLS += target