Qt on Android 开发之 C++与Java 交互

原创

wx635f8a025188b 2022-10-31 18:23:22 博主文章分类：//Qt || QML ©著作权

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简述

我做了一个小例子，来实现了 C++与Java之间的交互。
该示例是以整形和字符型举例说明，用QAndroidJniObject类的callStaticMethod方法进行与Java交互

Qt引入Android模块

首先要在Pro中加入Android开发模块

QT       += androidextras

Java示例

可以先看一下我写的java简单案例（为了方便演示都做成静态了）：

package com.demo.cppandjava;

public class democppandjava
{
    private static int tmpNum = 1;
    private static String tmpStr = "123";

    public static void setInt(int num) {
        tmpNum = num;
    }
    public static int getInt() {
        return tmpNum;
    }
    public static void setString(String str) {
        tmpStr = str;
    }
    public static String getString() {
        return tmpStr;
    }
}

Cpp与java交互

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_pbSet_clicked();
    void on_pbGetInt_clicked();
    void on_pbGetStr_clicked();

private:
    Ui::MainWindow *ui;

private:
    //Cpp与java交互
    void cppAssignmentJavaInt(int num);
    int cppUseJavaToInt();
    void cppAssignmentJavaString(QString str);
    QString cppUseJavaToString();
};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QAndroidJniObject>
#include <QAndroidJniEnvironment>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::cppAssignmentJavaInt(int num)
{
#ifdef Q_OS_ANDROID
    QAndroidJniObject::callStaticMethod<void>(
                "com/demo/cppandjava/democppandjava",
                "setInt",
                "(I)V",
                num);
#endif
}

int MainWindow::cppUseJavaToInt()
{
#ifdef Q_OS_ANDROID
    return QAndroidJniObject::callStaticMethod<jint>("com/demo/cppandjava/democppandjava", "getInt");
#endif
}

void MainWindow::cppAssignmentJavaString(QString str)
{
#ifdef Q_OS_ANDROID
    QAndroidJniObject strTMP = QAndroidJniObject::fromString(str);
    QAndroidJniObject::callStaticMethod<void>(
                "com/demo/cppandjava/democppandjava",
                "setString",
                "(Ljava/lang/String;)V",
                strTMP.object<jstring>());
#endif
}

QString MainWindow::cppUseJavaToString()
{
#ifdef Q_OS_ANDROID
    QAndroidJniObject str = QAndroidJniObject::callStaticObjectMethod("com/demo/cppandjava/democppandjava",
                                                     "getString",
                                                     "()Ljava/lang/String;");
    return str.toString();
#endif
}

void MainWindow::on_pbSet_clicked()
{
    int num = ui->spinBox->text().toInt();
    QString str = ui->lineEdit->text();
    cppAssignmentJavaInt(num);
    cppAssignmentJavaString(str);
}

void MainWindow::on_pbGetInt_clicked()
{
    ui->lText->setText(QString::number(cppUseJavaToInt()));
}

void MainWindow::on_pbGetStr_clicked()
{
    ui->lText->setText(cppUseJavaToString());
}