Qt 调用 java代码

方法一

1，java类

//MyJavaClass.java
public class MyJavaClass
{
    public static int mystatic(int n)             //静态函数；
    {
       return n+1;
    }
    public int getNum()                            //没有参数；
    {
        return 12345678;
    }
    public int setNum( int n )                     //有参调用
    {
        return n;
    }

    public String getStr(String perfix)                        //返回对象
    {
        String teststr = new String("hello " + perfix);
        return teststr;
    }

    boolean boolTest()                              //返回bool类型
    {
        return true;
    }

}

2，C++ 控制类

#ifndef TESTCLASS
#define TESTCLASS
#include 
#include 
#include 
#include 
#include 
#include 
#include 

class JavaHandler:public QObject
{
    Q_OBJECT
public:
    explicit JavaHandler(QObject *parent=0);

public:

   Q_INVOKABLE QString mystatic(int num);   //静态方法

   Q_INVOKABLE QString getNum(); // 无参

   Q_INVOKABLE QString setNum(int num); //有参

   Q_INVOKABLE QString getStr(QString perfix);  //参数和返回值都是对象

    Q_INVOKABLE QString boolTest();     //返回值为bool

private:
    jobject m_TestObject;       //java对象
};

#endif

#include "testclass.h"
#include 
#include 
#include 


static JavaVM* g_javaVM = 0;            //虚拟机指针

static jclass g_testClassID   = 0;          //类ID
static jmethodID g_mystaticID = 0;        //静态方法
static jmethodID g_getNumID = 0;          //无参方法
static jmethodID g_setNumID = 0;          //有参方法
static jmethodID g_getStrID = 0;          //参数和返回值为类对象
static jmethodID g_boolTestID = 0;        //返回值为bool型
static jmethodID g_constMethodID = 0;   //构造函数ID



JavaHandler::JavaHandler(QObject *parent)
{
    JNIEnv* env;
    if(g_javaVM->AttachCurrentThread(&env,NULL))
    {
            qCritical() << "AttachCurrentThread failed";
            return;
    }
    //[] new 一个对象
    m_TestObject = env->NewGlobalRef(env->NewObject(g_testClassID,g_constMethodID));
    if(!m_TestObject)
    {
        qCritical() << "Can not create the object";
        return;
    }
    g_javaVM->DetachCurrentThread();
}

QString JavaHandler::mystatic(int num)
{
    if(!m_TestObject)
        return QString("Error");

    JNIEnv* env;
    if(g_javaVM->AttachCurrentThread(&env,NULL) < 0)
    {
        return QString("Fail to Attach");
    }
    jint ret = env->CallStaticIntMethod(g_testClassID,g_mystaticID,num);

    g_javaVM->DetachCurrentThread();

    return QString::number(ret,10);

}

QString JavaHandler::getNum()
{
     if(!m_TestObject)
        return QString("Error");

    JNIEnv* env;
    if(g_javaVM->AttachCurrentThread(&env,NULL) < 0)
    {
        return QString("Fail to Attach");
    }

    jint ret = env->CallIntMethod(m_TestObject,g_getNumID);

    g_javaVM->DetachCurrentThread();

    return QString::number(ret,10);
}

QString JavaHandler::setNum(int num)
{
     if(!m_TestObject)
        return QString("Error");

    JNIEnv* env;
    if(g_javaVM->AttachCurrentThread(&env,NULL) < 0)
    {
        return QString("Fail to Attach");
    }

    jint ret = env->CallIntMethod(m_TestObject,g_setNumID,num);

    g_javaVM->DetachCurrentThread();

    return QString::number(ret,10);

}

QString JavaHandler::getStr(QString perfix)
{

    if(!m_TestObject)
        return QString("Error");

    JNIEnv* env;
    if(g_javaVM->AttachCurrentThread(&env,NULL) < 0)
    {
        return QString("Fail to Attach");
    }

    jstring str = env->NewString(reinterpret_cast(perfix.constData()),perfix.length());

    jobject retstr = env->CallObjectMethod(m_TestObject,g_getStrID,str);

    jstring jstrtemp = (jstring)retstr;


    qDebug() << "Can run here 3";
   const char *pstr= env->GetStringUTFChars(jstrtemp, 0);

    QString rstr(pstr);


    g_javaVM->DetachCurrentThread();

    return rstr;

    //return QString("Unknow");
}

QString JavaHandler::boolTest()
{
     if(!m_TestObject)
        return QString("Error");

    JNIEnv* env;
    if(g_javaVM->AttachCurrentThread(&env,NULL) < 0)
    {
        return QString("Fail to Attach");
    }

    jboolean ret = env->CallBooleanMethod(m_TestObject,g_boolTestID);

    g_javaVM->DetachCurrentThread();

    return (ret?"ture":"false");
}



JNIEXPORT jint JNI_OnLoad(JavaVM *vm,void *)
{
    JNIEnv *env;
    //[1] 指定JNI 版本，利用VM获得 env指针
    if(vm->GetEnv(reinterpret_cast(&env),JNI_VERSION_1_6) != JNI_OK)
    {
        qCritical() << "Can't get the enviroument";
        return -1;
    }
    //保存获得指针以便在任意上下文中使用
    g_javaVM = vm;

    //[2] 获取类ID
    jclass clazz = env->FindClass("com/MyJavaClass");
    if(!clazz)
    {
        qCritical() << "Can't find class MyJavaClass";
        return -1;
    }
    //方便调用静态方法
    g_testClassID = (jclass)env->NewGlobalRef(clazz);

     // search for its contructor

    g_constMethodID = env->GetMethodID(g_testClassID, "", "()V");
    if (!g_constMethodID)
    {
        qCritical()<<"Can't find QSimpleAudioPlayer class contructor";
        return -1;
    }

    g_mystaticID = env->GetStaticMethodID(g_testClassID,"mystatic","(I)I");
    if(!g_mystaticID)
    {
        qCritical() << "Can't find static method "<< endl;
        return -1;
    }


    g_getNumID = env->GetMethodID(g_testClassID,"getNum","()I");
    if(!g_getNumID)
    {
        qCritical() << "Can't find getNum method "<< endl;
        return -1;
    }

    g_boolTestID = env->GetMethodID(g_testClassID,"boolTest","()Z");
    if(!g_boolTestID)
    {
        qCritical() << "Can't find booltest method "<< endl;
        return -1;
    }

    g_setNumID = env->GetMethodID(g_testClassID,"setNum","(I)I");
    if(!g_setNumID)
    {
        qCritical() << "Can't find setNUM method "<< endl;
        return -1;
    }

    g_getStrID = env->GetMethodID(g_testClassID,"getStr", "(Ljava/lang/String;)Ljava/lang/String;");
    if(!g_getStrID)
    {
        qCritical() << "Can't find GetStr Method "<< endl;
        return -1;
    }

    qDebug() << "JNI Load Success !";
    return JNI_VERSION_1_6;
}

3，界面QML

import QtQuick 2.4
import QtQuick.Controls 1.3
import QtQuick.Window 2.2
import QtQuick.Dialogs 1.2
import java.handler 1.0

ApplicationWindow {
    title: qsTr("Hello World")
    width: 640
    height: 480
    visible: true

    menuBar: MenuBar {
        Menu {
            title: qsTr("&File")
            MenuItem {
                text: qsTr("&Open")
                onTriggered: messageDialog.show(qsTr("Open action triggered"));
            }
            MenuItem {
                text: qsTr("E&xit")
                onTriggered: Qt.quit();
            }
        }
    }

    MainForm {
        anchors.fill: parent
        button1.onClicked: messageDialog.show(javahelper.mystatic(10085))
        button2.onClicked: messageDialog.show(javahelper.setNum(1008611))
        button3.onClicked: messageDialog.show(javahelper.getNum());
        button4.onClicked: messageDialog.show(javahelper.boolTest());
        button5.onClicked: messageDialog.show(javahelper.getStr("world"));
    }

    MessageDialog {
        id: messageDialog
        title: qsTr("May I have your attention, please?")

        function show(caption) {
            messageDialog.text = caption;
            messageDialog.open();
        }
    }

    JavaHandler{
        id:javahelper

    }
}

4,main函数

#include 
#include 
#include 
#include 

#include "testclass.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

     qmlRegisterType("java.handler",1,0,"JavaHandler");

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

---

方法二

利用QAndroidJniObject::callStaticMethod的方式。

https://www.2cto.com/kf/201503/379581.html

 

---

如windows下无法使用真机调试，则参考：

1，adb  配置 

https://jingyan.baidu.com/article/22fe7cedf67e353002617f25.html

2，找不到设备

https://www.cnblogs.com/sanshuimiao/p/7809946.html

---

相关书籍

<>

链接：http://pan.baidu.com/s/1pL4Yoqf 密码：f5ix

 

---

 

参考：https://blog.csdn.net/lmhuanying1012/article/details/79666867

https://www.cnblogs.com/rophie/p/3931630.html

 

---