Qt on Android:使用JNI与第三方jar包

很多朋友在论坛和QQ群里问到这个，今天有时间写了个简单的示例。

    功能很简单，允许你输入一个web页面地址，使用Java的下载类库下载后用QTextEdit显示出来。

    版权所有：foruok。转载请注明出处：http://blog.csdn.net/foruok。

效果展示

    初始效果如图1所示：

                   图1 useJar示例初始效果

    图2为点击"GET"按钮后下载到对应页面的效果：

                   图2 下载页面成功

    下载部分，为了显示如何使用jar包，我用了asynchttpclient，参考我的博文：Android开源框架AsyncHttpClient (android-async-http)使用。

项目创建

    参考《Qt on Android：图文详解Hello World全过程》吧，没什么特别可说的。

    pro文件内添加“QT += androidextras”。

    创建一个AndroidManifest，package命名为an.qt.useJar。

    版权所有：foruok。转载请注明出处：http://blog.csdn.net/foruok。

添加Java源码

    你可以任意的文本编辑器中编辑java源码，然后通过Qt Creator项目视图加到项目里，在其它文件那里鼠标右键点击，选择添加现有文件即可。参考下面几张图吧。

                图3 添加Java源码之右键菜单

                       图4 添加Java源文件之选择Java源文件

                图5 添加Java源文件OK

    修改AndroidManifest，把activity标签的android:name属性值修改为an.qt.useJar.ExtendsQtWithJava。这是必须的，因为我们的ExtendsQtWithJava.java实现的Activity就是这个名字。

    好了，Java代码添加结束。

添加第三方jar包

    这个没什么好说的，放在android/libs目录下即可。看图：

              图6 放jar包

    只要放好位置，Qt Creator编译项目时就会把这个jar包打包到APK里。

Java源码使用jar包

    这是java编程的内容了，import包名，然后使用即可。

源码分析

    咱先看Java侧的代码吧。

Java代码

    ExtendsQtWithJava.java：

package an.qt.useJar;
import java.lang.String;
import android.content.Context;
import android.content.Intent;
import android.app.PendingIntent;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.location.Criteria;
import android.provider.Settings;
import android.os.Bundle;
import android.os.Environment;
import java.io.File;
import com.loopj.android.http.AsyncHttpClient;
import com.loopj.android.http.AsyncHttpResponseHandler;

public class ExtendsQtWithJava extends org.qtproject.qt5.android.bindings.QtActivity
{
    private static ExtendsQtWithJava m_instance;
    private final static String TAG = "extendsQt";
    private static String m_pageUri = null;
    private static Handler m_handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case  1:
                if(m_pageUri ==  null){
                    m_pageUri = (String)msg.obj;
                    m_instance.downloadText(m_pageUri);
                }else{
                    m_instance.notifyQt(0, (String)msg.obj, "Downloader is Busy now!");
                }
                break;
            };
        }
    };


    public ExtendsQtWithJava(){
        m_instance = this;
    }

    public static int networkState(){
        ConnectivityManager conMan = (ConnectivityManager) m_instance.getSystemService(Context.CONNECTIVITY_SERVICE);
        return conMan.getActiveNetworkInfo() == null ? 0 : 1;
    }

    public static AsyncHttpClient m_httpc = new AsyncHttpClient();
    public static ExtendsQtNative m_nativeNotify = null;

    public void downloadText(String uri){
        Log.d(TAG, "start downloadText");
        m_httpc.get(uri, null,  new AsyncHttpResponseHandler(){
            @Override
            public void onSuccess(String data){
                notifyQt(1, m_pageUri, data);
                m_pageUri = null;
            }
            @Override
            public  void onFailure(Throwable e, String data){
                notifyQt(-1, m_pageUri, data);
                m_pageUri = null;
            }
        });
    }

    public static void downloadWebPage(String uri){
        Log.d(TAG, "downloadWebPage");
        m_handler.sendMessage(m_handler.obtainMessage(1, uri));
    }

    private void notifyQt(int result, String uri, String data){
        if(m_nativeNotify ==  null){
            m_nativeNotify = new ExtendsQtNative();
        }
        m_nativeNotify.OnDownloaded(result, uri, data);
    }
}

package an.qt.useJar;
import java.lang.String;
import android.content.Context;
import android.content.Intent;
import android.app.PendingIntent;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.location.Criteria;
import android.provider.Settings;
import android.os.Bundle;
import android.os.Environment;
import java.io.File;
import com.loopj.android.http.AsyncHttpClient;
import com.loopj.android.http.AsyncHttpResponseHandler;

public class ExtendsQtWithJava extends org.qtproject.qt5.android.bindings.QtActivity
{
    private static ExtendsQtWithJava m_instance;
    private final static String TAG = "extendsQt";
    private static String m_pageUri = null;
    private static Handler m_handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case 1:
                if(m_pageUri == null){
                    m_pageUri = (String)msg.obj;
                    m_instance.downloadText(m_pageUri);
                }else{
                    m_instance.notifyQt(0, (String)msg.obj, "Downloader is Busy now!");
                }
                break;
            };
        }
    };
    

    public ExtendsQtWithJava(){
        m_instance = this;
    }

    public static int networkState(){
        ConnectivityManager conMan = (ConnectivityManager) m_instance.getSystemService(Context.CONNECTIVITY_SERVICE);
        return conMan.getActiveNetworkInfo() == null ? 0 : 1;
    }

    public static AsyncHttpClient m_httpc = new AsyncHttpClient();
    public static ExtendsQtNative m_nativeNotify = null;

    public void downloadText(String uri){
        Log.d(TAG, "start downloadText");
        m_httpc.get(uri, null, new AsyncHttpResponseHandler(){
            @Override
            public void onSuccess(String data){
                notifyQt(1, m_pageUri, data);
                m_pageUri = null;
            }
            @Override
            public void onFailure(Throwable e, String data){
                notifyQt(-1, m_pageUri, data);
                m_pageUri = null;
            }
        });
    }
    
    public static void downloadWebPage(String uri){
        Log.d(TAG, "downloadWebPage");
        m_handler.sendMessage(m_handler.obtainMessage(1, uri));
    }
    
    private void notifyQt(int result, String uri, String data){
        if(m_nativeNotify == null){
            m_nativeNotify = new ExtendsQtNative();
        }
        m_nativeNotify.OnDownloaded(result, uri, data);
    }
}

    ExtendsQtNative.java：

package an.qt.useJar;
import java.lang.String;

public class ExtendsQtNative
{
    public native void OnDownloaded(int result, String url, String content);
}

package an.qt.useJar;
import java.lang.String;

public class ExtendsQtNative
{
    public native void OnDownloaded(int result, String url, String content);
}

    基本思路是酱紫的：

    Qt调用java的downloadWebPage，Java代码使用asynchttpclient下载一个网页，然后调用ExtendsQtNative通知Qt C++代码。

C++代码

    分两部分，一部分是实现JNI方法。另一部分是调用Java类的方法。

实现JNI方法并注册

    先看与ExtendsQtNative对应的JNI实现，在main.cpp中，都列出吧：

#include "widget.h"
#include <QApplication>
#include <QAndroidJniEnvironment>
#include <QAndroidJniObject>
#include <jni.h>
#include "../simpleCustomEvent.h"
#include <QDebug>

QObject *g_listener = 0;

// result: -1 failed; 1 success; 0 busy;
static void onDownloaded(JNIEnv *env, jobject thiz,int result, jstring uri, jstring data)
{
    QString qstrData;
    const char *nativeString = env->GetStringUTFChars(data, 0);
    qstrData = nativeString;
    env->ReleaseStringUTFChars(data, nativeString);
    QCoreApplication::postEvent(g_listener, new SimpleCustomEvent(result, qstrData));
}

bool registerNativeMethods()
{
    JNINativeMethod methods[] {
        {"OnDownloaded", "(ILjava/lang/String;Ljava/lang/String;)V", (void*)onDownloaded}
    };

    const char *classname = "an/qt/useJar/ExtendsQtNative";
    jclass clazz;
    QAndroidJniEnvironment env;

    QAndroidJniObject javaClass(classname);
    clazz = env->GetObjectClass(javaClass.object<jobject>());
    qDebug() << "find ExtendsQtNative - " << clazz;
    bool result = false;
    if(clazz)
    {
        jint ret = env->RegisterNatives(clazz,
                                        methods,
                                         sizeof(methods) / sizeof(methods[0]));
        env->DeleteLocalRef(clazz);
        qDebug() << "RegisterNatives return - " << ret;
        result = ret >= 0;
    }
    if(env->ExceptionCheck()) env->ExceptionClear();
    return result;
}

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

    SimpleCustomEvent::eventType();
    registerNativeMethods();

    Widget w;
    g_listener = qobject_cast<QObject*>(&w);
    w.show();

    return a.exec();
}

#include "widget.h"
#include <QApplication>
#include <QAndroidJniEnvironment>
#include <QAndroidJniObject>
#include <jni.h>
#include "../simpleCustomEvent.h"
#include <QDebug>

QObject *g_listener = 0;

// result: -1 failed; 1 success; 0 busy;
static void onDownloaded(JNIEnv *env, jobject thiz,int result, jstring uri, jstring data)
{
    QString qstrData;
    const char *nativeString = env->GetStringUTFChars(data, 0);
    qstrData = nativeString;
    env->ReleaseStringUTFChars(data, nativeString);
    QCoreApplication::postEvent(g_listener, new SimpleCustomEvent(result, qstrData));
}

bool registerNativeMethods()
{
    JNINativeMethod methods[] {
        {"OnDownloaded", "(ILjava/lang/String;Ljava/lang/String;)V", (void*)onDownloaded}
    };

    const char *classname = "an/qt/useJar/ExtendsQtNative";
    jclass clazz;
    QAndroidJniEnvironment env;

    QAndroidJniObject javaClass(classname);
    clazz = env->GetObjectClass(javaClass.object<jobject>());
    qDebug() << "find ExtendsQtNative - " << clazz;
    bool result = false;
    if(clazz)
    {
        jint ret = env->RegisterNatives(clazz,
                                        methods,
                                        sizeof(methods) / sizeof(methods[0]));
        env->DeleteLocalRef(clazz);
        qDebug() << "RegisterNatives return - " << ret;
        result = ret >= 0;
    }
    if(env->ExceptionCheck()) env->ExceptionClear();
    return result;
}

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

    SimpleCustomEvent::eventType();
    registerNativeMethods();

    Widget w;
    g_listener = qobject_cast<QObject*>(&w);
    w.show();

    return a.exec();
}

    注册JNI方法，设置一个全局的对象接收通知。具体的，参考Qt帮助来理解。

调用Java方法

    对Java方法的调用在Widget.cpp中。直接看代码吧。

    widget.h：

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QLineEdit>
#include <QTextEdit>
#include <QLabel>

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = 0);
    ~Widget();

    bool event(QEvent *e);

public slots:
    void onGet();

private:
    QLineEdit * m_urlEdit;
    QTextEdit * m_resultView;
    QLabel * m_stateLabel;
};

#endif // WIDGET_H

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QLineEdit>
#include <QTextEdit>
#include <QLabel>

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = 0);
    ~Widget();

    bool event(QEvent *e);

public slots:
    void onGet();

private:
    QLineEdit * m_urlEdit;
    QTextEdit * m_resultView;
    QLabel * m_stateLabel;
};

#endif // WIDGET_H

    都是界面相关的，没什么好说的。看widget.cpp：

#include "widget.h"
#include <QVBoxLayout>
#include <QPushButton>
#include "../simpleCustomEvent.h"
#include <QAndroidJniObject>
#include <QAndroidJniEnvironment>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    QVBoxLayout *layout = new QVBoxLayout(this);
    QHBoxLayout *getLayout = new QHBoxLayout();
    layout->addLayout(getLayout);
    m_urlEdit = new QLineEdit("http://blog.csdn.net/foruok");
    getLayout->addWidget(m_urlEdit, 1);
    QPushButton *getButton = new QPushButton("GET");
    getLayout->addWidget(getButton);
    connect(getButton, SIGNAL(clicked()), this, SLOT(onGet()));

    m_resultView = new QTextEdit();
    m_resultView->setReadOnly(true);
    layout->addWidget(m_resultView, 1);
    m_stateLabel = new QLabel();
    layout->addWidget(m_stateLabel);
}

Widget::~Widget()
{

}

bool Widget::event(QEvent *e)
{
    if(e->type() == SimpleCustomEvent::eventType())
    {
        e->accept();
        SimpleCustomEvent *sce = (SimpleCustomEvent*)e;
        switch(sce->m_arg1)
        {
        case 1:
            m_resultView->setText(sce->m_arg2);
            m_stateLabel->setText("Success!");
            break;
        case 0:
            m_resultView->setText(sce->m_arg2);
            m_stateLabel->setText("Failed!");
            break;
        case -1:
            m_stateLabel->setText(sce->m_arg2);
            break;
        }
        return true;
    }
    return QWidget::event(e);
}

void Widget::onGet()
{
#ifdef WIN32
    m_resultView->setText("Sorry, Just for Android!");
#elif defined(ANDROID)
    QString url = m_urlEdit->text();
    QAndroidJniObject javaAction = QAndroidJniObject::fromString(url);
    QAndroidJniObject::callStaticMethod<void>("an/qt/useJar/ExtendsQtWithJava",
                                        "downloadWebPage",
                                       "(Ljava/lang/String;)V",
                                       javaAction.object<jstring>());
    m_stateLabel->setText("Downloading...");
#endif
}

#include "widget.h"
#include <QVBoxLayout>
#include <QPushButton>
#include "../simpleCustomEvent.h"
#include <QAndroidJniObject>
#include <QAndroidJniEnvironment>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    QVBoxLayout *layout = new QVBoxLayout(this);
    QHBoxLayout *getLayout = new QHBoxLayout();
    layout->addLayout(getLayout);
    m_urlEdit = new QLineEdit("http://blog.csdn.net/foruok");
    getLayout->addWidget(m_urlEdit, 1);
    QPushButton *getButton = new QPushButton("GET");
    getLayout->addWidget(getButton);
    connect(getButton, SIGNAL(clicked()), this, SLOT(onGet()));

    m_resultView = new QTextEdit();
    m_resultView->setReadOnly(true);
    layout->addWidget(m_resultView, 1);
    m_stateLabel = new QLabel();
    layout->addWidget(m_stateLabel);
}

Widget::~Widget()
{

}

bool Widget::event(QEvent *e)
{
    if(e->type() == SimpleCustomEvent::eventType())
    {
        e->accept();
        SimpleCustomEvent *sce = (SimpleCustomEvent*)e;
        switch(sce->m_arg1)
        {
        case 1:
            m_resultView->setText(sce->m_arg2);
            m_stateLabel->setText("Success!");
            break;
        case 0:
            m_resultView->setText(sce->m_arg2);
            m_stateLabel->setText("Failed!");
            break;
        case -1:
            m_stateLabel->setText(sce->m_arg2);
            break;
        }
        return true;
    }
    return QWidget::event(e);
}

void Widget::onGet()
{
#ifdef WIN32
    m_resultView->setText("Sorry, Just for Android!");
#elif defined(ANDROID)
    QString url = m_urlEdit->text();
    QAndroidJniObject javaAction = QAndroidJniObject::fromString(url);
    QAndroidJniObject::callStaticMethod<void>("an/qt/useJar/ExtendsQtWithJava",
                                       "downloadWebPage",
                                       "(Ljava/lang/String;)V",
                                       javaAction.object<jstring>());
    m_stateLabel->setText("Downloading...");
#endif
}

    调用Java的代码在onGet()槽中，很简单，不解释了。有疑问看Qt帮助手册有关QAndroidJniObject类的说明。

    OK，到此结束。

    版权所有：foruok。转载请注明出处：http://blog.csdn.net/foruok。

    我的Qt on Android系列文章：

• Qt on Android：图文详解Hello World全过程
• Windows下Qt 5.2 for Android开发入门
• Qt for Android 部署流程分析
• Qt on Android：将Qt调试信息输出到logcat中
• Qt on Android: Qt 5.3.0 发布，针对 Android 改进说明
• Qt on Android Episode 1（翻译）
• Qt on Android Episode 2（翻译）
• Qt on Android Episode 3（翻译）
• Qt on Android Episode 4（翻译）
• Qt for Android 编译纯C工程
• Windows下Qt for Android 编译安卓C语言可执行程序
• Qt on Android： Android SDK安装
• Qt on Android: http下载与Json解析
• Qt on Android 之设置应用名为中文
• Qt on Android：让 Qt Widgets 和 Qt Quick 应用全屏显示
• Qt on Android：怎样适应不同的屏幕尺寸