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：

[java] view plaincopyprint?

1. package an.qt.useJar; 
2. import java.lang.String; 
3. import android.content.Context; 
4. import android.content.Intent; 
5. import android.app.PendingIntent; 
6. import android.os.Handler; 
7. import android.os.Message; 
8. import android.util.Log; 
9. import android.net.ConnectivityManager; 
10. import android.net.NetworkInfo; 
11. import android.net.Uri; 
12. import android.location.Criteria; 
13. import android.provider.Settings; 
14. import android.os.Bundle; 
15. import android.os.Environment; 
16. import java.io.File; 
17. import com.loopj.android.http.AsyncHttpClient; 
18. import com.loopj.android.http.AsyncHttpResponseHandler; 
19.  
20. public class ExtendsQtWithJava extends org.qtproject.qt5.android.bindings.QtActivity 
21. { 
22.     private static ExtendsQtWithJava m_instance; 
23.     private final static String TAG = "extendsQt"; 
24.     private static String m_pageUri = null; 
25.     private static Handler m_handler = new Handler() { 
26.         @Override 
27.         public void handleMessage(Message msg) { 
28.             switch (msg.what) { 
29.             case 1: 
30.                 if(m_pageUri == null){ 
31.                     m_pageUri = (String)msg.obj; 
32.                     m_instance.downloadText(m_pageUri); 
33.                 }else{ 
34.                     m_instance.notifyQt(0, (String)msg.obj, "Downloader is Busy now!"); 
35.                 } 
36.                 break; 
37.             }; 
38.         } 
39.     }; 
40.      
41.  
42.     public ExtendsQtWithJava(){ 
43.         m_instance = this; 
44.     } 
45.  
46.     public static int networkState(){ 
47.         ConnectivityManager conMan = (ConnectivityManager) m_instance.getSystemService(Context.CONNECTIVITY_SERVICE); 
48.         return conMan.getActiveNetworkInfo() == null ? 0 : 1; 
49.     } 
50.  
51.     public static AsyncHttpClient m_httpc = new AsyncHttpClient(); 
52.     public static ExtendsQtNative m_nativeNotify = null; 
53.  
54.     public void downloadText(String uri){ 
55.         Log.d(TAG, "start downloadText"); 
56.         m_httpc.get(uri, null, new AsyncHttpResponseHandler(){ 
57.             @Override 
58.             public void onSuccess(String data){ 
59.                 notifyQt(1, m_pageUri, data); 
60.                 m_pageUri = null; 
61.             } 
62.             @Override 
63.             public void onFailure(Throwable e, String data){ 
64.                 notifyQt(-1, m_pageUri, data); 
65.                 m_pageUri = null; 
66.             } 
67.         }); 
68.     } 
69.      
70.     public static void downloadWebPage(String uri){ 
71.         Log.d(TAG, "downloadWebPage"); 
72.         m_handler.sendMessage(m_handler.obtainMessage(1, uri)); 
73.     } 
74.      
75.     private void notifyQt(int result, String uri, String data){ 
76.         if(m_nativeNotify == null){ 
77.             m_nativeNotify = new ExtendsQtNative(); 
78.         } 
79.         m_nativeNotify.OnDownloaded(result, uri, data); 
80.     } 
81. } 

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);
    }
}

[java] view plaincopyprint?

1. package an.qt.useJar; 
2. import java.lang.String; 
3.  
4. public class ExtendsQtNative 
5. { 
6.     public native void OnDownloaded(int result, String url, String content); 
7. } 

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

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

    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：

[cpp] view plaincopyprint?

1. #include "widget.h" 
2. #include <QApplication> 
3. #include <QAndroidJniEnvironment> 
4. #include <QAndroidJniObject> 
5. #include <jni.h> 
6. #include "../simpleCustomEvent.h" 
7. #include <QDebug> 
8.  
9. QObject *g_listener = 0; 
10.  
11. // result: -1 failed; 1 success; 0 busy; 
12. static void onDownloaded(JNIEnv *env, jobject thiz,int result, jstring uri, jstring data) 
13. { 
14.     QString qstrData; 
15.     const char *nativeString = env->GetStringUTFChars(data, 0); 
16.     qstrData = nativeString; 
17.     env->ReleaseStringUTFChars(data, nativeString); 
18.     QCoreApplication::postEvent(g_listener, new SimpleCustomEvent(result, qstrData)); 
19. } 
20.  
21. bool registerNativeMethods() 
22. { 
23.     JNINativeMethod methods[] { 
24.         {"OnDownloaded", "(ILjava/lang/String;Ljava/lang/String;)V", (void*)onDownloaded} 
25.     }; 
26.  
27.     const char *classname = "an/qt/useJar/ExtendsQtNative"; 
28.     jclass clazz; 
29.     QAndroidJniEnvironment env; 
30.  
31.     QAndroidJniObject javaClass(classname); 
32.     clazz = env->GetObjectClass(javaClass.object<jobject>()); 
33.     qDebug() << "find ExtendsQtNative - " << clazz; 
34.     bool result = false; 
35.     if(clazz) 
36.     { 
37.         jint ret = env->RegisterNatives(clazz, 
38.                                         methods, 
39.                                         sizeof(methods) / sizeof(methods[0])); 
40.         env->DeleteLocalRef(clazz); 
41.         qDebug() << "RegisterNatives return - " << ret; 
42.         result = ret >= 0; 
43.     } 
44.     if(env->ExceptionCheck()) env->ExceptionClear(); 
45.     return result; 
46. } 
47.  
48. int main(int argc, char *argv[]) 
49. { 
50.     QApplication a(argc, argv); 
51.  
52.     SimpleCustomEvent::eventType(); 
53.     registerNativeMethods(); 
54.  
55.     Widget w; 
56.     g_listener = qobject_cast<QObject*>(&w); 
57.     w.show(); 
58.  
59.     return a.exec(); 
60. } 

#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();
}

调用Java方法

    对Java方法的调用在Widget.cpp中。直接看代码吧。

    widget.h：

[cpp] view plaincopyprint?

1. #ifndef WIDGET_H 
2. #define WIDGET_H 
3.  
4. #include <QWidget> 
5. #include <QLineEdit> 
6. #include <QTextEdit> 
7. #include <QLabel> 
8.  
9. class Widget : public QWidget 
10. { 
11.     Q_OBJECT 
12.  
13. public: 
14.     Widget(QWidget *parent = 0); 
15.     ~Widget(); 
16.  
17.     bool event(QEvent *e); 
18.  
19. public slots: 
20.     void onGet(); 
21.  
22. private: 
23.     QLineEdit * m_urlEdit; 
24.     QTextEdit * m_resultView; 
25.     QLabel * m_stateLabel; 
26. }; 
27.  
28. #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

[cpp] view plaincopyprint?

1. #include "widget.h" 
2. #include <QVBoxLayout> 
3. #include <QPushButton> 
4. #include "../simpleCustomEvent.h" 
5. #include <QAndroidJniObject> 
6. #include <QAndroidJniEnvironment> 
7.  
8. Widget::Widget(QWidget *parent) 
9.     : QWidget(parent) 
10. { 
11.     QVBoxLayout *layout = new QVBoxLayout(this); 
12.     QHBoxLayout *getLayout = new QHBoxLayout(); 
13.     layout->addLayout(getLayout); 
14.     m_urlEdit = new QLineEdit("http://blog.csdn.net/foruok"); 
15.     getLayout->addWidget(m_urlEdit, 1); 
16.     QPushButton *getButton = new QPushButton("GET"); 
17.     getLayout->addWidget(getButton); 
18.     connect(getButton, SIGNAL(clicked()), this, SLOT(onGet())); 
19.  
20.     m_resultView = new QTextEdit(); 
21.     m_resultView->setReadOnly(true); 
22.     layout->addWidget(m_resultView, 1); 
23.     m_stateLabel = new QLabel(); 
24.     layout->addWidget(m_stateLabel); 
25. } 
26.  
27. Widget::~Widget() 
28. { 
29.  
30. } 
31.  
32. bool Widget::event(QEvent *e) 
33. { 
34.     if(e->type() == SimpleCustomEvent::eventType()) 
35.     { 
36.         e->accept(); 
37.         SimpleCustomEvent *sce = (SimpleCustomEvent*)e; 
38.         switch(sce->m_arg1) 
39.         { 
40.         case 1: 
41.             m_resultView->setText(sce->m_arg2); 
42.             m_stateLabel->setText("Success!"); 
43.             break; 
44.         case 0: 
45.             m_resultView->setText(sce->m_arg2); 
46.             m_stateLabel->setText("Failed!"); 
47.             break; 
48.         case -1: 
49.             m_stateLabel->setText(sce->m_arg2); 
50.             break; 
51.         } 
52.         return true; 
53.     } 
54.     return QWidget::event(e); 
55. } 
56.  
57. void Widget::onGet() 
58. { 
59. #ifdef WIN32 
60.     m_resultView->setText("Sorry, Just for Android!"); 
61. #elif defined(ANDROID) 
62.     QString url = m_urlEdit->text(); 
63.     QAndroidJniObject javaAction = QAndroidJniObject::fromString(url); 
64.     QAndroidJniObject::callStaticMethod<void>("an/qt/useJar/ExtendsQtWithJava", 
65.                                        "downloadWebPage", 
66.                                        "(Ljava/lang/String;)V", 
67.                                        javaAction.object<jstring>()); 
68.     m_stateLabel->setText("Downloading..."); 
69. #endif 
70. } 

#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
}

    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

Qt on Android:使用JNI与第三方jar包

原文：http://blog.csdn.net/weitao1234/article/details/39302171