如何使用QAndroidJniObject从Qt内部调用Java代码？

问题描述

从使用Qt Creator创建的Android项目的空Qt开始，如何执行本机Java代码？

例如，如果我有这个java方法：

  class HelloJava {
 public static String sayHello（int a，int b）{
 returnHello来自Java，a + b =+（a + b）; 
} 
} 
  

我有这个Qt方法应该调用 HelloJava.sayHello（）方法：

  QString call_HelloJava_sayHello b）{
 //这里有什么？ 
} 
  

我将Java代码放在我的项目中， call_HelloJava_sayHello（）方法？

解决方案

对主题非常详细：

  // Java类
 package org.qtproject.qt5; 
 class TestClass 
 {
 static String fromNumber（int x）{...} 
 static String [] stringArray（String s1，String s2）{...} 
} 
 
 
 // C ++代码
 
 //第一个函数的签名是（I）Ljava / lang / String; 
 QAndroidJniObject stringNumber = QAndroidJniObject :: callStaticObjectMethod（org / qtproject / qt5 / TestClass，
fromNumber
（I）Ljava / lang / String;，
 10 ）; 
 
 //第二个函数的签名是（Ljava / lang / String; Ljava / lang / String;）[Ljava / lang / String; 
 QAndroidJniObject string1 = QAndroidJniObject :: fromString（String1）; 
 QAndroidJniObject string2 = QAndroidJniObject :: fromString（String2）; 
 QAndroidJniObject stringArray = QAndroidJniObject :: callStaticObjectMethod（org / qtproject / qt5 / TestClass，
stringArray
（Ljava / lang / String; Ljava / lang / String;）[Ljava / lang / String;
 string1.object< jstring>（），
 string2.object< jstring>（））; 
  

所以你的函数的sig应该是（I; I; Ljava / lang / String;

还有：

所以看来你需要指定并且自动部署java文件。

只需将它添加到你的.pro文件位于 / path / to / project / myjava / src ：

  android {
 ANDROID_PACKAGE_SOURCE_DIR = $$ _ PRO_FILE_PWD_ / android 
 QT + = androidextras 
} 
  

_PRO_FILE_PWD _ 是将解析到项目目录的qmake变量。

Starting from an empty Qt for Android project, created with Qt Creator, how do I execute native Java code?

For example, if I have this java method:

class HelloJava {
    public static String sayHello(int a, int b) {
        return "Hello from Java, a+b=" + (a+b);
    }
}

And I have this Qt method which should call the HelloJava.sayHello() method:

QString call_HelloJava_sayHello(int a, int b) {
    // What goes in here?
}

Where do I put the Java code in my project, and what goes inside the call_HelloJava_sayHello() method?

解决方案

The Qt doc is pretty verbose on the subject:

// Java class
package org.qtproject.qt5;
class TestClass
{
   static String fromNumber(int x) { ... }
   static String[] stringArray(String s1, String s2) { ... }
}


// C++ code

// The signature for the first function is "(I)Ljava/lang/String;"
QAndroidJniObject stringNumber = QAndroidJniObject::callStaticObjectMethod("org/qtproject/qt5/TestClass",
                                                                           "fromNumber"
                                                                           "(I)Ljava/lang/String;",
                                                                           10);

// the signature for the second function is "(Ljava/lang/String;Ljava/lang/String;)[Ljava/lang/String;"
QAndroidJniObject string1 = QAndroidJniObject::fromString("String1");
QAndroidJniObject string2 = QAndroidJniObject::fromString("String2");
QAndroidJniObject stringArray = QAndroidJniObject::callStaticObjectMethod("org/qtproject/qt5/TestClass",
                                                                          "stringArray"
                                                                          "(Ljava/lang/String;Ljava/lang/String;)[Ljava/lang/String;"
                                                                           string1.object<jstring>(),
                                                                           string2.object<jstring>());

So the sig of your function should be "(I;I;)Ljava/lang/String;"

And also this:

So it seems you need to specify that and the java files are automatically deployed.

Just add this to your .pro file (assuming your java sources are placed at /path/to/project/myjava/src:

android {
    ANDROID_PACKAGE_SOURCE_DIR=$$_PRO_FILE_PWD_/android
    QT += androidextras
}

_PRO_FILE_PWD_ is a qmake variable that will resolve to the project directory.

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