Qt不编译callStaticObjectMethod（） [英] Qt does not compile callStaticObjectMethod()

问题描述

我写了以下代码从这个问题，它被编译和工作完美：

I wrote the following code from this question and it was compiled and worked perfectly:

QAndroidJniObject str =  QAndroidJniObject::callStaticObjectMethod<jstring>(
                               "org/.../TestClass"
                               ,"staticMethod");

现在我改变了java方法，它需要一个类型为string的输入参数。

Now I have changed the java method and it needs an input parameter of type string.

Java代码：

public class TestClass{
    public string str;
    public TestClass() {
        str = "Test From Java";
    }
    public static String staticMethod(String str) {
        return "Test From Java, "+str;
    }
}

但是添加方法签名和输入参数不起作用为了我。我写了这个代码来使用JNI调用所提到的java类中的静态方法：

But adding the method signature and input parameter does not work for me. I wrote this code to invoke the static method within the mentioned java class using JNI:

QAndroidJniObject val = QAndroidJniObject::fromString("Test String");
QAndroidJniObject str = QAndroidJniObject::callStaticObjectMethod<jstring>(
          "org/.../TestClass"
          ,"staticMethod"
          ,"(Ljava/lang/String;)Ljava/lang/String;"
          ,val.object<jstring>());

但是Qt的创建者不会构建它，打印此错误：

But Qt creator does not build it, printing this error:

...testclass.cpp:21: error:
no matching function for call to 'QAndroidJniObject::callStaticObjectMethod(
const char [36], const char [13], const char [39], _jstring*)'
                                                        ,val.object<jstring>());
                                                                              ^

感谢任何帮助。

为此：

jstring str = QAndroidJniObject::callStaticMethod<jstring>(
                      "org/.../TestClass"
                      ,"staticMethod"
                      ,"(Ljava/lang/String;)Ljava/lang/String;"
                      ,val.object<jstring>());

我收到以下错误：

... \testclass.cpp：21：错误：未定义引用'_jstring * QAndroidJniObject :: callStaticMethod <_jstring *>（char const *，char
const *，char const * ，...）'

...\testclass.cpp:21: error: undefined reference to '_jstring* QAndroidJniObject::callStaticMethod<_jstring*>(char const*, char const*, char const*, ...)'

##我也试过没有模板参数##的callStaticObjectMethod

## I also tried callStaticObjectMethod without template parameter ##

QAndroidJniObject str = QAndroidJniObject :: callStaticObjectMethod（org / ... TextClass，staticMethod，（Ljava / lang / String;）Ljava / lang / String; val.object（））;

QAndroidJniObject str = QAndroidJniObject::callStaticObjectMethod("org/...TextClass" ,"staticMethod" ,"(Ljava/lang/String;)Ljava/lang/String;",val.object());

它总是返回一个空字符串。我不知道它是真的emty或不。我使用 qCritical（）<< str.toString（）; 以打印该字符串，但打印一个空的qout然后！

It always returns an empty string. I'm not sure if it is really emty or not. I use qCritical() << str.toString(); to print the string but an empty qout is printed then!

推荐答案

尝试：

QAndroidJniObject str = QAndroidJniObject::callStaticObjectMethod(
          "org/.../TestClass"
          ,"staticMethod"
          ,"(Ljava/lang/String;)Ljava/lang/String;"
          ,val.object<jstring>());

我认为这个函数不带模板参数。

I think this function doesn't take template parameter.

比你可以：

str.toString() //returns QString

---

并确保已将Java源文件导入到您的Android构建。例如，如果你的java类在 android-sources 文件夹下添加到你的.pro文件：

---

And make sure you have imported the Java source files to your android build. For example if your java classes are under android-sources folder add this to your .pro file:

ANDROID_PACKAGE_SOURCE_DIR = $$PWD/android-sources

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