通过返回字符串的 JNI 从 C++ 调用 java 函数
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/4359453/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Calling a java function from C++ via JNI that returns a string
提问by klaus johan
Possible Duplicate:
How to access the Java method in a C++ application
可能的重复：
如何在 C++ 应用程序中访问 Java 方法
Suppose I have a Java class like this :
假设我有一个这样的 Java 类：
class MyClass
{
String value = "a string value";
String getValue()
{
return value;
}
}
I've been trying for hours to implement a JNI function that calls a Java function and returns a string. Could someone show me through a snippet how to call the "getValue" function from a C++ using JNI and obtain a jstring variable with the value of String variable from "MyClass.
我已经尝试了几个小时来实现一个调用 Java 函数并返回一个字符串的 JNI 函数。有人可以通过一个片段向我展示如何使用 JNI 从 C++ 调用“getValue”函数，并从“MyClass.getValue”中获取带有 String 变量值的 jstring 变量。
// C++
// C++
jobject result;
jMethodID method_getValue = m_env->GetMethodID(native_object,"getValue","()Ljava/lang/String;");
result = m_env->CallObjectMethod(native_object, method_getValue);
回答by Naytzyrhc
jMethodID method_getValue = m_env->GetMethodID(native_object,"getValue","()Ljava/lang/String;");
here, native_object is supposed to be the class definition object (jclass) of MyClass
这里，native_object 应该是 MyClass 的类定义对象（jclass）
jmethodID GetMethodID(JNIEnv *env, jclass clazz, const char *name, const char *sig);
whereas to here:
而到这里：
result = m_env->CallObjectMethod(native_object, method_getValue);
NativeType CallMethod(JNIEnv *env, jobject obj, jmethodID methodID, ...);
NativeType CallMethod(JNIEnv *env, jobject obj, jmethodID methodID, ...);
Your CallObjectMethod expects as first parameter an object from MyClass, no jclass. http://download.oracle.com/javase/1.4.2/docs/guide/jni/spec/functions.html
您的 CallObjectMethod 需要来自 MyClass 的对象作为第一个参数，而不是 jclass。 http://download.oracle.com/javase/1.4.2/docs/guide/jni/spec/functions.html
so either one of the calls is wrong here...
所以这里的任何一个电话都是错误的......
probably the getMethodID... you should definitely check for NULL there.
可能是 getMethodID ... 你绝对应该在那里检查 NULL。
cheers,
干杯，
