Question

我试过下面的例子。我有两个本机方法setMessage和printMessage。我在main方法中创建了两个ClassA对象，在a1对象上创建了setMessage，并且在a2对象上获得了相同的消息范围（参见输出）。

如何使用新范围创建新的ClassA对象。

ClassA.c

#include "ClassA.h"

char * message ;
JNIEXPORT void JNICALL Java_ClassA_setMessage (JNIEnv * env , jobject obj, jstring msg){
    message = (*env)->GetStringUTFChars(env, msg, 0);  
}

JNIEXPORT void JNICALL Java_ClassA_printMessage  (JNIEnv * env, jobject obj){
  printf("%s\n", message);
}

ClassA.java

public class ClassA { 
    static {
         System.loadLibrary("myapp");          
    }
    public native void setMessage(String msg);
    public native void printMessage();
}

ClassB.java

public class ClassB   { 
    public static void main(String[] args) {
        ClassA a1 = new ClassA();
        System.out.print("Print message with out setMessage() By a1 :");
        a1.printMessage();
        a1.setMessage("I am a1"); 
        System.out.print("Print message after setMessage() By a1 : ");
        a1.printMessage();


        ClassA a2 = new ClassA(); 
        System.out.print("Print message with out setMessage() By a2 :");
        a2.printMessage(); 


    a2.setMessage("I am a2");   
    System.out.print("Print message after setMessage() By a2  :  ");
    a2.printMessage();
    }
}

::::输出::::

  Print message with out setMessage() By a1 : (null)
  Print message after setMessage() By a1    :  I am a1
  Print message with out setMessage() By a2 :  I am a1
  Print message after setMessage() By a2    :  I am a2

Answer 1

在创建新对象之前清除“消息”。

如何在JNI中使用新范围创建新的Java对象

1 个答案: