如何设置“Double”的值。我的类的类型变量由JNI？ [英] How can I set the value of "Double" type variable of my Class by JNI?

问题描述

如果我只想将值设置为Double类型变量，我可以编写如下：

  public static native int getDoubleVar double dobj）; 
 JNIEXPORT jint JNICALL 
 test_jni_Native_testGet（JNIEnv * env，jclass type，jobject dobj）
 {
 jclass DoubleClass = env-> FindClass（java / lang / Double）; 
 jfieldID valueID = env-> GetFieldID（DoubleClass，value，D）; 
 env-> SetDoubleField（dobj，valueID，2.3）; 
 return 0; 
} 
  

这些代码toke effect。

但是，当我试图通过JNI设置类的Double变量的值时，我不能得到我想要的，当然，它崩溃了，这使我有点困惑。 / p>

Java代码：

  public class TestDouble 
 {
 
 public double value; 
 public long num; 
 public TestDouble（long num，Double value）
 {
 this.num = num; 
 this.value = value; 
} 
} 
  

原生：

  public static native int testGet（TestDouble tdobj）; 
  

c代码：

  JNIEXPORT jint JNICALL 
 test_jni_Native_testGet（JNIEnv * env，jclass type，jobject tdobj）
 {
 jclass tdobjClass = env-> FindClass（xxxx / TestDouble）; 
 jfieldID valueID = env-> GetFieldID（tdobjClass，value，D）; 
 env-> SetDoubleField（tdobj，jValueID，2.3）; 
 return 0; 
} 
  

我想设置类'TestDouble '，而'value'的类型是Double（不是double）。

  E / dalvikvm：VM aborting 
致命信号6 
在void debuggerd_signal_handler（int，siginfo_t *，void *）中向pid：5830发送停止信号
  

b $ b

我只是在这里粘贴关键错误的单词，很明显，错误发生在：

  env- > SetDoubleField（tdobj，jValueID，2.3）; 
  

那么我该如何处理这个问题呢？
非常感谢！

解决方案

我得到正确的答案：

  http://stackoverflow.com/questions/34848605/how-to-set-the-value-of-a-double-integer-type-of-a-java -class-by-jni 
 
 JNIEXPORT jint JNICALL test_jni_Native_testSet（JNIEnv * env，jclass type，jobject tdobj）
 {
 //创建整数类，获取构造函数并创建整数对象
 jclass intClass = env-> FindClass（env，java / lang / Integer）; 
 jmethodID initInt = env-> GetMethodID（env，intClass，< init>，（I）V）; 
 if（NULL == initInt）return -1; 
 jobject newIntObj = env-> NewObject（env，intClass，initInt，123）; 
 
 //现在将整数设置为值atttribute。为此，我会
 //建议你有一个java安装程序，并以相同的方式调用
 //如上所示
 
 //清除引用
 env-> DeleteLocalRef（env，newIntObj）; 
 return 0; 
} 
  

整数/双精度和其他包装类型可以以相同的方式处理。

If I just want to set value to Double type variable, I may code like:

public static native int getDoubleVar(Double dobj);
JNIEXPORT jint JNICALL
test_jni_Native_testGet(JNIEnv *env, jclass type, jobject dobj)
{
    jclass DoubleClass = env->FindClass("java/lang/Double");
    jfieldID valueID = env->GetFieldID(DoubleClass, "value", "D");
    env->SetDoubleField(dobj, valueID, 2.3);
    return 0;
}

These codes toke effect.

But, when I tried to set the value of a "Double" variable of a class by JNI, I can't get what I want, and of course, it broke down, which makes me a bit confused.

Java codes:

public class TestDouble
{

    public Double value;
    public long num;
    public TestDouble(long num, Double value)
    {
        this.num = num;
        this.value = value;
    }
}

Native:

public static native int testGet(TestDouble tdobj);

c codes:

JNIEXPORT jint JNICALL
test_jni_Native_testGet(JNIEnv *env, jclass type, jobject tdobj)
{
    jclass tdobjClass = env->FindClass("xxxx/TestDouble");
    jfieldID valueID = env->GetFieldID(tdobjClass, "value", "D");
    env->SetDoubleField(tdobj, jValueID, 2.3);
    return 0;
}

I'd like to set the value of 'value' of class 'TestDouble', and type of 'value' is "Double" (not double).

E/dalvikvm: VM aborting
Fatal signal 6
Send stop signal to pid:5830 in void debuggerd_signal_handler(int, siginfo_t*, void*)

I just paste the key wrong words here, and it's obvious that the error occurs at:

env->SetDoubleField(tdobj, jValueID, 2.3);

What can I do to deal with this problem then? Thanks a lot !

解决方案

I get the correct answer :

http://stackoverflow.com/questions/34848605/how-to-set-the-value-of-a-double-integer-type-of-a-java-class-by-jni

JNIEXPORT jint JNICALL test_jni_Native_testSet(JNIEnv *env, jclass type, jobject tdobj)
{
    //Create Integer class, get constructor and create Integer object
    jclass intClass = env->FindClass(env, "java/lang/Integer");
   jmethodID initInt = env->GetMethodID(env, intClass, "<init>", "(I)V");
    if (NULL == initInt) return -1;
    jobject newIntObj = env->NewObject(env, intClass, initInt, 123);

//Now set your integer into value atttribute. For this, I would
//recommend you to have a java setter and call it in the same way 
//as shown above

//clean reference
env->DeleteLocalRef(env, newIntObj); 
return 0;
}

Integer/Double and other wrapper types can be handled in the same way..

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