[英]Android - JNI NewObject() does not save values when passing it to Java
I am using native code to create an object which I then pass as an argument to a method I call. 我正在使用本机代码创建对象,然后将其作为参数传递给我调用的方法。 Nothing appears to go wrong in native code, but when I get the call in Java, the object seems to have nulled values. 在本机代码中似乎没什么问题,但是当我用Java调用时,该对象似乎具有空值。
Here's the code of the java object I create in native: 这是我在本机中创建的Java对象的代码:
package org.test;
import java.util.ArrayList;
public class JNITeam {
public int mTeamID;
public String mTeamName;
private ArrayList<String> mMembers;
public JNITeam(int id, String name) {
mTeamID = id;
mTeamName = name;
}
public void addMember(String name) {
mMembers.add(name);
}
}
Here's the native code used to create an instance of the class and pass it up to the Java method "onGetTeam", which takes an instance of the above class as a parameter. 这是用于创建类实例并将其传递给Java方法“ onGetTeam”的本机代码,该方法将上述类的实例作为参数。 It is run from a thread created in Native code, hence I have to attach the thread. 它是从本机代码中创建的线程运行的,因此我必须附加该线程。
JNIEnv* jenv = 0;
clientHandle->runningJVM->AttachCurrentThread(&jenv,0);
if (!jenv)
__android_log_print(ANDROID_LOG_INFO, ANDROID_DEBUG_TAG, "jenv is null");
jclass cls = jenv->GetObjectClass(clientHandle->job);
if (!cls)
__android_log_print(ANDROID_LOG_INFO, ANDROID_DEBUG_TAG, "cls is null");
jmethodID constructor = jenv->GetMethodID(clientHandle->JNITeamCls, "<init>", "(ILjava/lang/String;)V");
jint teamID = 2;
jstring js = jenv->NewStringUTF("test");
jobject dataObject = jenv->NewObject(clientHandle->JNITeamCls, constructor, teamID, js);
if (!dataObject)
__android_log_print(ANDROID_LOG_INFO, ANDROID_DEBUG_TAG, "dataobject is null");
if (jenv && cls && dataObject) {
jmethodID mid = jenv->GetMethodID(cls,"onGetTeam","(Lorg/test/JNITeam;)V");
if (mid) {
jenv->CallVoidMethod(clientHandle->job,mid);
}
else {
__android_log_print(ANDROID_LOG_INFO, ANDROID_DEBUG_TAG, "mid is null");
}
}
I do not want the object to be persistent; 我不希望该对象具有持久性。 I want it to ony be valid during the call to Java, then it can be garbage-collected. 我希望它在对Java的调用期间有效,然后可以对其进行垃圾回收。 However its data fields - that are set in the constructor - are just null when I call it, Why? 但是,当我将其数据字段(在构造函数中设置)设置为null时,为什么呢?
You're not passing the object you constructed to the method (or indeed doing anything with it). 您没有将构造的对象传递给方法(或实际上对它执行任何操作)。
Instead of 代替
jenv->CallVoidMethod(clientHandle->job,mid);
don't you want 你不想要
jenv->CallVoidMethod(clientHandle->job,mid,dataObject);
? ?
Also you're not checking whether that call succeeded or not. 另外,您不检查该呼叫是否成功。
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