[英]Return and access java object/class from jni
I have a Java method which returns a instance of object/class 'Readcommpacket'. 我有一个Java方法,该方法返回对象/类'Readcommpacket'的实例。 The call to the Java method is initiated from the NDK/JNI side(c++ -> java-> return-> java object-> c++).
从NDK / JNI端开始对Java方法的调用(c ++-> java-> return-> java object-> c ++)。 How do I complete this, I'm struggling with the proper JNI calls/signatures to complete this.
我如何完成此工作,我正努力使用适当的JNI调用/签名来完成此工作。 Any help is greatly appreciated.
任何帮助是极大的赞赏。
Java object/class used as a return. Java对象/类用作返回值。
public class ReadCommPacket {
public byte[] RCPbtyeread;
public int RCPbytecount;
public ReadCommPacket(byte[] btyeread, int bytecount){
this.RCPbtyeread = btyeread;
this.RCPbytecount = bytecount;
}
}
Java method called by JNI JNI调用的Java方法
public ReadCommPacket BTMsgToNDKComm(){
if(bluetoothConnectedRunnable != null){
return bluetoothConnectedRunnable.readBT();//returns ReadCommPacket obj
}
return new ReadCommPacket(null, -1);
}
JNI/NDK c/c++ code JNI / NDK c / c ++代码
void recvFromBlueTooth(char * recvdByte){
JniMethodInfo methodInfo;
if (! getMethodInfo(&methodInfo, "BTMsgToNDKComm", "V"))//what signature would I use?
{
LOGD("Cannot find method!");
return;
}
//retreive btye[] and int from Readcommpacket here. What JNI calls?
}
signature contains package name. 签名包含软件包名称。
let's suppose package name is com.example 假设包名称为com.example
then signature in your example will be: 那么您的示例中的签名将是:
()Lcom/example/ReadCommPacket
PS if you call this method from c++, make sure class name & method name will not be obfuscated by pro guard (if you use it) PS:如果您从C ++调用此方法,请确保Pro Guard不会混淆类名和方法名(如果使用它)
Run the command javap -s classname.class
The output will have the descriptor that you can use as it is Including ";" 运行命令
javap -s classname.class
输出将包含您可以使用的描述符,因为它包括“;”。
For example: javap -s abc.class
例如:
javap -s abc.class
Trying to return an instance of abc 尝试返回abc的实例
Public static com.getInstance();
descriptor: **()Lcom;**
public int init(java.lang.String, java.lang.String);
descriptor: **(Ljava/lang/String;Ljava/lang/String;)I**
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