之前用C++调用Java，只需要搞清楚Java和C++的类型对应关系，和callStaticMethod之类的函数调用即可，但是Java调用C++，我在《Qt On Android 核心编程》 书上看到作者说很简单，大体上是只需要定义java函数为native，然后C++定义一个多两个参数的对应函数，再关联即可，但可能Qt版本关系吧（作者用的是5.3版本，目前我用5.11和5.14），不管自己写还是用作者的例子，总是闪退，目前遇到的情况如下：
1、Qt的线程和Android主线程还不是同一个线程，所以两个线程分别应该在什么情况下使用？
2、registerNativeMethods()函数正确定义并正确返回，但调用后会导致部分C++调用Java函数闪退（如果不调用registerNativeMethods()，则没问题）。
3、Java调用Qt函数（作者的示例），调用完毕后会闪退，函数栈截取如下（这是5.14的错误，5.11的还不太一样，就是有个null 的object）：
E art : JNI ERROR (app bug): accessed deleted global reference 0x2008aa
F art : art/runtime/java_vm_ext.cc:470] JNI DETECTED ERROR IN APPLICATION: use of deleted global reference 0x2008aa
F art : art/runtime/java_vm_ext.cc:470] from java.lang.String an.qt.extendsQtWithJava.ExtendsQtNative.GetQtVersion()
F art : art/runtime/java_vm_ext.cc:470] "main" prio=5 tid=1 Runnable
F art : art/runtime/java_vm_ext.cc:470] | group="main" sCount=0 dsCount=0 obj=0x759b96b8 self=0xf0a05400
F art : art/runtime/java_vm_ext.cc:470] | sysTid=27734 nice=-10 cgrp=default sched=0/0 handle=0xf381c534
F art : art/runtime/java_vm_ext.cc:470] | state=R schedstat=( 385390111 19337303 757 ) utm=21 stm=17 core=4 HZ=100
F art : art/runtime/java_vm_ext.cc:470] | stack=0xff4b4000-0xff4b6000 stackSize=8MB
F art : art/runtime/java_vm_ext.cc:470] | held mutexes= "mutator lock"(shared held)
F art : art/runtime/java_vm_ext.cc:470] native: #00 pc 003577e5 /system/lib/libart.so (_ZN3art15DumpNativeStackERNSt3__113basic_ostreamIcNS0_11char_traitsIcEEEEiP12BacktraceMa**cPNS_9ArtMethodEPv+128)
F art : art/runtime/java_vm_ext.cc:470] native: #01 pc 00337dc1 /system/lib/libart.so (_ZNK3art6Thread9DumpStackERNSt3__113basic_ostreamIcNS1_11char_traitsIcEEEEbP12BacktraceMap+304)
F art : art/runtime/java_vm_ext.cc:470] native: #02 pc 0023ba63 /system/lib/libart.so (_ZN3art9JavaVMExt8JniAbortEPKcS2_+846)
F art : art/runtime/java_vm_ext.cc:470] native: #03 pc 0023c00f /system/lib/libart.so (_ZN3art9JavaVMExt9JniAbortFEPKcS2_z+66)
F art : art/runtime/java_vm_ext.cc:470] native: #04 pc 0033b81d /system/lib/libart.so (_ZNK3art6Thread13DecodeJObjectEP8_jobject+240)
F art : art/runtime/java_vm_ext.cc:470] native: #05 pc 003fbf8f /system/lib/libart.so (_ZN3art25JniMethodEndWithReferenceEP8_jobjectjPNS_6ThreadE+30)
F art : art/runtime/java_vm_ext.cc:470] native: #06 pc 00000067 /data/app/an.qt.extendsQtWithJava-1/oat/arm/base.odex (Java_an_qt_extendsQtWithJava_ExtendsQtNative_GetQtVersion__+82)
F art : art/runtime/java_vm_ext.cc:470] at an.qt.extendsQtWithJava.ExtendsQtNative.GetQtVersion(Native method)
F art : art/runtime/java_vm_ext.cc:470] at an.qt.extendsQtWithJava.ExtendsQtWithJava$1.handleMessage(ExtendsQtWithJava.java:43)
F art : art/runtime/java_vm_ext.cc:470] at android.os.Handler.dispatchMessage(Handler.java:105)
F art : art/runtime/java_vm_ext.cc:470] at android.os.Looper.loop(Looper.java:156)
F art : art/runtime/java_vm_ext.cc:470] at android.app.ActivityThread.main(ActivityThread.java:6517)
F art : art/runtime/java_vm_ext.cc:470] at java.lang.reflect.Method.invoke!(Native method)
F art : art/runtime/java_vm_ext.cc:470] at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:942)
F art : art/runtime/java_vm_ext.cc:470] at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:832)
F art : art/runtime/java_vm_ext.cc:470] at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:107)
