C++注冊函數(shù)給JAVA調(diào)用

網(wǎng)絡(luò)上根本沒人說這么個玩意, ?包括一些寫書的老怪物.甚至他們的寫法都是非線程安全的。JAVA調(diào)用C++有2種方式,第一種很累需要把函數(shù)寫成JAVA規(guī)定的格式,第二種很繞,需要讓JAVA事先主動調(diào)用C++,C++根據(jù)他傳遞過來的類指針來操作?，F(xiàn)在說的是不需要對應(yīng)安卓類名直接注冊的機制,關(guān)鍵是QT能用。因為Qt中無法用JNI_OnLoad,因此我說的這個東西很重要。Qt中的新類:QtAndtoid提供了在JAVA UI線程環(huán)境中執(zhí)行C++代碼的功能:runOnAndroidThreadSync。

示例:JAVA中按返回鍵通知QT ?OnESCdown函數(shù)將由C++注冊給java調(diào)用

?public??native?void?OnESCdown();
????????@Override
????????public?boolean?onKeyDown(int?keyCode,?KeyEvent?event)
????????{
????????????OnESCdown();//通知C++層的?onEscDown函數(shù)
????????????Log.i("mod:","keycode:"+keyCode);??
????????????if?(QtApplication.m_delegateObject?!=?null?&&?QtApplication.onKeyDown?!=?null)
????????????????return?(Boolean)?QtApplication.invokeDelegateMethod(QtApplication.onKeyDown,?keyCode,?event);
????????????else
????????????????return?super.onKeyDown(keyCode,?event);
????????}

C++:

static?void??onEscDown()
{
????????qDebug()<<"C++?onEscDown";
}


st
atic?const?JNINativeMethod?gMethods[]?=?{?//定義批量注冊的數(shù)組，是注冊的關(guān)鍵部分
????????????????????????????????????????????{?"OnESCdown",?"()V",?(void*)onEscDown?}?//?func2是在java中聲明的native函數(shù)名，"()V"是函數(shù)的簽名，可以通過javah獲取。
??????????????????????????????????????????};
void??RegJni()
{

????QtAndroid::runOnAndroidThreadSync([=](){

???????????QAndroidJniEnvironment?EV;
???????????qDebug()<<"RegisterNatives???0***********";
???????????qDebug()<<"RegisterNatives???1***********";

???????????const?char*?kClassName?="org/qtproject/qt5/android/bindings/QtActivity";

???????????jclass?clazz;
??????????clazz?=EV->FindClass(kClassName);
??????????if?(clazz?==?NULL)
??????????{
??????????????qDebug()<<"erro???clazz";
??????????????return?;
??????????}
??????????qDebug()<<"RegisterNatives???2***********";

??????????if?(EV->RegisterNatives(clazz,?gMethods,?sizeof(gMethods)?/?sizeof(gMethods[0]))?!=?JNI_OK)
??????????{
??????????????printf("register?native?method?failed!n");
??????????????return;
??????????}else{
??????????????qDebug()<<"RegisterNatives???搞定***********";
??????????}

????});

????//這里可以找到要注冊的類，前提是這個類已經(jīng)加載到j(luò)ava虛擬機中。?這里說明，動態(tài)庫和有native方法的類之間，沒有任何對應(yīng)關(guān)系。

????//????QAndroidJniObject?javaClass(kClassName);
????//????????clazz?=?env->GetObjectClass(javaClass.object());
????//????????qDebug()?<<"find?ExtendsQtNative"<<?clazz;


????EV->DeleteLocalRef(clazz);//刪除引用避免內(nèi)存泄漏
????qDebug()<<"RegisterNatives???OK***********";
}