NDK ReferenceTable overflow (max=512) 问题

JNI层开发会遇到ReferenceTable overflow问题，特别是当jni函数被反复调用上千上万次的时候，现汇总如下

对于FindClass 返回的一定需要调用DeleteLocalRef，还有如下类型的变量需要DeleteLocalRef：

.FindClass /NewString/ NewStringUTF/NewObject/ GetObjectField等产生的都是LocalRef

总体原则：释放所有对object的引用。

1.FindClass

jclass ref= (env)->FindClass("java/lang/String");

env->DeleteLocalRef(ref); 

2.NewString/ NewStringUTF/NewObject/NewByteArray

jstring     (*NewString)(JNIEnv*, const jchar*, jsize);    

const jchar* (*GetStringChars)(JNIEnv*, jstring, jboolean*);     

void        (*ReleaseStringChars)(JNIEnv*, jstring, const jchar*);

jstring     (*NewStringUTF)(JNIEnv*, const char*);    

const char* (*GetStringUTFChars)(JNIEnv*, jstring, jboolean*);     

void        (*ReleaseStringUTFChars)(JNIEnv*, jstring, const char*);

env->DeleteLocalRef(ref);

3.GetObjectField/GetObjectClass/GetObjectArrayElement

jclass ref = env->GetObjectClass(robj);

env->DeleteLocalRef(ref); 

4.GetByteArrayElements

jbyte* array= (*env)->GetByteArrayElements(env,jarray,&isCopy);

(*env)->ReleaseByteArrayElements(env,jarray,array,0);

5.const char* input =(*env)->GetStringUTFChars(env,jinput, &isCopy);

(*env)->ReleaseStringUTFChars(env,jinput,input);

 

6.NewGlobalRef/DeleteGlobalRef

 jobject     (*NewGlobalRef)(JNIEnv*, jobject);     

void        (*DeleteGlobalRef)(JNIEnv*, jobject);

例如，

jobject ref= env->NewGlobalRef(customObj);

env->DeleteGlobalRef(customObj);