我在头文件中有c++结构,
struct StatusLine
{
static jclass Class; // Lorg/apache/http/StatusLine;
static jmethodID GetStatusCode; // ()I
};
struct ByteArrayOutputStream
{
static jclass Class; // Ljava/io/ByteArrayOutputStream;
static jmethodID Constructor; // ()V
static jmethodID Close; // ()V
static jmethodID ToByteArray; // ()[B
};
struct HttpEntity
{
static jclass Class; // Lorg/apache/http/HttpEntity;
static jmethodID WriteTo; // (Ljava/io/OutputStream;)V
static jmethodID GetContent; // ()Ljava/io/InputStream;
};
和cpp文件是
#define JAVA_STATUS_LINE_CLASS "org/apache/http/StatusLine"
#define JAVA_HTTP_ENTITY_CLASS "org/apache/http/HttpEntity"
#define JAVA_BYTE_ARRAY_OUTPUT_STREAM_CLASS "java/io/ByteArrayOutputStream"
jclass StatusLine::Class = 0;
jmethodID StatusLine::GetStatusCode = 0;
jclass ByteArrayOutputStream::Class = 0;
jmethodID ByteArrayOutputStream::Constructor = 0;
jmethodID ByteArrayOutputStream::Close = 0;
jmethodID ByteArrayOutputStream::ToByteArray = 0;
jclass HttpEntity::Class = 0;
jmethodID HttpEntity::WriteTo = 0;
jmethodID HttpEntity::GetContent = 0;
void initializeJniPointers()
{
StatusLine::Class = GetJniEnv()->FindClass(JAVA_STATUS_LINE_CLASS);
StatusLine::GetStatusCode = GetJniEnv()->GetMethodID(StatusLine::Class, "getStatusCode", "()I");
ByteArrayOutputStream::Class = GetJniEnv()->FindClass(JAVA_BYTE_ARRAY_OUTPUT_STREAM_CLASS);
ByteArrayOutputStream::Constructor = GetJniEnv()->GetMethodID(ByteArrayOutputStream::Class, "<init>", "()V");
ByteArrayOutputStream::Close = GetJniEnv()->GetMethodID(ByteArrayOutputStream::Class, "close", "()V");
ByteArrayOutputStream::ToByteArray = GetJniEnv()->GetMethodID(ByteArrayOutputStream::Class, "toByteArray", "()[B");
HttpEntity::Class = GetJniEnv()->FindClass(JAVA_HTTP_ENTITY_CLASS);
HttpEntity::WriteTo = GetJniEnv()->GetMethodID(HttpEntity::Class, "writeTo", "(Ljava/io/OutputStream;)V");
HttpEntity::GetContent = GetJniEnv()->GetMethodID(HttpEntity::Class, "getContent", "()Ljava/io/InputStream;");
}
函数initializeJniPointers()在StatusLine::GetStatusCode = GetJniEnv()-> GetMethodID()处粉碎;因为StatusLine::Class为NULL。
但!我注意到:
如果我在项目的某些Java文件中编写此代码
StatusLine l =新的StatuLine()
{
...
}
函数在ByteArrayOutputStream::Constructor上崩溃,因为ByteArrayOutputStream::Class为NULL,如果我在Java中创建ByteArrayOutputStream的对象,则函数将进一步移至下一个对象,以此类推。 ,findClass将返回NULL。
有人可以解释我该怎么做吗?顺便说一句,我使用的是Android 2.3.5设备Samsung GT-S5363,我尝试了其他版本的android(老年)和设备,并且工作正常。
最佳答案
基本上,如果您询问FindClass
的线程不是主线程,并且您的线程系统中的线程没有建立Java类ID的映射,则可能发生这种情况。
进行检查,可能您必须首先在主线程中询问FindClass
(在JNI加载时或在其他位置),然后您将能够在任何线程中执行此操作。
http://discuss.cocos2d-x.org/t/jni-findclass-cannot-find-a-class-if-its-called-by-a-new-pthread/1873/4
也尝试一下,这对我有用:
https://svn.apache.org/repos/asf/mesos/branches/0.10.x/src/java/jni/convert.cpp
解决方案(来自上面的链接)是从您的应用程序中以JNI_OnLoad
查找Java类加载器,然后要求他从任何线程中查找类。否则,在调用env->FindClass
之后,JNI可以回退到系统类加载器,后者仅加载像String
这样的系统类。