我在处理JNA中的回调时遇到问题。
我试图使用一个使用回调来处理多个会话事件的C API（登录，注销，连接问题......）。
会话对象（称为sp_session）是一个不透明的结构。所有回调都在sp_session_callbacks结构中注册。根据API，我应该声明callbacks对象，并将其放入我将在创建sp_session对象时提供的Config对象中。如果我不想使用某些回调，我应该使用null初始化它们。 API正在使用__stdcall调用约定。
以下是与我的问题相关的C标题的摘录：
#define SP_CALLCONV __stdcall
typedef struct sp_session sp_session; ///< Representation of a session
typedef enum sp_error {
SP_ERROR_OK = 0,
SP_ERROR_BAD_API_VERSION = 1,
/* More errors */
} sp_error;
typedef struct sp_session_callbacks {
/**
* Called when login has been processed and was successful
*/
void (SP_CALLCONV *logged_in)(sp_session *session, sp_error error);
/**
* Called when logout has been processed. Either called explicitly
* if you initialize a logout operation, or implicitly if there
* is a permanent connection error
*
* @param[in] session Session
*/
void (SP_CALLCONV *logged_out)(sp_session *session);
/**
* Called when there is a connection error, and the library has problems
* reconnecting to the Spotify service. Could be called multiple times (as
* long as the problem is present)
*/
void (SP_CALLCONV *connection_error)(sp_session *session, sp_error error);
/* More callbacks */
} sp_session_callbacks;
/**
* Initialize a session. The session returned will be initialized, but you will need
* to log in before you can perform any other operation
*/
SP_LIBEXPORT(sp_error) sp_session_create(const sp_session_config *config, sp_session **sess);
这是我的等效JNA代码：
sp_session对象
public class sp_session extends PointerType{
public sp_session(Pointer address) {
super(address);
}
public sp_session() {
super();
}
}
包含所有回调的sp_session_callbacks对象
public class sp_session_callbacks extends Structure{
public LoggedIn logged_in;
public LoggedOut logged_out;
public ConnectionError connection_error;
}
回调对象（这里是LoggedIn，当然我每次回调都有一个）
public interface LoggedIn extends StdCallCallback {
public void logged_in(sp_session session, int error);
}
本地库，包含所有方法的声明
public interface JLibspotify extends StdCallLibrary{
int sessionCreate(sp_session_config config, PointerByReference sess);
int sessionLogin(sp_session session, String username, String password);
// All the other methods defined by the API
}
我的主要课程，将它们绑定在一起
public class Test{
static{
System.loadLibrary("libspotify");
}
public static void main(String[] args){
JLibspotify lib = (JLibspotify)Native.loadLibrary("libspotify", JLibspotify.class);
sp_session_config cfg = new sp_session_config();
}
sp_session_callbacks sessCallbacks = new sp_session_callbacks();
LoggedIn loggedInCallback = new LoggedIn(){
public void logged_in(sp_session session, int error) {
System.out.println("logged_in() called");
}
};
sessCallbacks.logged_in = loggedInCallback;
cfg.session_callbacks = sessCallbacks;
PointerByReference sessionPbr = new PointerByReference();
int error_id = sessionCreate(cfg, sessionPbr); // CRASHES HERE
sp_session mySession = new sp_session(sessionPbr.getValue());
}
}
因此，sessionCreate函数调用使JRE在帖子EXCEPTION_ACCESS_VIOLATION (0xc0000005) problematic frame: C [jna3666290841889849729.dll+0xa3f4]末尾的跟踪崩溃。
看起来，logged_in回调导致了这种情况，因为当我将其设置为null时，它运行正常。另外，如果我初始化connection_error回调，它具有完全相同的签名，它也不会崩溃。
我正在运行JNA的3.2.7版。我尝试使用前版（3.0.9），但也失败了。 我正在运行JDK 1.7测试版，但我尝试使用1.6并且它也失败了。
谢谢！
#
# A fatal error has been detected by the Java Runtime Environment:
#
# EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x0499a3f4, pid=1368, tid=1344
#
# JRE version: 7.0-b129
# Java VM: Java HotSpot(TM) Client VM (21.0-b01 mixed mode, sharing windows-x86 )
# Problematic frame:
# C [jna3666290841889849729.dll+0xa3f4]
#
# If you would like to submit a bug report, please visit:
# http://java.sun.com/webapps/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#
--------------- T H R E A D ---------------
Current thread (0x01b79400): JavaThread "main" [_thread_in_native, id=1344, stack(0x00340000,0x00390000)]
siginfo: ExceptionCode=0xc0000005, reading address 0x1993053a
Registers:
EAX=0x19930522, EBX=0x100dc77c, ECX=0x00010004, EDX=0x1008d3e0
ESP=0x0038f58c, EBP=0x0038f5b4, ESI=0x0038f5a4, EDI=0x100b79b0
EIP=0x0499a3f4, EFLAGS=0x00210212
Top of Stack: (sp=0x0038f58c)
0x0038f58c: 100dc77c 0038f5a4 00010004 0038f688
0x0038f59c: 05983de0 05981330 0598289c 05983de0
0x0038f5ac: 05983de0 00000014 0038f688 1008d3ea
0x0038f5bc: 05983de0 10030d77 0038fc44 100b79b0
0x0038f5cc: ffffffff 1008d334 00000000 05983de0
0x0038f5dc: 1008d3e0 05983fc4 1008d9fd 0038f770
0x0038f5ec: 00000000 00000000 7275016a 055310b0
0x0038f5fc: 00000000 00010001 00000000 00000000
Instructions: (pc=0x0499a3f4)
0x0499a3d4: 01 00 89 e5 57 56 8d 75 f0 53 83 ec 1c 8b 7d 14
0x0499a3e4: 8b 5f 4c 8b 03 89 4c 24 08 89 74 24 04 89 1c 24
0x0499a3f4: ff 50 18 83 ec 0c 85 c0 0f 94 c0 0f b6 c0 85 c0
0x0499a404: 89 45 ec 75 19 8b 03 31 d2 89 54 24 08 89 74 24
Register to memory mapping:
EAX=0x19930522 is an unknown value
EBX=0x100dc77c is an unknown value
ECX=0x00010004 is an unknown value
EDX=0x1008d3e0 is an unknown value
ESP=0x0038f58c is pointing into the stack for thread: 0x01b79400
EBP=0x0038f5b4 is pointing into the stack for thread: 0x01b79400
ESI=0x0038f5a4 is pointing into the stack for thread: 0x01b79400
EDI=0x100b79b0 is an unknown value
Stack: [0x00340000,0x00390000], sp=0x0038f58c, free space=317k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
C [jna3666290841889849729.dll+0xa3f4] Java_com_sun_jna_Native_initialize_1ffi_1type+0x1054
C [libspotify.dll+0x8d3ea] sp_error_message+0x35a
C [jna3666290841889849729.dll+0xcb77] Java_com_sun_jna_Native_initialize_1ffi_1type+0x37d7
C [jna3666290841889849729.dll+0xc7c2] Java_com_sun_jna_Native_initialize_1ffi_1type+0x3422
C [jna3666290841889849729.dll+0x4561] Java_com_sun_jna_Pointer__1getString+0xa31
C [jna3666290841889849729.dll+0x4d2e] Java_com_sun_jna_Function_invokeInt+0x2e
j com.sun.jna.Function.invokeInt(I[Ljava/lang/Object;)I+0
j com.sun.jna.Function.invoke([Ljava/lang/Object;Ljava/lang/Class;Z)Ljava/lang/Object;+315
j com.sun.jna.Function.invoke(Ljava/lang/Class;[Ljava/lang/Object;Ljava/util/Map;)Ljava/lang/Object;+214
j com.sun.jna.Library$Handler.invoke(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;+341
j $Proxy0.sp_session_create(Lcom/nbarraille/jspotify/model/sp_session_config;Lcom/sun/jna/ptr/PointerByReference;)I+20
j com.nbarraille.jspotify.main.Test.main([Ljava/lang/String;)V+273
v ~StubRoutines::call_stub
V [jvm.dll+0x115f6d]
V [jvm.dll+0x1b788e]
V [jvm.dll+0x115fed]
V [jvm.dll+0xa2507]
V [jvm.dll+0xac867]
C [javaw.exe+0x209e]
C [javaw.exe+0xa23b]
C [javaw.exe+0xa2c5]
C [kernel32.dll+0x51194] BaseThreadInitThunk+0x12
C [ntdll.dll+0x5b429] RtlInitializeExceptionChain+0x63
C [ntdll.dll+0x5b3fc] RtlInitializeExceptionChain+0x36
Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
j com.sun.jna.Function.invokeInt(I[Ljava/lang/Object;)I+0
j com.sun.jna.Function.invoke([Ljava/lang/Object;Ljava/lang/Class;Z)Ljava/lang/Object;+315
j com.sun.jna.Function.invoke(Ljava/lang/Class;[Ljava/lang/Object;Ljava/util/Map;)Ljava/lang/Object;+214
j com.sun.jna.Library$Handler.invoke(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;+341
j $Proxy0.sp_session_create(Lcom/nbarraille/jspotify/model/sp_session_config;Lcom/sun/jna/ptr/PointerByReference;)I+20
j com.nbarraille.jspotify.main.Test.main([Ljava/lang/String;)V+273
v ~StubRoutines::call_stub
--------------- P R O C E S S ---------------
Java Threads: ( => current thread )
0x0182fc00 JavaThread "Low Memory Detector" daemon [_thread_blocked, id=4664, stack(0x04170000,0x041c0000)]
0x0182ac00 JavaThread "C1 CompilerThread0" daemon [_thread_blocked, id=1728, stack(0x01b20000,0x01b70000)]
0x01829800 JavaThread "Attach Listener" daemon [_thread_blocked, id=112, stack(0x04020000,0x04070000)]
0x01826400 JavaThread "Signal Dispatcher" daemon [_thread_blocked, id=5836, stack(0x03ea0000,0x03ef0000)]
0x01819800 JavaThread "Finalizer" daemon [_thread_blocked, id=4724, stack(0x03f80000,0x03fd0000)]
0x01817800 JavaThread "Reference Handler" daemon [_thread_blocked, id=3940, stack(0x01ad0000,0x01b20000)]
=>0x01b79400 JavaThread "main" [_thread_in_native, id=1344, stack(0x00340000,0x00390000)]
Other Threads:
0x01816400 VMThread [stack: 0x01a30000,0x01a80000] [id=3876]
0x01843000 WatcherThread [stack: 0x040d0000,0x04120000] [id=4636]
VM state:not at safepoint (normal execution)
VM Mutex/Monitor currently owned by a thread: None
Heap
def new generation total 4928K, used 3630K [0x23450000, 0x239a0000, 0x289a0000)
eden space 4416K, 82% used [0x23450000, 0x237db858, 0x238a0000)
from space 512K, 0% used [0x238a0000, 0x238a0000, 0x23920000)
to space 512K, 0% used [0x23920000, 0x23920000, 0x239a0000)
tenured generation total 10944K, used 0K [0x289a0000, 0x29450000, 0x33450000)
the space 10944K, 0% used [0x289a0000, 0x289a0000, 0x289a0200, 0x29450000)
compacting perm gen total 12288K, used 860K [0x33450000, 0x34050000, 0x37450000)
the space 12288K, 7% used [0x33450000, 0x33527190, 0x33527200, 0x34050000)
ro space 10240K, 43% used [0x37450000, 0x3789ce40, 0x3789d000, 0x37e50000)
rw space 12288K, 53% used [0x37e50000, 0x384c2710, 0x384c2800, 0x38a50000)
Code Cache [0x01e90000, 0x01f20000, 0x03e90000)
total_blobs=234 nmethods=82 adapters=88 free_code_cache=32972224 largest_free_block=0
Dynamic libraries:
0x00880000 - 0x008b0000 C:\Program Files\Java\jdk1.7.0\bin\javaw.exe
0x778f0000 - 0x77a2d000 C:\Windows\SYSTEM32\ntdll.dll
0x77070000 - 0x77144000 C:\Windows\system32\kernel32.dll
0x75cf0000 - 0x75d3a000 C:\Windows\system32\KERNELBASE.dll
0x60000000 - 0x60041000 C:\Program Files\BitDefender\BitDefender 2011\Active Virus Control\Midas_00078_002\midas32.dll
0x61000000 - 0x61028000 C:\Program Files\BitDefender\BitDefender 2011\Active Virus Control\Midas_00078_002\plugin_base.m32
0x67000000 - 0x67048000 C:\Program Files\BitDefender\BitDefender 2011\Active Virus Control\Midas_00078_002\plugin_nt.m32
0x64000000 - 0x64021000 C:\Program Files\BitDefender\BitDefender 2011\Active Virus Control\Midas_00078_002\plugin_registry.m32
0x62000000 - 0x6202d000 C:\Program Files\BitDefender\BitDefender 2011\Active Virus Control\Midas_00078_002\plugin_extra.m32
0x65000000 - 0x6501a000 C:\Program Files\BitDefender\BitDefender 2011\Active Virus Control\Midas_00078_002\plugin_net.m32
0x63000000 - 0x630a6000 C:\Program Files\BitDefender\BitDefender 2011\Active Virus Control\Midas_00078_002\plugin_fragments.m32
0x75e10000 - 0x75eb0000 C:\Windows\system32\ADVAPI32.dll
0x775c0000 - 0x7766c000 C:\Windows\system32\msvcrt.dll
0x75d50000 - 0x75d69000 C:\Windows\SYSTEM32\sechost.dll
0x77670000 - 0x77711000 C:\Windows\system32\RPCRT4.dll
0x76f00000 - 0x76fc9000 C:\Windows\system32\USER32.dll
0x77a50000 - 0x77a9e000 C:\Windows\system32\GDI32.dll
0x77a30000 - 0x77a3a000 C:\Windows\system32\LPK.dll
0x75d70000 - 0x75e0d000 C:\Windows\system32\USP10.dll
0x74830000 - 0x749ce000 C:\Windows\WinSxS\x86_microsoft.windows.common-controls_6595b64144ccf1df_6.0.7600.16661_none_420fe3fa2b8113bd\COMCTL32.dll
0x772f0000 - 0x77347000 C:\Windows\system32\SHLWAPI.dll
0x775a0000 - 0x775bf000 C:\Windows\system32\IMM32.DLL
0x75eb0000 - 0x75f7c000 C:\Windows\system32\MSCTF.dll
0x72740000 - 0x727fe000 C:\Program Files\Java\jdk1.7.0\jre\bin\msvcr100.dll
0x01b80000 - 0x01e89000 C:\Program Files\Java\jdk1.7.0\jre\bin\client\jvm.dll
0x746c0000 - 0x746f2000 C:\Windows\system32\WINMM.dll
0x73920000 - 0x7392c000 C:\Program Files\Java\jdk1.7.0\jre\bin\verify.dll
0x73330000 - 0x73350000 C:\Program Files\Java\jdk1.7.0\jre\bin\java.dll
0x75d40000 - 0x75d45000 C:\Windows\system32\PSAPI.DLL
0x733a0000 - 0x733b3000 C:\Program Files\Java\jdk1.7.0\jre\bin\zip.dll
0x10000000 - 0x10259000 C:\Windows\System32\libspotify.dll
0x77150000 - 0x77185000 C:\Windows\system32\WS2_32.dll
0x77a40000 - 0x77a46000 C:\Windows\system32\NSI.dll
0x75ba0000 - 0x75cbc000 C:\Windows\system32\CRYPT32.dll
0x75ab0000 - 0x75abc000 C:\Windows\system32\MSASN1.dll
0x74ee0000 - 0x74f38000 C:\Windows\system32\WINHTTP.dll
0x74e90000 - 0x74edf000 C:\Windows\system32\webio.dll
0x754c0000 - 0x754d6000 C:\Windows\system32\CRYPTSP.dll
0x75260000 - 0x7529b000 C:\Windows\system32\rsaenh.dll
0x750a0000 - 0x750b7000 C:\Windows\system32\USERENV.dll
0x75a40000 - 0x75a4b000 C:\Windows\system32\profapi.dll
0x75a30000 - 0x75a3c000 C:\Windows\system32\CRYPTBASE.dll
0x728a0000 - 0x728b6000 C:\Program Files\Java\jdk1.7.0\jre\bin\net.dll
0x75480000 - 0x754bc000 C:\Windows\system32\mswsock.dll
0x75470000 - 0x75476000 C:\Windows\System32\wship6.dll
0x73950000 - 0x73960000 C:\Windows\system32\NLAapi.dll
0x75340000 - 0x75384000 C:\Windows\system32\DNSAPI.dll
0x71030000 - 0x71038000 C:\Windows\System32\winrnr.dll
0x71020000 - 0x71030000 C:\Windows\system32\napinsp.dll
0x71000000 - 0x71012000 C:\Windows\system32\pnrpnsp.dll
0x74fd0000 - 0x74fd5000 C:\Windows\System32\wshtcpip.dll
0x74d30000 - 0x74d4c000 C:\Windows\system32\IPHLPAPI.DLL
0x74d20000 - 0x74d27000 C:\Windows\system32\WINNSI.DLL
0x70c60000 - 0x70c66000 C:\Windows\system32\rasadhlp.dll
0x71ba0000 - 0x71bd8000 C:\Windows\System32\fwpuclnt.dll
0x73930000 - 0x7393f000 C:\Program Files\Java\jdk1.7.0\jre\bin\nio.dll
0x04990000 - 0x049e5000 C:\Users\nbarraille\AppData\Local\Temp\jna3666290841889849729.dll
VM Arguments:
jvm_args: -Djava.library.path=C:\Windows\System32 -Dfile.encoding=Cp1252
java_command: com.nbarraille.jspotify.main.Test
Launcher Type: SUN_STANDARD
Environment Variables:
PATH=C:/Program Files/Java/jdk1.7.0/bin/../jre/bin/client;C:/Program Files/Java/jdk1.7.0/bin/../jre/bin;C:/Program Files/Java/jdk1.7.0/bin/../jre/lib/i386;C:\Windows\System32
USERNAME=nbarraille
OS=Windows_NT
PROCESSOR_IDENTIFIER=x86 Family 6 Model 23 Stepping 10, GenuineIntel
--------------- S Y S T E M ---------------
OS: Windows 7 Build 7600
CPU:total 2 (2 cores per cpu, 1 threads per core) family 6 model 23 stepping 10, cmov, cx8, fxsr, mmx, sse, sse2, sse3, ssse3, sse4.1
Memory: 4k page, physical 3624108k(885020k free), swap 7246452k(3637664k free)
vm_info: Java HotSpot(TM) Client VM (21.0-b01) for windows-x86 JRE (1.7.0-ea-b129), built on Feb 10 2011 07:43:39 by "java_re" with unknown MS VC++:1600
time: Mon Mar 07 14:25:08 2011
elapsed time: 0 seconds
修改 * 用于在C *
中测试API的代码#include "api.h"
/* --- Data --- */
const uint8_t g_appkey[] = {/*My appkey*/};
/* --------------------------- SESSION CALLBACKS ------------------------- */
static void logged_in(sp_session *sess, sp_error error){
printf("logged_in() called: \n");
}
static void log_message(sp_session *sess, const char *data){
printf("log_message() called %s : \n", data);
}
static void notify_main_thread(sp_session *sess){
printf("notify_main_thread() called \n");
}
static sp_session_callbacks session_callbacks = {
//.logged_in = (void*)&logged_in,
//.notify_main_thread = (void*)¬ify_main_thread,
//.log_message = (void*)&log_message,
};
static sp_session_config spconfig = {
.api_version = 7,
.cache_location = "tmp",
.settings_location = "tmp",
.application_key = g_appkey,
.application_key_size = sizeof(g_appkey),
.user_agent = "jspotify",
.callbacks = &session_callbacks,
.userdata = NULL
};
int main(int argc, char **argv)
{
sp_session *sp;
const char *username = "foo";
const char *password = "bar";
spconfig.application_key_size = sizeof(g_appkey);
printf("Creating session \n");
sp_error err = sp_session_create(&spconfig, &sp);
if(err != 0){
printf("Error occured: %d \n", err);
return 0;
}
printf("Login\n");
sp_session_login(sp, username, password);
Sleep(10000);
return 0;
}
当我像这样运行它（没有回调）时，输出是：
Creating session
Login
当我注册回调（取消注释行）时，它甚至不打印任何东西！
看起来它在调用回调时没有打印任何东西，因为如果我评论sp_session_login行，只有notify_main_thread（这是唯一打印的）的声明将会阻止程序打印...
答案 0 :(得分：5)
当你有一个C结构时：
struct Foo {
Bar* bar
}
即。一个包含指向另一个结构的指针，你的JNA实现Bar（class Bar extends Structure）也必须实现Structure.ByReference接口 - 否则JNA会认为struct Foo包含{{1}的实例而不是指向struct Bar的指针，并且当C代码将Bar实例中的值解释为指针时，将导致非法的内存访问。
您需要将struct Bar添加到implements Structure.ByReference类。
感谢鼓励我看看JNA - 这很酷！
此代码的输出为：
sp_session_callbacks处理完成，退出代码为0
sp_session_create returned 0
sp_session_login returned 0
log_message() called:14:16:53.825 I [ap:1388] Connecting to AP ap.spotify.com:4070
log_message() called:14:16:54.061 I [ap:938] Connected to AP: 193.182.8.11:4070
log_message() called:14:16:54.765 E [ap:3396] Connection error: 401
这是一个C程序，它做同样的事情（回调较少 - 你需要添加更多）。它适用于OS X，因此您可能需要更改import com.sun.jna.*;
import com.sun.jna.ptr.PointerByReference;
import java.sql.Connection;
public class JNATest {
// static {
// System.loadLibrary("libspotify");
// }
public interface JLibspotify extends Library {
int sp_session_create(sp_session_config config, PointerByReference sess);
int sp_session_login(sp_session session, String username, String password);
// All the other methods defined by the API
}
public static class sp_session extends PointerType {
public sp_session(Pointer address) {
super(address);
}
public sp_session() {
super();
}
}
public static class sp_session_config extends Structure {
public int api_version = 7; // The version of the Spotify API your application is compiled with.
public String cache_location = ".";
public String settings_location = ".";
public Pointer application_key; // Your application key.
public int application_key_size; // The size of the application key in bytes
public String user_agent = "jspotify";
public sp_session_callbacks callbacks; // Delivery callbacks for session events. NULL if not interested in any callbacks
public Pointer userdata; // User supplied data for your application
public boolean compress_playlists;
public boolean dont_save_metadata_for_playlists;
public boolean initially_unload_playlists;
}
public interface LoggedIn extends Callback {
public void logged_in(sp_session session, int error);
}
public interface LoggedOut extends Callback {
public void logged_out(sp_session session, int error);
}
public interface ConnectionError extends Callback {
public void connection_error(sp_session session, int error);
}
public static class sp_session_callbacks extends Structure implements Structure.ByReference{
public LoggedIn logged_in; // Called when login has been processed and was successful
public LoggedOut logged_out; // Called when logout has been processded. Either called explicitly if you initialize a logout operation, or implicitly if there is a permanent connection error.
public Callback metadata_updated; // Called whenever metadata has been updated. If you have metadata cached outside of libspotify, you should purge your caches and fetch new versions.
public ConnectionError connection_error; // Called when there is a connection error, and the library has problems reconnecting to the Spotify service. Could be called multiple times (as long as the problem is present)
public Callback message_to_user; // Called when the acces point wants to display a message to the user. In the desktop client, these are shown in a blueish toolbar just below the search box.
public Callback notify_main_thread; // Called when processing needs to take place on the main thread. You need to call sp_session_process_events() in the main thread to get libspotify to do more work. Failure to do so may cause request timeouts, or a lost connections.
public Callback music_delivery; // Called when there is decompressed audio data available.
public Callback play_token_lost; // Music has been paused because only one account may play music at the same time.
public Callback log_message; // Logging callback
public Callback end_of_track; // End of track. Called when the currently played track has reached its end.
public Callback streaming_error; // Streaming error. Called when streaming cannot start or continue.
public Callback userinfo_updated; // Called after user info (anything related to sp_user objects) have been updated.
public Callback start_playback; // Called when audio playback should start. For this to work correctly the application must also implement get_audio_buffer_stats(). This function is called from an internal session thread - you need to have proper synchronization. This function must never block.
public Callback stop_playback; // Called when audio playback should stop. For this to work correctly the application must also implement get_audio_buffer_stats(). This function is called from an internal session thread - you need to have proper synchronization. This function must never block.
public Callback get_audio_buffer_stats; // Called to query application about its audio buffer. This function is called from an internal session thread - you need to have proper synchronization! This function must never block.
}
private static final char[] APP_KEY ={/* Appkey here**/;
public static void main(String[] args) throws InterruptedException {
JLibspotify lib = (JLibspotify) Native.loadLibrary("spotify", JLibspotify.class);
sp_session_config cfg = new sp_session_config();
Pointer ptr = new Memory(APP_KEY.length);
ptr.write(0, toBytes(APP_KEY), 0, APP_KEY.length);
cfg.application_key = ptr;
cfg.application_key_size = APP_KEY.length;
sp_session_callbacks sessCallbacks = new sp_session_callbacks();
LoggedIn loggedInCallback = new LoggedIn() {
public void logged_in(sp_session session, int error) {
System.out.println("logged_in() called");
}
};
ConnectionError connectionErrorCallback = new ConnectionError() {
public void connection_error(sp_session session, int error) {
System.out.println("connection_error() called");
}
};
LoggedOut loggedOutCallback = new LoggedOut() {
public void logged_out(sp_session session, int error) {
System.out.println("logged_out() called");
}
};
sessCallbacks.logged_in = loggedInCallback;
sessCallbacks.connection_error = connectionErrorCallback;
sessCallbacks.logged_out = loggedOutCallback;
sessCallbacks.log_message = new Callback() {
public void callback(sp_session session, String message) {
System.out.println("log_message() called:" + message);
}
};
cfg.callbacks = sessCallbacks;
PointerByReference sessionPbr = new PointerByReference();
int error_id = lib.sp_session_create(cfg, sessionPbr); // CRASHES HERE
System.out.println("sp_session_create returned " + error_id);
//
sp_session mySession = new sp_session(sessionPbr.getValue());
error_id = lib.sp_session_login(mySession, "foo", "bar");
System.out.println("sp_session_login returned " + error_id);
Thread.sleep(1000);
}
public static byte[] toBytes(char[] key){
byte[] b = new byte[key.length];
for(int i =0; i < key.length; i++){
if(key[i] > 127){
b[i] = (byte)(key[i] - 256);
}else{
b[i] = (byte)key[i];
}
}
return b;
}
}
。由于我无法在澳大利亚获得spotify，因此我无法测试它是否成功登录是否会收到回调，但日志回调是否有效。
#include如果C程序调用Java版本没有的回调，那么使用jna可能有问题 - 如果没有，也许有更多关于spotify以及何时调用回调的内容。我同意文档似乎说成功登录会调用回调，但也许它们已经过时了？