我在Objective C中有一个类来发现网络打印机。我找到了我的打印机，但是当我的代码稍后[在退出DiscoverDevices之后]检查null /修剪设备列表时，它会抛出EXC_BAD_ACCESS code=2。我是Objective C的新手，在这里真的需要你的帮助。也可以随意进行代码审查。
我怀疑PrinterCallBack_PUT_bluetoothDevices([jsonString description]);
String格式/地址的一些问题但不确定
代码如下：
#import "DiscoverDevices.h"
#import "ePOS-Print.h"
#import "java_lang_String.h";
#import "org_json_me_JSONObject.h";
#define DISCOVERY_INTERVAL 0.5
@interface DiscoverDevices()
- (void)timerFindPrinter:(NSTimer*)timer;
- (void)findStart;
- (void) doNothing;
@end
@implementation DiscoverDevices
@synthesize delegate = delegate_;
- (id)init {
self = [super init];
if (self) {
printerList_ = [[NSMutableArray alloc] init];
}
[self findStart];
[self timerFindPrinter:timer_];
//TODO:find a better way to wait till printer is discovered here
// for now works
for (int i=0; i<500; i++) {
if (printerList_.count>0) {
break;
}
[self timerFindPrinter:timer_];
}
NSLog(@"-----printerList = %@",printerList_);
NSError * error;
NSMutableDictionary *dictObj = [[NSMutableDictionary alloc] init];
for (int i=0; i<printerList_.count; i++) {
NSLog(@"printerList[%d] = %@",i,printerList_[i]);
[dictObj setObject:printerList_[i] forKey:printerList_[i]];
NSLog(@"jsonobject put [%d]",i);
}
NSLog(@"Dict : %@",dictObj);
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dictObj options:NSJSONWritingPrettyPrinted error:&error];
if (!jsonData) {
NSLog(@"Got an error: %@",error);
} else {
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
jsonString = [jsonString stringByReplacingOccurrencesOfString:@"\n" withString:@""];
jsonString = [jsonString stringByReplacingOccurrencesOfString:@" " withString:@""];
NSLog(@"In native discoverDevices devices found jsonstring = %@, %s", jsonString, object_getClassName([jsonString class]));
if ([jsonString length]>2) {
// This is where we set the list of printers found.
com_nvsoft_s2pay_print_PrinterCallBack_PUT_bluetoothDevices([jsonString description]);
NSLog(@"In native discoverDevices written json to callback now reading....");
NSLog(@"In native discoverDevices from cback json = %@, %s", com_nvsoft_s2pay_print_PrinterCallBack_GET_bluetoothDevices(),object_getClassName([com_nvsoft_s2pay_print_PrinterCallBack_GET_bluetoothDevices() class]));
}else{
com_nvsoft_s2pay_print_PrinterCallBack_PUT_bluetoothDevices(nil);
}
com_nvsoft_s2pay_print_PrinterCallBack_PUT_result(1);
NSLog(@"In native discoverDevices completed jsondaata");
}
NSLog(@"In native discoverDevices exiting after jsondaata");
NSLog(@"In native discoverDevices from cback json = %@", com_nvsoft_s2pay_print_PrinterCallBack_GET_bluetoothDevices());
return self;
}
- (void)dealloc
{
[printerList_ release];
[super dealloc];
}
//find printer timer
- (void)timerFindPrinter:(NSTimer*)timer
{
NSLog(@"In timerFindPrinter");
int result = 0;
NSArray *items = [EpsonIoFinder getResult:&result];
if(items != nil && result ==EPSONIO_OC_SUCCESS){
bool change = NO;
if([printerList_ count] != [items count]){
[printerList_ release];
printerList_ = [items retain];
change = YES;
}
/*if(change){
[self performSelectorOnMainThread:@selector(doNothing) withObject:nil waitUntilDone:YES];
}*/
}
}
//find start/restart
- (void)findStart
{
NSLog(@"In findStart");
//stop old finder
[EpsonIoFinder stop];
//stop find timer
if(timer_ != nil){
[timer_ invalidate];
[timer_ release];
timer_ = nil;
}
//clear list
[printerList_ release];
printerList_ = [[NSMutableArray alloc] init];
//if(printerView_ != nil){
// [printerView_ reloadData];
//}
//find start
int result = [EpsonIoFinder start:EPSONIO_OC_DEVTYPE_TCP FindOption:@"255.255.255.255"];
if(result != EPSONIO_OC_SUCCESS){
return ;
}
//start timer
timer_ = [NSTimer scheduledTimerWithTimeInterval:DISCOVERY_INTERVAL
target:self
selector:@selector(timerFindPrinter:)
userInfo:nil
repeats:YES];
}
@end
我的控制台输出是：
2014-02-26 11:50:24.661 S2PayApp[10749:1807] -----printerList = (
"192.168.0.13"
)
2014-02-26 11:50:24.662 S2PayApp[10749:1807] printerList[0] = 192.168.0.13
2014-02-26 11:50:24.662 S2PayApp[10749:1807] jsonobject put [0]
2014-02-26 11:50:24.663 S2PayApp[10749:1807] Dict : {
"192.168.0.13" = "192.168.0.13";
}
2014-02-26 11:50:24.664 S2PayApp[10749:1807] In native discoverDevices devices found jsonstring = {"192.168.0.13":"192.168.0.13"}, __NSCFString
2014-02-26 11:50:24.664 S2PayApp[10749:1807] In native discoverDevices written json to callback now reading....
2014-02-26 11:50:24.665 S2PayApp[10749:1807] In native discoverDevices from cback json = {"192.168.0.13":"192.168.0.13"}, __NSCFString
2014-02-26 11:50:24.665 S2PayApp[10749:1807] In native discoverDevices completed
jsondaata
2014-02-26 11:50:24.666 S2PayApp[10749:1807] In native discoverDevices exiting after jsondaata
2014-02-26 11:50:24.667 S2PayApp[10749:1807] In native discoverDevices from cback json = {"192.168.0.13":"192.168.0.13"}
2014-02-26 11:50:24.667 S2PayApp[10749:1807] --3-- In native discoverDevices from cback json = {"192.168.0.13":"192.168.0.13"}
2014-02-26 11:50:24.668 S2PayApp[10749:1807] completed discoveing ntwk printers
2014-02-26 11:50:24.669 S2PayApp[10749:1807] devices r9= {"192.168.0.13":"192.168.0.13"},__NSCFString
2014-02-26 11:50:24.669 S2PayApp[10749:1807] devices r4= {"192.168.0.13":"192.168.0.13"},__NSCFString
(lldb)
这是他的代码中断的确切类：
JAVA_BOOLEAN com_nvsoft_s2pay_util_StringUtil_isEmpty___java_lang_String(JAVA_OBJECT n1)
{
if (!__TIB_com_nvsoft_s2pay_util_StringUtil.classInitialized) __INIT_com_nvsoft_s2pay_util_StringUtil();
//XMLVM_BEGIN_WRAPPER[com_nvsoft_s2pay_util_StringUtil_isEmpty___java_lang_String]
XMLVM_ENTER_METHOD("com.nvsoft.s2pay.util.StringUtil", "isEmpty", "?")
XMLVMElem _r0;
XMLVMElem _r1;
XMLVMElem _r2;
_r2.o = n1;
XMLVM_SOURCE_POSITION("StringUtil.java", 152)
//NSLog(@"In StringUtil devices r2= %@", _r2.o);
if (_r2.o == JAVA_NULL) goto label22;
XMLVM_CHECK_NPE(2)
_r0.o = java_lang_String_trim__(_r2.o);
// ""
_r1.o = xmlvm_create_java_string_from_pool(13);
//NSLog(@"In StringUtil devices r0= %@,%s", _r0.o);
//NSLog(@"In StringUtil devices r1= %@,%s", _r1.o);
//java_lang_String_equals___java_lang_Object[1]
XMLVM_CHECK_NPE(0)
//************ Code breaks here
_r0.i = (*(JAVA_BOOLEAN (*)(JAVA_OBJECT, JAVA_OBJECT)) ((java_lang_String*) _r0.o)->tib->vtable[1])(_r0.o, _r1.o);
if (_r0.i != 0) goto label22;
// "null"
_r0.o = xmlvm_create_java_string_from_pool(9);
//java_lang_String_equals___java_lang_Object[1]
XMLVM_CHECK_NPE(2)
_r0.i = (*(JAVA_BOOLEAN (*)(JAVA_OBJECT, JAVA_OBJECT)) ((java_lang_String*) _r2.o)->tib->vtable[1])(_r2.o, _r0.o);
if (_r0.i == 0) goto label24;
label22:;
_r0.i = 1;
label23:;
XMLVM_EXIT_METHOD()
return _r0.i;
label24:;
_r0.i = 0;
goto label23;
//XMLVM_END_WRAPPER
}
答案 0 :(得分：0)
当你看到那种崩溃时，失败就在别处。我猜你有一个内存腐败导致了这个。这通常是通过使用错误的参数类型调用c函数或通过保持对GC对象的引用或保持对已发布的Objective-C对象的引用来访问无效内存引起的。
你可以在xcode的左侧看到崩溃中的调用堆栈，只是在那里的模式之间切换，你应该看到所有的线程都有一个很好的堆栈，可以告诉你发生了什么。虽然主要的iOS线程有点迟钝，但它有点令人困惑。