通过访问 Quartz 2D 编程指南和 SO 上的一些帖子，我拼凑了一些代码来读取 PDF 文件的内容。我认为它在 PDF 扫描仪部分失败了。当我释放扫描仪时，应用程序因以下错误而崩溃：
avi(2282,0x3de7bb88) malloc: *** error for object 0x693f7c0: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
我正在通过电子邮件附件打开 PDF 文件。我知道它至少可以识别文件，因为我可以获得页数。有人可以看看我下面的代码，看看我的错误发生在哪里吗？谢谢。
- (void) readPDFFile:(NSURL *)PDFURL {
//make a pdf document and point it to the url of our pdf file
CGPDFDocumentRef pdfDocument;
pdfDocument = CGPDFDocumentCreateWithURL((__bridge CFURLRef)(PDFURL));
//release the url
CFRelease((__bridge CFTypeRef)(PDFURL));
if (pdfDocument) {
//get page count
int pageCount = CGPDFDocumentGetNumberOfPages (pdfDocument);
//
if (pageCount > 0) {
//set up operator table
CGPDFOperatorTableRef pdfOpTable;
pdfOpTable = CGPDFOperatorTableCreate();
//call backs for Op Table
CGPDFOperatorTableSetCallback (pdfOpTable, "MP", &op_MP);
CGPDFOperatorTableSetCallback (pdfOpTable, "DP", &op_DP);
CGPDFOperatorTableSetCallback (pdfOpTable, "BMC", &op_BMC);
CGPDFOperatorTableSetCallback (pdfOpTable, "BDC", &op_BDC);
CGPDFOperatorTableSetCallback (pdfOpTable, "EMC", &op_EMC);
for(int i=0; i<pageCount; i++) {
//set up
CGPDFPageRef thisPage;
CGPDFScannerRef pdfScanner;
CGPDFContentStreamRef thisContentStream;
//get the page
thisPage = CGPDFDocumentGetPage (pdfDocument, i + 1 );
//get the page content stream
thisContentStream = CGPDFContentStreamCreateWithPage (thisPage);
//create a pdf scanner using our previously created table and callbacks
pdfScanner = CGPDFScannerCreate (thisContentStream, pdfOpTable, NULL);
//scan the pdf file
CGPDFScannerScan (pdfScanner); //-->call backs happen here
//release everything
CGPDFPageRelease (thisPage);
/*CGPDFScannerRelease (pdfScanner);
CGPDFContentStreamRelease (thisContentStream);*/
}
}
}
//release the pdf document
CGPDFDocumentRelease(pdfDocument);
}
static void op_MP (CGPDFScannerRef s, void *info) {
const char *name;
if (!CGPDFScannerPopName(s, &name))
return;
NSLog(@"MP /%s\n", name);
}
static void op_DP (CGPDFScannerRef s, void *info) {
const char *name;
if (!CGPDFScannerPopName(s, &name))
return;
NSLog(@"DP /%s\n", name);
}
static void op_BMC (CGPDFScannerRef s, void *info) {
const char *name;
if (!CGPDFScannerPopName(s, &name))
return;
NSLog(@"BMC /%s\n", name);
}
static void op_BDC (CGPDFScannerRef s, void *info) {
const char *name;
if (!CGPDFScannerPopName(s, &name))
return;
NSLog(@"BDC /%s\n", name);
}
static void op_EMC (CGPDFScannerRef s, void *info) {
const char *name;
if (!CGPDFScannerPopName(s, &name))
return;
NSLog(@"EMC /%s\n", name);
}
编辑：PDFURL 来自此过程：用户选择使用应用程序打开附加到电子邮件的 PDF 文件。在 AppDelegate.m 中：
- (BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation
{
/* NSLog(@"Open URL:\t%@\n"
"From source:\t%@\n"
"With annotation:%@",
url, sourceApplication, annotation);*/
NSMutableDictionary* userData = [[NSMutableDictionary alloc] init];
[userData setObject:@"Read PDF" forKey:@"Action"];
[userData setObject:url forKey:@"File Path"];
[[NSNotificationCenter defaultCenter] postNotificationName:@"theMessenger" object:self userInfo: userData];
//NSString *filepath = [url path];
//...
return YES;
}
在 viewcontroller.m 中
- (void) receiveNotification:(NSNotification* ) notification {
...
} else if ([strAction isEqualToString:@"Read PDF"]) {
NSURL* documentURL = [[notification userInfo] objectForKey:@"File Path"];
[self readPDFFile:documentURL];
}
...
编辑：如果我不发布此页面应用程序仍然崩溃：
libobjc.A.dylib`objc_release: 0x3be89f20: cmp r0, #0 0x3be89f22: it eq 0x3be89f24: bxeq lr 0x3be89f26: ldr r1, [r0] 0x3be89f28: movs r2, #2 0x3be89f2a: #160, [r0] ldr r1, [rf2] : bfi r1, r2, #0, #2 0x3be89f30: ldrb r1, [r1] 0x3be89f32: tst.w r1, #2 0x3be89f36: bne 0x3be89f3e ; objc_release + 30 0x3be89f38: movs r1, #0 0x3be89f3a: bw 0x3be981c0 ; -[NSObject release] 0x3be89f3e: movw r1, #19326 0x3be89f42: movt r1, #507 0x3be89f46: add r1, pc 0x3be89f48: ldr r1, [r1] 0x3be89f4a: bw 0x3be875a0 ; objc_msgSend 0x3be89f4e: nop