在 3G 上发送电子邮件时，presentModalViewController 崩溃答案

【问题标题】：presentModalViewController crash while sending email on 3G在 3G 上发送电子邮件时，presentModalViewController 崩溃
【发布时间】：2012-07-21 19:16:38
【问题描述】：

我正在尝试通过电子邮件并使用以下代码发送设备日志文件。我可以在 iPod Touch 和 iPad 中通过 Wi-Fi 网络发送电子邮件。但是当我试图在 3G 网络上用 iPhone 发送电子邮件时，出现了崩溃。我首次展示了代码，然后才知道这在做 presentModalViewController 时会崩溃。

请帮助我，如何解决这个问题。

- (IBAction)sendEmail:(id)sender
{
  MFMailComposeViewController *picker = [[MFMailComposeViewController alloc] init];
  picker.mailComposeDelegate = self;
 
  // Set the subject of email
  [picker setSubject:@"Debug Log"];
 
  // Add email addresses
  [picker setToRecipients:[NSArray arrayWithObjects:@"emailaddress1@domainName.com", @"emailaddress2@domainName.com", nil]];
 
  // Fill out the email body text
  NSString *emailBody = @"Debug Log content…… ";
 
  // This is not an HTML formatted email
  [picker setMessageBody:emailBody isHTML:NO];
 
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,    
NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *logPath = [documentsDirectory   
stringByAppendingPathComponent:@"console.log"];
NSData *data = [NSData dataWithContentsOfFile:logPath];
  [picker addAttachmentData:data mimeType:@"text/xml" fileName:@"console.log"];
 
  // Show email view    
  [self presentModalViewController:picker animated:YES];//app crash
 
  // Release picker
  [picker release];
}
 
- (void)mailComposeController:(MFMailComposeViewController*)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError*)error 
{
  // Called once the email is sent
  // Remove the email view controller   
  [self dismissModalViewControllerAnimated:YES];
}

【问题讨论】：

标签： iphone email ios5 3g presentmodalviewcontroller

【解决方案1】：

在发送邮件之前，检查是否在 iOS 设备中配置了电子邮件。

您可以在发送邮件之前通过代码检查发送邮件的能力，如下所示。

- (IBAction)sendEmail:(id)sender
{
  MFMailComposeViewController *picker = [[MFMailComposeViewController alloc] init];
  picker.mailComposeDelegate = self;
 
  // Set the subject of email
  [picker setSubject:@"Debug Log"];
 
  // Add email addresses
  [picker setToRecipients:[NSArray arrayWithObjects:@"emailaddress1@domainName.com", @"emailaddress2@domainName.com", nil]];
 
  // Fill out the email body text
  NSString *emailBody = @"Debug Log content…… ";
 
  // This is not an HTML formatted email
  [picker setMessageBody:emailBody isHTML:NO];
 
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,    
NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *logPath = [documentsDirectory   
stringByAppendingPathComponent:@"console.log"];
NSData *data = [NSData dataWithContentsOfFile:logPath];

  [picker addAttachmentData:data mimeType:@"text/xml" fileName:@"console.log"];
 
  // Show email view    
 Class mailClass = (NSClassFromString(@"MFMailComposeViewController"));
  if (mailClass != nil) {
    // We must always check whether the current device is configured for sending emails
    if ([mailClass canSendMail]) {
      [self presentModalViewController:picker animated:YES];
    } else {
      //do something
    }
  } else {
   //do something
  } 
  // Release picker
  [picker release];
}

- (void)mailComposeController:(MFMailComposeViewController*)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError*)error 
{
  // Called once the email is sent
  // Remove the email view controller   
  [self dismissModalViewControllerAnimated:YES];
}

【讨论】：

【解决方案2】：

简单的答案是使用以下代码 sn-p 封装您对 presentModalViewController 的调用：

Class mailClass = (NSClassFromString(@"MFMailComposeViewController"));
if (mailClass != nil)
{ 
    if ([mailClass canSendMail])
    {
        [self presentModalViewController:YOURMAILCOMPOSER animated:YES];
    }
}

这甚至会为您的用户提供一个自动生成的警报视图，告诉他们在继续之前设置邮件帐户...

【讨论】：