objective-c - 应用程序在 IOS7 中的 MFMailComposeViewController 对象上崩溃

Question

我在创作

MFMailComposeViewController *picker = [[MFMailComposeViewController alloc] init];

但是选择器还没有，应用程序因未捕获的异常'NSInvalidArgumentException'而崩溃并出现错误 Terminating app，原因:'Application tried to present a nil modal view controller on target。它在模拟器中工作正常但在 Device 中崩溃。 如何在 IOS 7 中使用 MFMailComposerViewController。

Answer 1

您应该在尝试发送邮件之前检查 MFMailComposeViewController 是否能够发送您的邮件(例如，用户在 iOS 设备上没有任何邮件帐户)。

所以在你的 Objective-C 案例中:

MFMailComposeViewController *myMailCompose = [[MFMailComposeViewController alloc] init];

if ([MFMailComposeViewController canSendMail]) {
    myMailCompose.mailComposeDelegate = self;
    [myMailCompose setSubject:@"Subject"];
    [myMailCompose setMessageBody:@"message" isHTML:NO];
    [self presentViewController:myMailCompose animated:YES completion:nil];
} else {
    // unable to send mail, notify your users somehow
}

swift 3:

let myMailCompose = MFMailComposeViewController()

if MFMailComposeViewController.canSendMail() {
    myMailCompose.mailComposeDelegate = self
    myMailCompose.setSubject("Subject")
    myMailCompose.setMessageBody("message", isHTML: false)
    self.present(myMailCompose, animated: true, completion: nil)
} else {
    // unable to send mail, notify your users somehow
}