Blocking Messages on Windows

Oct 13, 2025 by wbrum.org 112 views

Introduction

When developing applications using the FireMonkey framework in Delphi, it's common to encounter situations where you need to display a message to the user. One of the most straightforward ways to do this is by using the ShowMessage function, which displays a blocking message box that requires the user to interact with it before proceeding. However, on Android and Mac platforms, using blocking messages can have unintended consequences that may impact the user experience and even the stability of your application. In this article, we'll explore the implications of forcing blocking messages on these platforms.

Blocking Messages on Windows

On Windows, blocking messages are a common and familiar concept. When you call ShowMessage, the application freezes, and the message box appears on top of the application window. The user can then interact with the message box, and once they've made a choice, the application resumes execution. This behavior is well-understood by Windows users, and it's often used in situations where the user needs to confirm an action or make a decision.

Blocking Messages on Android and Mac

However, on Android and Mac platforms, the situation is different. On Android, the application is not frozen when a blocking message is displayed. Instead, the message box appears as a separate window, and the application continues to run in the background. This can lead to unexpected behavior, such as the application responding to user input while the message box is still visible. On Mac, the situation is similar, but the application is not frozen, and the message box appears as a separate window.

Implications of Forcing Blocking Messages

So, what happens if you use blocking messages on Android and Mac platforms? Here are some potential implications:

Application instability: On Android, forcing a blocking message can cause the application to become unresponsive or even crash. This is because the application is not designed to handle blocking messages in the same way as Windows.
Poor user experience: On Mac, displaying a blocking message can cause the application to become unresponsive, which can be frustrating for the user. Additionally, the message box may appear as a separate window, which can be confusing for the user.
Inconsistent behavior: On both Android and Mac, the behavior of blocking messages can be inconsistent. For example, the message box may appear as a separate window, or it may be displayed on top of the application window. This can make it difficult for users to understand what's happening.
Security risks: In some cases, forcing a blocking message can create security risks. For example, if the message box is displayed while the user is entering sensitive information, the user may be able to interact with the message box while still entering sensitive data.

Alternatives to Blocking Messages

So, what can you do instead of using blocking messages? Here are some alternatives:

Non-blocking messages: On Android and Mac, you can use non-blocking messages, which allow the user to interact with the application while the message box is still visible.
Async messages: You can use async messages, which allow the application to continue running in the background while the message box is displayed.
Custom message boxes: You can create custom message boxes that are designed specifically for your application and platform.

Best Practices for Using Messages in FMX

Here are some best practices for using messages in FMX:

Use non-blocking messages: On Android and Mac, use non-blocking messages to avoid freezing the application.
Use async messages: Use async messages to allow the application to continue running in the background while the message box is displayed.
Create custom message boxes: Create custom message boxes that are designed specifically for your application and platform.
Test thoroughly: Test your application thoroughly to ensure that messages are displayed correctly and do not cause any issues.

Conclusion

In conclusion, using blocking messages in FMX can have unintended consequences on Android and Mac platforms. By understanding the implications of forcing blocking messages, you can design your application to provide a better user experience and avoid potential security risks. By following best practices for using messages in FMX, you can create an application that is stable, responsive, and easy to use.

Additional Resources

FAQs

Q: What is the difference between blocking and non-blocking messages?

A: Blocking messages freeze the application, while non-blocking messages allow the user to interact with the application while the message box is still visible.

Q: Can I use blocking messages on Android and Mac?

A: No, it's not recommended to use blocking messages on Android and Mac platforms. Instead, use non-blocking messages or async messages to avoid freezing the application.

Q: How can I create custom message boxes in FMX?

A: You can create custom message boxes by using the TMessageDialog component and customizing its appearance and behavior.

Q: What are the best practices for using messages in FMX?

Q: What is the difference between blocking and non-blocking messages?

A: Blocking messages freeze the application, while non-blocking messages allow the user to interact with the application while the message box is still visible. On Windows, blocking messages are a common and familiar concept, but on Android and Mac platforms, it's not recommended to use blocking messages.

Q: Can I use blocking messages on Android and Mac?

A: No, it's not recommended to use blocking messages on Android and Mac platforms. Instead, use non-blocking messages or async messages to avoid freezing the application. On Android, the application is not frozen when a blocking message is displayed, but on Mac, the application is frozen, which can be frustrating for the user.

Q: How can I create custom message boxes in FMX?

A: You can create custom message boxes by using the TMessageDialog component and customizing its appearance and behavior. You can also use other components, such as TForm or TPageControl, to create custom message boxes.

Q: What are the best practices for using messages in FMX?

A: The best practices for using messages in FMX include:

Using non-blocking messages to avoid freezing the application.
Using async messages to allow the application to continue running in the background while the message box is displayed.
Creating custom message boxes that are designed specifically for your application and platform.
Testing thoroughly to ensure that messages are displayed correctly and do not cause any issues.

Q: How can I handle user input while a message box is displayed?

A: You can handle user input while a message box is displayed by using the OnClose event of the message box. This event is triggered when the user closes the message box, and you can use it to perform any necessary actions.

Q: Can I use messages in FMX to display multiple messages at once?

A: Yes, you can use messages in FMX to display multiple messages at once. You can use the TMessageDialog component to display multiple messages, or you can use other components, such as TForm or TPageControl, to create custom message boxes that can display multiple messages.

Q: How can I customize the appearance of a message box in FMX?

A: You can customize the appearance of a message box in FMX by using the TMessageDialog component and customizing its properties, such as the font, color, and size. You can also use other components, such as TForm or TPageControl, to create custom message boxes that can be customized.

Q: Can I use messages in FMX to display images or other multimedia content?

A: Yes, you can use messages in FMX to display images or other multimedia content. You can use the TMessageDialog component to display images, or you can use other components, such as TForm or TPageControl, to create custom message boxes that can display images or other multimedia content.

Q: How can I handle errors or exceptions when using messages in FMX?

A: You can handle errors or exceptions when using messages in FMX by using try-catch blocks to catch any exceptions that may occur. You can also use the OnClose event of the message box to handle any errors or exceptions that may occur when the user closes the message box.

Q: Can I use messages in FMX to display localized text or other content?

A: Yes, you can use messages in FMX to display localized text or other content. You can use the TMessageDialog component to display localized text, or you can use other components, such as TForm or TPageControl, to create custom message boxes that can display localized text or other content.

Q: How can I optimize the performance of messages in FMX?

A: You can optimize the performance of messages in FMX by using non-blocking messages or async messages to avoid freezing the application. You can also use other techniques, such as caching or lazy loading, to optimize the performance of messages in FMX.

Q: Can I use messages in FMX to display notifications or other alerts?

A: Yes, you can use messages in FMX to display notifications or other alerts. You can use the TMessageDialog component to display notifications or other alerts, or you can use other components, such as TForm or TPageControl, to create custom message boxes that can display notifications or other alerts.

Q: How can I customize the behavior of a message box in FMX?

A: You can customize the behavior of a message box in FMX by using the TMessageDialog component and customizing its properties, such as the font, color, and size. You can also use other components, such as TForm or TPageControl, to create custom message boxes that can be customized.

Q: Can I use messages in FMX to display progress bars or other indicators?

A: Yes, you can use messages in FMX to display progress bars or other indicators. You can use the TMessageDialog component to display progress bars or other indicators, or you can use other components, such as TForm or TPageControl, to create custom message boxes that can display progress bars or other indicators.

Q: How can I handle user input while a progress bar is displayed?

A: You can handle user input while a progress bar is displayed by using the OnClose event of the message box. This event is triggered when the user closes the message box, and you can use it to perform any necessary actions.

Q: Can I use messages in FMX to display custom controls or other components?

A: Yes, you can use messages in FMX to display custom controls or other components. You can use the TMessageDialog component to display custom controls or other components, or you can use other components, such as TForm or TPageControl, to create custom message boxes that can display custom controls or other components.

Q: How can I customize the appearance of a progress bar in FMX?

A: You can customize the appearance of a progress bar in FMX by using the TMessageDialog component and customizing its properties, such as the font, color, and size. You can also use other components, such as TForm or TPageControl, to create custom message boxes that can display progress bars with custom appearances.

Q: Can I use messages in FMX to display custom animations or other effects?

A: Yes, you can use messages in FMX to display custom animations or other effects. You can use the TMessageDialog component to display custom animations or other effects, or you can use other components, such as TForm or TPageControl, to create custom message boxes that can display custom animations or other effects.

Q: How can I handle errors or exceptions when using custom animations or other effects in FMX?

A: You can handle errors or exceptions when using custom animations or other effects in FMX by using try-catch blocks to catch any exceptions that may occur. You can also use the OnClose event of the message box to handle any errors or exceptions that may occur when the user closes the message box.

Q: Can I use messages in FMX to display custom sounds or other audio content?

A: Yes, you can use messages in FMX to display custom sounds or other audio content. You can use the TMessageDialog component to display custom sounds or other audio content, or you can use other components, such as TForm or TPageControl, to create custom message boxes that can display custom sounds or other audio content.

Q: How can I customize the behavior of a message box in FMX to display custom sounds or other audio content?

A: You can customize the behavior of a message box in FMX to display custom sounds or other audio content by using the TMessageDialog component and customizing its properties, such as the font, color, and size. You can also use other components, such as TForm or TPageControl, to create custom message boxes that can display custom sounds or other audio content.

Q: Can I use messages in FMX to display custom videos or other multimedia content?

A: Yes, you can use messages in FMX to display custom videos or other multimedia content. You can use the TMessageDialog component to display custom videos or other multimedia content, or you can use other components, such as TForm or TPageControl, to create custom message boxes that can display custom videos or other multimedia content.

Q: How can I customize the behavior of a message box in FMX to display custom videos or other multimedia content?

A: You can customize the behavior of a message box in FMX to display custom videos or other multimedia content by using the TMessageDialog component and customizing its properties, such as the font, color, and size. You can also use other components, such as TForm or TPageControl, to create custom message boxes that can display custom videos or other multimedia content.

Q: Can I use messages in FMX to display custom 3D graphics or other visual effects?

A: Yes, you can use messages in FMX to display custom 3D graphics