<\/p>\n
result = self.dlg.exec_()<\/p>\n
if result:
<\/div><\/div>\n\n\n\n
The call to exec_()<\/code> displays the dialog and waits for the user to interact with it.<\/p>\n\n\n\nOnly when the user clicks OK<\/strong> (or otherwise accepts the dialog) does the code continue executing.<\/p>\n\n\n\nIf you try to read the values before exec_()<\/code> is executed, you will usually get empty fields or default values.<\/p>\n\n\n\n\nThe user must first fill in the dialog and confirm it before the plugin can reliably access the entered data.<\/p>\n<\/blockquote>\n\n\n\n
This is one of the most important concepts to understand when working with Qt dialogs.<\/p>\n\n\n\n
The dialog collects information from the user.<\/p>\n\n\n\n
Your code retrieves that information only after the dialog has been validated.<\/p>\n\n\n\n
<\/span>A Useful Mental Model<\/span><\/h2>\n\n\n\nYou can think of a dialog as a form waiting to be completed.<\/p>\n\n\n\n
The process always follows the same sequence:<\/p>\n\n\n\n
\nThe plugin displays the dialog.<\/li>\n\n\n\n The user enters information.<\/li>\n\n\n\n The user clicks OK<\/strong>.<\/li>\n\n\n\nThe plugin retrieves the values.<\/li>\n\n\n\n The plugin performs an action.<\/li>\n<\/ol>\n\n\n\nIf one of these steps is missing, the workflow is incomplete.<\/p>\n\n\n\n
Understanding this sequence makes it much easier to understand how QGIS plugins interact with users.<\/p>\n\n\n\n
<\/span>A Complete Minimal Example<\/span><\/h2>\n\n\n\nLet’s put everything together in a simple and deliberately minimal example.<\/p>\n\n\n
<\/div>
<\/div>
<\/div><\/div>
<\/p>\n
result = self.dlg.exec_()<\/p>\n
if result:
print(\"Text:\", text)\nprint(\"Choice:\", choice)\nprint(\"Option enabled:\", enabled)\n<\/code><\/pre>\n<\/div><\/div>\n\n\n\n
At this stage, the plugin performs:<\/p>\n\n\n\n
\nno analysis,<\/li>\n\n\n\n no complex processing,<\/li>\n\n\n\n no interaction with QGIS layers.<\/li>\n<\/ul>\n\n\n\nThe goal is simply to prove that the plugin can successfully retrieve information entered by the user.<\/p>\n\n\n\n
Once you can do that, you have established the connection between the user interface and your Python code.<\/p>\n\n\n\n
That is a major milestone in plugin development.<\/p>\n\n\n\n
<\/span>Why Does Nothing Happen If You Don’t Read the Values?<\/span><\/h2>\n\n\n\nThis is one of the most common questions asked by beginners.<\/p>\n\n\n\n
A QGIS plugin is not an automatic form.<\/p>\n\n\n\n
There is no hidden magic behind the interface.<\/p>\n\n\n\n
When a user types text, selects an option, or checks a box, QGIS simply stores that information in the corresponding widget.<\/p>\n\n\n\n
If your code never reads the value, it is never used.<\/p>\n\n\n\n
Nothing happens because you have not instructed the plugin to do anything with the information.<\/p>\n\n\n\n
This behavior is intentional.<\/p>\n\n\n\n
It gives developers complete control over how the plugin behaves and what actions are performed.<\/p>\n\n\n\n
\n User input only becomes useful when your code explicitly retrieves and uses it.<\/p>\n<\/blockquote>\n\n\n\n
<\/span>What You Have Learned<\/span><\/h2>\n\n\n\nBy the end of this article, you now understand:<\/p>\n\n\n\n
\nwhere user-entered values are stored,<\/li>\n\n\n\n how to retrieve them in Python,<\/li>\n\n\n\n when those values should be read,<\/li>\n\n\n\n why nothing happens until the plugin explicitly uses them.<\/li>\n<\/ul>\n\n\n\nThese concepts form the foundation of every interactive QGIS plugin.<\/p>\n\n\n\n
Whether your plugin performs a simple calculation or a complex spatial analysis, it will almost always begin by collecting information from the user.<\/p>\n\n\n\n
<\/span>What’s Next?<\/span><\/h2>\n\n\n\nSo far, our plugin can retrieve information entered by the user.<\/p>\n\n\n\n
However, it still does not do anything useful with that information.<\/p>\n\n\n\n
In the next article, we will learn how to transform user input into concrete actions.<\/p>\n\n\n\n
We will see how to:<\/p>\n\n\n\n
\nvalidate user input,<\/li>\n\n\n\n apply business rules,<\/li>\n\n\n\n make decisions based on user choices,<\/li>\n\n\n\n control the behavior of a plugin.<\/li>\n<\/ul>\n\n\n\n\n Retrieving values is the first step.<\/p>\n<\/blockquote>\n\n\n\n
Using them intelligently is what makes a plugin truly useful.<\/p>\n\n\n\n
Next article:<\/strong> Developing a QGIS Plugin: Applying Business Logic to User Input<\/em><\/p>\n\n\n\nWhen you first start developing QGIS plugins, it is easy to assume that a button should automatically \u201cdo something\u201d when it is clicked. In reality, a button does nothing at all\u2014until you tell it what to…<\/p>\n","protected":false},"author":1,"featured_media":16325,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_bbp_topic_count":0,"_bbp_reply_count":0,"_bbp_total_topic_count":0,"_bbp_total_reply_count":0,"_bbp_voice_count":0,"_bbp_anonymous_reply_count":0,"_bbp_topic_count_hidden":0,"_bbp_reply_count_hidden":0,"_bbp_forum_subforum_count":0,"sfsi_plus_gutenberg_text_before_share":"","sfsi_plus_gutenberg_show_text_before_share":"","sfsi_plus_gutenberg_icon_type":"","sfsi_plus_gutenberg_icon_alignemt":"","sfsi_plus_gutenburg_max_per_row":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[3394,1377],"tags":[4678,4732,4734,4736,4730,4738,4740,4742],"class_list":["post-16862","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-pluigin-en","category-qgis-en","tag-pyqgis","tag-qcheckbox-fr","tag-qcombobox-fr","tag-qgis-dialog-fr","tag-qgis-plugin-development-fr","tag-qlineedit-fr","tag-qspinbox-fr","tag-qt-designer-fr"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t