Using Qt Designer in Java Integrating Code 128B in Java Using Qt Designer

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7. Using Qt Designer using barcode integrating for none control to generate, create none image in none applications. iPhone For Windows and none for none Linux users, it is convenient to set the buttons focus policies to No Focus . This makes no difference to mouse users, but is often helpful to keyboard users. It means that pressing Tab moves the keyboard focus only among the editing widgets in this example, the nd line edit, the replace line edit, the checkboxes, and the combobox which is usually more convenient than having to Tab over the buttons too.

Keyboard users can still press any button using its keyboard accelerator (Esc in the case of the close button). Unfortunately, buddies and buttons don t provide Mac OS X keyboard users with accelerators (unless they switch on support for assistive devices), so these users need to be able to Tab to all controls, including the buttons. To cater to all platforms, instead of setting the buttons focus policies in Qt Designer, we set them manually, after the user interface has been created by setupUi().

The MAC Boolean variable is True if the underlying window system is Mac OS X. It was set at the beginning of the le, after the imports, using the following rather enigmatic statement:. MAC = "qt_mac_s et_native_menubar" in dir(). A clearer way o none none f writing this is:. import PyQt4.Qt Gui MAC = hasattr(PyQt4.QtGui, "qt_mac_set_native_menubar").

These work beca none for none use the PyQt4.QtGui.qt_mac_set_native_menubar() function exists only on Mac OS X systems.

We will use a similar technique for X Window System detection in 11. The updateUi() method called at the end is our own custom method; we use it to enable or disable the buttons depending on whether the user has entered any text to nd..

@pyqtSignature( "QString") def on_findLineEdit_textEdited(self, text): self.__index = 0 self.updateUi().

Decorators 85 Thanks to setup Ui(), this method is automatically connected to by the findLineEdit s textEdited() signal. Whenever we want an automatic connection we use the @pyqtSignature decorator to specify the signal s arguments. The purpose of the decorator is to distinguish between signals that have the same name but different parameters.

In this particular case, there is only one textEdited() signal, so the decorator is not strictly necessary; but we always use the decorator as a matter of good practice. For example, if a later version of PyQt introduced another signal with the same name but with different arguments, code that used the decorator would continue to work, but code without it would not. Since this slot is called when the user changes the nd text, we reset the index position from which to start the search to 0 (the beginning).

Here, and in the initializer, we end with a call to updateUi().. Implementing Dialogs def updateUi(se lf): enable = not self.findLineEdit.text().

isEmpty() self.findButton.setEnabled(enable) self.

replaceButton.setEnabled(enable) self.replaceAllButton.

setEnabled(enable). We have already none for none seen many examples of a method of this kind. Here, we enable the Find, Replace, and Replace All buttons, if the user has entered a nd text. It does not matter whether there is any replace text, since it is perfectly valid to replace something with nothing, that is, to delete the text that is found.

This method is the reason why the form starts with every button except the Close button disabled. When the user closes the form, the text it holds (which may be different from the original text if the user has used replace or replace all) is accessible using the text() method..

def text(self): return self.__text Some Python pro none for none grammers would not provide a method for this; instead, they would have a self.text variable (rather than self.__text), and access the variable directly.

The rest of the dialog s functionality is implemented in methods that are invoked as a result of the user pressing one of the buttons (other than the Close button), plus a helper method. Their implementation is not speci cally relevant to using Qt Designer, but we will brie y review them for completeness..

@pyqtSignature( "") def on_findButton_clicked(self): regex = self.makeRegex() match =

__text, self.__index) if match is not None: self.__index = match.

end() self.emit(SIGNAL("found"), match.start()) else: self.

emit(SIGNAL("notfound")). A button s clic none none ked() signal has an optional Boolean argument that we are not interested in, so we specify an empty parameter list for the @pyqtSignature decorator. In contrast, we could not have used an empty parameter list for the on_findLineEdit_textEdited() slot s decorator, because the textEdited() signal s argument is not optional, so it must be included. To perform the search, we create a regular expression to specify the nd text and some of the search s characteristics.

Then we search the text using the regular expression, from the current index position. If a match was found we update the index position to be at the match s end, ready for a subsequent.
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