QSlider and Key Press Event

Question

I currently have a QSlider that scrolls through frames of image data using the mouse. I would like to be able to use the arrow keys to scroll through a single step (one frame).

This is my current sliderMoved code:

def sliderMoved(self,val):
    """
    retrieves the data array for the index value specified by the slider
    """

    if self.fileheader is None:
        print "[DEBUG] change_image_index(): self.fileheader is None"
        return

    idx=val
    self.x=idx
    frame=self.fileheader.frameAtIndex(idx)
    image=scipy.ndimage.filters.maximum_filter(frame.data, size=5)

    self.image.setImage(image, scale=((10.28/512),(2.486/96)))
    print self.image.imageItem.pixelSize()

    def keyPressEvent(self, event):
        if event.key()==Qt.Key_Right:
            frame=self.fileheader.frameAtIndex(idx+1)

To connect the slider to the events, I just use:

self.slider.sliderMoved.connect(self.sliderMoved)
self.slider.sliderMoved.connect(self.keyPressEvent)

The arrow key moves the slider, but it does not cause the image to skip frames... I know I'm missing something silly here...

Answer 1

Try connecting to the slider's valueChanged rather than sliderMoved.

import sys
from PyQt4.QtCore import Qt
from PyQt4.QtGui import QApplication, QWidget, QSlider, QLabel, QVBoxLayout

class Widget(QWidget):
    def __init__(self, parent=None):
        QWidget.__init__(self, parent)

        self.v_layout = QVBoxLayout()

        self.slider = QSlider()
        self.slider.setOrientation(Qt.Horizontal)
        self.label = QLabel('Slider at position 0')

        self.v_layout.addWidget(self.label)
        self.v_layout.addWidget(self.slider)

        self.setLayout(self.v_layout)

        self.slider.valueChanged.connect(self.slider_moved)

    def keyPressEvent(self, event):
        if event.key()==Qt.Key_Right:
            self.slider.setValue(self.slider.value() + 1)
        elif event.key()==Qt.Key_Left:
            self.slider.setValue(self.slider.value() - 1)
        else:
            QWidget.keyPressEvent(self, event)

    def slider_moved(self, position):
        self.label.setText('Slider at position %d' % position)


if __name__ == '__main__':
  app = QApplication(sys.argv)

  widget = Widget()
  widget.show()

  sys.exit(app.exec_())

From your keyPressEvent you can just change the value of the slider which will cause whatever functions that are connected to valueChanged to run.