PyQt-关于QSlider和QGraphicsTextItem的问题

Question

I'm totally stuck with 2 problems:

1) i'm using QSlider to set some values (they're float ~0.5, so i'm using *1000). SingleStep and PageStep work fine for keyboard input and mouse wheel, ticks're all set... But when i'm using mouse to drag the slider - it ignores all those ticks, steps, etc, and i want it to move only from one tick to another.

self.ui.x_coord.setMaximum(l_d*1000)
self.ui.x_coord.setSingleStep(l_d/N*1000)
self.ui.x_coord.setTickInterval(l_d/N*1000)
self.ui.x_coord.setTickPosition(QtGui.QSlider.TicksBothSides)
self.ui.x_coord.setPageStep(l_d/N * 10000)

is something missing here in my code (maybe smth like setMouseStep)?

2) That QSlider's connected to a function

self.graph = BPlot(self.ui)
self.ui.x_coord.valueChanged.connect(self.setCoordLabelValue)

....

def setCoordLabelValue(self):
    x = self.ui.x_coord.value()/1000
    y = self.ui.y_coord.value()/1000
    self.graph.setCoordText(x,y)

....

class BPlot(QtGui.QGraphicsView):
    def __init__(self, ui, parent=None):
        super(BPlot, self).__init__(parent)
        self.scene = QtGui.QGraphicsScene()
        self.ui = ui

        self.coordText = QtGui.QGraphicsTextItem(None, self.scene)
        self.coordText.setPlainText("123")

        self.x_offset = 40
        self.y_offset = 20

        self.currentPoint = QtGui.QGraphicsRectItem(None, self.scene)
        self.cph = 4
            self.cpw = 4

    def resizeEvent(self, event):
        size = event.size()

    def showEvent(self, event):
        aw = self.viewport().width()
        ah = self.viewport().height()
        self.scene.setSceneRect(0,0,aw,ah)
        self.setScene(self.scene)

        self.axis_pen = QtGui.QPen(QtCore.Qt.DashDotLine)
        self.scene.addLine(0, 3/4*ah, aw, 3/4*ah, self.axis_pen)

        self.normal_pen = QtGui.QPen(QtCore.Qt.SolidLine)
        self.scene.addLine(self.x_offset, 3/4*ah - self.y_offset, aw - self.x_offset, 3/4*ah - self.y_offset)
        self.currentPoint.setRect(self.x_offset - self.cpw/2, 3/4*ah - self.y_offset - self.cph/2, self.cpw, self.cph) 


    def setCoordText(self, x, y):
        self.coordText.setPlainText(str(x) + ":" + str(y))

the problem is that setCoordText func doesn't redraw coordText. If i'll use print(coordText.toPlainText()) - i'll get the right output, but on the screen there'll be still "123" from __init__

I already tried adding self.scene.update() to the end of setCoordText, with no luck.

Answer 1

Ugh... Solved. Logic, where're u, my dear friend???

def setCoordLabelValue(self):
    x = self.ui.x_coord.value()/1000
    y = self.ui.y_coord.value()/1000
    self.graph.setCoordText(x,y)
    self.graph.invalidateScene()

.......

def paintEvent(self, event):
        painter = QtGui.QPainter(self.viewport())

        # set color and width of line drawing pen
        painter.setPen(QtGui.QPen(QtCore.Qt.black, 2))

        # drawLine(x1, y1, x2, y2) from point (x1,y1) to (x2,y2)
        # draw the baseline
        painter.drawText(10,20,str(x_coord))
        # set up color and width of the bars
        width = 20
        painter.setPen(QtGui.QPen(QtCore.Qt.red, width))
        delta = width + 5
        x = 30
        painter.end()

        self.viewport().update()