如何在QGIS渲染shapefile时让Python等待
如何在QGIS渲染shapefile时让Python等待
提问于 2019-03-22 22:25:12
我已经为我的QGIS 2.8.1写了代码，它可以成功地截取一个形状文件的屏幕截图，但不幸的是，当我尝试多个shapefile时，它不能工作。
因此，基本上，如果我将下面代码中的allFiles = ["C:/Shapefiles/Map_00721.shp"]替换为allFiles = ["C:/Shapefiles/Map_00721.shp", "C:/Shapefiles/Map_00711.shp", "C:/Shapefiles/Map_00731.shp", "C:/Shapefiles/Map_00791.shp", "C:/Shapefiles/Map_00221.shp"]，循环将在数组上迭代，而不等待渲染和快照过程发生。
我试过在下面的代码中使用time.sleep，但它也停止了shapefile的渲染，结果并不像预期的那样。
import ogr,os
from PyQt4.QtGui import *
from PyQt4.QtCore import *
from qgis.core import *
import qgis.utils
import glob
from time import sleep
import math
import processing
from processing.core.Processing import Processing
from PyQt4.QtCore import QTimer
Processing.initialize()
Processing.updateAlgsList()
OutputFileName = "ABC" # Temprory global placeholder for filename
canvas = iface.mapCanvas()
def startstuffs():
qgis.utils.iface.zoomToActiveLayer() # Zoom to Layer
scale=canvas.scale() # Get current Scale
scale = scale * 1.5
canvas.zoomScale(scale) # Zoomout a bit
QTimer.singleShot(2000,saveImg) # Jump to save img
def saveImg():
qgis.utils.iface.mapCanvas().saveAsImage(OutputFileName)
QgsMapLayerRegistry.instance().removeAllMapLayers()
# Add array of address below
allFiles = ["C:/Shapefiles/Map_00721.shp"]
filesLen = len(allFiles)
TexLayer = "C:/US_County_NAD27.shp"
for lop in range(filesLen):
currentShpFile = allFiles[lop]
currentShpFileName = currentShpFile.strip("C:/Shapefiles/")
OutputFileName = "C:/ImageOut/" + currentShpFileName + ".png"
wb = QgsVectorLayer(currentShpFile, currentShpFileName, 'ogr')
wbTex = QgsVectorLayer(TexLayer, 'CountyGrid', 'ogr')
QgsMapLayerRegistry.instance().addMapLayer(wb) # Add the shapefile
QgsMapLayerRegistry.instance().addMapLayer(wbTex) # Add the county shapefile
qgis.utils.iface.setActiveLayer(wb) # Makes wb as active shapefile
QTimer.singleShot(3000, startstuffs) # This start stuffs
print "Done!"回答 1
Stack Overflow用户
回答已采纳
发布于 2019-03-26 05:15:07
避免使用time.sleep()，因为这会完全拖慢你的整个程序。取而代之的是使用processEvents()，它允许程序在后台呈现。
import time
def spin(seconds):
"""Pause for set amount of seconds, replaces time.sleep so program doesn't stall"""
time_end = time.time() + seconds
while time.time() < time_end:
QtGui.QApplication.processEvents()这种方法应该可以很好地快速修复，但从长远来看，它可能会产生难以跟踪的问题。对于永久解决方案，最好使用带有事件循环的QTimer。
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原文链接：
https://stackoverflow.com/questions/55301747
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