arcgis二次开发_cad二次开发_java arcgis二次开发(2)

然后跟踪到 setFilterExpression() 这个方法

void QgsAttributeTableDialog::setFilterExpression( QString filterString )
{
  mFilterQuery->setText( filterString );
  mFilterButton->setDefaultAction( mActionAdvancedFilter );
  mFilterButton->setPopupMode( QToolButton::MenuButtonPopup );
  mCbxCaseSensitive->setVisible( false );
  mFilterQuery->setVisible( true );
  mApplyFilterButton->setVisible( true );
  mMainView->setFilterMode( QgsAttributeTableFilterModel::ShowFilteredList );

  QgsFeatureIds filteredFeatures;
  QgsDistanceArea myDa;

  myDa.setSourceCrs( mLayer->crs().srsid() );
  myDa.setEllipsoidalMode( QgisApp::instance()->mapCanvas()->mapSettings().hasCrsTransformEnabled() );
  myDa.setEllipsoid( QgsProject::instance()->readEntry( "Measure", "/Ellipsoid", GEO_NONE ) );

  // 构造查询表达式
  QgsExpression filterExpression( filterString );
  // 检查有没有错误
  if ( filterExpression.hasParserError() )
  {
    QgisApp::instance()->messageBar()->pushMessage( tr( "Parsing error" ), filterExpression.parserErrorString(), QgsMessageBar::WARNING, QgisApp::instance()->messageTimeout() );
    return;
  }
  // 继续检查
  if ( ! filterExpression.prepare( mLayer->pendingFields() ) )
  {
    QgisApp::instance()->messageBar()->pushMessage( tr( "Evaluation error" ), filterExpression.evalErrorString(), QgsMessageBar::WARNING, QgisApp::instance()->messageTimeout() );
  }

  bool fetchGeom = filterExpression.needsGeometry();

  QApplication::setOverrideCursor( Qt::WaitCursor );
  // 重写鼠标指针形状之后，以下就开始查询了
  filterExpression.setGeomCalculator( myDa );
  QgsFeatureRequest request( mMainView->masterModel()->request() );
  request.setSubsetOfAttributes( filterExpression.referencedColumns(), mLayer->pendingFields() );
  if ( !fetchGeom )
  {
    request.setFlags( QgsFeatureRequest::NoGeometry );
  }
  QgsFeatureIterator featIt = mLayer->getFeatures( request );

  QgsFeature f;

  while ( featIt.nextFeature( f ) )
  {
    if ( filterExpression.evaluate( &f ).toInt() != 0 )
      filteredFeatures << f.id();

    // check if there were errors during evaluating
    if ( filterExpression.hasEvalError() )
      break;
  }

  featIt.close();

  mMainView->setFilteredFeatures( filteredFeatures );

  QApplication::restoreOverrideCursor();

  if ( filterExpression.hasEvalError() )
  {
    QgisApp::instance()->messageBar()->pushMessage( tr( "Error filtering" ), filterExpression.evalErrorString(), QgsMessageBar::WARNING, QgisApp::instance()->messageTimeout() );
    return;
  }
  mMainView->setFilterMode( QgsAttributeTableFilterModel::ShowFilteredList );
}

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