從GetEventParameter獲取錯誤代碼

Question

這是我必須處理平滑滾動的代碼片段。這裏是NSLog的輸出：

2010-06-21 16:04:10.524 PDFViewWXOSX[80161:a0f] first error: -9870 
2010-06-21 16:04:10.525 PDFViewWXOSX[80161:a0f] second error: 0 
2010-06-21 16:04:10.552 PDFViewWXOSX[80161:a0f] first error: 0 
2010-06-21 16:04:10.553 PDFViewWXOSX[80161:a0f] second error: 0 
2010-06-21 16:04:10.582 PDFViewWXOSX[80161:a0f] first error: 0 
2010-06-21 16:04:10.582 PDFViewWXOSX[80161:a0f] second error: 0 
2010-06-21 16:04:10.588 PDFViewWXOSX[80161:a0f] first error: -9870 
2010-06-21 16:04:10.589 PDFViewWXOSX[80161:a0f] second error: 0 
2010-06-21 16:04:10.652 PDFViewWXOSX[80161:a0f] first error: 0 
2010-06-21 16:04:10.652 PDFViewWXOSX[80161:a0f] second error: 0 
2010-06-21 16:04:10.723 PDFViewWXOSX[80161:a0f] first error: 0 
2010-06-21 16:04:10.723 PDFViewWXOSX[80161:a0f] second error: 0 

  SInt32 scroll_delta_x = 0, scroll_delta_y = 0; 
      OSErr err = noErr; 

      err = GetEventParameter(cEvent, kEventParamMouseWheelSmoothHorizontalDelta, 
            typeSInt32, NULL, sizeof(scroll_delta_x), NULL, 
            &scroll_delta_x); 
      NSLog(@"first error: %d", err); 
      if (err == noErr) { 
       deltaX = scroll_delta_x; 
      } 
      err = noErr; 
      err = GetEventParameter(cEvent, kEventParamMouseWheelSmoothVerticalDelta, 
            typeSInt32, NULL, sizeof(scroll_delta_y), NULL, 
            &scroll_delta_y); 
      NSLog(@"second error: %d", err); 
      if (err == noErr) { 
       deltaY = scroll_delta_y; 
      } 

我找不到有關錯誤-9870的任何信息。到底是怎麼回事？

Answer 1

錯誤-9870是在CarbonEventsCore.h中聲明的eventParameterNotFoundErr。對這些事件參數的標題註釋說，你應該準備好它們不存在的可能性。