請問各位前輩.. 弟目前寫了一段由Server端傳圖到client端做遠端視訊，但連線連個一天時卻會發生 canvas does not allow drawing的錯誤訊息。請問什麼原因會導致這個錯 誤出現呢。。以下是我網路部分程式碼 try{ if (AThread->Connection->Connected()){ if(APClosed){ szCommand = AThread->Connection->ReadInteger(true); AThread->Connection->WriteInteger(-100,true); return; } short int NetCHNum; szCommand = AThread->Connection->ReadInteger(true); AnsiString split_Num = IntToStr(szCommand).SubString(1,1); //Graphics::TBitmap *bmp_Source = new Graphics::TBitmap; TMemoryStream *msBuf1,*msBuf2,*msBuf3,*msBuf4; TJPEGImage *jpeg1,*jpeg2,*jpeg3,*jpeg4; switch(AThread->Connection->Tag) { case 1: msBuf1 = new TMemoryStream; jpeg1 = new TJPEGImage; break; case 2: msBuf2 = new TMemoryStream; jpeg2 = new TJPEGImage; break; case 3: msBuf3 = new TMemoryStream; jpeg3 = new TJPEGImage; break; case 4: msBuf4 = new TMemoryStream; jpeg4 = new TJPEGImage; break; } NetCHNum = NetCHCount; switch(NetCHNum) { case 0: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp1); break; case 2: jpeg2->Assign(NetBmp1); break; case 3: jpeg3->Assign(NetBmp1); break; case 4: jpeg4->Assign(NetBmp1); break; } break; case 1: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp2); break; case 2: jpeg2->Assign(NetBmp2); break; case 3: jpeg3->Assign(NetBmp2); break; case 4: jpeg4->Assign(NetBmp2); break; } break; case 2: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp3); break; case 2: jpeg2->Assign(NetBmp3); break; case 3: jpeg3->Assign(NetBmp3); break; case 4: jpeg4->Assign(NetBmp3); break; } break; case 3: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp4); break; case 2: jpeg2->Assign(NetBmp4); break; case 3: jpeg3->Assign(NetBmp4); break; case 4: jpeg4->Assign(NetBmp4); break; } break; case 4: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp5); break; case 2: jpeg2->Assign(NetBmp5); break; case 3: jpeg3->Assign(NetBmp5); break; case 4: jpeg4->Assign(NetBmp5); break; } break; case 5: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp6); break; case 2: jpeg2->Assign(NetBmp6); break; case 3: jpeg3->Assign(NetBmp6); break; case 4: jpeg4->Assign(NetBmp6); break; } break; case 6: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp7); break; case 2: jpeg2->Assign(NetBmp7); break; case 3: jpeg3->Assign(NetBmp7); break; case 4: jpeg4->Assign(NetBmp7); break; } break; case 7: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp8); break; case 2: jpeg2->Assign(NetBmp8); break; case 3: jpeg3->Assign(NetBmp8); break; case 4: jpeg4->Assign(NetBmp8); break; } break; case 8: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp9); break; case 2: jpeg2->Assign(NetBmp9); break; case 3: jpeg3->Assign(NetBmp9); break; case 4: jpeg4->Assign(NetBmp9); break; } break; case 9: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp10); break; case 2: jpeg2->Assign(NetBmp10); break; case 3: jpeg3->Assign(NetBmp10); break; case 4: jpeg4->Assign(NetBmp10); break; } break; case 10: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp11); break; case 2: jpeg2->Assign(NetBmp11); break; case 3: jpeg3->Assign(NetBmp11); break; case 4: jpeg4->Assign(NetBmp11); break; } break; case 11: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp12); break; case 2: jpeg2->Assign(NetBmp12); break; case 3: jpeg3->Assign(NetBmp12); break; case 4: jpeg4->Assign(NetBmp12); break; } break; case 12: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp13); break; case 2: jpeg2->Assign(NetBmp13); break; case 3: jpeg3->Assign(NetBmp13); break; case 4: jpeg4->Assign(NetBmp13); break; } break; case 13: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp14); break; case 2: jpeg2->Assign(NetBmp14); break; case 3: jpeg3->Assign(NetBmp14); break; case 4: jpeg4->Assign(NetBmp14); break; } break; case 14: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp15); break; case 2: jpeg2->Assign(NetBmp15); break; case 3: jpeg3->Assign(NetBmp15); break; case 4: jpeg4->Assign(NetBmp15); break; } break; case 15: switch(AThread->Connection->Tag) { case 1: jpeg1->Assign(NetBmp16); break; case 2: jpeg2->Assign(NetBmp16); break; case 3: jpeg3->Assign(NetBmp16); break; case 4: jpeg4->Assign(NetBmp16); break; } break; } //jpeg->Assign(NetBmp1); switch(AThread->Connection->Tag) { case 1: jpeg1->CompressionQuality = 72; jpeg1->Compress(); jpeg1->SaveToStream(msBuf1); delete jpeg1; break; case 2: jpeg2->CompressionQuality = 72; jpeg2->Compress(); jpeg2->SaveToStream(msBuf2); delete jpeg2; break; case 3: jpeg3->CompressionQuality = 72; jpeg3->Compress(); jpeg3->SaveToStream(msBuf3); delete jpeg3; break; case 4: jpeg4->CompressionQuality = 72; jpeg4->Compress(); jpeg4->SaveToStream(msBuf4); delete jpeg4; break; } jpeg1 = NULL; jpeg2 = NULL; jpeg3 = NULL; jpeg4 = NULL; //delete bmp_Source; //bmp_Source = NULL; if (split_Num == "1"){ if (NetCHNum != StrToInt(IntToStr(szCommand).SubString(2,3))){ AThread->Connection->WriteInteger(-1,true); switch(AThread->Connection->Tag) { case 1: delete msBuf1; break; case 2: delete msBuf2; break; case 3: delete msBuf3; break; case 4: delete msBuf4; break; } msBuf1 = NULL; msBuf2 = NULL; msBuf3 = NULL; msBuf4 = NULL; return; } } else if (split_Num == "4"){ CH1 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 0) % 16); CH2 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 1) % 16); CH3 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 2) % 16); CH4 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 3) % 16); if (CH1 != NetCHNum && CH2 != NetCHNum && CH3 != NetCHNum && CH4 != NetCHNum){ AThread->Connection->WriteInteger(-1,true); switch(AThread->Connection->Tag) { case 1: delete msBuf1; break; case 2: delete msBuf2; break; case 3: delete msBuf3; break; case 4: delete msBuf4; break; } msBuf1 = NULL; msBuf2 = NULL; msBuf3 = NULL; msBuf4 = NULL; return; } } else if (split_Num == "9"){ CH1 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 0) % 16); CH2 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 1) % 16); CH3 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 2) % 16); CH4 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 3) % 16); CH5 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 4) % 16); CH6 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 5) % 16); CH7 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 6) % 16); CH8 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 7) % 16); CH9 = ((StrToInt(IntToStr(szCommand).SubString(2,3)) 8) % 16); if (CH1 != NetCHNum && CH2 != NetCHNum && CH3 != NetCHNum && CH4 != NetCHNum && CH5!=NetCHNum && CH6!=NetCHNum && CH7!=NetCHNum && CH8!= NetCHNum && CH9!= NetCHNum) { AThread->Connection->WriteInteger(-1,true); switch(AThread->Connection->Tag) { case 1: delete msBuf1; break; case 2: delete msBuf2; break; case 3: delete msBuf3; break; case 4: delete msBuf4; break; } msBuf1 = NULL; msBuf2 = NULL; msBuf3 = NULL; msBuf4 = NULL; return; } } //jpeg->Assign(bmp_Dest); if (szCommand != 0){ AThread->Connection->WriteInteger(NetCHNum,true); switch(AThread->Connection->Tag) { case 1: msBuf1->Position=0; AThread->Connection->WriteStream(msBuf1,true,true); // transfer data stream to internet break; case 2: msBuf2->Position=0; AThread->Connection->WriteStream(msBuf2,true,true); // transfer data stream to internet break; case 3: msBuf3->Position=0; AThread->Connection->WriteStream(msBuf3,true,true); // transfer data stream to internet break; case 4: msBuf4->Position=0; AThread->Connection->WriteStream(msBuf4,true,true); // transfer data stream to internet break; } } else{ switch(AThread->Connection->Tag) { case 1: delete msBuf1; break; case 2: delete msBuf2; break; case 3: delete msBuf3; break; case 4: delete msBuf4; break; } msBuf1 = NULL; msBuf2 = NULL; msBuf3 = NULL; msBuf4 = NULL; AThread->Connection->Disconnect(); return; } switch(AThread->Connection->Tag) { case 1: delete msBuf1; break; case 2: delete msBuf2; break; case 3: delete msBuf3; break; case 4: delete msBuf4; break; } msBuf1 = NULL; msBuf2 = NULL; msBuf3 = NULL; msBuf4 = NULL; } }catch(const EIdConnClosedGracefully &eCloseErr){ //}catch(const EInvalidOperation &eCloseErr) //}catch(...){ AThread->Connection->Disconnect(); return; }

http://www.delphifaq.com/fq/q4053.shtml Msg 'Canvas does not allow drawing' Q: What does the error message 'Canvas does not allow drawing' mean? A: 1.you may have run out of resources, which means a new DC cannot be allocated. Usually this is a result of not freeing unused DCs or other objects 2.you are attempting to draw to an device context that is not yet valid. Such as in the create constructor of a component. 3.you are trying to draw on a canvas while your last draw-operation has not finished yet. In this case you can use Canvas.Lock or Canvas.TryLock to fix it. 小弟認為第 1. 點的原因比較大 原程式看不出有將 jpeg1 Free 的地方 (也有可能是小弟看不懂 C++ ) 另外, 您貼錯版了, 本版是 > --- >@