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Why dump in QAbstractAnimation::start

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  • T Toocold
    void func()
    {
    ...
        connect(pAnimationBannerOpacity, &QPropertyAnimation::finished,
            [&] { pAnimationTextGeometry->start(); });
    ...
        pAnimationBannerOpacity->start();
    }
    

    I want a Animation start when another Animation end.
    But I dump In QAbstractAnimation::start.
    Can anyone tell me why. Thanks.

    jsulmJ Offline
    jsulmJ Offline
    jsulm
    Lifetime Qt Champion
    wrote on last edited by
    #2

    @Toocold said in Why dump in QAbstractAnimation::start:

    But I dump In QAbstractAnimation::start

    What do you mean with that? The second animation does not start if the first one finishes?

    https://forum.qt.io/topic/113070/qt-code-of-conduct

    T 1 Reply Last reply
    0
    • jsulmJ jsulm

      @Toocold said in Why dump in QAbstractAnimation::start:

      But I dump In QAbstractAnimation::start

      What do you mean with that? The second animation does not start if the first one finishes?

      T Offline
      T Offline
      Toocold
      wrote on last edited by
      #3

      @jsulm I mean that my program crashed in this function.

      1 Reply Last reply
      0
      • T Toocold
        void func()
        {
        ...
            connect(pAnimationBannerOpacity, &QPropertyAnimation::finished,
                [&] { pAnimationTextGeometry->start(); });
        ...
            pAnimationBannerOpacity->start();
        }
        

        I want a Animation start when another Animation end.
        But I dump In QAbstractAnimation::start.
        Can anyone tell me why. Thanks.

        J.HilkJ Offline
        J.HilkJ Offline
        J.Hilk
        Moderators
        wrote on last edited by
        #4

        @Toocold do you happen to have called start(QAbstractAnimation::DeleteWhenStopped) instead of start(QAbstractAnimation::KeepWhenStopped)


        Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


        Q: What's that?
        A: It's blue light.
        Q: What does it do?
        A: It turns blue.

        T 1 Reply Last reply
        0
        • J.HilkJ J.Hilk

          @Toocold do you happen to have called start(QAbstractAnimation::DeleteWhenStopped) instead of start(QAbstractAnimation::KeepWhenStopped)

          T Offline
          T Offline
          Toocold
          wrote on last edited by
          #5

          @J-Hilk
          no.

          pAnimationBannerOpacity     = new QPropertyAnimation(m_pIntroduction->pOpacityBanner, "opacity", m_pIntroduction->pLableBanner);
          pAnimationTextGeometry      = new QPropertyAnimation(m_pIntroduction->pLableText, "geometry", m_pIntroduction->pLableBanner);
          

          I just set parent to them.
          The Animation like some's Opacity from 0 to 1, and then play Geometry Animation.

          jsulmJ 1 Reply Last reply
          0
          • T Toocold

            @J-Hilk
            no.

            pAnimationBannerOpacity     = new QPropertyAnimation(m_pIntroduction->pOpacityBanner, "opacity", m_pIntroduction->pLableBanner);
            pAnimationTextGeometry      = new QPropertyAnimation(m_pIntroduction->pLableText, "geometry", m_pIntroduction->pLableBanner);
            

            I just set parent to them.
            The Animation like some's Opacity from 0 to 1, and then play Geometry Animation.

            jsulmJ Offline
            jsulmJ Offline
            jsulm
            Lifetime Qt Champion
            wrote on last edited by
            #6

            @Toocold I suggest to use debugger and position a breakpoint at

            pAnimationTextGeometry->start();
            

            and check what happens when you execute that line. Is, fir example, pAnimationTextGeometry really pointing to an existing instance?

            https://forum.qt.io/topic/113070/qt-code-of-conduct

            T 1 Reply Last reply
            0
            • jsulmJ jsulm

              @Toocold I suggest to use debugger and position a breakpoint at

              pAnimationTextGeometry->start();
              

              and check what happens when you execute that line. Is, fir example, pAnimationTextGeometry really pointing to an existing instance?

              T Offline
              T Offline
              Toocold
              wrote on last edited by
              #7

              @jsulm
              In this Function

              void QAbstractAnimation::start(DeletionPolicy policy)
                  
                  {
                  
                      Q_D(QAbstractAnimation);
                  
                      if (d->state == Running)
                  
                          return;
                  
                      d->deleteWhenStopped = policy;
                  
                      d->setState(Running);
                  
                  }
              

              My program crashed because of "d" is Null.
              But it's strange, the QPropertyAnimation instance is newed in heap.
              And I set theirs' parent Null now and start(QAbstractAnimation::KeepWhenStopped) instead of.

              jsulmJ 1 Reply Last reply
              0
              • T Toocold

                @jsulm
                In this Function

                void QAbstractAnimation::start(DeletionPolicy policy)
                    
                    {
                    
                        Q_D(QAbstractAnimation);
                    
                        if (d->state == Running)
                    
                            return;
                    
                        d->deleteWhenStopped = policy;
                    
                        d->setState(Running);
                    
                    }
                

                My program crashed because of "d" is Null.
                But it's strange, the QPropertyAnimation instance is newed in heap.
                And I set theirs' parent Null now and start(QAbstractAnimation::KeepWhenStopped) instead of.

                jsulmJ Offline
                jsulmJ Offline
                jsulm
                Lifetime Qt Champion
                wrote on last edited by
                #8

                @Toocold said in Why dump in QAbstractAnimation::start:

                My program crashed because of "d" is Null.

                Then the object is invalid/not initialised.

                https://forum.qt.io/topic/113070/qt-code-of-conduct

                T 1 Reply Last reply
                1
                • jsulmJ jsulm

                  @Toocold said in Why dump in QAbstractAnimation::start:

                  My program crashed because of "d" is Null.

                  Then the object is invalid/not initialised.

                  T Offline
                  T Offline
                  Toocold
                  wrote on last edited by
                  #9

                  @jsulm

                          connect(pAnimationBannerOpacity, &QPropertyAnimation::finished,
                              [&]
                          {
                              if (pAnimationTextGeometry)
                              {
                                  pAnimationTextGeometry->start(QAbstractAnimation::KeepWhenStopped);
                              }
                          });
                  

                  But I checked it before invoking the function.
                  And It can work by added to QSequentialAnimationGroup Class.

                  jsulmJ JonBJ 2 Replies Last reply
                  0
                  • T Toocold

                    @jsulm

                            connect(pAnimationBannerOpacity, &QPropertyAnimation::finished,
                                [&]
                            {
                                if (pAnimationTextGeometry)
                                {
                                    pAnimationTextGeometry->start(QAbstractAnimation::KeepWhenStopped);
                                }
                            });
                    

                    But I checked it before invoking the function.
                    And It can work by added to QSequentialAnimationGroup Class.

                    jsulmJ Offline
                    jsulmJ Offline
                    jsulm
                    Lifetime Qt Champion
                    wrote on last edited by
                    #10

                    @Toocold said in Why dump in QAbstractAnimation::start:

                    if (pAnimationTextGeometry)

                    This only checks whether the pointer is not nullptr, but it still can point to not allocated memory.

                    https://forum.qt.io/topic/113070/qt-code-of-conduct

                    T 1 Reply Last reply
                    3
                    • T Toocold

                      @jsulm

                              connect(pAnimationBannerOpacity, &QPropertyAnimation::finished,
                                  [&]
                              {
                                  if (pAnimationTextGeometry)
                                  {
                                      pAnimationTextGeometry->start(QAbstractAnimation::KeepWhenStopped);
                                  }
                              });
                      

                      But I checked it before invoking the function.
                      And It can work by added to QSequentialAnimationGroup Class.

                      JonBJ Online
                      JonBJ Online
                      JonB
                      wrote on last edited by
                      #11

                      @Toocold
                      Because you cannot afford to deference a pointer if it's pointing to garbage, if you use a debugger as @jsulm suggested you can look in its "watch" window at what pAnimationTextGeometry actually points to. It's not foolproof, but if what the debugger shows doesn't look good, it's probably a bad pointer.

                      1 Reply Last reply
                      1
                      • jsulmJ jsulm

                        @Toocold said in Why dump in QAbstractAnimation::start:

                        if (pAnimationTextGeometry)

                        This only checks whether the pointer is not nullptr, but it still can point to not allocated memory.

                        T Offline
                        T Offline
                        Toocold
                        wrote on last edited by
                        #12

                        @jsulm @JonB Thanks for your suggestion.
                        I don't know how to check the pointer is point to an allocated memory.
                        So I defined the pointer in the lambda function, and it worked.
                        But why my pAnimationTextGeometry was recycled, I didn't give him a parent.

                        T 1 Reply Last reply
                        0
                        • T Toocold

                          @jsulm @JonB Thanks for your suggestion.
                          I don't know how to check the pointer is point to an allocated memory.
                          So I defined the pointer in the lambda function, and it worked.
                          But why my pAnimationTextGeometry was recycled, I didn't give him a parent.

                          T Offline
                          T Offline
                          Toocold
                          wrote on last edited by
                          #13

                          @jsulm @JonB
                          You can try this program, it will crash.

                          void func()
                          {
                              QLabel* p1 = new QLabel;
                              QLabel* p2 = new QLabel;
                              QPropertyAnimation*     pA1;
                              QPropertyAnimation*     pA2;
                          
                              p1->setText("123");
                              p2->setText("456");
                              p1->setGeometry(QRect(0, 0, 0, 0));
                              p2->setGeometry(QRect(0, 0, 0, 0));
                          
                              p1->show();
                              p2->show();
                          
                              pA1 = new QPropertyAnimation(p1, "geometry");
                              pA2 = new QPropertyAnimation(p2, "geometry");
                          
                              pA1->setDuration(1000);
                              pA1->setStartValue(QRect(0, 0, 0, 0));
                              pA1->setEndValue(QRect(660, 660, 60, 60));
                          
                              pA2->setDuration(1000);
                              pA2->setStartValue(QRect(0, 0, 0, 0));
                              pA2->setEndValue(QRect(330, 330, 30, 30));
                          
                              QObject::connect(pA1, &QPropertyAnimation::finished, [&] {
                                  pA2->start();
                              });
                          
                              pA1->start();
                          }
                          
                          int main(int argc, char** argv)
                          {
                              QApplication a(argc, argv);
                          
                              func();
                          
                              return a.exec();
                          }
                          
                          1 Reply Last reply
                          0
                          • Christian EhrlicherC Offline
                            Christian EhrlicherC Offline
                            Christian Ehrlicher
                            Lifetime Qt Champion
                            wrote on last edited by
                            #14

                            @Toocold said in Why dump in QAbstractAnimation::start:

                            QObject::connect(pA1, &QPropertyAnimation::finished, [&] {

                            C++ basics - you catch the variables by reference...

                            Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                            Visit the Qt Academy at https://academy.qt.io/catalog

                            T 1 Reply Last reply
                            2
                            • Christian EhrlicherC Christian Ehrlicher

                              @Toocold said in Why dump in QAbstractAnimation::start:

                              QObject::connect(pA1, &QPropertyAnimation::finished, [&] {

                              C++ basics - you catch the variables by reference...

                              T Offline
                              T Offline
                              Toocold
                              wrote on last edited by
                              #15

                              @Christian-Ehrlicher
                              Yeah...I didn't notice it.
                              Thank you.

                              Christian EhrlicherC 1 Reply Last reply
                              0
                              • T Toocold

                                @Christian-Ehrlicher
                                Yeah...I didn't notice it.
                                Thank you.

                                Christian EhrlicherC Offline
                                Christian EhrlicherC Offline
                                Christian Ehrlicher
                                Lifetime Qt Champion
                                wrote on last edited by
                                #16

                                @Toocold Then please mark this topic as solved, thx.

                                Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                                Visit the Qt Academy at https://academy.qt.io/catalog

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