一个非常有趣的qt小实例

/* This file is part of "bounce" by Gunnstein Lye <gl@ez.no> Copyright (C) 2000 eZ systems as, Norway (http://www.ez.no) bounce is part of a QCanvas tutorial on www.zez.org. bounce is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. You should have received a copy of the GNU General Public License along with bounce; see the file COPYING. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include "bouncecanvasview.hpp" #include "ball.hpp" #include <qwidget.h> #include <qevent.h> #include <qtimer.h> BounceCanvasView::BounceCanvasView( QCanvas *canvas, QWidget *parent, const char *name ) : QCanvasView( canvas, parent, name ) { // create and setup a timer Timer = new QTimer( this, "Timer" ); connect( Timer, SIGNAL( timeout() ), this, SLOT( timeout() ) ); MousePosQueue.setAutoDelete( true ); // delete removed items Moving = 0; // we are not holding the ball } BounceCanvasView::~BounceCanvasView() { } void BounceCanvasView::contentsMousePressEvent( QMouseEvent *e ) { // a list of all items underneath the mouse when it was pressed QCanvasItemList list = canvas()->collisions(e->pos()); // the RTTI of a QCanvasSprite is 1... if ( !list.isEmpty() && list.first()->rtti() == 1 ) { // ...which means we can safely cast to a Ball pointer. Ball *sphere = (Ball*)list.first(); // hit() will return false it we hit the transparent corners // of the planet image. if ( sphere->hit( e->pos() ) ) { Moving = sphere; canvas()->setAdvancePeriod( -1 ); // stops the animation when dragging MovingStart = e->pos(); Moving->setZ( 2 ); // raises the current item above other items when dragging. // (This in not really necessary here, since we have just one item.) Timer->start( 10, false ); // start the timer } } } void BounceCanvasView::contentsMouseMoveEvent( QMouseEvent *e ) { if ( Moving ) // if we are holding the ball... { // ...then move it Moving->moveBy( e->pos().x() - MovingStart.x(), e->pos().y() - MovingStart.y() ); MovingStart = e->pos(); canvas()->update(); // update visual change to canvas } } void BounceCanvasView::contentsMouseReleaseEvent( QMouseEvent* ) { if ( Moving ) // if we are holding the ball { Timer->stop(); // stop the timer if ( MousePosQueue.count() ) // if we have recorded mouse positions... { // ...then calculate average velocity int count = MousePosQueue.count(); QPoint velocity( 0, 0 ); QPoint pos; QPoint prevPos = *MousePosQueue.head(); while ( MousePosQueue.count() ) { pos = *MousePosQueue.dequeue(); velocity += pos - prevPos; prevPos = pos; } // set the balls new velocity Moving->setXVelocity( velocity.x() / count ); Moving->setYVelocity( velocity.y() / count ); } else // if we haven't recorded anything (fast click) { // set zero velocity (we drop the ball) Moving->setXVelocity( 0 ); Moving->setYVelocity( 0 ); } Moving->setZ( 1 ); canvas()->setAdvancePeriod( 10 ); // restart the animation Moving = 0; // clear the pointer, we are no longer holding the ball } } void BounceCanvasView::timeout() { MousePosQueue.enqueue( new QPoint( MovingStart ) ); // record position if ( MousePosQueue.count() > 10 ) // if larger than 10 items MousePosQueue.remove(); // remove one item }