src/corelib/doc/snippets/code/src_corelib_kernel_qobject.cpp

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  40
  41 //! [0]
  42 QLineEdit *lineEdit = static_cast<QLineEdit *>(
  43         qt_find_obj_child(myWidget, "QLineEdit", "my line edit"));
  44 if (lineEdit)
  45     lineEdit->setText("Default");
  46 //! [0]
  47
  48
  49 //! [1]
  50 QObject *obj = new QPushButton;
  51 obj->metaObject()->className();             // returns "QPushButton"
  52
  53 QPushButton::staticMetaObject.className();  // returns "QPushButton"
  54 //! [1]
  55
  56
  57 //! [2]
  58 QPushButton::staticMetaObject.className();  // returns "QPushButton"
  59
  60 QObject *obj = new QPushButton;
  61 obj->metaObject()->className();             // returns "QPushButton"
  62 //! [2]
  63
  64
  65 //! [3]
  66 QObject *obj = new QTimer;          // QTimer inherits QObject
  67
  68 QTimer *timer = qobject_cast<QTimer *>(obj);
  69 // timer == (QObject *)obj
  70
  71 QAbstractButton *button = qobject_cast<QAbstractButton *>(obj);
  72 // button == 0
  73 //! [3]
  74
  75
  76 //! [4]
  77 QTimer *timer = new QTimer;         // QTimer inherits QObject
  78 timer->inherits("QTimer");          // returns true
  79 timer->inherits("QObject");         // returns true
  80 timer->inherits("QAbstractButton"); // returns false
  81
  82 // QVBoxLayout inherits QObject and QLayoutItem
  83 QVBoxLayout *layout = new QVBoxLayout;
  84 layout->inherits("QObject");        // returns true
  85 layout->inherits("QLayoutItem");    // returns true (even though QLayoutItem is not a QObject)
  86 //! [4]
  87
  88
  89 //! [5]
  90 qDebug("MyClass::setPrecision(): (%s) invalid precision %f",
  91        qPrintable(objectName()), newPrecision);
  92 //! [5]
  93
  94
  95 //! [6]
  96 class MainWindow : public QMainWindow
  97 {
  98 public:
  99     MainWindow();
 100
 101 protected:
 102     bool eventFilter(QObject *obj, QEvent *ev);
 103
 104 private:
 105     QTextEdit *textEdit;
 106 };
 107
 108 MainWindow::MainWindow()
 109 {
 110     textEdit = new QTextEdit;
 111     setCentralWidget(textEdit);
 112
 113     textEdit->installEventFilter(this);
 114 }
 115
 116 bool MainWindow::eventFilter(QObject *obj, QEvent *event)
 117 {
 118     if (obj == textEdit) {
 119         if (event->type() == QEvent::KeyPress) {
 120             QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
 121             qDebug() << "Ate key press" << keyEvent->key();
 122             return true;
 123         } else {
 124             return false;
 125         }
 126     } else {
 127         // pass the event on to the parent class
 128         return QMainWindow::eventFilter(obj, event);
 129     }
 130 }
 131 //! [6]
 132
 133
 134 //! [7]
 135 myObject->moveToThread(QApplication::instance()->thread());
 136 //! [7]
 137
 138
 139 //! [8]
 140 class MyObject : public QObject
 141 {
 142     Q_OBJECT
 143
 144 public:
 145     MyObject(QObject *parent = 0);
 146
 147 protected:
 148     void timerEvent(QTimerEvent *event);
 149 };
 150
 151 MyObject::MyObject(QObject *parent)
 152     : QObject(parent)
 153 {
 154     startTimer(50);     // 50-millisecond timer
 155     startTimer(1000);   // 1-second timer
 156     startTimer(60000);  // 1-minute timer
 157 }
 158
 159 void MyObject::timerEvent(QTimerEvent *event)
 160 {
 161     qDebug() << "Timer ID:" << event->timerId();
 162 }
 163 //! [8]
 164
 165
 166 //! [9]
 167 QList<QObject *> list = window()->queryList("QAbstractButton"));
 168 foreach (QObject *obj, list)
 169     static_cast<QAbstractButton *>(obj)->setEnabled(false);
 170 //! [9]
 171
 172
 173 //! [10]
 174 QPushButton *button = parentWidget->findChild<QPushButton *>("button1");
 175 //! [10]
 176
 177
 178 //! [11]
 179 QListWidget *list = parentWidget->findChild<QListWidget *>();
 180 //! [11]
 181
 182
 183 //! [12]
 184 QList<QWidget *> widgets = parentWidget.findChildren<QWidget *>("widgetname");
 185 //! [12]
 186
 187
 188 //! [13]
 189 QList<QPushButton *> allPButtons = parentWidget.findChildren<QPushButton *>();
 190 //! [13]
 191
 192
 193 //! [14]
 194 monitoredObj->installEventFilter(filterObj);
 195 //! [14]
 196
 197
 198 //! [15]
 199 class KeyPressEater : public QObject
 200 {
 201     Q_OBJECT
 202     ...
 203
 204 protected:
 205     bool eventFilter(QObject *obj, QEvent *event);
 206 };
 207
 208 bool KeyPressEater::eventFilter(QObject *obj, QEvent *event)
 209 {
 210     if (event->type() == QEvent::KeyPress) {
 211         QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
 212         qDebug("Ate key press %d", keyEvent->key());
 213         return true;
 214     } else {
 215         // standard event processing
 216         return QObject::eventFilter(obj, event);
 217     }
 218 }
 219 //! [15]
 220
 221
 222 //! [16]
 223 KeyPressEater *keyPressEater = new KeyPressEater(this);
 224 QPushButton *pushButton = new QPushButton(this);
 225 QListView *listView = new QListView(this);
 226
 227 pushButton->installEventFilter(keyPressEater);
 228 listView->installEventFilter(keyPressEater);
 229 //! [16]
 230
 231
 232 //! [17]
 233 MyWindow::MyWindow()
 234 {
 235     QLabel *senderLabel = new QLabel(tr("Name:"));
 236     QLabel *recipientLabel = new QLabel(tr("Name:", "recipient"));
 237 //! [17]
 238 }
 239
 240
 241 //! [18]
 242 int n = messages.count();
 243 showMessage(tr("%n message(s) saved", "", n));
 244 //! [18]
 245
 246
 247 //! [19]
 248 n == 1 ? tr("%n message saved") : tr("%n messages saved")
 249 //! [19]
 250
 251
 252 //! [20]
 253 label->setText(tr("F\374r \310lise"));
 254 //! [20]
 255
 256
 257 //! [21]
 258 if (receivers(SIGNAL(valueChanged(QByteArray))) > 0) {
 259     QByteArray data;
 260     get_the_value(&data);       // expensive operation
 261     emit valueChanged(data);
 262 }
 263 //! [21]
 264
 265
 266 //! [22]
 267 QLabel *label = new QLabel;
 268 QScrollBar *scrollBar = new QScrollBar;
 269 QObject::connect(scrollBar, SIGNAL(valueChanged(int)),
 270                  label,  SLOT(setNum(int)));
 271 //! [22]
 272
 273
 274 //! [23]
 275 // WRONG
 276 QObject::connect(scrollBar, SIGNAL(valueChanged(int value)),
 277                  label, SLOT(setNum(int value)));
 278 //! [23]
 279
 280
 281 //! [24]
 282 class MyWidget : public QWidget
 283 {
 284     Q_OBJECT
 285
 286 public:
 287     MyWidget();
 288
 289 signals:
 290     void buttonClicked();
 291
 292 private:
 293     QPushButton *myButton;
 294 };
 295
 296 MyWidget::MyWidget()
 297 {
 298     myButton = new QPushButton(this);
 299     connect(myButton, SIGNAL(clicked()),
 300             this, SIGNAL(buttonClicked()));
 301 }
 302 //! [24]
 303
 304
 305 //! [25]
 306 QObject::connect: Cannot queue arguments of type 'MyType'
 307 (Make sure 'MyType' is registered using qRegisterMetaType().)
 308 //! [25]
 309
 310
 311 //! [26]
 312 disconnect(myObject, 0, 0, 0);
 313 //! [26]
 314
 315
 316 //! [27]
 317 myObject->disconnect();
 318 //! [27]
 319
 320
 321 //! [28]
 322 disconnect(myObject, SIGNAL(mySignal()), 0, 0);
 323 //! [28]
 324
 325
 326 //! [29]
 327 myObject->disconnect(SIGNAL(mySignal()));
 328 //! [29]
 329
 330
 331 //! [30]
 332 disconnect(myObject, 0, myReceiver, 0);
 333 //! [30]
 334
 335
 336 //! [31]
 337 myObject->disconnect(myReceiver);
 338 //! [31]
 339
 340
 341 //! [32]
 342 if (signal == QMetaMethod::fromSignal(&MyObject::valueChanged)) {
 343     // signal is valueChanged
 344 }
 345 //! [32]
 346
 347
 348 //! [33]
 349 void on_<object name>_<signal name>(<signal parameters>);
 350 //! [33]
 351
 352
 353 //! [34]
 354 void on_button1_clicked();
 355 //! [34]
 356
 357
 358 //! [35]
 359 class MyClass : public QObject
 360 {
 361     Q_OBJECT
 362     Q_CLASSINFO("Author", "Pierre Gendron")
 363     Q_CLASSINFO("URL", "http://www.my-organization.qc.ca")
 364
 365 public:
 366     ...
 367 };
 368 //! [35]
 369
 370
 371 //! [36]
 372 Q_PROPERTY(type name
 373            READ getFunction
 374            [WRITE setFunction]
 375            [RESET resetFunction]
 376            [NOTIFY notifySignal]
 377            [DESIGNABLE bool]
 378            [SCRIPTABLE bool]
 379            [STORED bool]
 380            [USER bool]
 381            [CONSTANT]
 382            [FINAL])
 383 //! [36]
 384
 385
 386 //! [37]
 387 Q_PROPERTY(QString title READ title WRITE setTitle USER true)
 388 //! [37]
 389
 390
 391 //! [38]
 392 class MyClass : public QObject
 393 {
 394     Q_OBJECT
 395     Q_ENUMS(Priority)
 396
 397 public:
 398     MyClass(QObject *parent = 0);
 399     ~MyClass();
 400
 401     enum Priority { High, Low, VeryHigh, VeryLow };
 402     void setPriority(Priority priority);
 403     Priority priority() const;
 404 };
 405 //! [38]
 406
 407
 408 //! [39a]
 409 class QLibrary : public QObject
 410 {
 411     ...
 412     Q_FLAGS(LoadHint LoadHints)
 413     ...
 414 //! [39a]
 415
 416 //! [39b]
 417     ...
 418 public:
 419     enum LoadHint {
 420         ResolveAllSymbolsHint = 0x01,
 421         ExportExternalSymbolsHint = 0x02,
 422         LoadArchiveMemberHint = 0x04
 423     };
 424     Q_DECLARE_FLAGS(LoadHints, LoadHint)
 425     ...
 426 //! [39b]
 427
 428
 429 //! [40]
 430 //: This name refers to a host name.
 431 hostNameLabel->setText(tr("Name:"));
 432
 433 /*: This text refers to a C++ code example. */
 434 QString example = tr("Example");
 435 //! [40]
 436
 437 //! [41]
 438 QPushButton *button = parentWidget->findChild<QPushButton *>("button1", Qt::FindDirectChildOnly);
 439 //! [41]
 440
 441
 442 //! [42]
 443 QListWidget *list = parentWidget->findChild<QListWidget *>(QString(), Qt::FindDirectChildOnly);
 444 //! [42]
 445
 446
 447 //! [43]
 448 QList<QPushButton *> childButtons = parentWidget.findChildren<QPushButton *>(QString(), Qt::FindDirectChildOnly);
 449 //! [43]
 450
 451 //! [44]
 452 QLabel *label = new QLabel;
 453 QLineEdit *lineEdit = new QLineEdit;
 454 QObject::connect(lineEdit, &QLineEdit::textChanged,
 455                  label,  &QLabel::setText);
 456 //! [44]
 457
 458 //! [45]
 459 void someFunction();
 460 QPushButton *button = new QPushButton;
 461 QObject::connect(button, &QPushButton::clicked, someFunction);
 462 //! [45]
 463
 464 //! [46]
 465 QByteArray page = ...;
 466 QTcpSocket *socket = new QTcpSocket;
 467 socket->connectToHost("qt-project.org", 80);
 468 QObject::connect(socket, &QTcpSocket::connected, [=] () {
 469         socket->write("GET " + page + "\r\n");
 470     });
 471 //! [46]
 472
 473 //! [47]
 474 disconnect(myObject, &MyObject::mySignal(), 0, 0);
 475 //! [47]
 476
 477 //! [48]
 478 QObject::disconnect(lineEdit, &QLineEdit::textChanged,
 479                  label,  &QLabel::setText);
 480 //! [48]
 481
 482 //! [49]
 483 if (isSignalConnected(QMethaMethod::fromSignal(&MyObject::valueChanged))) {
 484     QByteArray data;
 485     data = get_the_value();       // expensive operation
 486     emit valueChanged(data);
 487 }
 488 //! [49]
 489
 490 //! [meta data]
 491 //: This is a comment for the translator.
 492 //= qtn_foo_bar
 493 //~ loc-layout_id foo_dialog
 494 //~ loc-blank False
 495 //~ magic-stuff This might mean something magic.
 496 QString text = MyMagicClass::tr("Sim sala bim.");
 497 //! [meta data]
 498
 499 //! [explicit tr context]
 500 QString text = QScrollBar::tr("Page up");
 501 //! [explicit tr context]