Gestures
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GXT touch support is implemented using GestureRecognizers which convert touch events into logical gestures such as tap, double-tap, and long press. The base class for all GestureRecognizers is com.sencha.gxt.core.client.gestures.AbstractGestureRecognizer, which handles the raw touch events and controls the flow of events to GestureRecognizer implementations.
GXT 4 provides three helper methods to add a GestureRecognizer to a widget or cell. These methods are
These methods handle all the plumbing necessary for touch events to be forwarded to the GestureRecognizer so you don't have to. This includes:
The following sections show how to correctly add a GestureRecognizer to your Widget or Cell. You typically call one of the helper methods above in the constructor of the Widget or Cell in which you want to handle the gesture.
In widgets that extend com.sencha.gxt.widget.core.client.Component, use
Component.addGestureRecognizer(). For example, to handle a long press in a custom
widget that extends Component, add the following to your widget constructor:
public MyCustomComponent() {
...
longPressOrTapGestureRecognizer = new LongPressOrTapGestureRecognizer() {
@Override
protected void onLongPress(TouchData touchData) {
super.onLongPress(touchData);
doSomething();
}
addGestureRecognizer(longPressOrTapGestureRecognizer);
...
}
For an example in GXT itself, see the source code for the com.sencha.gxt.widget.core.client.DatePicker constructor.
In cells that extend com.sencha.gxt.cell.core.client.AbstractEventCell or
com.sencha.gxt.cell.core.client.AbstractEventInputCell, use
AbstractEventCell.addCellGestureAdapter(). For example, to handle a tap in a custom
Cell, extend AbstractEventCell and add the following in the constructor:
public MyCustomCell() {
...
addCellGestureAdapter(new TapGestureRecognizer.CellTapGestureRecognizer<C>() {
@Override
protected void onTap(TouchData tap, Context context, Element parent, C value, ValueUpdater<C> valueUpdater) {
doSomething();
}
}
...
}
For an example in GXT itself, see the com.sencha.gxt.cell.core.client.ButtonCell constructor.
GXT provides an adapter that lets you add a GestureRecognizer to any com.google.gwt.user.client.ui.Widget. Simply construct a new instance of com.sencha.gxt.core.client.gestures.TouchEventToGestureAdapter and pass it the Widget and the GestureRecognizer. For example, to handle a double tap in a custom Widget, add the following in the widget's constructor:
public MyCustomWidget() {
...
doubleTapGestureRecognizer = new DoubleTapGestureRecognizer() {
@Override
protected void onDoubleTap(TouchData touchData) {
super.onDoubleTap(touchData);
doSomething();
}
}
new TouchEventToGestureAdapter(this, doubleTapGestureRecognizer);
...
}
For an example in GXT itself, see the com.sencha.gxt.widget.core.client.tips.ToolTip constructor.
Again, the three GXT methods described above handle all the event plumbing so all you have to do is implement the GestureRecognizer's handler method(s) in your Widget or Cell.
GXT provides the following GestureRecognizers.
| Gestures | Description |
|---|---|
| com.sencha.gxt.core.client.gestures.AbstractGestureRecognizer | Base touch gesture class |
| com.sencha.gxt.core.client.gestures.AbstractTwoTouchGestureRecognizer | Base multi touch gesture class |
| com.sencha.gxt.core.client.gestures.CellGestureAdapter | Base Cell gesture class |
| com.sencha.gxt.core.client.gestures.DragGestureRecognizer | Drag gesture |
| com.sencha.gxt.core.client.gestures.DoubleTapGestureRecognizer | Double tap gesture |
| com.sencha.gxt.core.client.gestures.GestureChain | Multi gesture chaining |
| com.sencha.gxt.core.client.gestures.LongPressOrTapGestureRecognizer | Long press gesture |
| com.sencha.gxt.core.client.gestures.PinchAndRotateGestureRecognizer | Pinch and rotate gesture |
| com.sencha.gxt.core.client.gestures.ScrollGestureRecognizer | Scroll gesture |
| com.sencha.gxt.core.client.gestures.TapGestureRecognizer | Tap gesture |
The following examples show how you might use each GestureRecognizer in a custom widget that extends com.sencha.gxt.widget.core.client.Component. To wire up the GestureRecognizer to a Cell or other Widget, use the appropriate helper method above.
This is an example of wiring up dragging at a low level. It's much simpler to use the GXT com.sencha.gxt.fx.client.Draggable system. You can find an example of using GXT Draggable in the Explorer examples.
dragGestureRecognizer = new DragGestureRecognizer() {
@Override
protected boolean onStart(TouchData startedTouch) {
super.onStart(startedTouch);
return onTouchStart(startedTouch);
}
@Override
protected void onMove(List<TouchData> touches) {
super.onMove(touches);
onTouchMove(touches);
}
@Override
protected void onCancel(List<TouchData> touches) {
super.onCancel(touches);
onTouchEnd(touches);
}
@Override
protected void onEnd(List<TouchData> touches) {
super.onEnd(touches);
onTouchEnd(touches);
}
};
// wire it up
addGestureRecognizer(dragGestureRecognizer);
doubleTapGestureRecognizer = new DoubleTapGestureRecognizer() {
@Override
protected void onTap(TouchData touchData) {
super.onTap(touchData);
onTap(touchData);
}
@Override
protected void onDoubleTap(TouchData touchData) {
super.onDoubleTap(touchData);
onDoubleTap(touchData);
}
}
// wire it up
addGestureRecognizer(doubleTapGestureRecognizer);
longPressOrTapGestureRecognizer = new LongPressOrTapGestureRecognizer() {
@Override
protected void onLongPress(TouchData touchData) {
super.onLongPress(touchData);
onLongPress(touchData);
}
};
// wire it up
addGestureRecognizer(longPressOrTapGestureRecognizer);
pinchAndRotateGestureRecognizer = new PinchAndRotateGestureRecognizer();
// wire it up
addGestureRecognizer(pinchAndRotateGestureRecognizer);
The ScrollGestureRecognizer is slightly different than the others. To use it, you pass
it the DOM element which will be scrolled and the ScrollGestureRecognizer creates the
scrolling effect by setting the element's scrollTop property. Thus, it is not
necessary to implement any onScroll() methods.
scrollGestureRecognizer = new ScrollGestureRecognizer(scrollElement, ScrollDirection.BOTH);
// wire it up
addGestureRecognizer(scrollGestureRecognizer);
In some cases, it may be necessary to customize the behavior of the ScrollGestureRecognizer depending on the particular DOM elements involved. Below is an example of that from GXT's com.sencha.gxt.widget.core.client.grid.LiveGridView class:
@Override
protected void onAfterRenderView() {
super.onAfterRenderView();
if (scrollGestureRecognizer == null) {
scrollGestureRecognizer = new ScrollGestureRecognizer(getScroller(), ScrollDirection.BOTH) {
@Override
protected void onScrollMoveHorizontal(Element scrollElement, TouchData touch) {
// use the scroll container scroller for horz
// use the live view scroller for vert
super.onScrollMoveHorizontal(LiveGridView.this.scroller, touch);
}
};
grid.addGestureRecognizer(scrollGestureRecognizer);
}
}
tapGestureRecognizer = new TapGestureRecognizer() {
@Override
protected void onTap(List<TouchData> touches) {
super.onTap(touches);
onTap();
}
};
// wire it up
addGestureRecognizer(tapGestureRecognizer);
| Utilities and Data | Description |
|---|---|
| com.sencha.gxt.core.client.gestures.TouchData | Data fired in the touch events |
| com.sencha.gxt.core.client.gestures.TouchEventToGestureAdapter | Sink and observe touch events with the recognizer |
| com.sencha.gxt.widget.core.client.event.XEvent | Base event for both mouse and touch NativeEvent |
| com.sencha.gxt.core.client.GXT.isDesktop() | Desktop has been detected |
| com.sencha.gxt.core.client.GXT.isTouch() | Touch has been detected |
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