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tips4javatips4java
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‎source/ComponentMover.java‎

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import java.awt.*;
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import java.awt.event.*;
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import javax.swing.JComponent;
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import javax.swing.SwingUtilities;
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/**
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* This class allows you to move a Component by using a mouse. The Component
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* moved can be a high level Window (ie. Window, Frame, Dialog) in which case
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* the Window is moved within the desktop. Or the Component can belong to a
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* Container in which case the Component is moved within the Container.
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*
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* When moving a Window, the listener can be added to a child Component of
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* the Window. In this case attempting to move the child will result in the
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* Window moving. For example, you might create a custom "Title Bar" for an
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* undecorated Window and moving of the Window is accomplished by moving the
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* title bar only. Multiple components can be registered as "window movers".
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*
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* Components can be registered when the class is created. Additional
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* components can be added at any time using the registerComponent() method.
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*/
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public class ComponentMover extends MouseAdapter
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{
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private Insets dragInsets = new Insets(0, 0, 0, 0);
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private Dimension snapSize = new Dimension(1, 1);
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private Insets edgeInsets = new Insets(0, 0, 0, 0);
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private boolean changeCursor = true;
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private boolean autoLayout = false;
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private Class destinationClass;
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private Component destinationComponent;
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private Component destination;
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private Component source;
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private Point pressed;
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private Point location;
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private Cursor originalCursor;
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private boolean autoscrolls;
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private boolean potentialDrag;
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/**
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* Constructor for moving individual components. The components must be
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* regisetered using the registerComponent() method.
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*/
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public ComponentMover()
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{
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}
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/**
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* Constructor to specify a Class of Component that will be moved when
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* drag events are generated on a registered child component. The events
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* will be passed to the first ancestor of this specified class.
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*
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* @param destinationClass the Class of the ancestor component
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* @param component the Components to be registered for forwarding
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* drag events to the ancestor Component.
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*/
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public ComponentMover(Class destinationClass, Component... components)
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{
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this.destinationClass = destinationClass;
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registerComponent( components );
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}
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/**
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* Constructor to specify a parent component that will be moved when drag
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* events are generated on a registered child component.
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*
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* @param destinationComponent the component drage events should be forwareded to
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* @param components the Components to be registered for forwarding drag
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* events to the parent component to be moved
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*/
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public ComponentMover(Component destinationComponent, Component... components)
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{
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this.destinationComponent = destinationComponent;
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registerComponent( components );
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}
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/**
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* Get the auto layout property
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*
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* @return the auto layout property
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*/
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public boolean isAutoLayout()
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{
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return autoLayout;
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}
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/**
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* Set the auto layout property
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*
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* @param autoLayout when true layout will be invoked on the parent container
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*/
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public void setAutoLayout(boolean autoLayout)
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{
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this.autoLayout = autoLayout;
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}
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/**
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* Get the change cursor property
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*
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* @return the change cursor property
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*/
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public boolean isChangeCursor()
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{
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return changeCursor;
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}
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/**
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* Set the change cursor property
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*
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* @param changeCursor when true the cursor will be changed to the
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* Cursor.MOVE_CURSOR while the mouse is pressed
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*/
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public void setChangeCursor(boolean changeCursor)
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{
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this.changeCursor = changeCursor;
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}
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/**
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* Get the drag insets
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*
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* @return the drag insets
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*/
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public Insets getDragInsets()
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{
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return dragInsets;
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}
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/**
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* Set the drag insets. The insets specify an area where mouseDragged
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* events should be ignored and therefore the component will not be moved.
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* This will prevent these events from being confused with a
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* MouseMotionListener that supports component resizing.
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*
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* @param dragInsets
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*/
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public void setDragInsets(Insets dragInsets)
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{
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this.dragInsets = dragInsets;
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}
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/**
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* Get the bounds insets
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*
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* @return the bounds insets
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*/
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public Insets getEdgeInsets()
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{
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return edgeInsets;
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}
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/**
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* Set the edge insets. The insets specify how close to each edge of the parent
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* component that the child component can be moved. Positive values means the
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* component must be contained within the parent. Negative values means the
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* component can be moved outside the parent.
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*
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* @param edgeInsets
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*/
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public void setEdgeInsets(Insets edgeInsets)
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{
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this.edgeInsets = edgeInsets;
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}
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/**
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* Remove listeners from the specified component
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*
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* @param component the component the listeners are removed from
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*/
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public void deregisterComponent(Component... components)
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{
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for (Component component : components)
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component.removeMouseListener( this );
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}
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/**
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* Add the required listeners to the specified component
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*
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* @param component the component the listeners are added to
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*/
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public void registerComponent(Component... components)
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{
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for (Component component : components)
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component.addMouseListener( this );
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}
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/**
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* Get the snap size
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*
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* @return the snap size
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*/
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public Dimension getSnapSize()
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{
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return snapSize;
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}
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/**
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* Set the snap size. Forces the component to be snapped to
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* the closest grid position. Snapping will occur when the mouse is
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* dragged half way.
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*/
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public void setSnapSize(Dimension snapSize)
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{
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if (snapSize.width < 1
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|| snapSize.height < 1)
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throw new IllegalArgumentException("Snap sizes must be greater than 0");
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this.snapSize = snapSize;
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}
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/**
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* Setup the variables used to control the moving of the component:
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*
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* source - the source component of the mouse event
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* destination - the component that will ultimately be moved
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* pressed - the Point where the mouse was pressed in the destination
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* component coordinates.
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*/
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@Override
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public void mousePressed(MouseEvent e)
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{
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source = e.getComponent();
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int width = source.getSize().width - dragInsets.left - dragInsets.right;
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int height = source.getSize().height - dragInsets.top - dragInsets.bottom;
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Rectangle r = new Rectangle(dragInsets.left, dragInsets.top, width, height);
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if (r.contains(e.getPoint()))
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setupForDragging(e);
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}
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private void setupForDragging(MouseEvent e)
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{
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source.addMouseMotionListener( this );
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potentialDrag = true;
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// Determine the component that will ultimately be moved
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if (destinationComponent != null)
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{
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destination = destinationComponent;
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}
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else if (destinationClass == null)
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{
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destination = source;
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}
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else // forward events to destination component
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{
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destination = SwingUtilities.getAncestorOfClass(destinationClass, source);
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}
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pressed = e.getLocationOnScreen();
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location = destination.getLocation();
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if (changeCursor)
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{
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originalCursor = source.getCursor();
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source.setCursor( Cursor.getPredefinedCursor(Cursor.MOVE_CURSOR) );
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}
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// Making sure autoscrolls is false will allow for smoother dragging of
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// individual components
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if (destination instanceof JComponent)
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{
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JComponent jc = (JComponent)destination;
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autoscrolls = jc.getAutoscrolls();
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jc.setAutoscrolls( false );
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}
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}
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/**
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* Move the component to its new location. The dragged Point must be in
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* the destination coordinates.
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*/
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@Override
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public void mouseDragged(MouseEvent e)
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{
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Point dragged = e.getLocationOnScreen();
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int dragX = getDragDistance(dragged.x, pressed.x, snapSize.width);
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int dragY = getDragDistance(dragged.y, pressed.y, snapSize.height);
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int locationX = location.x + dragX;
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int locationY = location.y + dragY;
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// Mouse dragged events are not generated for every pixel the mouse
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// is moved. Adjust the location to make sure we are still on a
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// snap value.
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while (locationX < edgeInsets.left)
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locationX += snapSize.width;
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while (locationY < edgeInsets.top)
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locationY += snapSize.height;
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Dimension d = getBoundingSize( destination );
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while (locationX + destination.getSize().width + edgeInsets.right > d.width)
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locationX -= snapSize.width;
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while (locationY + destination.getSize().height + edgeInsets.bottom > d.height)
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locationY -= snapSize.height;
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// Adjustments are finished, move the component
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destination.setLocation(locationX, locationY);
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}
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/*
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* Determine how far the mouse has moved from where dragging started
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* (Assume drag direction is down and right for positive drag distance)
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*/
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private int getDragDistance(int larger, int smaller, int snapSize)
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{
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int halfway = snapSize / 2;
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int drag = larger - smaller;
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drag += (drag < 0) ? -halfway : halfway;
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drag = (drag / snapSize) * snapSize;
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return drag;
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}
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/*
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* Get the bounds of the parent of the dragged component.
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*/
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private Dimension getBoundingSize(Component source)
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{
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if (source instanceof Window)
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{
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GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
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Rectangle bounds = env.getMaximumWindowBounds();
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return new Dimension(bounds.width, bounds.height);
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}
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else
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{
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return source.getParent().getSize();
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}
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}
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/**
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* Restore the original state of the Component
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*/
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@Override
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public void mouseReleased(MouseEvent e)
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{
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if (!potentialDrag) return;
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source.removeMouseMotionListener( this );
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potentialDrag = false;
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if (changeCursor)
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source.setCursor( originalCursor );
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if (destination instanceof JComponent)
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{
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((JComponent)destination).setAutoscrolls( autoscrolls );
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}
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// Layout the components on the parent container
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if (autoLayout)
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{
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if (destination instanceof JComponent)
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{
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((JComponent)destination).revalidate();
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}
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else
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{
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destination.validate();
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}
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}
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}
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}

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