[Chapter 23] ComponentPeer
Author: John Zukowski
Date: Thu Jul 31 15:28:07 1997

#

| Chapter 23 java.awt.peer Reference |

# ComponentPeer

## Name

ComponentPeer

##

## Description

`ComponentPeer` is an interface that defines the basis for all non-menu GUI peer interfaces.

## Interface Definition

    public abstract interface java.awt.peer.ComponentPeer {
      // Interface Methods
      public abstract int checkImage (Image image, int width, int height,
        ImageObserver observer);
      public abstract Image createImage (ImageProducer producer);
      public abstract Image createImage (int width, int height);
      public abstract void disable();
      public abstract void dispose();
      public abstract void enable();
      public abstract ColorModel getColorModel();
      public abstract FontMetrics getFontMetrics (Font f);
      public abstract Graphics getGraphics();
      public abstract Point getLocationOnScreen();
      public abstract Dimension getMinimumSize();
      public abstract Dimension getPreferredSize();
      public abstract Toolkit getToolkit();
      public abstract boolean handleEvent (Event e);
      public abstract void hide();
      public abstract boolean isFocusTraversable();
      public abstract Dimension minimumSize();
      public abstract void paint (Graphics g);
      public abstract Dimension preferredSize ();
      public abstract boolean prepareImage (Image image, int width, int height,
        ImageObserver observer);
      public abstract void print (Graphics g);
      public abstract void repaint (long tm, int x, int y, int width, int height);
      public abstract void requestFocus();
      public abstract void reshape (int x, int y, int width, int height);
      public abstract void setBackground (Color c);
      public abstract void setBounds (int x, int y, int width, int height);
      public abstract void setCursor (Cursor cursor);
      public abstract void setEnabled (boolean b);
      public abstract void setFont (Font f);
      public abstract void setForeground (Color c);
      public abstract void setVisible (boolean b);
      public abstract void show();
    }

## Interface Methods

### checkImage

#### public abstract int checkImage (Image image, int width, int height, ImageObserver observer)

Parameters

  image

    `Image` to check.

  width

    Horizontal size to which the image will be scaled.

  height

    Vertical size to which the image will be scaled.

  observer

    An `ImageObserver` to monitor image loading; normally, the object on which the image will be rendered.

Returns

  `ImageObserver` flags ORed together indicating status.

Description

  Checks status of image construction.

### createImage

#### public abstract Image createImage (ImageProducer producer)

Parameters

  producer

    An object that implements the `ImageProducer` interface to create a new image.

Returns

  Newly created image instance.

Description

  Creates an `Image` based upon an `ImageProducer`.

#### public abstract Image createImage (int width, int height)

Parameters

  width

    Horizontal size for in-memory `Image`.

  height

    Vertical size for in-memory `Image`.

Returns

  Newly created image instance.

Description

  Creates an in-memory `Image` for double buffering.

### disable

#### public abstract void disable()

Description

  Disables component so that it is unresponsive to user interactions. Replaced by `setEnabled(false)`.

### dispose

#### public abstract void dispose()

Description

  Releases resources used by peer.

### enable

#### public abstract void enable()

Description

  Enables component so that it is responsive to user interactions. Replaced by `setEnabled(true)`.

### getColorModel

#### public abstract ColorModel getColorModel()

Returns

  `ColorModel` used to display the current component.

### getFontMetrics

#### public abstract FontMetrics getFontMetrics (Font f)

Parameters

  f

    A font whose metrics are desired.

Returns

  Font sizing information for the desired font.

### getGraphics

#### public abstract Graphics getGraphics()

Throws

  InternalException

    If acquiring a graphics context is unsupported

Returns

  Component's graphics context.

### getLocationOnScreen

#### public abstract Point getLocationOnScreen()

Returns

  The location of the component in the screen's coordinate space.

### getMinimumSize

#### public abstract Dimension getMinimumSize()

Returns

  The minimum dimensions of the component.

### getPreferredSize

#### public abstract Dimension getPreferredSize()

Returns

  The preferred dimensions of the component.

### getToolkit

#### public abstract Toolkit getToolkit()

Returns

  `Toolkit` of `Component`.

### handleEvent

#### public abstract boolean handleEvent (Event e)

Parameters

  e

    `Event` instance identifying what caused the method to be called.

Returns

  `true` if the peer handled the event, `false` to propagate the event to the parent container.

Description

  High-level event handling routine.

### hide

#### public abstract void hide()

Description

  Hides the component. Replaced by `setVisible(false)`.

### isFocusTraversable

#### public abstract boolean isFocusTraversable()

Returns

  `true` if the peer can be tabbed onto, `false` otherwise.

Description

  Determines if this peer is navigable using the keyboard.

### minimumSize

#### public abstract Dimension minimumSize()

Returns

  The minimum dimensions of the component. Replaced by `getMinimumSize()`.

### paint

#### public abstract void paint (Graphics g)

Parameters

  g

    Graphics context of the component.

Description

  Draws something in graphics context.

### preferredSize

#### public abstract Dimension preferredSize()

Returns

  The preferred dimensions of the component. Replaced by `getPreferredSize()`.

### prepareImage

#### public abstract boolean prepareImage (Image image, int width, int height, ImageObserver observer)

Parameters

  image

    `Image` to load.

  width

    Horizontal size to which the image will be scaled.

  height

    Vertical size to which the image will be scaled.

  observer

    An `ImageObserver` to monitor image loading; normally, the object on which the image will be rendered.

Returns

  `true` if the image has already loaded, `false` otherwise.

Description

  Forces the image to start loading.

### print

#### public abstract void print (Graphics g)

Parameters

  g

    Graphics context of component.

Description

  Print something from the graphics context.

### repaint

#### public abstract void repaint (long tm, int x, int y, int width, int height)

Parameters

  tm

    Millisecond delay allowed before repaint.

  x

    Horizontal origin of bounding box to redraw.

  y

    Vertical origin of bounding box to redraw.

  width

    Width of bounding box to redraw.

  height

    Height of bounding box to redraw.

Description

  Requests scheduler to redraw portion of component within a time period.

### requestFocus

#### public abstract void requestFocus()

Description

  Requests this `Component` gets the input focus.

### reshape

#### public abstract void reshape (int x, int y, int width, int height)

Parameters

  x

    New horizontal position for component.

  y

    New vertical position for component.

  width

    New width for component.

  height

    New height for component.

Description

  Relocates and resizes the component's peer. Replaced by `setBounds(int, int, int, int)`.

### setBackground

#### public abstract void setBackground (Color c)

Parameters

  c

    New color for the background.

Description

  Changes the background color of the component.

### setBounds

#### public abstract void setBounds (int x, int y, int width, int height)

Parameters

  x

    New horizontal position for component.

  y

    New vertical position for component.

  width

    New width for component.

  height

    New height for component.

Description

  Relocates and resizes the component's peer.

### setCursor

#### public abstract void setCursor (Cursor cursor)

Parameters

  cursor

    New cursor.

Description

  Changes the cursor of the component.

### setEnabled

#### public abstract void setEnabled (boolean b)

Parameters

  b

    `true` to enable the peer; `false` to disable it.

Description

  Enables or disables the peer.

### setFont

#### public abstract void setFont (Font f)

Parameters

  f

    New font for the component.

Description

  Changes the font used to display text in the component.

### setForeground

#### public abstract void setForeground (Color c)

Parameters

  c

    New foreground color for the component.

Description

  Changes the foreground color of the component.

### setVisible

#### public abstract void setVisible (boolean b)

Parameters

  b

    `true` to show the peer; `false` to hide it.

Description

  Shows or hides the peer.

### show

#### public abstract void show()

Description

  Makes the peer visible. Replaced by `setVisible(true)`.

## See Also

`ButtonPeer`, `CanvasPeer`, `CheckboxPeer`, `ChoicePeer`, `Color`, `ColorModel`, `ContainerPeer`, Cursor, `Dimension`, `Event`, `Font`, `FontMetrics`, `Graphics`, `Image`, `ImageObserver`, `ImageProducer`, `LabelPeer`, `ListPeer`, `ScrollbarPeer`, `TextComponentPeer`, `Toolkit`

ChoicePeer |  | ContainerPeer