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mwt
Class Component

java.lang.Object
  mwt.Component

Direct Known Subclasses:: Button, Label, Window

public class Component
extends java.lang.Object
extends java.lang.Object

A component is an object having a graphical representation that can be displayed on the screen (canvas) and can interact with the user.

Containers

In MWT components can be containers, this means, that you could append child components.
This behavior is determined when the component is created. It cannot be changed later.
Examples of no-container components are buttons, checkboxes and labels. Examples of container components are the panels and frames/forms.

Components added are tracked in a list. The order of the list will define the components' front-to-back stacking order within the container component.
If no index is specified when adding a component to a container, it will be added to the end of the list (and hence to the bottom of the stacking order).

Trying to append childs to a no-container component will throw an exception.

Position and Size

A component position (x and y coordinates) is relative to its parent container.
The size is defined by its width and height.

When a component is being painted, the Graphics object is translated and clipped in order to make it relative to component's position, and disable painting outside its bounds.
Note: you can change the graphics clip if you want, using Graphics.setClip(int, int, int, int)) howewer, this trick is not MWT related.

Focus

A component accepts focus when is visible, enabled, focusable and is not a container.
Components are visible and enabled by default.
A component may be hidden (not visible) or disabled even if isVisible() and/or isEnabled()() returns true. This is because the component's parent hierarchy affects this properties. In other words, if a container is hidden or disabled, all its child hierarchy is hidden and disabled too.
Use isHierarchyVisible() and isHierarchyEnabled() to know if a component and all its hierarchy is visible and/or enabled.

The focusable property determines if a component should not accept focus regardless of its visible and enabled properties.

Note that if you switch any of these properties to false whenever a component or one of its childs has focus, you may want change its container window's focus "manually", otherwise it will remains focus until the next window key event.

Events

Component's events can be handled overriding methods.

Appearance	`paint(Graphics, Window)`
Behavior	`add(Component, int)`
Behavior	`remove(int)`
Focus	`focusGained()`
Focus	`focusLost()`
Key	`keyEvent(long, Window)`
Property Changed	`setX(int)`
	`setY(int)`
	`setWidth(int)`
	`setHeight(int)`
	`setVisible(boolean)`
	`setEnabled(boolean)`
	`setFocusable(boolean)`
	`setDoubleBuffered(boolean)`
Getters	`getX()`
	`getY()`
	`getWidth()`
	`getHeight()`

Normally the appearance and key methods are overriden. This way, you can handle the component's input and output.

The focus methods can be used in different ways. For example, you can validate a component when it loses focus, if the validation fails you can set the focus back.

Avoid overriding setters (property changed methods) and getters unless is absolutely necessary.
Otherwise the java virtual machine will call this methods indirectly via a virtual table, instead of calling them directly (which -may- impact performance significally).

Align Constants

This class contains aligns constant that can be used in different ways. For example, text alignment.

`ALIGN_TOP_LEFT`
`ALIGN_TOP_CENTER`
`ALIGN_TOP_RIGHT`
`ALIGN_MIDDLE_LEFT`
`ALIGN_MIDDLE_CENTER`
`ALIGN_MIDDLE_RIGHT`
`ALIGN_BOTTOM_LEFT`
`ALIGN_BOTTOM_CENTER`
`ALIGN_BOTTOM_RIGHT`

Field Summary
`static int`	`ALIGN_BOTTOM_CENTER` Constant for component/text alignment.
`static int`	`ALIGN_BOTTOM_LEFT` Constant for component/text alignment.
`static int`	`ALIGN_BOTTOM_RIGHT` Constant for component/text alignment.
`static int`	`ALIGN_MIDDLE_CENTER` Constant for component/text alignment.
`static int`	`ALIGN_MIDDLE_LEFT` Constant for component/text alignment.
`static int`	`ALIGN_MIDDLE_RIGHT` Constant for component/text alignment.
`static int`	`ALIGN_TOP_CENTER` Constant for component/text alignment.
`static int`	`ALIGN_TOP_LEFT` Constant for component/text alignment.
`static int`	`ALIGN_TOP_RIGHT` Constant for component/text alignment.

Constructor Summary
`Component(int x, int y, int width, int height, boolean isContainer)` Creates a new component with the given position and size.

Method Summary
`boolean`	`acceptsFocus()` Checks if this component accepts focus.
`void`	`add(Component c)` Appends the given component as a child.
`void`	`add(Component c, int index)` Appends a child component at the given position.
`protected void`	`focusGained()` Called when this component gains focus.
`protected void`	`focusLost()` Called when this component loses focus.
`int`	`getChild(Component c)` Gets the index of the specified component.
`Component`	`getChild(int index)` Gets the component at the specified index.
`Component`	`getChild(java.lang.String id, boolean recursive)` Gets the child with the given id.
`int`	`getChildCount()` Gets the number of components currently added.
`Component`	`getComponent(int index)` Deprecated. use `getChild(int)` instead
`int`	`getComponentCount()` Deprecated. use `getChildCount()` instead
`int`	`getComponentIndex(Component c)` Deprecated. use `getChild(Component)` instead
`int`	`getHeight()` Gets the height of this component, in pixels.
`java.lang.String`	`getId()` Gets the id.
`Component`	`getParent()` Gets the parent component container.
`int`	`getWidth()` Gets the width of this component, in pixels.
`int`	`getX()` Gets the x coordinate of this component within the parent.
`int`	`getY()` Gets the y coordinate of this component within the parent.
`boolean`	`isContainer()` Checks if this component is a container.
`boolean`	`isDoubleBuffered()` Checks if this component should be double buffered.
`boolean`	`isEnabled()` Checks if this component should be enabled when its parent hierarchy is enabled.
`boolean`	`isFocusable()` Checks if this component is focusable.
`boolean`	`isHierarchyEnabled()` Checks if this component and its parent hierarchy is enabled.
`boolean`	`isHierarchyVisible()` Checks if this component and its parent hierarchy is visible.
`boolean`	`isVisible()` Checks if this component should be visible when its parent hierarchy is visible.
`protected boolean`	`keyEvent(long key, Window window)` Processes a key event.
`protected void`	`paint(javax.microedition.lcdui.Graphics g, Window window)` Paints this component.
`protected void`	`paintChilds(javax.microedition.lcdui.Graphics g, Window window)` Paints the childs components into the given graphics object.
`void`	`remove(int index)` Deprecated. use `removeChild(int)` instead
`void`	`removeChild(int index)` Removes the component at the specified index.
`void`	`setDoubleBuffered(boolean doubleBuffered)` Enables or disables the double buffer.
`void`	`setEnabled(boolean enabled)` Enables or disables this component.
`void`	`setFocusable(boolean focusStop)` Enables or disables focusable.
`void`	`setHeight(int height)` Sets the height of this component, in pixels.
`void`	`setId(java.lang.String id)` Sets the id.
`void`	`setVisible(boolean visible)` Shows or hides this component.
`void`	`setWidth(int width)` Sets the width of this component, in pixels.
`void`	`setX(int x)` Sets the x coordinate of this component within the parent.
`void`	`setY(int y)` Sets the y coordinate of this component within the parent.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail