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| <title>Component implementation</title> |
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| <H1 CLASS="Head">Component implementation</H1> |
| Components registered with the types extension point are much like part components. |
| They can take a set of dependencies in their constructor and must implement the |
| interface they were registered for. This example shows the implementation of the |
| NullNameableService.<br> |
| <br> |
| <div style="margin-left: 40px;"><code>/**</code><br> |
| <code> * Default implementation of the Nameable service. All methods are |
| no-ops.</code><br> |
| <code> * </code><br> |
| <code> * @since 3.1</code><br> |
| <code> */</code><br> |
| <code>public class NullNameableService implements INameable {</code><br> |
| <br> |
| <code> /**</code><br> |
| <code> * Component constructor. Do not invoke directly.</code><br> |
| <code> */</code><br> |
| <code> public NullNameableService() {</code><code>}</code><br> |
| <br> |
| <code> public void setName(String newName) {}</code><br> |
| <code> public void setContentDescription(String contentDescription) |
| {</code><code>}</code><br> |
| <code> public void setImage(ImageDescriptor theImage) {</code><code>}</code><br> |
| <code> public void setTooltip(String toolTip) {</code><code>}</code><br> |
| <code>}</code><br> |
| </div> |
| <br> |
| This may be a simple example as the class doesn't do anything, however it demonstrates |
| a common pattern. The INameable service is used to tell the parent about some |
| state in the child. With this type of interface, the default implementation typically |
| doesn't do anything. This makes sense: if the parent doesn't care about the state |
| of its child, it can be ignored. By convention, we use the "Null" prefix to indicate |
| that this is a component that doesn't do anything. This type of object is usually |
| registered as a singleton since it would be wasteful to create multiple instances |
| of such a trivial object. Clients should ensure that any new interfaces that report |
| state are capable of being multiplexed.<br> |
| <br> |
| If the purpose of the interface is to allocate resources or generate output, the |
| default implementation will typically do something more useful. The following |
| example shows the implementation of the DefaultMessageDialogs class. Since this |
| class is intended for generating interactive output, it has a useful default implementation |
| and would not support multiplexing. Since this class needs access to a part's |
| Composite, it cannot be a singleton. By convention, we use the class prefix "Default" |
| to indicate that this is a default component with some useful behavior.<br> |
| <br> |
| <span style="font-weight: bold;"> </span> |
| <div style="margin-left: 40px;"><code>/**</code><br> |
| <code> * Default implementation of the IMessageDialogs interface. Takes |
| the part's </code><br> |
| <code> * control as context and allows the part to open dialogs in a child |
| shell.</code><br> |
| <code> * </code><br> |
| <code> * @since 3.1</code><br> |
| <code> */</code><br> |
| <code>public class DefaultMessageDialogs implements IMessageDialogs {</code><br> |
| <br> |
| <code> private Composite control;</code><br> |
| <code> </code><br> |
| <code> /**</code><br> |
| <code> * Component constructor. Do not invoke directly.</code><br> |
| <code> */</code><br> |
| <code> public DefaultMessageDialogs(Composite control) {</code><br> |
| <code> this.control = control;</code><br> |
| <code> }</code><br> |
| <code> </code><br> |
| <code> public void open(IStatus message) {</code><br> |
| <code> if (message.getSeverity() == |
| IStatus.ERROR) {</code><br> |
| <code> ErrorDialog.openError(control.getShell(), |
| null, null, message);</code><br> |
| <code> } else {</code><br> |
| <code> open(message.getSeverity(), |
| message.getMessage());</code><br> |
| <code> }</code><br> |
| <code> }</code><br> |
| <br> |
| <code> public void openError(String message, Throwable cause) |
| {</code><br> |
| <code> open(new Status(IStatus.ERROR, |
| </code><br> |
| <code> |
| WorkbenchPlugin.getDefault().getBundle().getSymbolicName(),</code><br> |
| <code> |
| IStatus.OK,</code><br> |
| <code> |
| message,</code><br> |
| <code> |
| cause));</code><br> |
| <code> }</code><br> |
| <code> </code><br> |
| <code> public void open(int severity, String message) {</code><br> |
| <code> if (severity == IStatus.ERROR) |
| {</code><br> |
| <code> MessageDialog.openError(control.getShell(), |
| null, message);</code><br> |
| <code> } else if (severity == IStatus.WARNING) |
| {</code><br> |
| <code> MessageDialog.openWarning(control.getShell(), |
| null, message);</code><br> |
| <code> } else {</code><br> |
| <code> MessageDialog.openInformation(control.getShell(), |
| null, message);</code><br> |
| <code> } </code><br> |
| <code> }</code><br> |
| <code>}</code><br> |
| </div> |
| <p>Here is the associated extension point markup for DefaultMessageDialog.</p> |
| <div style="margin-left: 40px;"><code><extension</code><code> point="org.eclipse.core.component.types"></code><br> |
| <code> <component</code><br> |
| <code> |
| initializer="org.eclipse.ui.part.SiteInitializer"</code><br> |
| <code> interface="org.eclipse.ui.part.services.IMessageDialogs"</code><br> |
| <code> implementation="org.eclipse.ui.internal.part.services.DefaultMessageDialogs"</code><br> |
| <code> singleton="false"</code><code>/></code><br> |
| <code></extension></code><br> |
| </div> |
| <h2> </h2> |
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