Eclipse开发-基于FieldEditorPreferencePage内部其他FieldEditor的新值更改FieldEditor

Question

在Nodeclipse preference Page中，我希望在更改expressPath时更新expressVersion。

我在下面添加了代码，但是它不会触发PropertyChangeEvent，所以这个逻辑不会被执行。

这里出了什么问题？

    expressPath = new FileFieldEditor(PreferenceConstants.EXPRESS_PATH, "Express path:", getFieldEditorParent());
    //TODO update expressVersion on expressPath selection
    IPropertyChangeListener listener = new IPropertyChangeListener() {
        @Override
        public void propertyChange(PropertyChangeEvent event) {
            if (event.getProperty().equals(FieldEditor.IS_VALID)) {
                String newValue = (String) event.getNewValue();
                expressVersion.setStringValue( ProcessUtils.getCurrentVersionOf(newValue) );
            }
        }               
     };
    expressPath.setPropertyChangeListener(listener);
    addField(expressPath);

    expressVersion = new StringFieldEditor(PreferenceConstants.EXPRESS_VERSION, "Selected Express version:", getFieldEditorParent());
    expressVersion.setEnabled(false, getFieldEditorParent());
    addField(expressVersion);        

Answer 1

查看FieldEditorPreferencePage的源代码，我发现initialize()正在重置所有文件的PropertyChangeListeners

/**
 * Initializes all field editors.
 */
protected void initialize() {
    if (fields != null) {
        Iterator<FieldEditor> e = fields.iterator();
        while (e.hasNext()) {
            FieldEditor pe = e.next();
            pe.setPage(this);
            pe.setPropertyChangeListener(this);
            pe.setPreferenceStore(getPreferenceStore());
            pe.load();
        }
    }
}

initialize()在createFieldEditors()之后调用；

protected Control createContents(Composite parent) {
    fieldEditorParent = new Composite(parent, SWT.NULL);
    GridLayout layout = new GridLayout();
    layout.numColumns = 1;
    layout.marginHeight = 0;
    layout.marginWidth = 0;
    fieldEditorParent.setLayout(layout);
    fieldEditorParent.setFont(parent.getFont());

    createFieldEditors();

    if (style == GRID) {
        adjustGridLayout();
    }

    initialize();
    checkState();
    return fieldEditorParent;
}

所以可以用下面的代码来解决这个问题

@Override
protected void initialize() {
    super.initialize();
    expressPath.setPropertyChangeListener(new MyPropertyChangeListener(this));
}

private class MyPropertyChangeListener implements IPropertyChangeListener{

    private FieldEditorPreferencePage page;

    public MyPropertyChangeListener(FieldEditorPreferencePage nodePreferencePage) {
        page = nodePreferencePage;
    }

    @Override
    public void propertyChange(PropertyChangeEvent event) {
        page.propertyChange(event);

        // The IS_VALID property is only fired when the valid state changes.
        if (event.getProperty().equals(FieldEditor.IS_VALID)) {
            isValidPath = ((Boolean) event.getNewValue()).booleanValue();
            if (!isValidPath) {
                expressVersion.setStringValue( "Selected path is not valid" );
            }
            return;
        }
        if (!isValidPath) { // if it is still not valid file, we don't need to check again
            return;
        }
        if (event.getProperty().equals(FieldEditor.VALUE)) {
            String newExecutablePath = (String) event.getNewValue();
            expressVersion.setStringValue( ProcessUtils.getCurrentVersionOf(newExecutablePath));
        }
    }
}