创建基于gwtext的数据绑定应用（2） 事件拦截器

事件拦截器是Dataset与被绑定对象的纽带，通过事件拦截器实现数据绑定

public interface DatasetInterceptor {
	public boolean doBeforeIntercept(Dataset dataset, String action, Object[] params);
	
	public void onIntercept(Dataset dataset, String action, Object[] params);
	
	public void doAfterIntercept(Dataset dataset, String action, Object[] params, int resultCode);
}

一个简单的数据绑定TextField，当Dataset发生ACTION_MOVE（当前记录行变动）事件时动态修改绑定字段内容，如下：

public class DatasetText extends TextField implements DatasetFormField {
	private Dataset dataset;
	private DatasetField field;
	
	private DatasetInterceptor interceptor;
	
	public DatasetText(Dataset dataset, DatasetField field) {
		this.dataset = dataset;
		this.field = field;
		this.init();
		this.bind();
	}
	
	public DatasetText(DatasetField field) {
		this(null, field);
	}
	
	private void init() {
		setFieldLabel(field.getTitle());
		setName(field.getName());
		setWidth(field.getEditWidth());
		if(dataset != null) {
			
			this.addListener(new TextFieldListenerAdapter(){

				@Override
				public void onBlur(Field field) {
					dataset.set(field.getName(), DatasetText.this.getText());
				}

				@Override
				public void onFocus(Field field) {
					DatasetText.this.selectText();
				}
				
			});
		}
	}

	@Override
	public void bind() {
		if(this.dataset == null) return;
		if(this.interceptor == null)
			this.interceptor = new DatasetInterceptorFormAdapter(Constants.ACTION_MOVE){
				@Override
				public void doAction(Dataset dataset, Object params) {
					Record rec = dataset.getRecordAtCursor();
					if(rec != null)
						DatasetText.this.setValue(rec.getAsString(field.getName()));
				}
			};
		this.dataset.addInterceptor(this.interceptor);
		Record rec = dataset.getRecordAtCursor();
		if(rec != null)
			this.setValue(rec.getAsString(field.getName()));
	}

	@Override
	public void unbind() {
		if(this.dataset == null) return;
		this.dataset.removeInterceptor(this.interceptor);
	}

	@Override
	public Dataset getDataset() {
		return this.dataset;
	}

	@Override
	public DatasetField getField() {
		return this.field;
	}
}