001// Copyright 2004, 2005 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry.form;
016
017import org.apache.hivemind.ApplicationRuntimeException;
018import org.apache.tapestry.AbstractComponent;
019import org.apache.tapestry.IMarkupWriter;
020import org.apache.tapestry.IRequestCycle;
021import org.apache.tapestry.Tapestry;
022
023/**
024 *  Implements a component that manages an HTML <input type=radio> form element.
025 *  Such a component must be wrapped (possibly indirectly)
026 *  inside a {@link RadioGroup} component.
027 *
028 *  [<a href="../../../../../ComponentReference/Radio.html">Component Reference</a>]
029 *
030 * 
031 *  <p>{@link Radio} and {@link RadioGroup} are generally not used (except
032 *  for very special cases).  Instead, a {@link PropertySelection} component is used.
033 *
034 *
035 *  @author Howard Lewis Ship
036 * 
037 **/
038
039public abstract class Radio extends AbstractComponent
040{
041    /**
042     *  Renders the form element, or responds when the form containing the element
043     *  is submitted (by checking {@link Form#isRewinding()}.
044     *
045     *
046     **/
047
048    protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
049    {
050
051        RadioGroup group = RadioGroup.get(cycle);
052        if (group == null)
053            throw new ApplicationRuntimeException(
054                Tapestry.getMessage("Radio.must-be-contained-by-group"),
055                this,
056                null,
057                null);
058
059        // The group determines rewinding from the form.
060
061        boolean rewinding = group.isRewinding();
062
063        int option = group.getNextOptionId();
064
065        if (rewinding)
066        {
067            // If not disabled and this is the selected button within the radio group,
068            // then update set the selection from the group to the value for this
069            // radio button.  This will update the selected parameter of the RadioGroup.
070
071            if (!isDisabled() && !group.isDisabled() && group.isSelected(option))
072                group.updateSelection(getValue());
073            return;
074        }
075
076        writer.beginEmpty("input");
077
078        writer.attribute("type", "radio");
079
080        writer.attribute("name", group.getName());
081
082        // As the group if the value for this Radio matches the selection
083        // for the group as a whole; if so this is the default radio and is checked.
084
085        if (group.isSelection(getValue()))
086            writer.attribute("checked", "checked");
087
088        if (isDisabled() || group.isDisabled())
089            writer.attribute("disabled", "disabled");
090
091        // The value for the Radio matches the option number (provided by the RadioGroup).
092        // When the form is submitted, the RadioGroup will know which option was,
093        // in fact, selected by the user.
094
095        writer.attribute("value", option);
096
097        renderInformalParameters(writer, cycle);
098
099    }
100
101    public abstract boolean isDisabled();
102
103    public abstract Object getValue();
104}