解读 LWUIT 之四：LWUIT 控件（中）

解读 LWUIT 之四：LWUIT 控件（中）
LWUIT 开发指南下载

作者写的 Hello RadioButton、Hello CheckBox、Hello ComboBox 源代码下载

本文继上篇博客继续对 LWUIT 常见控件进行介绍。本文主要介绍 LWUIT 常用控件单选按钮（RadioButton）、复选按钮（CheckBox）、组合按钮（ComboBox）的使用并附源代码。文章对这三种控件分别进行了说明和比较。

注：源码编写中关于 .res 的编写这里不再赘述，详细编写步骤请参考作者的前一篇博客《解读 LWUIT 之二：关于 LWUIT 开发指南中的 Hello World》。每个项目的 .res 具体配置请到作者上传源码中的 res 目录下使用 ResourceEdit 查看。

com.sun.lwuit.RadioButton 控件

RadioButton 必须和 ButtonGroup 配合才能使用。ButtonGroup 管理一组选中和未选中的单选按钮的组件，一次只产生一个选中的按钮，通过调用它的 getRadioButton(int index) 方法获得一个指定的单选按钮，而通过调用它的 getSelectedIndex() 方法获得被选中的按钮的索引。作者写的 HelloRadioButton 源代码如下：

package com.defonds.lwuit;

import com.sun.lwuit.ButtonGroup;
import com.sun.lwuit.Command;
import com.sun.lwuit.Display;
import com.sun.lwuit.Form;
import com.sun.lwuit.Label;
import com.sun.lwuit.RadioButton;
import com.sun.lwuit.animations.CommonTransitions;
import com.sun.lwuit.events.ActionEvent;
import com.sun.lwuit.events.ActionListener;
import com.sun.lwuit.layouts.BoxLayout;
import com.sun.lwuit.plaf.UIManager;
import com.sun.lwuit.util.Resources;

public class HelloMidlet extends javax.microedition.midlet.MIDlet implements ActionListener{
	
	private Form exampleContainer;// declare a Form
	private ButtonGroup group1;//declare a ButtonGroup
	private RadioButton selectedButton = new RadioButton();//remember the selected radioButton
	private RadioButton rb1;//declare a ButtonGroup
	private RadioButton rb2;//declare a ButtonGroup
	private Label radioButtonsLabel;//declare a Label
	
	public void startApp() {
		// init the LWUIT Display
		Display.init(this);
		// Setting the application theme is discussed
		// later in the theme chapter and the resources chapter
		try {
			Resources r = Resources.open("/myresources.res");
			UIManager.getInstance().setThemeProps(r.getTheme("myresources"));
		} catch (java.io.IOException e) {}
		
		exampleContainer = new Form("Form Title");// Create a Form;//Create a Form
		group1 = new ButtonGroup();//Create a ButtonGroup
		rb1 = new RadioButton("First RadioButton in Group 1");//Create a ButtonGroup
		rb2 = new RadioButton("Second RadioButton in Group 1");//Create a ButtonGroup
		radioButtonsLabel = new Label("RadioButton:");//Create a Label
		
		rb1.addActionListener(this);//add a listener to the button
		rb2.addActionListener(this);//add a listener to the button
		
		group1.add(rb1);//add rb1 to group1
		group1.add(rb2);//add rb2 to group1
		
		exampleContainer.setLayout(new BoxLayout(BoxLayout.Y_AXIS));//Set LayoutManager
		exampleContainer.addComponent(rb1);//Add a RadioButton to the Form content pane
		exampleContainer.addComponent(rb2);//Add a RadioButton to the Form content pane
		exampleContainer.addComponent(radioButtonsLabel);//Add a Label to the Form content pane
		exampleContainer.setTransitionOutAnimator(CommonTransitions.createFade(400));//Set Transitions animation of Fade
		exampleContainer.addCommand(new Command("Run", 2));//Add Command key
		exampleContainer.show();//Show it
	}

	public void pauseApp() {}

	public void destroyApp(boolean unconditional) {}
	
	//implements the method of ActionListener
	public void actionPerformed(ActionEvent evt) {
		selectedButton = group1.getRadioButton(group1.getSelectedIndex());//get the radioButton which is selected by the user
		System.out.println(selectedButton.getText());
		radioButtonsLabel.setText("RadioButton:" + selectedButton.getText());//reset the text of the label
	}
}

HelloRadioButton 运行效果图如下（作者毕竟美术功底有限）：



com.sun.lwuit.CheckBox 控件

CheckBox 类似于 Html 表单中的 CheckBox，不同的是 Html 中的 CheckBox 多个一起提交时名字一样，而 LWUIT 中的 CheckBox 自行管理，需要程序员分别把结果组织。HelloCheckBox 源代码如下：

package com.defonds.lwuit;

import com.sun.lwuit.CheckBox;
import com.sun.lwuit.Command;
import com.sun.lwuit.Display;
import com.sun.lwuit.Form;
import com.sun.lwuit.Label;
import com.sun.lwuit.animations.CommonTransitions;
import com.sun.lwuit.events.ActionEvent;
import com.sun.lwuit.events.ActionListener;
import com.sun.lwuit.layouts.BoxLayout;
import com.sun.lwuit.plaf.UIManager;
import com.sun.lwuit.util.Resources;

public class HelloMidlet extends javax.microedition.midlet.MIDlet implements ActionListener{
	
	private Form exampleContainer;// declare a Form
	private CheckBox checkBox1;//declare a CheckBox
	private CheckBox checkBox2;//declare a CheckBox
	private CheckBox checkBox3;//declare a CheckBox
	private Label checkBoxLabel;//declare a Label
	
	private String str = new String(" ");//a String used to remember the checkBox selected
	
	public void startApp() {
		// init the LWUIT Display
		Display.init(this);
		// Setting the application theme is discussed
		// later in the theme chapter and the resources chapter
		try {
			Resources r = Resources.open("/myresources.res");
			UIManager.getInstance().setThemeProps(r.getTheme("myresources"));
		} catch (java.io.IOException e) {}
		
		exampleContainer = new Form("Form Title");// Create a Form
		checkBox1 = new CheckBox("Check Box1");//Create a CheckBox
		checkBox2 = new CheckBox("Check Box2");//Create a CheckBox
		checkBox3 = new CheckBox("Check Box3");//Create a CheckBox
		checkBoxLabel = new Label("selected");//Create a Label
		
		checkBox1.addActionListener(this);//add a listener to the CheckBox
		checkBox2.addActionListener(this);//add a listener to the CheckBox
		checkBox3.addActionListener(this);//add a listener to the CheckBox
		
		exampleContainer.setLayout(new BoxLayout(BoxLayout.Y_AXIS));//Set LayoutManager
		exampleContainer.addComponent(checkBox1);//Add a CheckBox to the Form content pane
		exampleContainer.addComponent(checkBox2);//Add a CheckBox to the Form content pane
		exampleContainer.addComponent(checkBox3);//Add a CheckBox to the Form content pane
		exampleContainer.addComponent(checkBoxLabel);//Add a Label to the Form content pane
		exampleContainer.setTransitionOutAnimator(CommonTransitions.createFade(400));//Set Transitions animation of Fade
		exampleContainer.addCommand(new Command("Run", 2));//Add Command key
		exampleContainer.show();//Show it
	}

	public void pauseApp() {}

	public void destroyApp(boolean unconditional) {}
	
	//implements the method of ActionListener
	public void actionPerformed(ActionEvent evt) {
		if(checkBox1.isSelected()){
			str = "1,";
		}
		if(checkBox2.isSelected()){
			str += "2,";
		}
		if(checkBox3.isSelected()){
			str += "3,";
		}
		checkBoxLabel.setText(str + "selected");//reset the text of the label
		str = " ";
	}
}

HelloCheckBox 运行效果图如下：



com.sun.lwuit.ComboBox 控件

ComboBox 类似于 RadioButton，也是一次只能有一个选择的列表。但是 ComboBox 可以自行使用，并不依赖于 ButtonGroup。由于 ComboBox 可以自行定义呈现器，所以它可以不必像 RadioButton 似的占用太多空间。因此当显示空间有限，或者有多组选项的时候，ComboBox 更合适。作者写的 HelloComboBox 源代码如下：

package com.defonds.lwuit;

import com.sun.lwuit.CheckBox;
import com.sun.lwuit.ComboBox;
import com.sun.lwuit.Command;
import com.sun.lwuit.Component;
import com.sun.lwuit.Display;
import com.sun.lwuit.Form;
import com.sun.lwuit.Label;
import com.sun.lwuit.List;
import com.sun.lwuit.animations.CommonTransitions;
import com.sun.lwuit.events.ActionEvent;
import com.sun.lwuit.events.ActionListener;
import com.sun.lwuit.layouts.BoxLayout;
import com.sun.lwuit.list.ListCellRenderer;
import com.sun.lwuit.plaf.UIManager;
import com.sun.lwuit.util.Resources;

public class HelloMidlet extends javax.microedition.midlet.MIDlet implements ActionListener{
	
	private Form exampleContainer;// declare a Form
	private Label comboBoxLabel;//declare a Label
	private String[] content = { "Red", "Blue", "Green", "Yellow" };
	private ComboBox comboBox;//declare a ComboBox
	
	public void startApp() {
		// init the LWUIT Display
		Display.init(this);
		// Setting the application theme is discussed
		// later in the theme chapter and the resources chapter
		try {
			Resources r = Resources.open("/myresources.res");
			UIManager.getInstance().setThemeProps(r.getTheme("myresources"));
		} catch (java.io.IOException e) {}
		
		exampleContainer = new Form("Form Title");// Create a Form
		comboBoxLabel = new Label(" ");
		comboBox = new ComboBox(content);//Creating the combo box
		comboBox.setListCellRenderer(new checkBoxRenderer());//Setting a checkBox renderer
		comboBox.addActionListener(this);//Adding a action listener to catch user clicking
		
		exampleContainer.setLayout(new BoxLayout(BoxLayout.Y_AXIS));//Set LayoutManager
		exampleContainer.addComponent(comboBox);//Add a ComboBox to the Form content pane
		exampleContainer.addComponent(comboBoxLabel);//Add a Label to the Form content pane
		exampleContainer.setTransitionOutAnimator(CommonTransitions.createFade(400));//Set Transitions animation of Fade
		exampleContainer.addCommand(new Command("Run", 2));//Add Command key
		exampleContainer.show();//Show it
	}

	public void pauseApp() {}

	public void destroyApp(boolean unconditional) {}
	
	//implements the method of ActionListener
	public void actionPerformed(ActionEvent evt) {
		comboBoxLabel.setText(content[comboBox.getSelectedIndex()] + " selected");
	}
	
	/**
	* Demonstrates implementation of a renderer derived from a CheckBox
	*/
	private static class checkBoxRenderer extends CheckBox implements ListCellRenderer{
		/** Creates a new instance of checkBoxRenderer */
		public checkBoxRenderer(){
			super("");
		}
		
		// Setting the current check box text and status
		public Component getListCellRendererComponent(List list,
				Object value, int index, boolean isSelected) {
			setText("" + value);
			if (isSelected){
				setFocus(true);
				setSelected(true);
			}else{
				setFocus(false);
				setSelected(false);
			}
			return this;
		}
		
		// Returning the list focus component
		public Component getListFocusComponent(List list) {
			setText("");
			setFocus(true);
			setSelected(true);
			return this;
		}
	}
}

HelloComboBox 运行效果图如下：