drummercanvas.java

击鼓程序的实现。注：其中的背景图片Logo.png文件请放在资源文件夹中。

package Drummer;

import java.util.*;
import java.io.*;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.media.*;
import javax.microedition.media.control.*;

public class DrummerCanvas extends Canvas implements CommandListener {

	private static final String TITLE = "Drummer例子";

	private static final String LOGO = "/Logo.png";

	private Command backCommand = new Command("返回", Command.BACK, 1);

	private Command exitCommand = new Command("退出", Command.EXIT, 1);

	private Command helpCommand = new Command("帮助", Command.ITEM, 10);

	private static int TITLE_TOP = 2;

	private static int LOGO_GAP = 2;

	private static int CURR_DRUM_GAP = 2;

	private static int STATUS_GAP = 2;

	private Image logo = null;

	private Display parent;

	private String status = "";

	private String currDrum = "";

	private int displayWidth = -1;

	private int displayHeight = -1;

	private int textHeight = 10;

	private int logoTop = 0;

	private int currDrumTop = 0;

	private int statusTop = 0;

	private MIDIControl mc;

	//MIDI鼓声数据
	private static final int[] DRUM_NUMBERS = { 0, // not used
			0x2A, // 1: closed hihat
			0x2E, // 2: open hihat
			0x36, // 3: Tambourine
			0x32, // 4: hi tom
			0x2F, // 5: mid tom
			0x2B, // 6: low tom
			0x33, // 7: ride cymbal
			0x38, // 8: cow bell
			0x31, // 9: crash cymbal
			0x24, // *: bass drum
			0x27, // 0: hand clap
			0x28, // #: snare drum
	};
	//屏幕显示的当前敲击的鼓声名称
	private static final String[] DRUM_NAMES = { "", // not used
			"Closed Hi-Hat", // 1
			"Open Hi-Hat", // 2
			"Tambourine", // 3
			"Hi Tom", // 4
			"Mid Tom", // 5
			"Low Tom", // 6
			"Ride Cymbal", // 7
			"Cow Bell", // 8
			"Crash Cymbal", // 9
			"Bass Drum", // *
			"Hand Clap", // 0
			"Snare Drum", // #
	};

	private static final String[] SHORT_DRUM_NAMES = { "", "CH", "OH", "TB",
			"HT", "MT", "LT", "RC", "CB", "CC", "BD", "HC", "SD", };

	private static final int[] DRUM_KEYS = { 0, // not used
			KEY_NUM1, KEY_NUM2, KEY_NUM3, KEY_NUM4, KEY_NUM5, KEY_NUM6,
			KEY_NUM7, KEY_NUM8, KEY_NUM9, KEY_STAR, KEY_NUM0, KEY_POUND, };

	public DrummerCanvas(Display dis) {
		super();

		this.parent = dis;
		show();

	}

	public void commandAction(Command c, Displayable s) {
		if (c == backCommand) {
			parent.setCurrent(this);

		} else if (c == helpCommand) {
			showHelp();
		}
		if (c ==exitCommand) {
		}
	}

	private void status(String s) {
		status = s;
		repaint(0, statusTop, displayWidth, textHeight);
		serviceRepaints();
	}
	//提示当前敲鼓声音
	private void setCurrDrum(int num) {
		currDrum = DRUM_NAMES[num];
		repaint(0, currDrumTop, displayWidth, textHeight);
		serviceRepaints();
	}

	public void updateDisplay() {
		repaint();
		serviceRepaints();
	}
	//初始化DrummerDemo
	public void show() {
		addCommand(exitCommand);
		addCommand(helpCommand);
		setCommandListener(this);
		status("Prefetching and getting MIDIControl");
		updateDisplay();
		new Thread(new Runnable() {
			public void run() {
				try {
					mc = getMIDIControl();
					status("Ready.");
				} catch (Exception e) {
					//status(Utils.friendlyException(e));
					mc = null;
				}
			}
		}).start();
	}

	protected void keyPressed(int keycode) {
		try {
			for (int num = 1; num < DRUM_KEYS.length; num++) {
				if (keycode == DRUM_KEYS[num]) {
					playDrum(num);
					return;
				}
			}			
		} catch (Throwable t) {

		}
	}
	//播放鼓声
	private void playDrum(int num) {
		if (mc == null)
			return;
		setCurrDrum(num);
		mc.shortMidiEvent(0x99, DRUM_NUMBERS[num], 120);
		mc.shortMidiEvent(0x99, DRUM_NUMBERS[num], 0);
	}

	private boolean intersects(int clipY, int clipHeight, int y, int h) {
		return (clipY <= y + h && clipY + clipHeight >= y);
	}

	public void paint(Graphics g) {
		try {
			if (displayHeight == -1) {
				displayWidth = getWidth();
				displayHeight = getHeight();
				textHeight = g.getFont().getHeight();
				logo = getLogo();

				int currTop = TITLE_TOP + textHeight;
				if (logo != null) {
					currTop += LOGO_GAP;
					logoTop = currTop;
					currTop += logo.getHeight();
				}

				// curr drum: before-last line
				currDrumTop = displayHeight - 2 * textHeight - STATUS_GAP;
				// status: last line.
				statusTop = displayHeight - textHeight;
			}

			int clipX = g.getClipX();
			int clipY = g.getClipY();
			int clipWidth = g.getClipWidth();
			int clipHeight = g.getClipHeight();
			// 绘画背景
			g.setColor(0);
			g.fillRect(clipX, clipY, clipWidth, clipHeight);
			// 绘画标题
			if (intersects(clipY, clipHeight, TITLE_TOP, textHeight)) {
				g.setColor(0xFF7f00);
				g.drawString(TITLE, displayWidth >> 1, TITLE_TOP, Graphics.TOP
						| Graphics.HCENTER);
			}
			// 显示图标
			if (logo != null
					&& intersects(clipY, clipHeight, logoTop, logo.getHeight())) {
				g.drawImage(logo, displayWidth / 2, logoTop, Graphics.TOP
						| Graphics.HCENTER);
			}

			// 提示当前鼓声名称
			if (intersects(clipY, clipHeight, currDrumTop, textHeight)) {
				g.setColor(0xE0E0FF);
				g.drawString(currDrum, 0, currDrumTop, Graphics.TOP
						| Graphics.LEFT);
			}
			// 状态
			if (intersects(clipY, clipHeight, displayHeight - textHeight,
					textHeight)) {
				g.setColor(0xFAFAFA);
				g.drawString(status, 0, displayHeight, Graphics.BOTTOM
						| Graphics.LEFT);
			}

		} catch (Throwable t) {

		}
	}

	/**
	 * 显示帮组
	 */
	public void showHelp() {
		List list = new List("Drummer Help", Choice.IMPLICIT);
		list.append("Use the numeric keys", null);
		list.append("to play drums. Each", null);
		list.append("Key corresponds to a", null);
		list.append("different drum.", null);

		list.addCommand(backCommand);
		list.setCommandListener(this);
		parent.setCurrent(list);
	}

	private Image getLogo() {
		if (logo == null) {
			try {
				logo = Image.createImage(LOGO);
			} catch (Exception ex) {
				logo = null;
			}
			if (logo == null) {

			}
		}
		return logo;
	}

	MIDIControl getMIDIControl() throws Exception {
		Player mp = null;

		if (mp == null) {
			mp = Manager.createPlayer(Manager.MIDI_DEVICE_LOCATOR);
			mp.prefetch();
		}
		return (MIDIControl) mp
				.getControl("javax.microedition.media.control.MIDIControl");
	}

}