tonescanvas.java

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import javax.microedition.lcdui.*;

class TonesCanvas
    extends Canvas
    implements CommandListener
{
    // Constants and frequencies for tone playing
    static final int SILENT = -1;  // 静音
    static final int NATURAL = 0;
    static final int SHARP = 1;

    // 计算位置
    static final int CLEF_G_LINE_Y = 30; // 'G' 线
    static final int NOTE_WIDTH = 7;
    static final int NOTE_HEIGHT = 7;
    static final int SHARP_WIDTH = 5;
    static final int LINE_SPACING = 6;
    static final int TOP_LINE_Y = CLEF_G_LINE_Y - 3 * LINE_SPACING;
    static final int MIDDLE_C_Y = TOP_LINE_Y + 5 * LINE_SPACING;
    static final int LAYOUT_HEIGHT = MIDDLE_C_Y + NOTE_HEIGHT / 2 + 1;
    static final int SHARP_OFFSET = SHARP_WIDTH + 2; // 2 for spacing
    static final int LEGER_LINE_WIDTH = NOTE_WIDTH + 4;

    final TonesMIDlet parent;
    final Image trebleImg;
    final Image noteImg;
    final Image sharpImg;
    final Command exitCommand;
    final TonePlayer tonePlayer;

    int note = SILENT;
    int currentKey;
    boolean sharp = false;

    TonesCanvas(TonesMIDlet parent)
    {
        this.parent = parent;
        trebleImg = createImage("/treble.png");
        noteImg   = createImage("/note.png");
        sharpImg  = createImage("/sharp.png");

        // 生成 NokiaTonePlayer 或其他Player,
        tonePlayer = makeTonePlayer();

        exitCommand = new Command("Exit", Command.EXIT, 1);
        addCommand(exitCommand);
        setCommandListener(this);
    }

    public void paint(Graphics g)
    {
        int width = getWidth();
        int height = getHeight();
        g.setColor(0x00FFFFFF);   // white
        g.fillRect(0, 0, width, height);

        int topOffset = (getHeight() - LAYOUT_HEIGHT) / 2;

        // 画高音符 treble clef
        g.drawImage(trebleImg, 1, topOffset, 
			Graphics.TOP | Graphics.LEFT);

        if (note != SILENT)
        {
            // 画音符
            drawNote(g, topOffset, width);
        }

        drawLines(g, topOffset, width);
    }


    // 画五条线
    private void drawLines(Graphics g, int topOffset, int width)
    {
        g.setColor(0x00000000);   // black
        for (int i = 0; i < 5; ++i)
        {
            int y = topOffset + TOP_LINE_Y + LINE_SPACING * i;
            g.drawLine(0, y, width-1, y);
        }
    }

    // 画音符
	private void drawNote(Graphics g, int offset, int width)
    {
        int y = offset + MIDDLE_C_Y - note * LINE_SPACING / 2;
        int x = width / 2;
        g.drawImage(noteImg, x, y, Graphics.HCENTER | Graphics.VCENTER);

        // this next bit should be made more smart if it ever
        // needs to be more general
        if (note == 0)   // C should have a 'leger line' through it
        {
            g.setColor(0x00000000);   // black
            g.drawLine(x-LEGER_LINE_WIDTH/2, y, x+LEGER_LINE_WIDTH/2, y);
        }

        // is sharp set, and can this note be sharp (E & B can't)
        if (sharp && tonePlayer.maySharp( note ) )
        {
            g.drawImage(sharpImg, x - SHARP_OFFSET, y,
                        Graphics.HCENTER | Graphics.VCENTER);
        }
    }

    public void commandAction(Command c, Displayable d)
    {
        if (c == exitCommand)
        {
            parent.exitRequested();
        }
    }

    public void keyPressed(int keyCode)
    {
        if (keyCode == Canvas.KEY_POUND)
        {
            sharp = !sharp;    // toggle sharp state
        }
        else
        {
            switch (keyCode)
            {
            case Canvas.KEY_NUM1:
                note = 0;   // middle C
                break;
            case Canvas.KEY_NUM2:
                note = 1;   // D
                break;
            case Canvas.KEY_NUM3:
                note = 2;   // E
                break;
            case Canvas.KEY_NUM4:
                note = 3;   // F
                break;
            case Canvas.KEY_NUM5:
                note = 4;   // G
                break;
            case Canvas.KEY_NUM6:
                note = 5;   // A
                break;
            case Canvas.KEY_NUM7:
                note = 6;   // B
                break;
            case Canvas.KEY_NUM8:
                note = 7;   // C
                break;
            case Canvas.KEY_NUM9:
                note = 8;   // D
                break;
            case Canvas.KEY_STAR:
                note = 9;   // E
                break;
            case Canvas.KEY_NUM0:
                note = 10;  // F
                break;
            default:
                note = SILENT;
                break;
            }

            if (note != SILENT)
            {
                startNote();
            }
            currentKey = keyCode;
        }
        repaint();
    }


    public void keyReleased(int keyCode)
    {
        if (keyCode == currentKey)
        {
            note = SILENT;
            stopNote();
        }
        repaint();
    }

    private void startNote()
    {
        tonePlayer.play( note,sharp );
    }

    void stopNote()
    {
        tonePlayer.stop();
    }

    private static Image createImage(String filename)
    {
        Image image = null;
        try
        {
            image = Image.createImage(filename);
        }
        catch (java.io.IOException e)
        {
        }
        return image;
    }

    private static TonePlayer makeTonePlayer()
    {
        TonePlayer player = null;

		// 首先试图使用NokiaTonePlayer
        try
        {
            // 如果不在在Nokia UI API，则下面的语句会抛出异常
            Class.forName("com.nokia.mid.sound.Sound");
            // 如果没有异常，我们可以创建NokiaTonePlayer
            // 这里使用newInstance()而不用new ,可以消除类的依赖
            Class clas = Class.forName("NokiaTonePlayer");
            player = (TonePlayer)(clas.newInstance());
			System.out.println( "NokiaTonePlayer Created" );
        }
        catch (Exception e){}

		// 其次试图使用 MMATonePlayer
        if( player == null ) try
        {
            Class.forName("javax.microedition.media.Player");
            Class clas = Class.forName("MMATonePlayer");
            player = (TonePlayer)(clas.newInstance());
 			System.out.println( "MMATonePlayer Created" );
       }
        catch (Exception e){}

		// 如果以上两步都没有创建成功，则创建一个dumy的TonePlayer
		if( player == null )
		{
            player = new TonePlayer();
		}
        
		return player;
    }
}