Java Tutorial/J2ME/Canvas
Содержание
<source lang="java">
import javax.microedition.lcdui.Canvas; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Graphics; import javax.microedition.lcdui.Image; import javax.microedition.midlet.MIDlet; public class Navigate2MIDlet extends MIDlet implements CommandListener {
private Command exitCommand;
Displayable nd;
Image image = null;
public Navigate2MIDlet() {
try {
image = Image.createImage("/J.png");
} catch (Exception e) {
}
Display display = Display.getDisplay(this);
nd = new Navigate2Canvas(image);
exitCommand = new Command("exit", Command.EXIT, 1);
nd.addCommand(exitCommand);
nd.setCommandListener(this);
display.setCurrent(nd);
}
public void startApp() {
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
public void commandAction(Command c, Displayable s) {
notifyDestroyed();
}
} class Navigate2Canvas extends Canvas {
private Image image;
private int newX = 0;
private int newY = 0;
private int stepX = 0;
private int stepY = 0;
public Navigate2Canvas(Image image) {
this.image = image;
newX = 0;
newY = 0;
stepX = getWidth() / 4;
stepY = getHeight() / 4;
}
public void steppingXY(int x, int y) {
newX += x;
newY += y;
}
public void paint(Graphics g) {
int width = this.getWidth();
int height = this.getHeight();
g.setGrayScale(255);
g.fillRect(0, 0, width - 1, height - 1);
g.setGrayScale(0);
g.drawRect(0, 0, width - 1, height - 1);
g.translate(newX, newY);
g.drawImage(image, 0, 0, g.TOP | g.LEFT);
}
protected void keyPressed(int keyCode) {
int gameaction = getGameAction(keyCode);
switch (gameaction) {
case UP:
steppingXY(0, stepY);
break;
case DOWN:
steppingXY(0, -stepY);
break;
case LEFT:
steppingXY(stepX, 0);
break;
case RIGHT:
steppingXY(-stepX, 0);
break;
}
repaint();
}
}</source>
Canvas key pressed and key typed events
<source lang="java">
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*
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* may be used to endorse or promote products derived from this software
* without specific prior written permission.
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* ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
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import javax.microedition.lcdui.Canvas; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Graphics; import javax.microedition.midlet.MIDlet; public class EventEx3 extends MIDlet {
Display display;
Command exit;
public EventEx3() {
display = Display.getDisplay(this);
}
public void destroyApp(boolean unconditional) {
}
public void pauseApp() {
System.out.println("App paused.");
}
public void startApp() {
display = Display.getDisplay(this);
Canvas canvas = new Canvas() { // anonymous class
public void paint(Graphics g) {
}
protected void keyPressed(int keyCode) {
if (keyCode > 0) {
System.out.println("keyPressed " + ((char) keyCode));
} else {
System.out.println("keyPressed action " + getGameAction(keyCode));
}
}
protected void keyReleased(int keyCode) {
if (keyCode > 0) {
System.out.println("keyReleased " + ((char) keyCode));
} else {
System.out.println("keyReleased action " + getGameAction(keyCode));
}
}
}; // end of anonymous class
exit = new Command("Exit", Command.STOP, 1);
canvas.addCommand(exit);
canvas.setCommandListener(new CommandListener() {
public void commandAction(Command c, Displayable d) {
if (c == exit) {
notifyDestroyed();
} else {
System.out.println("Saw the command: " + c);
}
}
});
display.setCurrent(canvas);
}
}</source>
Canvas size
<source lang="java">
import javax.microedition.lcdui.Canvas; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Graphics; import javax.microedition.midlet.MIDlet; public class CanvasSizeMIDlet extends MIDlet implements CommandListener {
private Command exitCommand;
Display display;
public void startApp() {
display = Display.getDisplay(this);
exitCommand = new Command("Exit", Command.EXIT, 1);
Displayable SizeCanvas = new SizeCanvas();
SizeCanvas.addCommand(exitCommand);
SizeCanvas.setCommandListener(this);
display.setCurrent(SizeCanvas);
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
public void commandAction(Command c, Displayable s) {
if (c == exitCommand) {
destroyApp(false);
notifyDestroyed();
}
}
} class SizeCanvas extends Canvas {
int width = 0;
int height = 0;
public void paint(Graphics g) {
width = getWidth();
height = getHeight();
g.setGrayScale(255);
g.fillRect(0, 0, width - 1, height - 1);
g.setGrayScale(0);
g.drawString("Stroke Style:" + g.getStrokeStyle(), 0, 60, Graphics.TOP | Graphics.LEFT);
g.drawRect(0, 0, width - 1, height - 1);
g.setStrokeStyle(Graphics.DOTTED);
g.drawLine(00, 40, 60, 60);
g.drawString(Integer.toBinaryString(width), 0, 0, Graphics.TOP | Graphics.LEFT);
g.drawString(Integer.toBinaryString(height), 10, 20, Graphics.TOP | Graphics.LEFT);
}
}</source>
extends Canvas to create your own drawable area
<source lang="java">
import javax.microedition.lcdui.Canvas; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Graphics; import javax.microedition.midlet.MIDlet; public class CanvasMyMidlet extends MIDlet {
public CanvasMyMidlet() { // constructor
}
public void startApp() {
Canvas canvas = new MyCanvas();
Display display = Display.getDisplay(this);
display.setCurrent(canvas);
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
} class MyCanvas extends Canvas {
public void paint(Graphics g) {
g.setColor(255, 0, 0);
g.fillRect(0, 0, getWidth(), getHeight());
g.setColor(255, 255, 255);
g.drawString("Hello World!", 0, 0, g.TOP | g.LEFT);
}
}</source>
Get Canvas properties
<source lang="java">
import javax.microedition.lcdui.Canvas; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Form; import javax.microedition.lcdui.Graphics; import javax.microedition.lcdui.StringItem; import javax.microedition.midlet.MIDlet; public class AttributesMIDlet extends MIDlet
implements CommandListener {
private Display display;
protected boolean started;
private Command exitCommand;
protected void startApp() {
if (!started) {
display = Display.getDisplay(this);
Canvas canvas = new DummyCanvas();
Form form = new Form("Attributes");
exitCommand = new Command("Exit", Command.EXIT, 0);
form.addCommand(exitCommand);
boolean isColor = display.isColor();
form.append(new StringItem(isColor ? "Colors: " : "Grays: ",
String.valueOf(display.numColors())));
form.append(new StringItem("Width: ", String.valueOf(canvas.getWidth())));
form.append(new StringItem("Height: ", String.valueOf(canvas.getHeight())));
form.append(new StringItem("Pointer? ", String.valueOf(canvas.hasPointerEvents())));
form.append(new StringItem("Motion? ",String.valueOf(canvas.hasPointerMotionEvents())));
form.append(new StringItem("Repeat? ",String.valueOf(canvas.hasRepeatEvents())));
form.append(new StringItem("Buffered? ", String.valueOf(canvas.isDoubleBuffered())));
form.setCommandListener(this);
display.setCurrent(form);
started = true;
}
}
protected void pauseApp() {
}
protected void destroyApp(boolean unconditional) {
}
public void commandAction(Command c, Displayable d) {
if (c == exitCommand) {
notifyDestroyed();
}
}
static class DummyCanvas extends Canvas {
protected void paint(Graphics g) {
}
}
}</source>
<source lang="java">
import javax.microedition.lcdui.Canvas; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Graphics; import javax.microedition.lcdui.Image; import javax.microedition.midlet.MIDlet; public class NavigateMIDlet extends MIDlet implements CommandListener {
int stepX;
int stepY;
private Command leftCommand;
private Command rightCommand;
private Display display;
Displayable nd;
Image image = null;
public NavigateMIDlet() {
try {
image = Image.createImage("/M.png");
} catch (Exception e) {
}
Display display = Display.getDisplay(this);
nd = new NavigateCanvas(image);
stepX = ((NavigateCanvas) nd).getWidth() / 4;
stepY = ((NavigateCanvas) nd).getHeight() / 4;
leftCommand = new Command("<Left", Command.SCREEN, 1);
rightCommand = new Command("Right>", Command.SCREEN, 1);
nd.addCommand(rightCommand);
nd.addCommand(leftCommand);
nd.setCommandListener(this);
display.setCurrent(nd);
}
public void startApp() {
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
public void commandAction(Command c, Displayable d) {
if (d == nd && c == leftCommand) {
((NavigateCanvas) nd).steppingXY(stepX, 0);
((NavigateCanvas) nd).repaint();
} else if (d == nd && c == rightCommand) {
((NavigateCanvas) nd).steppingXY(-stepX, 0);
((NavigateCanvas) nd).repaint();
}
}
} class NavigateCanvas extends Canvas {
private Image image;
private int newX = 0;
private int newY = 0;
public NavigateCanvas(Image image) {
this.image = image;
newX = 0;
newY = 0;
}
public void steppingXY(int x, int y) {
newX += x;
newY += y;
}
public void paint(Graphics g) {
int width = this.getWidth();
int height = this.getHeight();
g.setGrayScale(255);
g.fillRect(0, 0, width - 1, height - 1);
g.setGrayScale(0);
g.drawRect(0, 0, width - 1, height - 1);
g.translate(newX, newY);
g.drawImage(image, 0, 0, g.TOP | g.LEFT);
}
}</source>
Use Canvas to draw a clock
<source lang="java">
import javax.microedition.lcdui.Canvas; import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Graphics; import javax.microedition.midlet.MIDlet; public class ClockMIDlet extends MIDlet implements CommandListener {
private Command exitCommand;
Display display;
public void startApp() {
Display display = Display.getDisplay(this);
Displayable d = new ClockCanvas(10, 10, 10);
exitCommand = new Command("Exit", Command.EXIT, 1);
d.addCommand(exitCommand);
d.setCommandListener(this);
display.setCurrent(d);
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
public void commandAction(Command c, Displayable s) {
notifyDestroyed();
}
} class ClockCanvas extends Canvas {
private int hour;
private int minute;
private int second;
protected int xCenter, yCenter;
protected int clockRadius;
int width = 0;
int height = 0;
ClockCanvas(int hour, int minute, int second) {
this.hour = hour;
this.minute = minute;
this.second = second;
}
public void paint(Graphics g) {
width = getWidth();
height = getHeight();
g.setGrayScale(255);
g.fillRect(0, 0, width - 1, height - 1);
g.setGrayScale(0);
g.drawRect(0, 0, width - 1, height - 1);
clockRadius = Math.min(width, height) - 20;
xCenter = getWidth() / 2;
yCenter = getHeight() / 2;
g.drawArc(10, 12, clockRadius, clockRadius, 0, 360);
g.drawString("12", xCenter, 0, Graphics.TOP | Graphics.HCENTER);
g.drawString("9", 1, yCenter, Graphics.BASELINE | Graphics.LEFT);
g.drawString("3", width - 1, yCenter, Graphics.BASELINE | Graphics.RIGHT);
g.drawString("6", xCenter, height, Graphics.BOTTOM | Graphics.RIGHT);
}
}</source>
