The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...
/*
* Copyright (C) 2011 The Android开源工程
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.apis.view;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Paint.Style;
import android.os.Handler;
import android.os.SystemClock;
import android.os.Vibrator;
import android.util.AttributeSet;
import android.view.InputDevice;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
/**
* A trivial joystick based physics game to demonstrate joystick handling.
*
* If the game controller has a vibrator, then it is used to provide feedback
* when a bullet is fired or the ship crashes into an obstacle. Otherwise, the
* system vibrator is used for that purpose.
*
* @see GameControllerInput
*/
public class GameView extends View {
private final long ANIMATION_TIME_STEP = 1000 / 60;
private final int MAX_OBSTACLES = 12;
private final Random mRandom;
private Ship mShip;
private final List<Bullet> mBullets;
private final List<Obstacle> mObstacles;
private long mLastStepTime;
private InputDevice mLastInputDevice;
private static final int DPAD_STATE_LEFT = 1 << 0;
private static final int DPAD_STATE_RIGHT = 1 << 1;
private static final int DPAD_STATE_UP = 1 << 2;
private static final int DPAD_STATE_DOWN = 1 << 3;
private int mDPadState;
private float mShipSize;
private float mMaxShipThrust;
private float mMaxShipSpeed;
private float mBulletSize;
private float mBulletSpeed;
private float mMinObstacleSize;
private float mMaxObstacleSize;
private float mMinObstacleSpeed;
private float mMaxObstacleSpeed;
private final Runnable mAnimationRunnable = new Runnable() {
public void run() {
animateFrame();
}
};
public GameView(Context context, AttributeSet attrs) {
super(context, attrs);
mRandom = new Random();
mBullets = new ArrayList<Bullet>();
mObstacles = new ArrayList<Obstacle>();
setFocusable(true);
setFocusableInTouchMode(true);
float baseSize = getContext().getResources().getDisplayMetrics().density * 5f;
float baseSpeed = baseSize * 3;
mShipSize = baseSize * 3;
mMaxShipThrust = baseSpeed * 0.25f;
mMaxShipSpeed = baseSpeed * 12;
mBulletSize = baseSize;
mBulletSpeed = baseSpeed * 12;
mMinObstacleSize = baseSize * 2;
mMaxObstacleSize = baseSize * 12;
mMinObstacleSpeed = baseSpeed;
mMaxObstacleSpeed = baseSpeed * 3;
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
// Reset the game when the view changes size.
reset();
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
ensureInitialized();
// Handle DPad keys and fire button on initial down but not on auto-repeat.
boolean handled = false;
if (event.getRepeatCount() == 0) {
switch (keyCode) {
case KeyEvent.KEYCODE_DPAD_LEFT:
mShip.setHeadingX(-1);
mDPadState |= DPAD_STATE_LEFT;
handled = true;
break;
case KeyEvent.KEYCODE_DPAD_RIGHT:
mShip.setHeadingX(1);
mDPadState |= DPAD_STATE_RIGHT;
handled = true;
break;
case KeyEvent.KEYCODE_DPAD_UP:
mShip.setHeadingY(-1);
mDPadState |= DPAD_STATE_UP;
handled = true;
break;
case KeyEvent.KEYCODE_DPAD_DOWN:
mShip.setHeadingY(1);
mDPadState |= DPAD_STATE_DOWN;
handled = true;
break;
default:
if (isFireKey(keyCode)) {
fire();
handled = true;
}
break;
}
}
if (handled) {
step(event.getEventTime());
return true;
}
return super.onKeyDown(keyCode, event);
}
@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
ensureInitialized();
// Handle keys going up.
boolean handled = false;
switch (keyCode) {
case KeyEvent.KEYCODE_DPAD_LEFT:
mShip.setHeadingX(0);
mDPadState &= ~DPAD_STATE_LEFT;
handled = true;
break;
case KeyEvent.KEYCODE_DPAD_RIGHT:
mShip.setHeadingX(0);
mDPadState &= ~DPAD_STATE_RIGHT;
handled = true;
break;
case KeyEvent.KEYCODE_DPAD_UP:
mShip.setHeadingY(0);
mDPadState &= ~DPAD_STATE_UP;
handled = true;
break;
case KeyEvent.KEYCODE_DPAD_DOWN:
mShip.setHeadingY(0);
mDPadState &= ~DPAD_STATE_DOWN;
handled = true;
break;
default:
if (isFireKey(keyCode)) {
handled = true;
}
break;
}
if (handled) {
step(event.getEventTime());
return true;
}
return super.onKeyUp(keyCode, event);
}
private static boolean isFireKey(int keyCode) {
return KeyEvent.isGamepadButton(keyCode)
|| keyCode == KeyEvent.KEYCODE_DPAD_CENTER
|| keyCode == KeyEvent.KEYCODE_SPACE;
}
@Override
public boolean onGenericMotionEvent(MotionEvent event) {
ensureInitialized();
// Check that the event came from a joystick since a generic motion event
// could be almost anything.
if ((event.getSource() & InputDevice.SOURCE_CLASS_JOYSTICK) != 0
&& event.getAction() == MotionEvent.ACTION_MOVE) {
// Cache the most recently obtained device information.
// The device information may change over time but it can be
// somewhat expensive to query.
if (mLastInputDevice == null || mLastInputDevice.getId() != event.getDeviceId()) {
mLastInputDevice = event.getDevice();
// It's possible for the device id to be invalid.
// In that case, getDevice() will return null.
if (mLastInputDevice == null) {
return false;
}
}
// Ignore joystick while the DPad is pressed to avoid conflicting motions.
if (mDPadState != 0) {
return true;
}
// Process all historical movement samples in the batch.
final int historySize = event.getHistorySize();
for (int i = 0; i < historySize; i++) {
processJoystickInput(event, i);
}
// Process the current movement sample in the batch.
processJoystickInput(event, -1);
return true;
}
return super.onGenericMotionEvent(event);
}
private void processJoystickInput(MotionEvent event, int historyPos) {
// Get joystick position.
// Many game pads with two joysticks report the position of the second joystick
// using the Z and RZ axes so we also handle those.
// In a real game, we would allow the user to configure the axes manually.
float x = getCenteredAxis(event, mLastInputDevice, MotionEvent.AXIS_X, historyPos);
if (x == 0) {
x = getCenteredAxis(event, mLastInputDevice, MotionEvent.AXIS_HAT_X, historyPos);
}
if (x == 0) {
x = getCenteredAxis(event, mLastInputDevice, MotionEvent.AXIS_Z, historyPos);
}
float y = getCenteredAxis(event, mLastInputDevice, MotionEvent.AXIS_Y, historyPos);
if (y == 0) {
y = getCenteredAxis(event, mLastInputDevice, MotionEvent.AXIS_HAT_Y, historyPos);
}
if (y == 0) {
y = getCenteredAxis(event, mLastInputDevice, MotionEvent.AXIS_RZ, historyPos);
}
// Set the ship heading.
mShip.setHeading(x, y);
step(historyPos < 0 ? event.getEventTime() : event.getHistoricalEventTime(historyPos));
}
private static float getCenteredAxis(MotionEvent event, InputDevice device,
int axis, int historyPos) {
final InputDevice.MotionRange range = device.getMotionRange(axis, event.getSource());
if (range != null) {
final float flat = range.getFlat();
final float value = historyPos < 0 ? event.getAxisValue(axis)
: event.getHistoricalAxisValue(axis, historyPos);
// Ignore axis values that are within the 'flat' region of the joystick axis center.
// A joystick at rest does not always report an absolute position of (0,0).
if (Math.abs(value) > flat) {
return value;
}
}
return 0;
}
@Override
public void onWindowFocusChanged(boolean hasWindowFocus) {
// Turn on and off animations based on the window focus.
// Alternately, we could update the game state using the Activity onResume()
// and onPause() lifecycle events.
if (hasWindowFocus) {
getHandler().postDelayed(mAnimationRunnable, ANIMATION_TIME_STEP);
mLastStepTime = SystemClock.uptimeMillis();
} else {
getHandler().removeCallbacks(mAnimationRunnable);
mDPadState = 0;
if (mShip != null) {
mShip.setHeading(0, 0);
mShip.setVelocity(0, 0);
}
}
super.onWindowFocusChanged(hasWindowFocus);
}
private void fire() {
if (mShip != null && !mShip.isDestroyed()) {
Bullet bullet = new Bullet();
bullet.setPosition(mShip.getBulletInitialX(), mShip.getBulletInitialY());
bullet.setVelocity(mShip.getBulletVelocityX(mBulletSpeed),
mShip.getBulletVelocityY(mBulletSpeed));
mBullets.add(bullet);
getVibrator().vibrate(20);
}
}
private void ensureInitialized() {
if (mShip == null) {
reset();
}
}
private void crash() {
getVibrator().vibrate(new long[] { 0, 20, 20, 40, 40, 80, 40, 300 }, -1);
}
private void reset() {
mShip = new Ship();
mBullets.clear();
mObstacles.clear();
}
private Vibrator getVibrator() {
if (mLastInputDevice != null) {
Vibrator vibrator = mLastInputDevice.getVibrator();
if (vibrator.hasVibrator()) {
return vibrator;
}
}
return (Vibrator)getContext().getSystemService(Context.VIBRATOR_SERVICE);
}
void animateFrame() {
long currentStepTime = SystemClock.uptimeMillis();
step(currentStepTime);
Handler handler = getHandler();
if (handler != null) {
handler.postAtTime(mAnimationRunnable, currentStepTime + ANIMATION_TIME_STEP);
invalidate();
}
}
private void step(long currentStepTime) {
float tau = (currentStepTime - mLastStepTime) * 0.001f;
mLastStepTime = currentStepTime;
ensureInitialized();
// Move the ship.
mShip.accelerate(tau, mMaxShipThrust, mMaxShipSpeed);
if (!mShip.step(tau)) {
reset();
}
// Move the bullets.
int numBullets = mBullets.size();
for (int i = 0; i < numBullets; i++) {
final Bullet bullet = mBullets.get(i);
if (!bullet.step(tau)) {
mBullets.remove(i);
i -= 1;
numBullets -= 1;
}
}
// Move obstacles.
int numObstacles = mObstacles.size();
for (int i = 0; i < numObstacles; i++) {
final Obstacle obstacle = mObstacles.get(i);
if (!obstacle.step(tau)) {
mObstacles.remove(i);
i -= 1;
numObstacles -= 1;
}
}
// Check for collisions between bullets and obstacles.
for (int i = 0; i < numBullets; i++) {
final Bullet bullet = mBullets.get(i);
for (int j = 0; j < numObstacles; j++) {
final Obstacle obstacle = mObstacles.get(j);
if (bullet.collidesWith(obstacle)) {
bullet.destroy();
obstacle.destroy();
break;
}
}
}
// Check for collisions between the ship and obstacles.
for (int i = 0; i < numObstacles; i++) {
final Obstacle obstacle = mObstacles.get(i);
if (mShip.collidesWith(obstacle)) {
mShip.destroy();
obstacle.destroy();
break;
}
}
// Spawn more obstacles offscreen when needed.
// Avoid putting them right on top of the ship.
OuterLoop: while (mObstacles.size() < MAX_OBSTACLES) {
final float minDistance = mShipSize * 4;
float size = mRandom.nextFloat() * (mMaxObstacleSize - mMinObstacleSize)
+ mMinObstacleSize;
float positionX, positionY;
int tries = 0;
do {
int edge = mRandom.nextInt(4);
switch (edge) {
case 0:
positionX = -size;
positionY = mRandom.nextInt(getHeight());
break;
case 1:
positionX = getWidth() + size;
positionY = mRandom.nextInt(getHeight());
break;
case 2:
positionX = mRandom.nextInt(getWidth());
positionY = -size;
break;
default:
positionX = mRandom.nextInt(getWidth());
positionY = getHeight() + size;
break;
}
if (++tries > 10) {
break OuterLoop;
}
} while (mShip.distanceTo(positionX, positionY) < minDistance);
float direction = mRandom.nextFloat() * (float) Math.PI * 2;
float speed = mRandom.nextFloat() * (mMaxObstacleSpeed - mMinObstacleSpeed)
+ mMinObstacleSpeed;
float velocityX = (float) Math.cos(direction) * speed;
float velocityY = (float) Math.sin(direction) * speed;
Obstacle obstacle = new Obstacle();
obstacle.setPosition(positionX, positionY);
obstacle.setSize(size);
obstacle.setVelocity(velocityX, velocityY);
mObstacles.add(obstacle);
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// Draw the ship.
if (mShip != null) {
mShip.draw(canvas);
}
// Draw bullets.
int numBullets = mBullets.size();
for (int i = 0; i < numBullets; i++) {
final Bullet bullet = mBullets.get(i);
bullet.draw(canvas);
}
// Draw obstacles.
int numObstacles = mObstacles.size();
for (int i = 0; i < numObstacles; i++) {
final Obstacle obstacle = mObstacles.get(i);
obstacle.draw(canvas);
}
}
static float pythag(float x, float y) {
return (float) Math.sqrt(x * x + y * y);
}
static int blend(float alpha, int from, int to) {
return from + (int) ((to - from) * alpha);
}
static void setPaintARGBBlend(Paint paint, float alpha,
int a1, int r1, int g1, int b1,
int a2, int r2, int g2, int b2) {
paint.setARGB(blend(alpha, a1, a2), blend(alpha, r1, r2),
blend(alpha, g1, g2), blend(alpha, b1, b2));
}
private abstract class Sprite {
protected float mPositionX;
protected float mPositionY;
protected float mVelocityX;
protected float mVelocityY;
protected float mSize;
protected boolean mDestroyed;
protected float mDestroyAnimProgress;
public void setPosition(float x, float y) {
mPositionX = x;
mPositionY = y;
}
public void setVelocity(float x, float y) {
mVelocityX = x;
mVelocityY = y;
}
public void setSize(float size) {
mSize = size;
}
public float distanceTo(float x, float y) {
return pythag(mPositionX - x, mPositionY - y);
}
public float distanceTo(Sprite other) {
return distanceTo(other.mPositionX, other.mPositionY);
}
public boolean collidesWith(Sprite other) {
// Really bad collision detection.
return !mDestroyed && !other.mDestroyed
&& distanceTo(other) <= Math.max(mSize, other.mSize)
+ Math.min(mSize, other.mSize) * 0.5f;
}
public boolean isDestroyed() {
return mDestroyed;
}
public boolean step(float tau) {
mPositionX += mVelocityX * tau;
mPositionY += mVelocityY * tau;
if (mDestroyed) {
mDestroyAnimProgress += tau / getDestroyAnimDuration();
if (mDestroyAnimProgress >= 1.0f) {
return false;
}
}
return true;
}
public abstract void draw(Canvas canvas);
public abstract float getDestroyAnimDuration();
protected boolean isOutsidePlayfield() {
final int width = GameView.this.getWidth();
final int height = GameView.this.getHeight();
return mPositionX < 0 || mPositionX >= width
|| mPositionY < 0 || mPositionY >= height;
}
protected void wrapAtPlayfieldBoundary() {
final int width = GameView.this.getWidth();
final int height = GameView.this.getHeight();
while (mPositionX <= -mSize) {
mPositionX += width + mSize * 2;
}
while (mPositionX >= width + mSize) {
mPositionX -= width + mSize * 2;
}
while (mPositionY <= -mSize) {
mPositionY += height + mSize * 2;
}
while (mPositionY >= height + mSize) {
mPositionY -= height + mSize * 2;
}
}
public void destroy() {
mDestroyed = true;
step(0);
}
}
private class Ship extends Sprite {
private static final float CORNER_ANGLE = (float) Math.PI * 2 / 3;
private static final float TO_DEGREES = (float) (180.0 / Math.PI);
private float mHeadingX;
private float mHeadingY;
private float mHeadingAngle;
private float mHeadingMagnitude;
private final Paint mPaint;
private final Path mPath;
public Ship() {
mPaint = new Paint();
mPaint.setStyle(Style.FILL);
setPosition(getWidth() * 0.5f, getHeight() * 0.5f);
setVelocity(0, 0);
setSize(mShipSize);
mPath = new Path();
mPath.moveTo(0, 0);
mPath.lineTo((float)Math.cos(-CORNER_ANGLE) * mSize,
(float)Math.sin(-CORNER_ANGLE) * mSize);
mPath.lineTo(mSize, 0);
mPath.lineTo((float)Math.cos(CORNER_ANGLE) * mSize,
(float)Math.sin(CORNER_ANGLE) * mSize);
mPath.lineTo(0, 0);
}
public void setHeadingX(float x) {
mHeadingX = x;
updateHeading();
}
public void setHeadingY(float y) {
mHeadingY = y;
updateHeading();
}
public void setHeading(float x, float y) {
mHeadingX = x;
mHeadingY = y;
updateHeading();
}
private void updateHeading() {
mHeadingMagnitude = pythag(mHeadingX, mHeadingY);
if (mHeadingMagnitude > 0.1f) {
mHeadingAngle = (float) Math.atan2(mHeadingY, mHeadingX);
}
}
private float polarX(float radius) {
return (float) Math.cos(mHeadingAngle) * radius;
}
private float polarY(float radius) {
return (float) Math.sin(mHeadingAngle) * radius;
}
public float getBulletInitialX() {
return mPositionX + polarX(mSize);
}
public float getBulletInitialY() {
return mPositionY + polarY(mSize);
}
public float getBulletVelocityX(float relativeSpeed) {
return mVelocityX + polarX(relativeSpeed);
}
public float getBulletVelocityY(float relativeSpeed) {
return mVelocityY + polarY(relativeSpeed);
}
public void accelerate(float tau, float maxThrust, float maxSpeed) {
final float thrust = mHeadingMagnitude * maxThrust;
mVelocityX += polarX(thrust);
mVelocityY += polarY(thrust);
final float speed = pythag(mVelocityX, mVelocityY);
if (speed > maxSpeed) {
final float scale = maxSpeed / speed;
mVelocityX = mVelocityX * scale;
mVelocityY = mVelocityY * scale;
}
}
@Override
public boolean step(float tau) {
if (!super.step(tau)) {
return false;
}
wrapAtPlayfieldBoundary();
return true;
}
public void draw(Canvas canvas) {
setPaintARGBBlend(mPaint, mDestroyAnimProgress,
255, 63, 255, 63,
0, 255, 0, 0);
canvas.save(Canvas.MATRIX_SAVE_FLAG);
canvas.translate(mPositionX, mPositionY);
canvas.rotate(mHeadingAngle * TO_DEGREES);
canvas.drawPath(mPath, mPaint);
canvas.restore();
}
@Override
public float getDestroyAnimDuration() {
return 1.0f;
}
@Override
public void destroy() {
super.destroy();
crash();
}
}
private class Bullet extends Sprite {
private final Paint mPaint;
public Bullet() {
mPaint = new Paint();
mPaint.setStyle(Style.FILL);
setSize(mBulletSize);
}
@Override
public boolean step(float tau) {
if (!super.step(tau)) {
return false;
}
return !isOutsidePlayfield();
}
public void draw(Canvas canvas) {
setPaintARGBBlend(mPaint, mDestroyAnimProgress,
255, 255, 255, 0,
0, 255, 255, 255);
canvas.drawCircle(mPositionX, mPositionY, mSize, mPaint);
}
@Override
public float getDestroyAnimDuration() {
return 0.125f;
}
}
private class Obstacle extends Sprite {
private final Paint mPaint;
public Obstacle() {
mPaint = new Paint();
mPaint.setARGB(255, 127, 127, 255);
mPaint.setStyle(Style.FILL);
}
@Override
public boolean step(float tau) {
if (!super.step(tau)) {
return false;
}
wrapAtPlayfieldBoundary();
return true;
}
public void draw(Canvas canvas) {
setPaintARGBBlend(mPaint, mDestroyAnimProgress,
255, 127, 127, 255,
0, 255, 0, 0);
canvas.drawCircle(mPositionX, mPositionY,
mSize * (1.0f - mDestroyAnimProgress), mPaint);
}
@Override
public float getDestroyAnimDuration() {
return 0.25f;
}
}
}