Android(安卓)弹球游戏

本文内容摘自《疯狂Android讲义第3版》李刚著
package shortcut.song.com.myapplication;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.os.Handler;import android.os.Message;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.DisplayMetrics;import android.view.Display;import android.view.KeyEvent;import android.view.MotionEvent;import android.view.View;import android.view.Window;import android.view.WindowManager;import java.util.Random;import java.util.Timer;import java.util.TimerTask;public class PinBallActivity extends AppCompatActivity {    private int tableWidth; //桌面宽度；    private int tableHeight; //桌面高度    private int racketY; //球拍的垂直位置；    //球拍的高宽    private final int RACKET_WIDTH = 90;    private final int RACKET_HEIGHT = 30;    //球的大小    private final int BALL_SIZE = 16;    //小球运动的速度    private int ySpeed = 15;    Random random = new Random();    //返回一个-0.5 ~ 0.5的比率，用于控制小球的运动方向；    private double xyRate = random.nextDouble() - 0.5;    //小球横向运动速度    private int xSpeed = (int)(ySpeed * xyRate * 2);    //小球的座标    private int ballX = random.nextInt(200) + 20;    private int ballY = random.nextInt(10) + 20;    //球拍的水平位置    private int racketX = random.nextInt(200);    private boolean isLose = false;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //去掉窗口标题        requestWindowFeature(Window.FEATURE_NO_TITLE);        //设置全屏        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);        final GameView gameView = new GameView(this);        setContentView(gameView);        WindowManager windowManager = getWindowManager();        Display display = windowManager.getDefaultDisplay();        DisplayMetrics displayMetrics = new DisplayMetrics();        display.getMetrics(displayMetrics);        //获得屏幕宽高        tableHeight = displayMetrics.heightPixels;        tableWidth = displayMetrics.widthPixels;        racketY = tableHeight - 80;        final Handler handler = new Handler(){            @Override            public void handleMessage(Message msg) {                if(msg.what == 0x1234){                    gameView.invalidate();                }            }        };        gameView.setOnKeyListener(new View.OnKeyListener() {            @Override            public boolean onKey(View v, int keyCode, KeyEvent event) {                switch(event.getKeyCode())                {                    case KeyEvent.KEYCODE_A:                        if (racketX > 0) racketX -= 10;                        break;                    case KeyEvent.KEYCODE_D:                        if (racketX < tableWidth - RACKET_WIDTH) racketX += 10;                        break;                }                gameView.invalidate();                return false;            }        });        final Timer timer = new Timer();        timer.schedule(new TimerTask() {            @Override            public void run() {                if (ballX <= 0 || ballX >= tableWidth - BALL_SIZE)                {                    xSpeed -= xSpeed;                }                if (ballY >= racketY - BALL_SIZE && (ballX < racketX || ballX > racketX + RACKET_WIDTH) )                {                    timer.cancel();                    isLose = true;                }                else if (ballY <= 0 || (ballY >= racketY - BALL_SIZE && ballX > racketX && ballX <= racketX + RACKET_WIDTH))                {                    ySpeed = -ySpeed;                }                //小球座标增加                ballX += xSpeed;                ballY += ySpeed;                //发送消息，通知重绘组件                handler.sendEmptyMessage(0x1234);            }        }, 0, 100);    }    class GameView extends View{        Paint paint = new Paint();        public GameView(Context context){            super(context);            setFocusable(true);        }        @Override        protected void onDraw(Canvas canvas) {            paint.setStyle(Paint.Style.FILL);            paint.setAntiAlias(true);            if(isLose){                paint.setColor(Color.RED);                paint.setTextSize(40);                canvas.drawText("Game Over!",tableWidth / 2 - 100, 200, paint);            }            else            {                paint.setColor(Color.rgb(255,0,0));                canvas.drawCircle(ballX, ballY,BALL_SIZE, paint);                paint.setColor(Color.rgb(80, 80, 200));                canvas.drawRect(racketX, racketY, racketX + RACKET_WIDTH, racketY + RACKET_HEIGHT, paint);            }            super.onDraw(canvas);        }    }}
运行效果：

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