Android 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：