【Android】弹跳的小球——SurfaceView-优快云博客

本文链接：https://blog.youkuaiyun.com/felicitia/article/details/9079711

简单介绍：

用安卓实现的一个黑色全屏上，红色的小球的随机跳动，加速度越来越快。

采用surfaceview实现，在activity中设置为全屏，并将小球弹跳的surfaceview设置为显示的view，主要代码都在surfaceview中实现。

将小球的初始位置设置为屏幕的中央，将初始的方向设置为向下（用角度表示，右方向为0°，顺时针方向角度增加），加速度设置为1。然后开启线程进行surfaceview的重绘，线程Thread.sleep(10)之后进行一次重绘，并且加速度加0.2，否则太快。每次重绘时判断是否碰壁，写了一个static final的类来记录碰了哪边的壁，然后对弹跳方向进行180°之内（因为不能方向是弹出屏幕的）的随机，不随机的话路线会固定，所以随机。

主要代码：

public class GameView extends SurfaceView implements Callback{

	private float x;
	private float y;
	private double angle;//右方向为正方向，角度为零，顺时针
	private int radius;
	private SurfaceHolder surfaceHolder;
	private AnimThread thread;
	private double accelerate;
	private int lastDir = Direction.MID;

	public GameView(Context context) {
		super(context);
		// TODO Auto-generated constructor stub
		surfaceHolder = this.getHolder();
		surfaceHolder.addCallback(this);
		this.setFocusable(true);
		thread = new AnimThread(surfaceHolder, getContext());
	}

	@Override
	public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
		// TODO Auto-generated method stub

	}

	@Override
	public void surfaceCreated(SurfaceHolder arg0) {
		// TODO Auto-generated method stub
		x = getWidth()/2;
		y = getHeight()/2;
		radius = 30;
		angle = Math.PI*0.5;
		accelerate = 1;
		thread.isRunning = true;
		thread.start();
	}

	@Override
	public void surfaceDestroyed(SurfaceHolder holder) {
		// TODO Auto-generated method stub
		thread.isRunning = false;
		try {
			thread.join();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}

	}

	public void drawCircle(Canvas canvas, Paint paint) {
		canvas.drawColor(Color.BLACK); // 清空屏幕
		canvas.drawCircle(x, y, radius, paint);
		y += Math.sin(angle)*accelerate;
		x += Math.cos(angle)*accelerate;
		switch(getDirection(x,y))
		{
		case Direction.UP:
			angle = Math.random()*Math.PI;
			break;
		case Direction.DOWN:
			angle = (1+Math.random())*Math.PI;
			break;
		case Direction.LEFT:
			angle = (Math.random()-0.5)*Math.PI;
			break;
		case Direction.RIGHT:
			angle = (0.5+Math.random())*Math.PI;
			break;
		}
	}

	public int getDirection(float x, float y)
	{
		if(y<=radius && lastDir!=Direction.UP)
		{
			lastDir = Direction.UP;
			y = radius;
			Log.i("dir", "up");
			return Direction.UP;
		}
		else if(y>=(getHeight()-radius) && lastDir!=Direction.DOWN)
		{
			lastDir = Direction.DOWN;
			y = getHeight()-radius;
			Log.i("dir","down");
			return Direction.DOWN;
		}
		else if(x<=radius && lastDir!=Direction.LEFT)
		{
			lastDir = Direction.LEFT;
			x = radius;
			Log.i("dir","left");
			return Direction.LEFT;
		}
		else if(x>=getWidth()-radius && lastDir!=Direction.RIGHT)
		{
			lastDir = Direction.RIGHT;
			x = getWidth()-radius;
			Log.i("dir","right");
			return Direction.RIGHT;
		}
		return Direction.MID;
	}
	static final class Direction
	{
		public static final  int LEFT = 0;
		public static final  int RIGHT = 1;
		public static final  int UP = 2;
		public static final  int DOWN = 3;
		public static final int MID = 4;
	}

	class AnimThread extends Thread implements Runnable {
		private boolean isRunning;
		private SurfaceHolder holder;
		private Context context;
		private Paint paint;
		public AnimThread(SurfaceHolder holder , Context context) {
			this.holder = holder;
			this.context = context;
			isRunning = false;
			paint = new Paint();
			paint.setColor(Color.RED);
			paint.setStyle(Paint.Style.FILL);
		}

		public void run() { // 计算绘制动画的坐标
			Canvas canvas = null;
			while(isRunning)
			{
				accelerate += 0.2;
				canvas = holder.lockCanvas(null);
				drawCircle(canvas, paint);
				try {
					Thread.sleep(10);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}finally{
					holder.unlockCanvasAndPost(canvas);
				}
			}
		}
	}
}