GameView.java中包含了一个绘图线程DrawThread，在线程的run方法中锁定Canvas、绘制精灵、更新精灵位置、释放Canvas等操作。因为精灵素材是一张大图，所以这里进行了裁剪生成一个二维数组。使用这个二维数组初始化了精灵四个方向的动画，下面看Sprite.java的源码。
public class Sprite {
public static final int DOWN = 0;
public static final int LEFT = 1;
public static final int RIGHT = 2;
public static final int UP = 3;
public float x;
public float y;
public int width;
public int height;
//精灵行走速度
public double speed;
//精灵当前行走方向
public int direction;
//精灵四个方向的动画
public FrameAnimation[] frameAnimations;
public Sprite(FrameAnimation[] frameAnimations, int positionX,
int positionY, int width, int height, float speed) {
this.frameAnimations = frameAnimations;
this.x = positionX;
this.y = positionY;
this.width = width;
this.height = height;
this.speed = speed;
}
public void updatePosition(long deltaTime) {
switch (direction) {
case LEFT:
//让物体的移动速度不受机器性能的影响,每帧精灵需要移动的距离为：移动速度*时间间隔
this.x = this.x - (float) (this.speed * deltaTime);
break;
case DOWN:
this.y = this.y + (float) (this.speed * deltaTime);
break;
case RIGHT:
this.x = this.x + (float) (this.speed * deltaTime);
break;
case UP:
this.y = this.y - (float) (this.speed * deltaTime);
break;
}
}
/**
* 根据精灵的当前位置判断是否改变行走方向
*/
public void setDirection() {
if (this.x <= 0
&& (this.y + this.height) < GameSurfaceView.SCREEN_HEIGHT) {
if (this.x < 0)
this.x = 0;
this.direction = Sprite.DOWN;
} else if ((this.y + this.height) >= GameSurfaceView.SCREEN_HEIGHT
&& (this.x + this.width) < GameSurfaceView.SCREEN_WIDTH) {
if ((this.y + this.height) > GameSurfaceView.SCREEN_HEIGHT)
this.y = GameSurfaceView.SCREEN_HEIGHT - this.height;
this.direction = Sprite.RIGHT;
} else if ((this.x + this.width) >= GameSurfaceView.SCREEN_WIDTH
&& this.y > 0) {
if ((this.x + this.width) > GameSurfaceView.SCREEN_WIDTH)
this.x = GameSurfaceView.SCREEN_WIDTH - this.width;
this.direction = Sprite.UP;
} else {
if (this.y < 0)
this.y = 0;
this.direction = Sprite.LEFT;
}
}
public void draw(Canvas canvas) {
FrameAnimation frameAnimation = frameAnimations[this.direction];
Bitmap bitmap = frameAnimation.nextFrame();
if (null != bitmap) {
canvas.drawBitmap(bitmap, x, y, null);
}
}
}
