Android怎么实现小球自由碰撞动画

这篇文章主要介绍“Android怎么实现小球自由碰撞动画”，在日常操作中，相信很多人在Android怎么实现小球自由碰撞动画问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”Android怎么实现小球自由碰撞动画”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！

前言

本文将基于Android对一个小球自由碰撞动画项目做一个简单介绍，并展示部分关键代码以及实际效果动态图

1. add balls List

添加颜色为绿，黄，红，黑，蓝，灰的小球，并设置其大小

ballList.add(new Ball(80, Color.GREEN, 700, width / 2, height / 2));        ballList.add(new Ball(100, Color.YELLOW, 600, width / 4 * 3, height / 4 * 3));        ballList.add(new Ball(120, Color.RED, 800, width / 3 * 3, height / 3 * 3));        ballList.add(new Ball(100, Color.BLACK, 800, width / 3 * 4, height / 3 * 4));        ballList.add(new Ball(120, Color.BLUE, 800, width / 5 * 3, height / 5 * 3));        ballList.add(new Ball(100, Color.DKGRAY, 800, width / 4 * 5, height / 5 * 4));

2.ball parameter

int radius;  //半径大小      long speed =-1;  //碰撞速度    int color;  //颜色    long degree =-1;  //初始方向值    int bgAlpha;  //透明度     long lifeSpan =-1;

3. 判断是否有发生碰撞的小球

关键代码

private void checkoutBall() {        for (int i = 0; i < ballList.size(); i++) {            Ball ball1 = ballList.get(i);            Ball ball2 = (Ball) distanceMap.get(ball1);            if (ball2.getX() == -1 && ball2.getY() == -1) {                continue;            }            int distance2 = Math.abs(ball1.getX() - ball2.getX()) * Math.abs(ball1.getX() - ball2.getX())                    + Math.abs(ball1.getY() - ball2.getY()) * Math.abs(ball1.getY() - ball2.getY());            //最小距离小于阈值，发生碰撞 计算碰撞角度            if (distance2 <= (ball1.getRadius() + ball2.getRadius())                    * (ball1.getRadius() + ball2.getRadius())) {                int x1 = ball1.getX();                int y1 = ball1.getY();                int x2 = ball2.getX();                int y2 = ball2.getY();                //两球的角度差为180  即两球正碰 交换运动方向                if (Math.abs(ball1.getDegree() - ball2.getDegree()) == 180) {                    int temp = ball1.getDegree();                    ball1.setDegree(ball2.getDegree());                    ball2.setDegree(temp);                } else if (y1 == y2) {                    //正弦值不存在   角度为90                    if (x1 > x2) {                        ball1.setDegree(90);                        ball2.setDegree(270);                    } else {                        ball1.setDegree(270);                        ball2.setDegree(90);                    }                } else {                    //斜碰  两球圆心连接线的角度做反向运动                    float tan = (x1 - x2) / (y1 - y2);                    //正弦对应的角度在[-90,90]   在这取绝对值让角度值为正值                    int angle = (int) Math.abs(Math.atan(tan));                    if (x1 > x2 && y1 > y2) {                        //正弦值为正数    角度为[0,90] ball1在右下   ball2在左上                        ball1.setDegree(angle + 90);                        ball2.setDegree(angle + 270);                    } else if (x1 > x2 && y1 < y2) {                        //正弦值为负数   角度为[-90,0] ball1在右上   ball2在左下                        ball1.setDegree(90 - angle);                        ball2.setDegree(270 - angle);                    } else if (x1 < x2 && y1 > y2) {                        //正弦值为负数   角度为[-90,0] ball1在右下   ball2在左上                        ball1.setDegree(270 - angle);                        ball2.setDegree(90 - angle);                    } else if (x1 < x2 && y1 < y2) {                        //正弦值为正数   角度为[0,90] ball1在左上   ball2在右下                        ball1.setDegree(angle + 270);                        ball2.setDegree(angle + 90);                    } else if (x1 == x1) {                        //正弦值为0  angle为0                        if (y1 > y2) {                            ball1.setDegree(180);                            ball2.setDegree(angle);                        } else {                            ball1.setDegree(angle);                            ball2.setDegree(180);                        }                    }                }                //发生碰撞 重新初始化数据                distanceMap.put(ball2, new Ball());                distanceMap.put(ball1, new Ball());            }        }    }

collision detection

碰撞后重新调用onDraw(绘制小球）

private class MyThread extends Thread {        @Override        public void run() {            while (true) {                actionBall();                postInvalidate();  //  更新界面，重新调用onDraw()                try {//                    sleep(1000 / 36);                    sleep(10);                } catch (Exception e) {                    e.printStackTrace();                }            }        }    }

onDraw

 protected void onDraw(canvas canvas) {        super.onDraw(canvas);        for (int i = 0; i < ballList.size(); i++) {            Ball ball = ballList.get(i);            Paint paint = new Paint();            paint.setColor(ball.getColor());            paint.setAlpha(ball.getAlpha());            paint.setStyle(Paint.Style.FILL);            paint.setStrokeWidth(1);            canvas.drawCircle(ball.getX(), ball.getY(), ball.getRadius(), paint);        }    }

4.application display

静态界面

动态效果图

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