Android实现花瓣飘落效果-技术圈

效果展示

实现原理

首先需要生成绘制小花的坐标点，坐标点的横坐标是根据控件的宽度随机生成的，而纵坐标则设置为小花图片高度的负值（这样可以实现小花从屏幕外进入）。
将这些点存储到集合当中。
遍历集合根据点的位置绘制小花
绘制完后不断增加各个点的纵坐标

实现步骤

1.定义变量将变量初始化

    private SurfaceHolder mHolder;    private boolean mFlag = true;//绘制小花线程的开关标志    private ArrayList<PointF> mFlowers;//小花点的坐标集合    private Random mRandom;//负责随机数生成    private Bitmap mBitmap;//小花的图案
    public FlowerView(Context context) {        super(context);        init();    }
    public FlowerView(Context context, AttributeSet attrs) {        super(context, attrs);        init();    }
    public FlowerView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init();    }    private void init(){        mHolder = getHolder();        mHolder.addCallback(this);        //设置背景透明        this.setZOrderOnTop(true);        mHolder.setFormat(PixelFormat.TRANSLUCENT);
        mFlowers = new ArrayList<>();        mRandom = new Random();
        mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_hua);
    }

2.实现添加花朵坐标点的方法

/**     * 添加花朵     */    private void addFlower(){        PointF point = new PointF();        point.x=mRandom.nextInt(getWidth());//根据控件宽度随机生成X轴坐标        point.y=-mBitmap.getHeight();//纵坐标设置为小花图像的负值（产生从屏幕外进入的效果）        mFlowers.add(point);//将坐标点添加进集合    }

3.实现SurfaceHolder.Callback及Runnable接口

public class FlowerView extends SurfaceView implements SurfaceHolder.Callback,Runnable

4.在run方法中实现绘制逻辑

 @Override    public void run() {        while (mFlag){            try {                Thread.sleep(80);//控制小花的下落速度                Canvas canvas = mHolder.lockCanvas();                PointF pointF = null;                //清屏操作（否则会残留一些无用图像）                if(canvas!=null){                    canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);                }else {                    continue;                }                for(PointF point: mFlowers){                    pointF = point;                    canvas.drawBitmap(mBitmap,pointF.x,pointF.y,null);                    int i = mRandom.nextInt(getHeight()/50)+getHeight()/50;//修改雨滴线的纵坐标，使其看起来在下雨                    pointF.y=pointF.y+i;                }                mHolder.unlockCanvasAndPost(canvas);                addFlower();                //当绘制点的纵坐标大于控件高度时，将该点移除                if(mFlowers.size()>0&&pointF!=null&&pointF.y>=getHeight()){                    mFlowers.remove(pointF);                }
            }catch (Exception e){}        }    }

5.在SurfaceHolder.Callback的回调方法中开启绘制线程

 @Override    public void surfaceCreated(SurfaceHolder holder) {        mFlag = true;//surface创建时将线程开关打开        new Thread(this).start();//开启线程绘制    }
    @Override    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {        mFlowers.clear();//当控件发生改变时清除之前的绘制点    }
    @Override    public void surfaceDestroyed(SurfaceHolder holder) {        mFlag = false;//当surface销毁时关掉绘制线程    }

完整代码展示

public class FlowerView extends SurfaceView implements SurfaceHolder.Callback,Runnable{    private SurfaceHolder mHolder;    private boolean mFlag = true;//绘制小花线程的开关标志    private ArrayList<PointF> mFlowers;//小花点的坐标集合    private Random mRandom;//负责随机数生成    private Bitmap mBitmap;//小花的图案
    public FlowerView(Context context) {        super(context);        init();    }
    public FlowerView(Context context, AttributeSet attrs) {        super(context, attrs);        init();    }
    public FlowerView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init();    }    private void init(){        mHolder = getHolder();        mHolder.addCallback(this);        //设置背景透明        this.setZOrderOnTop(true);        mHolder.setFormat(PixelFormat.TRANSLUCENT);
        mFlowers = new ArrayList<>();        mRandom = new Random();
        mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_hua);
    }
    @Override    public void surfaceCreated(SurfaceHolder holder) {        mFlag = true;        new Thread(this).start();    }
    @Override    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {        mFlowers.clear();    }
    @Override    public void surfaceDestroyed(SurfaceHolder holder) {        mFlag = false;    }
    @Override    public void run() {        while (mFlag){            try {                Thread.sleep(80);                Canvas canvas = mHolder.lockCanvas();                PointF pointF = null;                //清屏操作                if(canvas!=null){                    canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);                }else {                    continue;                }                for(PointF point: mFlowers){                    pointF = point;                    canvas.drawBitmap(mBitmap,pointF.x,pointF.y,null);                    int i = mRandom.nextInt(getHeight()/50)+getHeight()/50;//修改雨滴线的纵坐标，使其看起来在下雨                    pointF.y=pointF.y+i;                }                mHolder.unlockCanvasAndPost(canvas);                addFlower();                if(mFlowers.size()>0&&pointF!=null&&pointF.y>=getHeight()){                    mFlowers.remove(pointF);                }
            }catch (Exception e){}        }    }
    /**     * 添加花朵     */    private void addFlower(){        PointF point = new PointF();        point.x=mRandom.nextInt(getWidth());        point.y=-mBitmap.getHeight();        mFlowers.add(point);    }}

到这里就结束啦.