Android实现花瓣飘落效果 Android实现花瓣飘落效果的步骤
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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); } }
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