Android實現花瓣飄落效果的步驟

效果展示

實現原理 首先需要生成繪制小花的坐標點，坐標點的橫坐標是根據控件的寬度隨機生成的，而縱坐標則設置為小花圖片高度的負值（這樣可以實現小花從屏幕外進入）。 將這些點存儲到集合當中。 遍歷集合根據點的位置繪制小花 繪制完后不斷增加各個點的縱坐標實現步驟

1.定義變量將變量初始化

private SurfaceHolder mHolder; private boolean mFlag = true;//繪制小花線程的開關標志 private ArrayList<PointF> mFlowers;//小花點的坐標集合 private Random mRandom;//負責隨機數生成 private Bitmap mBitmap;//小花的圖案 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);//設置背景透明this.setZOrderOnTop(true);mHolder.setFormat(PixelFormat.TRANSLUCENT);mFlowers = new ArrayList<>();mRandom = new Random();mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_hua); }

2.實現添加花朵坐標點的方法

/** * 添加花朵 */ private void addFlower(){PointF point = new PointF();point.x=mRandom.nextInt(getWidth());//根據控件寬度隨機生成X軸坐標point.y=-mBitmap.getHeight();//縱坐標設置為小花圖像的負值（產生從屏幕外進入的效果）mFlowers.add(point);//將坐標點添加進集合 }

3.實現SurfaceHolder.Callback及Runnable接口

public class FlowerView extends SurfaceView implements SurfaceHolder.Callback,Runnable

4.在run方法中實現繪制邏輯

@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（否則會殘留一些無用圖像）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;//修改雨滴線的縱坐標，使其看起來在下雨 pointF.y=pointF.y+i;}mHolder.unlockCanvasAndPost(canvas);addFlower();//當繪制點的縱坐標大于控件高度時，將該點移除if(mFlowers.size()>0&&pointF!=null&&pointF.y>=getHeight()){ mFlowers.remove(pointF);} }catch (Exception e){}} }

5.在SurfaceHolder.Callback的回調方法中開啟繪制線程

@Override public void surfaceCreated(SurfaceHolder holder) {mFlag = true;//surface創建時將線程開關打開new Thread(this).start();//開啟線程繪制 } @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {mFlowers.clear();//當控件發生改變時清除之前的繪制點 } @Override public void surfaceDestroyed(SurfaceHolder holder) {mFlag = false;//當surface銷毀時關掉繪制線程 }完整代碼展示

public class FlowerView extends SurfaceView implements SurfaceHolder.Callback,Runnable{ private SurfaceHolder mHolder; private boolean mFlag = true;//繪制小花線程的開關標志 private ArrayList<PointF> mFlowers;//小花點的坐標集合 private Random mRandom;//負責隨機數生成 private Bitmap mBitmap;//小花的圖案 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);//設置背景透明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;//修改雨滴線的縱坐標，使其看起來在下雨 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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