Android自定义View实现多片叶子旋转滑动（五）

上一篇《Android 自定义View(四) 叶子飘动+旋转效果》实现了单片叶子的滑动及旋转，下面实现多片叶子的滑动旋转功能

实现思路比较简单，就是添加一个叶子Leaf类，储存每片叶子的信息，

然后随机产生叶子的坐标及旋转角度，最后实时获取每片叶子信息，添加到画布中

1、Leaf.java 叶子类

 private class Leaf {
  // 叶子的坐标
  float x, y;
  // 旋转角度
  int rotateAngle;
  // 起始时间(ms)
  long startTime;
 }

2、初始化每片叶子的信息，然后保存到list中

 //使叶子初始时间有间隔
 int addTime;
 private Leaf getLeaf() {
  Random random = new Random();
  Leaf leaf = new Leaf();
  //随机初始化叶子初始角度
  leaf.rotateAngle = random.nextInt(360);
  //随机初始化叶子启动时间
  addTime += random.nextInt((int) (cycleTime));
  leaf.startTime = System.currentTimeMillis() + cycleTime + addTime;
  return leaf;
 }
 private List<Leaf> getLeafs(int leafSize) {
  List<Leaf> list = new LinkedList<Leaf>();
  for (int i=0; i<leafSize; i++) {
   list.add(getLeaf());
  }
  return list;
 }

3、接下去就是改写getLocation()及getRotate()方法，使其返回每片叶子的坐标及旋转角度

 //获取每片叶子在XY轴上的滑动值
 private void getLocation(Leaf leaf) {
  float betweenTime = leaf.startTime - System.currentTimeMillis();
  //周期结束再加一个cycleTime
  if(betweenTime < 0) {
   leaf.startTime = System.currentTimeMillis() + cycleTime + new Random().nextInt((int) (cycleTime));
   betweenTime = cycleTime;
  }
  //通过时间差计算出叶子的坐标
  float fraction = (float) betweenTime / cycleTime;
  float x = (int)(width * fraction);
  leaf.x = x;
  float w = (float) ((float) 2 * Math.PI / width);
  int y = (int) (18 * Math.sin(w * x)) + (height-mLeafHeight)/2;
  leaf.y = y;
 }
 //获取每片叶子的旋转角度
 private void getRotate(Leaf leaf) {
  float scale = ((leaf.startTime - System.currentTimeMillis())%cycleTime)/ (float)cycleTime;
  int rotate = (int)(scale * 360);
  leaf.rotateAngle = rotate;
 }

4、在onDraw()方法中，画出每片叶子

 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  //画叶子
  int size = leafList.size();
  for (int i=0; i<size; i++) {
   Leaf leaf = leafList.get(i);
   //获取叶子坐标
   getLocation(leaf);
   //获取叶子旋转角度
   getRotate(leaf);
   canvas.save();
   Matrix matrix = new Matrix();
   //设置滑动
   matrix.postTranslate(leaf.x, leaf.y);
   //设置旋转
   matrix.postRotate(leaf.rotateAngle, leaf.x + mLeafWidth / 2, leaf.y + mLeafHeight / 2);
   //添加叶子到画布
   canvas.drawBitmap(mLeafBitmap, matrix, new Paint());
   canvas.restore();
  }
  //调用onDraw()重复滑动
  postInvalidate();
 }

完整代码：

public class LeafView extends View {
 private String TAG = "--------LeafView";
 private Resources mResources;
 //背景图、叶子
 private Bitmap mLeafBitmap, bgBitmap;
 //整个控件的宽度和高度
 private int width, height;
 private Paint bgPaint;
 private RectF bgRect;
 private Rect bgDestRect;
 //存放叶子lsit
 private List<Leaf> leafList;
 //叶子的宽和高
 private int mLeafWidth, mLeafHeight;
 //叶子滑动一周的时间5秒
 private final static long cycleTime = 5000;
 //叶子数量
 private final static int leafNumber = 5;
 public LeafView(Context context, AttributeSet attrs) {
  super(context, attrs);
  mResources = getResources();
  mLeafBitmap = ((BitmapDrawable) mResources.getDrawable(R.drawable.leaf, null)).getBitmap();
  mLeafWidth = mLeafBitmap.getWidth();
  mLeafHeight = mLeafBitmap.getHeight()
  bgBitmap = ((BitmapDrawable) mResources.getDrawable(R.drawable.leaf_kuang, null)).getBitmap();
  bgPaint = new Paint();
  bgPaint.setColor(mResources.getColor(R.color.bg_color));
  //获取所有叶子的信息，放入list
  leafList = getLeafs(leafNumber);
 }
 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  super.onSizeChanged(w, h, oldw, oldh);
  width = w;
  height = h;
  bgDestRect = new Rect(0, 0 , width, height);
 }
 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  bgRect = new RectF(0, 0 , width, height);
  //画背景颜色到画布
  canvas.drawRect(bgRect, bgPaint);
  //画背景图片到画布
  canvas.drawBitmap(bgBitmap, null, bgDestRect, null);
  //画叶子
  int size = leafList.size();
  for (int i=0; i<size; i++) {
   Leaf leaf = leafList.get(i);
   //获取叶子坐标
   getLocation(leaf);
   //获取叶子旋转角度
   getRotate(leaf);
   canvas.save();
   Matrix matrix = new Matrix();
   //设置滑动
   matrix.postTranslate(leaf.x, leaf.y);
   //设置旋转
   matrix.postRotate(leaf.rotateAngle, leaf.x + mLeafWidth / 2, leaf.y + mLeafHeight / 2);
   //添加叶子到画布
   canvas.drawBitmap(mLeafBitmap, matrix, new Paint());
   canvas.restore();
  }
  //调用onDraw()重复滑动
  postInvalidate();
 }
 //获取每片叶子在XY轴上的滑动值
 private void getLocation(Leaf leaf) {
  float betweenTime = leaf.startTime - System.currentTimeMillis();
  //周期结束再加一个cycleTime
  if(betweenTime < 0) {
   leaf.startTime = System.currentTimeMillis() + cycleTime + new Random().nextInt((int) (cycleTime));
   betweenTime = cycleTime;
  }
  //通过时间差计算出叶子的坐标
  float fraction = (float) betweenTime / cycleTime;
  float x = (int)(width * fraction);
  leaf.x = x;
  float w = (float) ((float) 2 * Math.PI / width);
  int y = (int) (18 * Math.sin(w * x)) + (height-mLeafHeight)/2;
  leaf.y = y;
 }
 //获取每片叶子的旋转角度
 private void getRotate(Leaf leaf) {
  float scale = ((leaf.startTime - System.currentTimeMillis())%cycleTime)/ (float)cycleTime;
  int rotate = (int)(scale * 360);
  leaf.rotateAngle = rotate;
 }
 private class Leaf {
  // 叶子的坐标
  float x, y;
  // 旋转角度
  int rotateAngle;
  // 起始时间(ms)
  long startTime;
 }
 private List<Leaf> getLeafs(int leafSize) {
  List<Leaf> list = new LinkedList<Leaf>();
  for (int i=0; i<leafSize; i++) {
   list.add(getLeaf());
  }
  return list;
 }
 //使叶子初始时间有间隔
 int addTime;
 private Leaf getLeaf() {
  Random random = new Random();
  Leaf leaf = new Leaf();
  leaf.rotateAngle = random.nextInt(360);
  addTime += random.nextInt((int) (cycleTime));
  leaf.startTime = System.currentTimeMillis() + cycleTime + addTime;
  return leaf;
 }
}

这里还有很多瑕疵，比如叶子的滑动范围覆盖了边框等等

需要图片等信息的可以从下面的Github地址下载，不过原文比较复杂

参考 https://github.com/Ajian-studio/GALeafLoading

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