Android自定义View实现水波纹效果

介绍：水波纹散开效果的控件在 App 里面还是比较常见的，例如 网易云音乐歌曲识别，附近搜索场景。

看下实现的效果：

实现思路： 先将最大圆半径与最小圆半径间距分成几等份，从内到外，Paint 透明度依次递减，绘制出同心圆，然后不断的改变这些同心圆的半径大小，延迟一定时间重绘，便达到了想外散开的动画效果了。

public class WaveView extends View { private static final String TAG = "WaveView"; private int waveColor; private int waveCount; private Bitmap waveCenterIcon; private Paint paint; private int mWidth; private int mHeight; private int centerX; private int centerY; private float radius; // 最外圆半径，即最大半径 private float innerRadius; // 最内圆的半径，即最小半径 private int centerIconWidth; private int centerIconHeight; private float[] waveDegreeArr; private boolean isRunning = true; public WaveView(Context context) {  this(context, null); } public WaveView(Context context, AttributeSet attrs) {  super(context, attrs);  readAttrs(context, attrs);  init(); } private void init() {  paint = new Paint(Paint.ANTI_ALIAS_FLAG);  paint.setColor(waveColor);  paint.setStyle(Paint.Style.FILL);  waveDegreeArr = new float[waveCount];  // 设置中间 drawable 点击事件 } private void readAttrs(Context context, AttributeSet attrs) {  TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.WaveView);  try {   waveColor = typedArray.getColor(R.styleable.WaveView_waveColor, 0xffff0000);   waveCount = typedArray.getInt(R.styleable.WaveView_waveCount, 4);   Drawable centerDrawable = typedArray.getDrawable(R.styleable.WaveView_waveCenterIcon);   waveCenterIcon = ((BitmapDrawable) centerDrawable).getBitmap();  } catch (Exception e) {  } finally {   typedArray.recycle();  } } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) {  super.onSizeChanged(w, h, oldw, oldh);  mWidth = w;  mHeight = h;  centerX = mWidth / 2;  centerY = mHeight / 2;  radius = Math.min(mWidth, mHeight) / 2f;  centerIconWidth = waveCenterIcon.getWidth();  centerIconHeight = waveCenterIcon.getHeight();  innerRadius = Math.max(centerIconWidth, centerIconHeight) * 1.2f;  for (int i = 0; i < waveCount; i++) {   waveDegreeArr[i] = innerRadius + (radius - innerRadius) / waveCount * i;  } } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  int widthMode = MeasureSpec.getMode(widthMeasureSpec);  int heightMode = MeasureSpec.getMode(heightMeasureSpec);  if (widthMode == MeasureSpec.UNSPECIFIED || widthMode == MeasureSpec.AT_MOST) {   widthMeasureSpec = MeasureSpec.makeMeasureSpec(dp2Px(120), MeasureSpec.EXACTLY);  }  if (heightMode == MeasureSpec.UNSPECIFIED || heightMode == MeasureSpec.AT_MOST) {   heightMeasureSpec = MeasureSpec.makeMeasureSpec(dp2Px(120), MeasureSpec.EXACTLY);  }  super.onMeasure(widthMeasureSpec, heightMeasureSpec); } @Override protected void onDraw(canvas canvas) {  drawWave(canvas);  drawCenterCircle(canvas);  drawCenterIcon(canvas); } private void drawCenterCircle(Canvas canvas) {  canvas.drawCircle(centerX, centerY, innerRadius, paint); } private void drawWave(Canvas canvas) {  for (int i = 0; i < waveCount; i++) {   paint.setAlpha((int) (255 - 255 * waveDegreeArr[i] / radius));   canvas.drawCircle(centerX, centerY, waveDegreeArr[i], paint);  }  for (int i = 0; i < waveDegreeArr.length; i++) {   if ((waveDegreeArr[i] += 4) > radius) {    waveDegreeArr[i] = innerRadius;   }  }  if (isRunning) {   postInvalidateDelayed(50);  } } private void drawCenterIcon(Canvas canvas) {  paint.setAlpha(255);  int left = centerX - centerIconWidth / 2;  int top = centerY - centerIconHeight / 2;  canvas.drawBitmap(waveCenterIcon, left, top, paint); } @Override public boolean onTouchEvent(MotionEvent event) {  switch (event.getAction()) {   case MotionEvent.ACTION_UP:    // 处理事件逻辑    handleEvent(event);    return true;  }  return true; } private void handleEvent(MotionEvent event) {  float touchX = event.getX();  float touchY = event.getY();  Log.i(TAG, "handleEvent: " + "(" + touchX + "," + touchY + ")");  float distanceX = Math.abs(touchX - centerX);  float distanceY = Math.abs(touchY - centerY);  // 计算触摸点距离中心点的距离  float distance = (float) Math.sqrt(distanceX * distanceX + distanceY * distanceY);  // 当点击的点距离中心点距离小于最内圆半径时，认为是点击有效，否则无效  if (distance < innerRadius) {   if (listener != null) {    listener.onCenterWaveClick();   }  } } OnCenterWaveClickListener listener; public interface OnCenterWaveClickListener {  void onCenterWaveClick(); } public void setOnCenterWaveClickListener(OnCenterWaveClickListener listener) {  this.listener = listener; } public void toggle() {  isRunning = !isRunning;  invalidate(); } public boolean isWaveRunning() {  return isRunning; } private int dp2Px(int dpValue) {  return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dpValue, getResources().getDisplayMetrics()); }}