Android实现水波纹控件的方法

有很多app使用过水波纹的这样的效果，看着很酷酷的样子，所以自己就撸码写了一个。

实现思路：

利用贝塞尔曲线绘制圆弧（也就是水波的波纹）
通过动画改变绘制的起始点使水波纹平移

首先，定义我们需要的自定义属性。

<?xml version="1.0" encoding="utf-8"?>
<resources>


 <declare-styleable name="waveStyleable">
  <!-- 水波纹的长度-->
  <attr name="waveLength" format="float"></attr>
  <!-- 水波纹的高度-->
  <attr name="waveHeight" format="float"></attr>
  <!-- 水波纹的速度-->
  <attr name="waveSpeed" format="float"></attr>
  <!--水波纹上方的头像 -->
  <attr name="waveTopIcon" format="reference"></attr>
  <!--水波的颜色 -->
  <attr name="waveColor" format="color"></attr>
  <!--水波距离底部的距离 -->
  <attr name="distanceY" format="float"></attr>

 </declare-styleable>

</resources>

自定义view绘制水波纹控件

public class WaveView extends View {

 private Paint paint;
 private Path path;
 private float waveLength ;
 private float waveHeight ;
 private float waveSpeed ;
 private Bitmap bitmap;
 private int waveColor ;
 private int strokeWidth = 3;
 private Region region;
 private int width,height;
 public int translateX ;
 private float distanceY;

 public WaveView(Context context) {
  super(context);
 }

 public WaveView(Context context, AttributeSet attrs) {
  super(context, attrs);

  TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.waveStyleable);
  waveLength = array.getFloat(R.styleable.waveStyleable_waveLength,300);
  waveColor = array.getColor(R.styleable.waveStyleable_waveColor,0x00ff00);
  waveHeight = array.getFloat(R.styleable.waveStyleable_waveHeight,100);
  waveSpeed = array.getFloat(R.styleable.waveStyleable_waveSpeed,5);
  distanceY = array.getFloat(R.styleable.waveStyleable_distanceY,100);

  Drawable waveTopICon = array.getDrawable(R.styleable.waveStyleable_waveTopIcon);
  array.recycle();
  bitmap = drawableToBitmap(waveTopICon);
  initPaint();
  startAnimal();
 }

 private void initPaint() {
  paint = new Paint();
  paint.setStyle(Paint.Style.FILL);
  paint.setColor(waveColor);
  paint.setStrokeWidth(strokeWidth);
  //绘制贝塞尔曲线的path
  path = new Path();
 }

 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  //绘制贝塞尔曲线
  drawPath(canvas,path);
  //绘制wave上部的头像
  drawIcon(canvas);
 }

 private void drawIcon(Canvas canvas) {
  float baseLine = height-distanceY;
  if(region.getBounds().top==baseLine){
   canvas.drawBitmap(bitmap,width/2-bitmap.getWidth()/2,region.getBounds().bottom-bitmap.getHeight(),paint);
  }else {
   if(region.getBounds().top==0){
    canvas.drawBitmap(bitmap,width/2-bitmap.getWidth()/2,height-bitmap.getHeight()-distanceY,paint);
   }
   canvas.drawBitmap(bitmap,width/2-bitmap.getWidth()/2,region.getBounds().top-bitmap.getHeight(),paint);
  }
 }

 private void drawPath(Canvas canvas, Path path) {

  path.reset();
  //path的起始点，向手机外多绘制一段
  path.moveTo(-2* waveLength +translateX,getHeight()-distanceY);
  for(int i = 0; i<getWidth()+ waveLength; i+= waveLength){
   path.rQuadTo(waveLength /2,-waveHeight, waveLength,0);
   path.rQuadTo(waveLength /2,waveHeight, waveLength,0);
  }
  region = new Region();
  Region clip = new Region();
  clip.set((int) (getWidth()/2-0.1),0,getWidth()/2,getHeight()*2);
  region.setPath(path,clip);

  path.lineTo(getWidth(),getHeight());
  path.lineTo(-waveLength,getHeight());
  path.close();

  canvas.drawPath(path,paint);
 }


 public void startAnimal(){
  ValueAnimator animator = ValueAnimator.ofFloat(0,1);
  animator.setDuration(3000);
  animator.setRepeatCount(ValueAnimator.INFINITE);
  animator.setInterpolator(new LinearInterpolator());
  animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
   @Override
   public void onAnimationUpdate(ValueAnimator animation) {

    translateX += waveSpeed;
    if(-2* waveLength +translateX >= 0){
     translateX = 0;
    }
    postInvalidate();
   }
  });
  animator.start();
 }


 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);

  //获取宽高模式
  int widthMode = MeasureSpec.getMode(widthMeasureSpec);
  int heightMode = MeasureSpec.getMode(heightMeasureSpec);
  width = MeasureSpec.getSize(widthMeasureSpec);
  height = MeasureSpec.getSize(heightMeasureSpec);

  if (widthMode == MeasureSpec.AT_MOST){
   width = (int) waveLength;
  }
  if(heightMode == MeasureSpec.AT_MOST){
   height = (int) (waveHeight+ distanceY+bitmap.getHeight());
  }
  setMeasuredDimension(width,height);

 }

 /**
  * dp转化为px
  * @param dpValue
  * @param context
  * @return
  */

 public float dp2px(float dpValue,Context context){
  return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,dpValue,context.getResources().getDisplayMetrics());
 }

 /**
  * 如果图片底部有很多空白会导致图片不能贴到波纹底部
  * @param bitmap
  * @return
  */

 public Bitmap makeRoundCorner(Bitmap bitmap)
 {
  int width = bitmap.getWidth();
  int height = bitmap.getHeight();
  int left = 0, top = 0, right = width, bottom = height;
  float roundPx = height/2;
  if (width > height) {
   left = (width - height)/2;
   top = 0;
   right = left + height;
   bottom = height;
  } else if (height > width) {
   left = 0;
   top = (height - width)/2;
   right = width;
   bottom = top + width;
   roundPx = width/2;
  }

  Bitmap output = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
  Canvas canvas = new Canvas(output);
  int color = 0xff424242;
  Paint paint = new Paint();
  Rect rect = new Rect(left, top, right, bottom);
  RectF rectF = new RectF(rect);

  paint.setAntiAlias(true);
  canvas.drawARGB(0, 0, 0, 0);
  paint.setColor(color);
  canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
  paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
  canvas.drawBitmap(bitmap, rect, rect, paint);
  return output;
 }

 public Bitmap drawableToBitmap(Drawable drawable) {

  Bitmap bitmap = Bitmap.createBitmap(

    drawable.getIntrinsicWidth(),

    drawable.getIntrinsicHeight(),

    drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888

      : Bitmap.Config.RGB_565);

  Canvas canvas = new Canvas(bitmap);

  drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());

  drawable.draw(canvas);

  return makeRoundCorner(bitmap);

 }

}

相关类：

Path： 可以绘制二次曲线或者三次曲线到画布上，moveTo()方法将path移动到手机屏幕的（-2* waveLength，distanceY）这个点，然后以这个点为起始点绘制二次曲线曲线，rQuadTo（），以最后点为相对位置点进行取点绘制。在属性动画里面，不断改变起始点的位置，这样绘制的水波纹就会平移。

Region：表示区域的类，通过set(path,rect)可以获取到矩形区域与path弧线相交的新的矩形。如果rect的宽度无限小，那么获取的矩形区域会近似为一个点，这个点就是图片移动的y坐标。

xml文件使用：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:id="@+id/activity_main"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 tools:context="com.iwintrue.waveapplication.MainActivity">

 <com.iwintrue.waveapplication.WaveView
 xmlns:app="http://schemas.android.com/apk/res-auto"
 app:waveLength = "200"
 app:waveHeight = "50"
 app:waveSpeed = "10"
 app:waveColor = "#0ff"
 app:distanceY = "100"
 app:waveTopIcon = "@mipmap/icon"
 android:layout_centerInParent="true"
 android:id="@+id/waterView"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:background="#f00"
 />
</RelativeLayout>

核心代码就是这么多，代码中也有解释，关键的类也做了注解了。要是还有那里有疑问，多多交流哈

github地址：https://github.com/zhoukai1526/WaveApplication

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持呐喊教程。

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