Android选中突出背景效果的底部导航栏功能

mPath.moveTo(0, 0);//起始点

mPath.lineTo(x,y);

mPath.quadTo(x1,y1,x2,y2）;

mPaint.setStyle(Paint.Style.FILL_AND_STROKE);

mPath.lineTo(getWidth(), getHeight());
mPath.lineTo(0, getHeight());
mPath.close(); //封闭path路径

mPaint.setColor(Color.WHITE);

1(0,0)
 
2(i/2/2,y/2)
3(i-i/2/2,y/2)
4(i,0)
a(i/2/2/2,y/2/2/2)
 
b(i/2,y)
 
c(i-i/2/2/2,y/2/2/2)

//第一条贝塞尔曲线     a          2
mPath.quadTo(i / 2 / 2 / 2 , -(minHeight / 2 / 2 / 2), i / 2 / 2 , -(minHeight / 2));
//第二条贝塞尔曲线     b      3
mPath.quadTo(i / 2 + i , -minHeight, i - i / 2 / 2 + i , -(minHeight / 2));
//第三条贝塞尔曲线     c      4
mPath.quadTo(i - i / 2 / 2 / 2 , -(minHeight / 2 / 2 / 2), i + i * (count - 1), 0);

//第一条贝塞尔曲线     a          2
mPath.quadTo(i / 2 / 2 / 2 + i * (count - 1), -(minHeight / 2 / 2 / 2), i / 2 / 2 + i * (count - 1) + minHeight / 5, -(minHeight / 2));
//第二条贝塞尔曲线     b      3
mPath.quadTo(i / 2 + i * (count - 1), -minHeight, i - i / 2 / 2 + i * (count - 1) - minHeight / 5, -(minHeight / 2));
//第三条贝塞尔曲线     c      4
mPath.quadTo(i - i / 2 / 2 / 2 + i * (count - 1), -(minHeight / 2 / 2 / 2), i + i * (count - 1), 0);

package com.wavewave.mylibrary;
 
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.View;
 
import androidx.annotation.Nullable;
 
/**
 * @author wavewave
 * @CreateDate: 2020/10/28 10:23 AM
 * @Description: 底部导航 选中突出View 背景
 * @Version: 1.0
 */
public class BottomOutNavigation extends View {
 private Paint mPaint;
 //起始点
 private int beginY = dip2px(0);
 //边距
 private int margin = dip2px(0);
 /**
  * 默认 突出最高点 Y
  */
 private int minHeight = dip2px(40);
 
 //第几个从0开始
 private int count = 1;
 /**
  * 默认3个 根据实际情况写
  */
 private int maxCount = 3;
 public static String TAG = "LineView";
 private int height;
 private int width;
 private Path mPath;
 
 public BottomOutNavigation(Context context) {
  this(context, null);
 }
 
 public BottomOutNavigation(Context context, @Nullable AttributeSet attrs) {
  this(context, attrs, 0);
 }
 
 public BottomOutNavigation(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
  init();
 }
 
 private void init() {
  mPath = new Path();
  mPaint = new Paint();
//  mPaint.setStyle(Paint.Style.STROKE);
  mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
  mPaint.setColor(Color.WHITE);
  mPaint.setAntiAlias(true);//抗锯齿
  //2、通过Resources获取
  DisplayMetrics dm = getResources().getDisplayMetrics();
  height = dm.heightPixels;
  width = dm.widthPixels;
 }
 
 /**
  * 设置选择
  *
  * @param count
  */
 public void setCount(int count) {
  this.count = count;
  invalidate();
 }
 
 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  int i = width / maxCount;//单个所占大小
  Log.d(TAG, "i:" + i);
  mPath.reset();
  mPath.moveTo(0, 0);//起始点
  mPath.lineTo(margin + i * (count - 1), 0);
//
  //第一条贝塞尔曲线     a          2
  mPath.quadTo(i / 2 / 2 / 2 + i * (count - 1), -(minHeight / 2 / 2 / 2), i / 2 / 2 + i * (count - 1) + minHeight / 5, -(minHeight / 2));
  //第二条贝塞尔曲线     b      3
  mPath.quadTo(i / 2 + i * (count - 1), -minHeight, i - i / 2 / 2 + i * (count - 1) - minHeight / 5, -(minHeight / 2));
  //第三条贝塞尔曲线     c      4
  mPath.quadTo(i - i / 2 / 2 / 2 + i * (count - 1), -(minHeight / 2 / 2 / 2), i + i * (count - 1), 0);
 
  mPath.lineTo(width, beginY);
  mPath.lineTo(getWidth(), getHeight());
  mPath.lineTo(0, getHeight());
  mPath.close(); //封闭path路径
  canvas.drawPath(mPath, mPaint);
 }
 /**
  * 根据屏幕的分辨率从 dp 的单位 转成为 px(像素)
  */
 public int dip2px(float dpValue) {
  final float scale = getResources().getDisplayMetrics().density;
  return (int) (dpValue * scale + 0.5f);
 }
 
}