导言

有时候我们需要自定义音量效果。很显然这种效果也可以用自定义View。

image.png

题外话：
1.不要看到一个有图片和其他元素组合一起的就是一个自定义ViewGroup
2.假如自定义view不需要用到wrap_content的情况的时候，可以不用重写onMeasure方法

如下这种情况：

image.png

分析

1.需要画出两种颜色圆弧
2.这些圆弧具有一定的间隙
3.画图片
4.计算圆的内切正方形的位置
5.如果图片小于内切正方形，就居中画出图片
6.如果图片大于内切正方形，就显示整个图片到内切正方形处

1.画圆弧的时候要设置画笔参数

mPaint.setAntiAlias(true); // 消除锯齿
mPaint.setStrokeWidth(mCircleWidth); // 设置圆环的宽度
mPaint.setStrokeCap(Paint.Cap.ROUND); // 定义线段断电形状为圆头
mPaint.setAntiAlias(true); // 消除锯齿
mPaint.setStyle(Paint.Style.STROKE); // 设置空心

2. canvas.drawArc // 这是画圆弧的api

3.canvas.drawBitmap(@NonNull Bitmap bitmap, @Nullable Rect src, @NonNull Rect dst,

        @Nullable Paint paint): 第二个参数设置为null， 第三个参数是图片的Rect

1.attrs.xml

 <attr name="firstColor" format="color" />
    <attr name="secondColor" format="color" />
    <attr name="circleWidth" format="dimension" />
    <attr name="dotCount" format="integer" />
    <attr name="splitSize" format="integer" />
    <attr name="bg" format="reference"></attr>

<declare-styleable name="CustomVolumControlBar">
        <attr name="firstColor" />
        <attr name="secondColor" />
        <attr name="circleWidth" />
        <attr name="dotCount" />
        <attr name="splitSize" />
        <attr name="bg" />
</declare-styleable>

2.CustomVolumeControlBar.java

package com.zhy.customeview04.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.View;

import com.zhy.customeview04.R;

public class CustomVolumControlBar extends View
{
    /**
     * 第一圈的颜色
     */
    private int mFirstColor;

    /**
     * 第二圈的颜色
     */
    private int mSecondColor;
    /**
     * 圈的宽度
     */
    private int mCircleWidth;
    /**
     * 画笔
     */
    private Paint mPaint;
    /**
     * 当前进度
     */
    private int mCurrentCount = 3;

    /**
     * 中间的图片
     */
    private Bitmap mImage;
    /**
     * 每个块块间的间隙
     */
    private int mSplitSize;
    /**
     * 个数
     */
    private int mCount;

    private Rect mRect;

    public CustomVolumControlBar(Context context, AttributeSet attrs)
    {
        this(context, attrs, 0);
    }

    public CustomVolumControlBar(Context context)
    {
        this(context, null);
    }

    /**
     * 必要的初始化，获得一些自定义的值
     * 
     * @param context
     * @param attrs
     * @param defStyle
     */
    public CustomVolumControlBar(Context context, AttributeSet attrs, int defStyle)
    {
        super(context, attrs, defStyle);
        TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomVolumControlBar, defStyle, 0);
        int n = a.getIndexCount();

        for (int i = 0; i < n; i++)
        {
            int attr = a.getIndex(i);
            switch (attr)
            {
            case R.styleable.CustomVolumControlBar_firstColor:
                mFirstColor = a.getColor(attr, Color.GREEN);
                break;
            case R.styleable.CustomVolumControlBar_secondColor:
                mSecondColor = a.getColor(attr, Color.CYAN);
                break;
            case R.styleable.CustomVolumControlBar_bg:
                mImage = BitmapFactory.decodeResource(getResources(), a.getResourceId(attr, 0));
                break;
            case R.styleable.CustomVolumControlBar_circleWidth:
                mCircleWidth = a.getDimensionPixelSize(attr, (int) TypedValue.applyDimension(
                        TypedValue.COMPLEX_UNIT_PX, 20, getResources().getDisplayMetrics()));
                break;
            case R.styleable.CustomVolumControlBar_dotCount:
                mCount = a.getInt(attr, 20);// 默认20
                break;
            case R.styleable.CustomVolumControlBar_splitSize:
                mSplitSize = a.getInt(attr, 20);
                break;
            }
        }
        a.recycle();
        mPaint = new Paint();
        mRect = new Rect();
    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        mPaint.setAntiAlias(true); // 消除锯齿
        mPaint.setStrokeWidth(mCircleWidth); // 设置圆环的宽度
        mPaint.setStrokeCap(Paint.Cap.ROUND); // 定义线段断电形状为圆头
        mPaint.setAntiAlias(true); // 消除锯齿
        mPaint.setStyle(Paint.Style.STROKE); // 设置空心
        int centre = getWidth() / 2; // 获取圆心的x坐标
        int radius = centre - mCircleWidth / 2;// 半径
        /**
         * 画块块去
         */
        drawOval(canvas, centre, radius);

        /**
         * 计算内切正方形的位置
         */
        int relRadius = radius - mCircleWidth / 2;// 获得内圆的半径
        /**
         * 内切正方形的距离顶部 = mCircleWidth + relRadius - √2 / 2
         */
        mRect.left = (int) (relRadius - Math.sqrt(2) * 1.0f / 2 * relRadius) + mCircleWidth;
        /**
         * 内切正方形的距离左边 = mCircleWidth + relRadius - √2 / 2
         */
        mRect.top = (int) (relRadius - Math.sqrt(2) * 1.0f / 2 * relRadius) + mCircleWidth;
        mRect.bottom = (int) (mRect.left + Math.sqrt(2) * relRadius);
        mRect.right = (int) (mRect.left + Math.sqrt(2) * relRadius);

        /**
         * 如果图片比较小，那么根据图片的尺寸放置到正中心
         */
        if (mImage.getWidth() < Math.sqrt(2) * relRadius)
        {
            mRect.left = (int) (mRect.left + Math.sqrt(2) * relRadius * 1.0f / 2 - mImage.getWidth() * 1.0f / 2);
            mRect.top = (int) (mRect.top + Math.sqrt(2) * relRadius * 1.0f / 2 - mImage.getHeight() * 1.0f / 2);
            mRect.right = (int) (mRect.left + mImage.getWidth());
            mRect.bottom = (int) (mRect.top + mImage.getHeight());

        }
        // 绘图
        canvas.drawBitmap(mImage, null, mRect, mPaint);
    }

    /**
     * 根据参数画出每个小块
     * 
     * @param canvas
     * @param centre
     * @param radius
     */
    private void drawOval(Canvas canvas, int centre, int radius)
    {
        /**
         * 根据需要画的个数以及间隙计算每个块块所占的比例*360
         */
        float itemSize = (360 * 1.0f - mCount * mSplitSize) / mCount;

        RectF oval = new RectF(centre - radius, centre - radius, centre + radius, centre + radius); // 用于定义的圆弧的形状和大小的界限

        mPaint.setColor(mFirstColor); // 设置圆环的颜色
        for (int i = 0; i < mCount; i++)
        {
            canvas.drawArc(oval, i * (itemSize + mSplitSize), itemSize, false, mPaint); // 根据进度画圆弧
        }

        mPaint.setColor(mSecondColor); // 设置圆环的颜色
        for (int i = 0; i < mCurrentCount; i++)
        {
            canvas.drawArc(oval, i * (itemSize + mSplitSize), itemSize, false, mPaint); // 根据进度画圆弧
        }
    }

    /**
     * 当前数量+1
     */
    public void up()
    {
        mCurrentCount++;
        postInvalidate();
    }

    /**
     * 当前数量-1
     */
    public void down()
    {
        mCurrentCount--;
        postInvalidate();
    }

    private int xDown, xUp;

    @Override
    public boolean onTouchEvent(MotionEvent event)
    {

        switch (event.getAction())
        {
        case MotionEvent.ACTION_DOWN:
            xDown = (int) event.getY();
            break;

        case MotionEvent.ACTION_UP:
            xUp = (int) event.getY();
            if (xUp > xDown)// 下滑
            {
                down();
            } else
            {
                up();
            }
            break;
        }

        return true;
    }

}

3.使用activity.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:zhy="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#55ffffff"
    android:orientation="vertical"
    tools:context=".MainActivity" >

  <com.xsh.customviewstudy.view.CustomVolumControlBar
      android:layout_width="200dp"
      android:layout_height="200dp"
      android:layout_marginTop="20dp"
      zhy:bg="@drawable/customize"
      zhy:circleWidth="12dp"
      zhy:dotCount="20"
      zhy:firstColor="#252420"
      zhy:secondColor="#FDFDFD"
      zhy:splitSize="25" />

  <com.xsh.customviewstudy.view.CustomVolumControlBar
      android:layout_width="130dp"
      android:layout_height="130dp"
      android:layout_gravity="center"
      android:layout_marginTop="20dp"
      zhy:bg="@drawable/icon"
      zhy:circleWidth="10dp"
      zhy:dotCount="10"
      zhy:firstColor="#00ff00"
      zhy:secondColor="#ff0000"
      zhy:splitSize="15" />

  <com.xsh.customviewstudy.view.CustomVolumControlBar
      android:layout_width="100dp"
      android:layout_height="100dp"
      android:layout_gravity="bottom"
      android:layout_marginLeft="10dp"
      android:layout_marginBottom="20dp"
      zhy:bg="@drawable/icon_qq_small"
      zhy:circleWidth="10dp"
      zhy:dotCount="8"
      zhy:firstColor="#ADC6E5"
      zhy:secondColor="#0362DB"
      zhy:splitSize="25" />

</LinearLayout>

源码参考我的github地址

参考：

http://blog.csdn.net/lmj623565791/article/details/24529807