<declare-styleable name="CustomTitleView">
 <attr name="titleColor" format="color" />
 <attr name="titleSize" format="dimension" />
 <attr name="titleBackground" format="color" />
 <attr name="titleLenth" format="integer" />
 </declare-styleable>

 //文本
 private StringBuffer mTitleText;
 //文本的颜色
 private int mTitleColor;
 //文本的大小
 private int mTitleSize;
 //背景颜色
 private int mBackground;
 //控制生成的随机字符串长度
 private int mLenth;
 //绘制时控制文本绘制的范围
 private Rect mBound;
 //画笔
 private Paint mPaint;
 //随机数对象
 private Random random = new Random();
 //字符串边距
 private int padding_left;
 //随机的值
 String[] data = {"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z",
  "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z",
  "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"};

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

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

 public CustomTitleView(Context context, AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);
 setOnClickListener(this);
 TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.CustomTitleView);
 int n = typedArray.getIndexCount();
 for (int i = 0; i < n; i++) {
  int attr = typedArray.getIndex(i);
  switch (attr) {
  case R.styleable.CustomTitleView_titleColor:
   mTitleColor = typedArray.getColor(attr, Color.BLACK);
   break;
  case R.styleable.CustomTitleView_titleSize:
   mTitleSize = typedArray.getDimensionPixelSize(attr, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 16, getResources().getDisplayMetrics()));
   break;
  case R.styleable.CustomTitleView_titleBackground:
   mBackground = typedArray.getColor(attr, Color.BLACK);
   break;
  case R.styleable.CustomTitleView_titleLenth:
   mLenth = typedArray.getInteger(attr, 4);
   break;
  }
 }
 //回收
 typedArray.recycle();
 mPaint = new Paint();
 randomText();
 mPaint.setTextSize(mTitleSize);
 //创建一个矩形
 mBound = new Rect();
 //第一个参数为要测量的文字，第二个参数为测量起始位置，第三个参数为测量的最后一个字符串的位置，第四个参数为rect对象
 mPaint.getTextBounds(mTitleText.toString(), 0, mTitleText.length(), mBound);
 }

/**
 * 计算宽高
 *
 * @param lenth widthMeasureSpec或heightMeasureSpec
 * @param isWidth true为计算宽度,false为计算高度
 */
 private int getMeasuredLength(int lenth, boolean isWidth) {
 if (isWidth) {
  if (MeasureSpec.getMode(lenth) == MeasureSpec.EXACTLY) {
  //设置了精确尺寸,通过MeasureSpec.getSize()获得尺寸返回宽度
  return MeasureSpec.getSize(lenth);
  } else {
  //设置了warp_content，则需要我们自己计算
  /**
   * 首先给画笔设置文字大小
   * 通过getTextBounds方法获得绘制的Text的宽度
   * 然后因为我们的自定义View只有一个text所以我们只需要getPaddingLeft()+getPaddingRight()+textwidth即可计算出显示出view所需要最小的宽度
   * 一般计算宽度为getPaddingLeft()+getPaddingRight()+自己绘画的文字或者图片的宽度，因为计算的是所需宽度，假设我们绘制了图片+文字，那么就需要判断图片的宽度跟文字的宽度那个更大比如getPaddingLeft()+getPaddingRight()+Math.max(图片的宽度，文字的宽度)即得出所需宽度
   */
  if (MeasureSpec.getMode(lenth) == MeasureSpec.AT_MOST) {
   mPaint.setTextSize(mTitleSize);
   mPaint.getTextBounds(mTitleText.toString(), 0, mTitleText.length(), mBound);
   float textwidth = mBound.width();
   int desired = (int) (getPaddingLeft() + textwidth + getPaddingRight());
   return Math.min(desired,MeasureSpec.getSize(lenth));
  }

  }
 } else {
  if (MeasureSpec.getMode(lenth) == MeasureSpec.EXACTLY) {
  //用户设置了精确尺寸,通过MeasureSpec.getSize()获得尺寸返回高度
  return MeasureSpec.getSize(lenth);
  } else {
  if (MeasureSpec.getMode(lenth) == MeasureSpec.AT_MOST) {
   //设置了warp_content，则需要我们自己计算
   mPaint.setTextSize(mTitleSize);
   mPaint.getTextBounds(mTitleText.toString(), 0, mTitleText.length(), mBound);
   float texthgeight = mBound.height();
   int desired = (int) (getPaddingTop() + texthgeight + getPaddingBottom());
   return Math.min(desired,MeasureSpec.getSize(lenth));
  }
  }
 }
 return 0;
 }

@Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 setMeasuredDimension(getMeasuredLength(widthMeasureSpec, true), getMeasuredLength(heightMeasureSpec, false));
 }

//xx表示widthMeasureSpec或者heightMeasureSpec

if(MeasureSpec.getMode(xx)==MeasureSpec.EXACTLY){
 //进入这里则代表设置了match_parent或者将控件的layout_width或layout_height指定为具体数值时如andorid:layout_width="100dp"，这样我们就可以直接通过MeasureSpec.getSize(xx)方法获得宽或高 
}else if(MeasureSpec.getMode(xx)==MeasureSpec.EXACTLY){
 //进入这里代表设置了wrap_content，那么则需要我们自己计算宽或高
}else{
 //进入这个则代表代表是未指定尺寸，这种情况不多，一般都是父控件是AdapterView，通过measure方法传入的模式
}

 @Override
 protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 padding_left = 0;
 mPaint.setColor(mBackground);
 canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mPaint);
 mPaint.setColor(mTitleColor);
 for (int i = 0; i < mTitleText.length(); i++) {
  randomTextStyle(mPaint);
  padding_left += mPaint.measureText(String.valueOf(mTitleText.charAt(i)))+10;
  canvas.drawText(String.valueOf(mTitleText.charAt(i)), padding_left, getHeight() / 2 + mBound.height() / 2, mPaint);
 }
 }
private void randomTextStyle(Paint paint) {
 paint.setFakeBoldText(random.nextBoolean()); //true为粗体，false为非粗体
 float skewX = random.nextInt(11) / 10;
 skewX = random.nextBoolean() ? skewX : -skewX;
 paint.setTextSkewX(skewX); //float类型参数，负数表示右斜，整数左斜
 paint.setUnderlineText(true); //true为下划线，false为非下划线
 paint.setStrikeThruText(false); //true为删除线，false为非删除线
 }

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:cq="http://schemas.android.com/apk/res-auto"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="horizontal">

 <chapter.com.rxjavachapter.CustomTitleView
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_centerInParent="true"
 android:padding="10dp"
 cq:titleBackground="@android:color/black"
 cq:titleColor="#ff0000"
 cq:titleLenth="4"
 cq:titleSize="10sp" />

</RelativeLayout>

 @Override
 public void onClick(View v) {
 randomText();
 postInvalidate();
 }
/**
 * 获得随机的字符串
 *
 * @return
 */
 private void randomText() {
 mTitleText = new StringBuffer();
 for (int i = 0; i < mLenth; i++) {
  mTitleText.append(data[(int) (Math.random() * data.length)]);
 }
 }

 /**
 * 获得到随机的值
 *
 * @return
 */
 public String getCode() {
 return mTitleText.toString();
 }

 /**
 * 判断是否相同
 *
 * @return
 */
 public boolean isEqual(String code) {
 if (code != null) {
  return code.toUpperCase().equals(getCode().toUpperCase()) ? true : false;
 } else {
  return false;
 }
 }