<?xml version="1.0" encoding="utf-8"?>
<resources>
 <attr name="textColor" format="color"/>
 <attr name="textContent" format="string"/>
 <attr name="textSize" format="dimension"/>

 <declare-styleable name="VerificationCodeView">
 <attr name="textContent" />
 <attr name="textColor" />
 <attr name="textSize" />
 </declare-styleable>
</resources>

public class VerificationCodeView extends View {
 /**
 * 文本
 */
 private String mTitleText;
 /**
 * 文本的顏色
 */
 private int mTextColor;
 /**
 * 文本的大小
 */
 private int mTextSize;

 /**
 * 繪制時(shí)控制文本繪制的范圍
 */
 private Rect mBound;
 /**
 * 初始化畫筆
 */
 private Paint mTextPaint;
 private Paint mPointPaint;
 private Paint mPathPaint;
 /**
 * 干擾點(diǎn)坐標(biāo)的集合
 */
 private ArrayList<PointF> mPoints = new ArrayList<PointF>();
 /**
 * 繪制貝塞爾曲線的路徑集合
 */
 private ArrayList<Path> mPaths = new ArrayList<Path>();

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

 public VerificationCodeView(Context context, AttributeSet attributeSet) {
 this(context, attributeSet, 0);
 }

 public VerificationCodeView(Context context, AttributeSet attributeSet, int defStyle) {
 super(context, attributeSet, defStyle);
 TypedArray typedArray = context.getTheme().obtainStyledAttributes(attributeSet, R.styleable.VerificationCodeView, defStyle, 0);
 int size = typedArray.getIndexCount();
 for (int i = 0; i < size; i++) {
  int content = typedArray.getIndex(i);
  switch (content) {
  case R.styleable.VerificationCodeView_textContent:
   mTitleText = typedArray.getString(content);
   break;
  case R.styleable.VerificationCodeView_textColor:
   mTextColor = typedArray.getColor(content, Color.BLACK);
   break;
  case R.styleable.VerificationCodeView_textSize:
   // 默認(rèn)設(shè)置為16sp，TypeValue也可以把sp轉(zhuǎn)化為px
   mTextSize = typedArray.getDimensionPixelSize(content, (int) TypedValue.applyDimension(
    TypedValue.COMPLEX_UNIT_SP, 16, getResources().getDisplayMetrics()));
   break;
  }
 }
 typedArray.recycle();
 //設(shè)置點(diǎn)擊事件變換數(shù)字
 this.setOnClickListener(new OnClickListener() {
  @Override
  public void onClick(View v) {
  mTitleText = randomText();
  postInvalidate();
  }
 });
 }

 /**
 * EXACTLY：一般是設(shè)置了明確的值或者是MATCH_PARENT
 * AT_MOST：表示子布局限制在一個(gè)最大值內(nèi)，一般為WARP_CONTENT
 * UNSPECIFIED：表示子布局想要多大就多大，很少使用
 *
 * @param widthMeasureSpec
 * @param heightMeasureSpec
 */
 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 int widthMode = MeasureSpec.getMode(widthMeasureSpec);
 int widthSize = MeasureSpec.getSize(widthMeasureSpec);
 int heightMode = MeasureSpec.getMode(heightMeasureSpec);
 int heightSize = MeasureSpec.getSize(heightMeasureSpec);
 //用來設(shè)置要畫的布局的大小
 if (widthMode != MeasureSpec.EXACTLY) {
  widthSize = (int) (getPaddingLeft() + mBound.width() + getPaddingRight());
 }

 if (heightMode != MeasureSpec.EXACTLY) {
  heightSize = (int) (getPaddingTop() + mBound.height() + getPaddingBottom());
 }

 setMeasuredDimension(widthSize, heightSize);
 }

 @Override
 protected void onDraw(Canvas canvas) {
 //生成隨機(jī)的背景顏色
 mTextPaint.setColor(Color.YELLOW);
 canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mTextPaint);
 //生成隨機(jī)的文字顏色
 mTextPaint.setColor(mTextColor);
 //將文字畫在布局的中間
 canvas.drawText(mTitleText, getWidth() / 2 - mBound.width() / 2, getHeight() / 2 + mBound.height() / 2, mTextPaint);
 }
 /**
 * 生成隨機(jī)的四位數(shù)字驗(yàn)證碼
 *
 * @return
 */
 private String randomText() {
 Random random = new Random();
 Set<Integer> set = new HashSet<Integer>();
 while (set.size() < 4) {
  int randomInt = random.nextInt(10);
  set.add(randomInt);
 }
 StringBuffer sb = new StringBuffer();
 for (Integer i : set) {
  sb.append("" + i);
 }

 return sb.toString();
 }
}

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

 <com.example.aotuman.verification.view.VerificationCodeView
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:paddingTop="10dp"
 android:paddingBottom="10dp"
 android:paddingLeft="10dp"
 android:paddingRight="10dp"
 verification:textContent="3712"
 verification:textColor="#ff0000"
 verification:textSize="40sp" />
</RelativeLayout>

@Override
 protected void onDraw(Canvas canvas) {
 initData();
 Random mRandom = new Random();
 //生成隨機(jī)的背景顏色
 mTextPaint.setARGB(255, mRandom.nextInt(200) + 20, mRandom.nextInt(200) + 20, mRandom.nextInt(200) + 20);
 canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mTextPaint);
 //生成隨機(jī)的文字顏色
 mTextPaint.setARGB(255, mRandom.nextInt(200) + 20, mRandom.nextInt(200) + 20, mRandom.nextInt(200) + 20);
 //將文字畫在布局的中間
 canvas.drawText(mTitleText, getWidth() / 2 - mBound.width() / 2, getHeight() / 2 + mBound.height() / 2, mTextPaint);

 // 產(chǎn)生干擾效果1 -- 干擾點(diǎn)
 for (PointF pointF : mPoints) {
  mPointPaint.setARGB(255, mRandom.nextInt(200) + 20, mRandom.nextInt(200) + 20, mRandom.nextInt(200) + 20);
  canvas.drawPoint(pointF.x, pointF.y, mPointPaint);
 }
 // 產(chǎn)生干擾效果2 -- 干擾線
 for (Path path : mPaths) {
  mPathPaint.setARGB(255, mRandom.nextInt(200) + 20, mRandom.nextInt(200) + 20, mRandom.nextInt(200) + 20);
  canvas.drawPath(path, mPathPaint);
 }

 private void initData() {
 Random mRandom = new Random();
 // 獲取控件的寬和高，此時(shí)已經(jīng)測(cè)量完成
 int mHeight = getHeight();
 int mWidth = getWidth();
 mPoints.clear();
 // 生成干擾點(diǎn)坐標(biāo)
 for (int i = 0; i < 150; i++) {
  PointF pointF = new PointF(mRandom.nextInt(mWidth) + 10, mRandom.nextInt(mHeight) + 10);
  mPoints.add(pointF);
 }
 mPaths.clear();
 // 生成干擾線坐標(biāo)
 for (int i = 0; i < 2; i++) {
  Path path = new Path();
  int startX = mRandom.nextInt(mWidth / 3) + 10;
  int startY = mRandom.nextInt(mHeight / 3) + 10;
  int endX = mRandom.nextInt(mWidth / 2) + mWidth / 2 - 10;
  int endY = mRandom.nextInt(mHeight / 2) + mHeight / 2 - 10;
  path.moveTo(startX, startY);
  path.quadTo(Math.abs(endX - startX) / 2, Math.abs(endY - startY) / 2, endX, endY);
  mPaths.add(path);
 }
 }

 private void init() {
 // 初始化文字畫筆
 /**
  * 獲得繪制文本的寬和高
  */
 mTextPaint = new Paint();
 mTextPaint.setTextSize(mTextSize);

 mBound = new Rect();
 //獲取到的存在mBound里面
 mTextPaint.getTextBounds(mTitleText, 0, mTitleText.length(), mBound);
 // 初始化干擾點(diǎn)畫筆
 mPointPaint = new Paint();
 mPointPaint.setStrokeWidth(6);
 mPointPaint.setStrokeCap(Paint.Cap.ROUND); // 設(shè)置斷點(diǎn)處為圓形
 // 初始化干擾線畫筆
 mPathPaint = new Paint();
 mPathPaint.setStrokeWidth(5);
 mPathPaint.setColor(Color.GRAY);
 mPathPaint.setStyle(Paint.Style.STROKE); // 設(shè)置畫筆為空心
 mPathPaint.setStrokeCap(Paint.Cap.ROUND); // 設(shè)置斷點(diǎn)處為圓形
 }