public class ClockView extends View{
 private Paint circlePaint,dialPaint,numberPaint;
 //view 的寬高
 private float mWidth,mHeight;
 //圓的半徑
 private float circleRadius;
 //圓心X,Y坐標(biāo)
 private float circleX,circleY;
 private int second,minute;
 private double hour;

 private Handler handler = new Handler(Looper.getMainLooper()){
  @Override
  public void handleMessage(Message msg) {
   super.handleMessage(msg);
   if(msg.what==0){
    invalidate();
   }
  }
 };

 public ClockView(Context context, AttributeSet attrs) {
  super(context, attrs);
  initPaint();
 }

 private void initPaint(){
  //刻盤圓，小時(shí)刻度，時(shí)針和分針的畫筆
  circlePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
  circlePaint.setColor(Color.BLACK);
  circlePaint.setStyle(Paint.Style.STROKE);
  circlePaint.setStrokeWidth(10);

  //分鐘刻度的畫筆
  dialPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
  dialPaint.setColor(Color.BLACK);
  dialPaint.setStrokeWidth(5);

  //數(shù)字的畫筆
  numberPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
  numberPaint.setColor(Color.BLACK);
  numberPaint.setStrokeWidth(5);
  numberPaint.setTextSize(30);
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  mWidth = getMeasuredWidth();
  mHeight = getMeasuredHeight();
  if(mWidth<mHeight){
   //圓的半徑為view的寬度的一半再減9，防止貼邊
   circleRadius = mWidth/2-9;
   circleX = mWidth/2;
   circleY = mHeight/2;
  } else{
   circleRadius = mHeight/2-9;
   circleX = mWidth/2;
   circleY = mHeight/2;
  }
 }

 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  setTimes();
  drawCirclePoint(canvas);
  drawCircle(canvas);
  drawDial(canvas);
  drawPointer(canvas);
 }

 /**圓心
  * @param canvas
  */
 private void drawCirclePoint(Canvas canvas){
  canvas.drawCircle(circleX,circleY,5,circlePaint);
 }

 private void drawCircle(Canvas canvas){
  canvas.drawCircle(circleX,circleY,circleRadius,circlePaint);
 }

 /**畫刻度及時(shí)間
  * @param canvas
  */
 private void drawDial(Canvas canvas){
  //時(shí)鐘用長(zhǎng)一點(diǎn)的刻度，畫筆用畫圓的畫筆
  Point hourStartPoint = new Point(circleX,circleY-circleRadius);
  Point hourEndPoint = new Point(circleX,circleY-circleRadius+40);
  //分鐘的刻度要稍微短一些，畫筆用畫圓的畫筆
  Point startPoint2 = new Point(circleX,circleY-circleRadius);
  Point endPoint2 = new Point(circleX,circleY-circleRadius+10);
  //開(kāi)始畫刻度和數(shù)字，總共60個(gè)刻度，12個(gè)時(shí)鐘刻度，被5整除畫一個(gè)時(shí)鐘刻度，被其余的為分針刻度
  String clockNumber;
  for(int i=0;i<60;i++){
   if(i%5==0){
    if(i==0){
     clockNumber = "12";
    } else{
     clockNumber = String.valueOf(i/5);
    }
    //時(shí)針刻度
    canvas.drawLine(hourStartPoint.getX(),hourStartPoint.getY(),hourEndPoint.getX(),hourEndPoint.getY(),circlePaint);
    //畫數(shù)字，需在時(shí)針刻度末端加30
    canvas.drawText(clockNumber,circleX-numberPaint.measureText(clockNumber)/2,hourEndPoint.getY()+30,numberPaint);
   } else{
    //畫分針刻度
    canvas.drawLine(startPoint2.getX(),startPoint2.getY(),endPoint2.getX(),endPoint2.getY(),circlePaint);
   }
   //畫布旋轉(zhuǎn)6度
   canvas.rotate(360/60,circleX,circleY);
  }
 }

 /**畫指針
  * X點(diǎn)坐標(biāo) cos(弧度)*r
  * Y點(diǎn)坐標(biāo) sin(弧度)*r
  * toRadians將角度轉(zhuǎn)成弧度
  * 安卓坐標(biāo)系與數(shù)學(xué)坐標(biāo)系不同的地方是X軸是相反的，所以為了調(diào)整方向，需要將角度+270度
  * @param canvas
  */
 private void drawPointer(Canvas canvas){
  canvas.translate(circleX,circleY);
  float hourX = (float) Math.cos(Math.toRadians(hour*30+270))*circleRadius*0.5f;
  float hourY = (float) Math.sin(Math.toRadians(hour*30+270))*circleRadius*0.5f;
  float minuteX = (float) Math.cos(Math.toRadians(minute*6+270))*circleRadius*0.8f;
  float minuteY = (float) Math.sin(Math.toRadians(minute*6+270))*circleRadius*0.8f;
  float secondX = (float) Math.cos(Math.toRadians(second*6+270))*circleRadius*0.8f;
  float secondY = (float) Math.sin(Math.toRadians(second*6+270))*circleRadius*0.8f;
  canvas.drawLine(0,0,hourX,hourY,circlePaint);
  canvas.drawLine(0,0,minuteX,minuteY,circlePaint);
  canvas.drawLine(0,0,secondX,secondY,dialPaint);
  //一秒重繪一次
  handler.sendEmptyMessageDelayed(0,1000);
 }

 public void startClock(){
  setTimes();
  invalidate();
 }

 private void setTimes(){
  Date date = new Date();
  Calendar calendar = Calendar.getInstance();
  calendar.setTime(date);
  second = getTimes(date,Calendar.SECOND);
  minute = getTimes(date,Calendar.MINUTE);
  hour = getTimes(date,Calendar.HOUR)+minute/12*0.2;
 }

 private int getTimes(Date date,int calendarField){
  Calendar calendar = Calendar.getInstance();
  calendar.setTime(date);
  return calendar.get(calendarField);
 }

 public void stopClock(){
  handler.removeMessages(0);
 }
}

public Point(float x, float y) {
 this.x = x;
 this.y = y;
}

public float getX() {
 return x;
}

public void setX(float x) {
 this.x = x;
}

public float getY() {
 return y;
}

public void setY(float y) {
 this.y = y;
}

public class ClockActivity extends Activity{

  private ClockView clockView;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.clock_layout);
   clockView = (ClockView) findViewById(R.id.clock);
  }

  @Override
  protected void onResume() {
   super.onResume();
   clockView.startClock();
  }

  @Override
  protected void onStop() {
   super.onStop();
   clockView.stopClock();
  }
 }

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical" android:layout_width="match_parent"
 android:gravity="center"
 android:layout_height="match_parent">
 <com.example.customview.view.ClockView
  android:layout_width="match_parent"
  android:id="@+id/clock"
  android:layout_height="match_parent" />
</LinearLayout>