Android编程基于自定义控件实现时钟功能的方法

package com.example.clock;
import java.util.Calendar;
import java.util.Date;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.AttributeSet;
import android.view.View;
public class ClockView extends View {
  private Paint circlePaint, dialPaint, numberPaint;
  // view 的宽高
  private float mWidth, mHeight;
  // 圆的半径
  private float circleRadius;
  // 圆心X,Y坐标
  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() {
    // 刻盘圆，小时刻度，时针和分针的画笔
    circlePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    circlePaint.setColor(Color.BLACK);
    circlePaint.setStyle(Paint.Style.STROKE);
    circlePaint.setStrokeWidth(10);
    // 分钟刻度的画笔
    dialPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    dialPaint.setColor(Color.BLACK);
    dialPaint.setStrokeWidth(5);
    // 数字的画笔
    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) {
      // 圆的半径为view的宽度的一半再减9，防止贴边
      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);
  }
  /**
   * 圆心
   * 
   * @param canvas
   */
  private void drawCirclePoint(Canvas canvas) {
    canvas.drawCircle(circleX, circleY, 5, circlePaint);
  }
  private void drawCircle(Canvas canvas) {
    canvas.drawCircle(circleX, circleY, circleRadius, circlePaint);
  }
  /**
   * 画刻度及时间
   * 
   * @param canvas
   */
  private void drawDial(Canvas canvas) {
    // 时钟用长一点的刻度，画笔用画圆的画笔
    Point hourStartPoint = new Point(circleX, circleY - circleRadius);
    Point hourEndPoint = new Point(circleX, circleY - circleRadius + 40);
    // 分钟的刻度要稍微短一些，画笔用画圆的画笔
    Point startPoint2 = new Point(circleX, circleY - circleRadius);
    Point endPoint2 = new Point(circleX, circleY - circleRadius + 10);
    // 开始画刻度和数字，总共60个刻度，12个时钟刻度，被5整除画一个时钟刻度，被其余的为分针刻度
    String clockNumber;
    for (int i = 0; i < 60; i++) {
      if (i % 5 == 0) {
        if (i == 0) {
          clockNumber = "12";
        } else {
          clockNumber = String.valueOf(i / 5);
        }
        // 时针刻度
        canvas.drawLine(hourStartPoint.getX(), hourStartPoint.getY(),
            hourEndPoint.getX(), hourEndPoint.getY(), circlePaint);
        // 画数字，需在时针刻度末端加30
        canvas.drawText(clockNumber,
            circleX - numberPaint.measureText(clockNumber) / 2,
            hourEndPoint.getY() + 30, numberPaint);
      } else {
        // 画分针刻度
        canvas.drawLine(startPoint2.getX(), startPoint2.getY(),
            endPoint2.getX(), endPoint2.getY(), circlePaint);
      }
      // 画布旋转6度
      canvas.rotate(360 / 60, circleX, circleY);
    }
  }
  /**
   * 画指针 X点坐标 cos(弧度)*r Y点坐标 sin(弧度)*r toRadians将角度转成弧度
   * 安卓坐标系与数学坐标系不同的地方是X轴是相反的，所以为了调整方向，需要将角度+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);
    // 一秒重绘一次
    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);
  }
}

package com.example.clock;
public class Point {
  private float x;
  private float y;
  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;
  }
}

package com.example.clock;
import android.app.Activity;
import android.os.Bundle;
public class ClockActivity extends Activity {
  /** Called when the activity is first created. */
  private ClockView clockView;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    clockView = (ClockView) findViewById(R.id.clock);
  }
  @Override
  protected void onResume() {
    super.onResume();
    clockView.startClock();
  }
  @Override
  protected void onStop() {
    super.onStop();
    clockView.stopClock();
  }
}

<?xml version="1.0" encoding="utf-8"?>
<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>