自定义时钟的实现过程

配置文件：

 android:orientation="vertical" android:layout_width="fill_parent"
 android:layout_height="fill_parent" android:background="#FFF"
 android:gravity="center">
   android:layout_width="wrap_content" android:layout_height="wrap_content"
  clockImageSrc="@drawable/clock1" scale="0.75" handCenterWidthScale="0.477"
  handCenterHeightScale="0.512" minuteHandSize="54" hourHandSize="40"/>

代码：

import java.util.Calendar;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.View;

public class HandClock extends View implements Runnable
{
 private int clockImageResourceId;
 private Bitmap bitmap;
 private float scale;
 private float handCenterWidthScale;
 private float handCenterHeightScale;
 private int minuteHandSize;
 private int hourHandSize;
 private Handler handler = new Handler();

 @Override
 public void run()
 {
  // 重新绘制View
  invalidate();
  // 重新设置定时器，在60秒后调用run方法
  handler.postDelayed(this, 60 * 1000);
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
 {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  // 根据图像的实际大小等比例设置View的大小
  setMeasuredDimension((int) (bitmap.getWidth() * scale), (int) (bitmap
    .getHeight() * scale));
 }

 @Override
 protected void onDraw(Canvas canvas)
 {
  super.onDraw(canvas);
  Paint paint = new Paint();
  Rect src = new Rect();
  Rect target = new Rect();
  src.left = 0;
  src.top = 0;
  src.right = bitmap.getWidth();
  src.bottom = bitmap.getHeight();

  target.left = 0;
  target.top = 0;
  target.bottom = (int) (src.bottom * scale);
  target.right = (int) (src.right * scale);
  // 画表盘图像
  canvas.drawBitmap(bitmap, src, target, paint);
  // 计算表盘中心点的横纵坐标
  float centerX = bitmap.getWidth() * scale * handCenterWidthScale;
  float centerY = bitmap.getHeight() * scale * handCenterHeightScale;
  // 表表盘中心点画一个半径为5的实心圆圈
  canvas.drawCircle(centerX, centerY, 5, paint);
  // 设置分针为3个象素粗
  paint.setStrokeWidth(3);
  Calendar calendar = Calendar.getInstance();
  int currentMinute = calendar.get(Calendar.MINUTE);
  int currentHour = calendar.get(Calendar.HOUR);
  // 计算分针和时间的角度
  double minuteRadian = Math
    .toRadians((360 - ((currentMinute * 6) - 90)) % 360);
  double hourRadian = Math.toRadians((360 - ((currentHour * 30) - 90))
    % 360 - (30 * currentMinute / 60));
  // 在表盘上画分针
  canvas.drawLine(centerX, centerY, (int) (centerX + minuteHandSize
    * Math.cos(minuteRadian)), (int) (centerY - minuteHandSize
    * Math.sin(minuteRadian)), paint);
  // 设置实针为4个象素粗
  paint.setStrokeWidth(4);
  // 在表盘上画分针
  canvas.drawLine(centerX, centerY, (int) (centerX + hourHandSize
    * Math.cos(hourRadian)), (int) (centerY - hourHandSize
    * Math.sin(hourRadian)), paint);
 }

 public HandClock(Context context, AttributeSet attrs)
 {
  super(context, attrs);
  // 读取相应的属性值
  clockImageResourceId = attrs.getAttributeResourceValue(null,
    "clockImageSrc", 0);
  if (clockImageResourceId > 0)
   bitmap = BitmapFactory.decodeResource(getResources(),
     clockImageResourceId);
  scale = attrs.getAttributeFloatValue(null, "scale", 1);
  handCenterWidthScale = attrs.getAttributeFloatValue(null,
    "handCenterWidthScale", bitmap.getWidth() / 2);
  handCenterHeightScale = attrs.getAttributeFloatValue(null,
    "handCenterHeightScale", bitmap.getHeight() / 2);
  //  在读取分针和时针长度后，将其值按图像的缩放比例进行缩放
  minuteHandSize = (int) (attrs.getAttributeIntValue(null,
    "minuteHandSize", 0) * scale);
  hourHandSize = (int) (attrs.getAttributeIntValue(null, "hourHandSize",
    0) * scale);
  int currentSecond = Calendar.getInstance().get(Calendar.SECOND);
  //  将定时器设在0分时执行run方法
  handler.postDelayed(this, (60 - currentSecond) * 1000);
 }

 @Override
 protected void onDetachedFromWindow()
 {
  super.onDetachedFromWindow();
  //  删除回调类
  handler.removeCallbacks(this);
 }

}