本文实例讲述了Android编程基于自定义控件实现时钟功能的方法。分享给大家供大家参考，具体如下：
在学习安卓群英传自定义控件章节的时候，有一个例子是绘制时钟，在实现了书上的例子后就想看这个时钟能不能动起来。
这里选择延迟一秒发送消息重绘view来实现的动画，对外提供了开启时钟，关闭时钟的方法，当activity执行onResume方法的时候，执行startClock()方法，当移除view或activity执行onStop方法的时候可以执行stopClock()方法。
首先根据view的宽高来确定圆心的位置，并画出一个圆。再通过view高度的一半减去圆的半径，确定刻度的起始位置，选择刻度的长度并绘制出来。然后再刻度下方绘制出数字。最终将画布进行旋转，时钟总共有60个刻度，循环旋转，每次旋转6度即可。
最后是绘制指针，通过计算算出指针对应每个刻度的X,Y坐标并绘制直线。
代码实现
自定义控件的代码（ClockView.java）：
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);
}
}
Point.java：
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;
}
}
Acitivity（ClockActivity.java）：
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布局（main.xml）：
<?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>
更多关于Android相关内容感兴趣的读者可查看本站专题：《Android开发入门与进阶教程》、《Android调试技巧与常见问题解决方法汇总》、《Android基本组件用法总结》、《Android视图View技巧总结》、《Android布局layout技巧总结》及《Android控件用法总结》
希望本文所述对大家Android程序设计有所帮助。
