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>

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希望本文所述对大家Android程序设计有所帮助。