自定义View(二)

一、概述

在上一篇分析了自定义View的基础知识，如果还是不清楚自定义View的请看上篇博客自定义View(一)。这篇主要是一个自定View的一个简单实例—-一个时钟效果。运行如下。



其实这个效果之前写过一篇网页版的，利用HTML5的context写的，有兴趣的可以看看。

简单分析下：

由图可以看出这个自定义View由一个圆，3个指针直线，然后就是断直线了，至于它的自动走动可以用post系列方法重复调用onDraw即可。这里的重点是canvas的rotate、translate两个方法的灵活使用。

二、代码

布局如下:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >

<com.lw.myclock.MyClock
android:layout_width="300dp"
android:layout_height="300dp"
/>

</RelativeLayout>

初始化方法，用来创建画笔，并且设置画笔的style和颜色

public void init(){
mPaint.setColor(Color.BLUE);
mPaint.setStyle(Style.STROKE);
//去掉锯齿
mPaint.setAntiAlias(true);
mPaint.setStrokeWidth(3);
}

获取当前时间

//获取当前时间
d = new Date();
int hours = d.getHours();
int minutes = d.getMinutes();

下面则是开始真正画了，主要是通过canvas的translate()来设置画布的中心点，然后调用rotat()e控制画布旋转来画出短线。

//1.画圆
canvas.translate(150, 150);
canvas.drawCircle(0, 0, radius, mPaint);
//2.画时钟刻度线
for (int i = 0; i <= 11 ; i++) {
mPaint.setStrokeWidth(3);
canvas.drawLine(0, -150, 0, -135, mPaint) ;
mPaint.setStrokeWidth(1);
if( i == 0 ){
canvas.drawText(12 + "",-5,-130,mPaint) ;
}else{
canvas.drawText(i + "",-5,-130,mPaint) ;
}
canvas.rotate(30) ;
}
//画分钟刻度线
for (int i = 0; i < 60 ; i++) {
mPaint.setStrokeWidth(1) ;
canvas.drawLine(0, -150, 0, -145, mPaint) ;
canvas.rotate(6);
}

这里每次开始画之前需要调用save()方法，每次画好之后需要调用restore()方法

//画时钟刻度指针
canvas.save() ;
mPaint.setStrokeWidth(4);
canvas.rotate(hours * 30 + (minutes * 6) * 30 / 360  );
canvas.drawLine(0, 10, 0, -90, mPaint);
canvas.restore() ;
//画分钟刻度指针
canvas.save() ;
mPaint.setStrokeWidth(2);
//初始化分钟指针，主要让其指定到12点位置
System.out.println("minutes:" + minutes * 6 );
canvas.rotate(minutes * 6 ) ;
canvas.drawLine(0, 10, 0, -100, mPaint);
canvas.restore() ;
//画秒钟刻度线
canvas.save() ;
mPaint.setStrokeWidth(1);
canvas.rotate(seconds * 6 );
System.out.println("seconds:" + seconds);
canvas.drawLine(0, 10, 0, -120, mPaint) ;
canvas.restore() ;
//画中心圆点
canvas.save() ;
mPaint.setStrokeWidth(3);
canvas.drawCircle(0, 0, 2, mPaint);
canvas.restore() ;

这里比较复杂的是时钟角度的变化

canvas.rotate(hours * 30 + (minutes * 6) * 30 / 360  ) ;

假如此时时间是11点30分，11点则是hours * 30，30分钟旋转的角度则是 (minutes * 6) * 30 / 360 。

然后就开始调用post方法每一个1s调用。

全部代码如下：

package com.lw.myclock;

import java.util.Date;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.util.AttributeSet;
import android.view.View;
/**
* 自定义时钟
* @author lw
*
*/
public class MyClock extends View {

private Paint mPaint = new Paint();
private Date d;

public MyClock(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public MyClock(Context context) {
this(context,null);
}
public void init(){
mPaint.setColor(Color.BLUE);
mPaint.setStyle(Style.STROKE);
//去掉锯齿
mPaint.setAntiAlias(true);
mPaint.setStrokeWidth(3);
}
@Override
protected void onDraw(final Canvas canvas) {
super.onDraw(canvas);

int width = getWidth();
int height = getHeight();
int paddingBottom = getPaddingBottom();
int paddingTop = getPaddingTop();
int paddingLeft = getPaddingLeft();
int paddingRight = getPaddingRight();
width = width - paddingLeft - paddingRight ;
height = height - paddingBottom - paddingTop ;
//300 300
//获取当前时间
d = new Date();
int hours = d.getHours();
int minutes = d.getMinutes();
int seconds = d.getSeconds();
int radius = Math.min(width, height) / 2 ;//1.画圆
canvas.translate(150, 150);
canvas.drawCircle(0, 0, radius, mPaint);
//2.画时钟刻度线
for (int i = 0; i <= 11 ; i++) {
mPaint.setStrokeWidth(3);
canvas.drawLine(0, -150, 0, -135, mPaint) ;
mPaint.setStrokeWidth(1);
if( i == 0 ){
canvas.drawText(12 + "",-5,-130,mPaint) ;
}else{
canvas.drawText(i + "",-5,-130,mPaint) ;
}
canvas.rotate(30) ;
}
//画分钟刻度线
for (int i = 0; i < 60 ; i++) {
mPaint.setStrokeWidth(1) ;
canvas.drawLine(0, -150, 0, -145, mPaint) ;
canvas.rotate(6);
}//画时钟刻度指针
canvas.save() ;
mPaint.setStrokeWidth(4);
canvas.rotate(hours * 30 + (minutes * 6) * 30 / 360  ) ;
canvas.drawLine(0, 10, 0, -90, mPaint);
canvas.restore() ;
//画分钟刻度指针
canvas.save() ;
mPaint.setStrokeWidth(2);
//初始化分钟指针，主要让其指定到12点位置
System.out.println("minutes:" + minutes * 6 );
canvas.rotate(minutes * 6 ) ;
canvas.drawLine(0, 10, 0, -100, mPaint);
canvas.restore() ;
//画秒钟刻度线
canvas.save() ;
mPaint.setStrokeWidth(1);
canvas.rotate(seconds * 6 );
System.out.println("seconds:" + seconds);
canvas.drawLine(0, 10, 0, -120, mPaint) ;
canvas.restore() ;
//画中心圆点
canvas.save() ;
mPaint.setStrokeWidth(3);
canvas.drawCircle(0, 0, 2, mPaint);
canvas.restore() ;
//递归调用
postInvalidateDelayed(1000) ;
}
}

OK，这个简单实例到这就结束了。

源码下载