Android画个时钟玩玩

先看下最终的效果

 

开始实现
新建一个clockview集成view

  public class clockview extends view {

  }

先重写onmeasure方法，这里要先说一下view的测量模式，一共有三种：
1、exactly

即精确值模式，当我们将控件的layout_width属性或layout_height属性指定为具体数值时，比如android:layout_width="100dp"，或者指定为math_parent属性时（占据父view的大小），系统使用的是exactly模式。

2、at_most

即最大值模式，当控件的layout_width属性或layout_height属性指定为wrap_content时，控件大小一般随着控件的子控件或内容的变化而变化，此时控件的尺寸只要不超过父控件允许的最大尺寸即可。

3、unspecified

这个属性比较奇怪——它不指定其大小测量模式，view想多大就多大，通常情况下在绘制自定义view时才会使用。

因为view的onmeasure方法只支持exactly模式，当layout_width和layout_height为wrap_content时，view的大小就显得很奇怪了，如下图。

所以我们重写一下onmeasure方法可以指定view width、height的最小值

  /**
   * 当布局为wrap_content时设置默认长宽
   * @param widthmeasurespec
   * @param heightmeasurespec
   */
  @override
  protected void onmeasure(int widthmeasurespec, int heightmeasurespec) {
    setmeasureddimension(measure(widthmeasurespec), measure(heightmeasurespec));
  }

  private int measure(int origin){
    int result = default_min_width;
    int specmode = measurespec.getmode(origin);
    int specsize = measurespec.getsize(origin);
    if(specmode == measurespec.exactly){
      result = specsize;
    }else{
      if(specmode == measurespec.at_most){
        result = math.min(result, specsize);
      }
    }
    return result;
  }

下面就是最重要的重写ondraw方法来绘制表盘、刻度、指针……，大致流程如下
1、画表盘，用drawcircle绘制一个圆作为表盘, 圆心坐标为(getwidth()/2, getheight()/2)，半径为math.min(getheight()/2, getwidth()/2)。

//画外圆
float borderwidth = default_border_width;
paint paintcircle = new paint();
paintcircle.setstyle(paint.style.stroke);
paintcircle.setantialias(true);
paintcircle.setstrokewidth(borderwidth);
canvas.drawcircle(getwidth() / 2, getheight() / 2, math.min(getheight() / 2, getwidth() / 2) - borderwidth / 2, paintcircle);

2、画刻度线，在这里我们可以利用一个`canvas.rotate'方法就可以不用计算角度了

//画刻度线
float degreelength = 0f;
paint paintdegree = new paint();
paintdegree.setantialias(true);
for(int i=0;i<60;i++){
  if(i % 5 == 0){
    paintdegree.setstrokewidth(6);
    degreelength = default_long_degree_length;
  }else{
    paintdegree.setstrokewidth(3);
    degreelength = default_short_degree_length;
  }
  canvas.drawline(getwidth()/2, math.abs(getwidth()/2 - getheight()/2), getwidth()/2, math.abs(getwidth()/2 - getheight()/2) + degreelength, paintdegree);
  canvas.rotate(360/60, getwidth()/2, getheight()/2);
}

3、画刻度上的数字

//刻度数字
int degressnumbersize = 30;
canvas.translate(getwidth() / 2, getheight() / 2);
paint paintdegreenumber = new paint();
paintdegreenumber.settextalign(paint.align.center);
paintdegreenumber.settextsize(degressnumbersize);
paintdegreenumber.setfakeboldtext(true);
for(int i=0;i<12;i++){
  float[] temp = calculatepoint((i+1)*30, r - default_long_degree_length - degressnumbersize/2 - 15);
  canvas.drawtext((i+1)+"", temp[2], temp[3] + degressnumbersize/2-6, paintdegreenumber);
}

/**
 * 根据角度和长度计算线段的起点和终点的坐标
 * @param angle
 * @param length
 * @return
 */
private float[] calculatepoint(float angle, float length){
  float[] points = new float[4];
  if(angle <= 90f){
    points[0] = -(float) math.sin(angle*math.pi/180) * default_point_back_length;
    points[1] = (float) math.cos(angle*math.pi/180) * default_point_back_length;
    points[2] = (float) math.sin(angle*math.pi/180) * length;
    points[3] = -(float) math.cos(angle*math.pi/180) * length;
  }else if(angle <= 180f){
    points[0] = -(float) math.cos((angle-90)*math.pi/180) * default_point_back_length;
    points[1] = -(float) math.sin((angle-90)*math.pi/180) * default_point_back_length;
    points[2] = (float) math.cos((angle-90)*math.pi/180) * length;
    points[3] = (float) math.sin((angle-90)*math.pi/180) * length;
  }else if(angle <= 270f){
    points[0] = (float) math.sin((angle-180)*math.pi/180) * default_point_back_length;
    points[1] = -(float) math.cos((angle-180)*math.pi/180) * default_point_back_length;
    points[2] = -(float) math.sin((angle-180)*math.pi/180) * length;
    points[3] = (float) math.cos((angle-180)*math.pi/180) * length;
  }else if(angle <= 360f){
    points[0] = (float) math.cos((angle-270)*math.pi/180) * default_point_back_length;
    points[1] = (float) math.sin((angle-270)*math.pi/180) * default_point_back_length;
    points[2] = -(float) math.cos((angle-270)*math.pi/180) * length;
    points[3] = -(float) math.sin((angle-270)*math.pi/180) * length;
  }
  return points;
}

4、画指针

//画指针
paint painthour = new paint();
painthour.setantialias(true);
painthour.setstrokewidth(15);
paint paintminute = new paint();
paintminute.setantialias(true);
paintminute.setstrokewidth(10);
paint paintsecond = new paint();
paintsecond.setantialias(true);
paintsecond.setstrokewidth(5);
calendar now = calendar.getinstance();
float[] hourpoints = calculatepoint(now.get(calendar.hour_of_day)%12/12f*360, hourpointerlength);
canvas.drawline(hourpoints[0], hourpoints[1], hourpoints[2], hourpoints[3], painthour);
float[] minutepoints = calculatepoint(now.get(calendar.minute)/60f*360, minutepointerlength);
canvas.drawline(minutepoints[0], minutepoints[1], minutepoints[2], minutepoints[3], paintminute);
float[] secondpoints = calculatepoint(now.get(calendar.second)/60f*360, secondpointerlength);
canvas.drawline(secondpoints[0], secondpoints[1], secondpoints[2], secondpoints[3], paintsecond);

5、画圆心

//画圆心
paint paintcenter = new paint();
paintcenter.setcolor(color.white);
canvas.drawcircle(0, 0, 2, paintcenter);
最后只要启动一个无限循环的线程，每隔1秒针重绘一下view就能让指针动起来了
private thread timethread = new thread() {
  @override
  public void run() {
    try {
      while(true){
        updatehandler.sendemptymessage(0);
        thread.sleep(1000);
      }
    } catch (interruptedexception e) {
      e.printstacktrace();
    }
  }
};

private handler updatehandler = new handler() {
  @override
  public void handlemessage(message msg) {
    invalidate();
  }
};

以上就是教大家如何利用android画个时钟的详细步骤代码，希望对大家的学习android软件编程有所帮助。