Android自定义控件实现时钟效果

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：

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);
 }
}

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：

public class ClockActivity extends Activity{

  private ClockView clockView;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.clock_layout);
   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：

<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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