先看下最終的效果
開始實(shí)現(xiàn)
新建一個(gè)ClockView集成View
public class ClockView extends View {
}
先重寫onMeasure方法闷旧，這里要先說一下View的測量模式刷允，一共有三種：
-
EXACTLY
即精確值模式椭豫，當(dāng)我們將控件的
layout_width屬性或layout_height屬性指定為具體數(shù)值時(shí)洽损，比如android:layout_width="100dp"蛉幸，或者指定為math_parent屬性時(shí)（占據(jù)父View的大行ち浮）孤页，系統(tǒng)使用的是EXACTLY模式。 -
AT_MOST
即最大值模式尿赚，當(dāng)控件的
layout_width屬性或layout_height屬性指定為wrap_content時(shí)散庶，控件大小一般隨著控件的子控件或內(nèi)容的變化而變化，此時(shí)控件的尺寸只要不超過父控件允許的最大尺寸即可凌净。 -
UNSPECIFIED
這個(gè)屬性比較奇怪——它不指定其大小測量模式悲龟，View想多大就多大，通常情況下在繪制自定義View時(shí)才會(huì)使用冰寻。
因?yàn)閂iew的
onMeasure方法只支持EXACTLY模式须教，當(dāng)layout_width和layout_height為wrap_content時(shí)，View的大小就顯得很奇怪了斩芭，如下圖轻腺。
所以我們重寫一下onMeasure方法可以指定View width、height的最小值
/**
* 當(dāng)布局為wrap_content時(shí)設(shè)置默認(rèn)長寬
* @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寫onDraw方法來繪制表盤划乖、刻度贬养、指針……，大致流程如下
- 畫表盤琴庵，用
drawCircle繪制一個(gè)圓作為表盤, 圓心坐標(biāo)為(getWidth()/2, getHeight()/2)误算，半徑為Math.min(getHeight()/2, getWidth()/2)。
//畫外圓
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);
- 畫刻度線迷殿，在這里我們可以利用一個(gè)`canvas.rotate'方法就可以不用計(jì)算角度了
//畫刻度線
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);
}
- 畫刻度上的數(shù)字
//刻度數(shù)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);
}
/**
* 根據(jù)角度和長度計(jì)算線段的起點(diǎn)和終點(diǎn)的坐標(biāo)
* @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;
}
- 畫指針
//畫指針
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);
- 畫圓心
//畫圓心
Paint paintCenter = new Paint();
paintCenter.setColor(Color.WHITE);
canvas.drawCircle(0, 0, 2, paintCenter);
最后只要啟動(dòng)一個(gè)無限循環(huán)的線程儿礼，每隔1秒針重繪一下View就能讓指針動(dòng)起來了
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();
}
};
全部測試代碼下載地址:
https://github.com/hellsam/clockdemo_android
歡迎留言交流，如有描述不當(dāng)或錯(cuò)誤的地方還請留言告知
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