Android为开发者提供了大量的控件,这些控件只能满足一般性的需求,有时候需要开发者重新定制控件。控件的定制有三种形式:对原有控件的重写;对原有控件进行组合;自定义新的控件。Android中所有控件类都是View的子类。
本例主要是讲一个自定义时钟控件,该控件直接继承View类。
1.控件类
首先需要编写控件类,该类继承View类,并实现接口Runnable。时钟控件主要包含的参数:clockimageresourceid,scale,handcenterwidthscale,handcenterheightscale,minutehandsize,hourhandsize。
1 public class HandClock extends View implements Runnable {
2
3 private int clockImageResourceId;//图像资源id
4 private Bitmap bitmap;//图像资源
5 private float scale;//图像显示的比例
6 private float handCenterWidthScale;//横坐标显示比例
7 private float handCenterHeightScale;//纵坐标显示比例
8 private int minuteHandSize;//分钟长度
9 private int hourHandSize;//时针长度
10 private Handler hanlder=new Handler();
11 public HandClock(Context context, AttributeSet attrs) {
12 super(context, attrs);
13 // TODO Auto-generated constructor stub
14 //读取属性值
15 clockImageResourceId=attrs.getAttributeResourceValue(null, "clockImageSrc", 0);
16 if(clockImageResourceId>0)
17 {
18 bitmap=BitmapFactory.decodeResource(getResources(), clockImageResourceId);
19 }
20 scale=attrs.getAttributeFloatValue(null, "scale", 1);
21 handCenterWidthScale=attrs.getAttributeFloatValue(null, "handCenterWidthScale", bitmap.getWidth()/2);
22 handCenterHeightScale=attrs.getAttributeFloatValue(null, "handCenterHeightScale", bitmap.getHeight()/2);
23 minuteHandSize=(int)(attrs.getAttributeIntValue(null, "minuteHandSize",0)*scale);
24 hourHandSize=(int)(attrs.getAttributeIntValue(null, "hourHandSize", 0)*scale);
25 int curentSecond=Calendar.getInstance().get(Calendar.SECOND);
26 hanlder.postDelayed(this, (60-curentSecond)*1000);
27 }
28
29 protected void onDetachedFromWindow()
30 {
31 super.onDetachedFromWindow();
32 hanlder.removeCallbacks(this);
33 }
34 @Override
35 public void run() {
36 // TODO Auto-generated method stub
37 invalidate();
38 hanlder.postDelayed(this,60*1000);
39 }
40 protected void onMeasure(int widthMeasurespc,int heightMeasurespe)
41 {
42 super.onMeasure(widthMeasurespc, heightMeasurespe);
43 setMeasuredDimension((int)(bitmap.getWidth()*scale),(int)(bitmap.getHeight()*scale));
44
45 }
46 protected void onDraw(Canvas canvas)
47 {
48 super.onDraw(canvas);
49 Paint paint=new Paint();
50 Rect src=new Rect();
51 Rect target=new Rect();
52 src.left=0;
53 src.top=0;
54 src.right=bitmap.getWidth();
55 src.bottom=bitmap.getHeight();
56 target.left=0;
57 target.top=0;
58 target.bottom=(int)(src.bottom*scale);
59 target.right=(int)(src.right*scale);
60 //画表盘图像
61 canvas.drawBitmap(bitmap, src, target,paint);
62 //计算表盘中心点的横坐标
63 float centerX=bitmap.getWidth()*scale*handCenterWidthScale;
64 //计算表盘中心店的纵坐标
65 float centerY=bitmap.getHeight()*scale*handCenterHeightScale;
66
67 canvas.drawCircle(centerX, centerY, 5, paint);
68 paint.setStrokeWidth(3);
69 Calendar calendar=Calendar.getInstance();
70 int currentMin=calendar.get(Calendar.MINUTE);
71 int currentHour=calendar.get(Calendar.HOUR);
72 //计算时针和分针角度
73 double minuteRadian=Math.toRadians((360-((currentMin*6)-90))%360);
74 double hourRadian=Math.toRadians((360-((currentHour*30)-90))%360-(30*currentMin/60));
75 //画分针
76 canvas.drawLine(centerX, centerY,(int)(centerX+minuteHandSize*Math.cos(minuteRadian)),(int)(centerY-minuteHandSize*Math.sin(minuteRadian)),paint);
77 paint.setStrokeWidth(4);
78 //画时针
79 canvas.drawLine(centerX, centerY,(int)(centerX+hourHandSize*Math.cos(hourRadian)),(int)(centerY-hourHandSize*Math.sin(hourRadian)),paint);
80 }
81
82 }
这里面有很多重点,比如说时针与分针角度的计算,重绘的时间等。Runnable接口是软定时器类,这里定义一分钟重绘一次。
2.handclok.xml
在一个xml页面引用刚刚自定义的控件。
1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
2 android:layout_width="match_parent"
3 android:layout_height="match_parent"
4 android:orientation="vertical" >
5
6 <com.example.myandroiddemp.HandClock
7 android:layout_width="wrap_content"
8 android:layout_height="wrap_content"
9 clockImageSrc="@drawable/clock1"
10 scale="0.7"
11 handCenterWidthScale="0.5"
12 handCenterHeightScale="0.5"
13 minuteHandSize="54"
14 hourHandSize="40"/>
15
16 </LinearLayout>