android自定义控件 - 码农教程

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>