android自定义控件

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。

public class HandClock extends View implements Runnable {

    private int clockImageResourceId;//图像资源id
    private Bitmap bitmap;//图像资源
    private float scale;//图像显示的比例
    private float handCenterWidthScale;//横坐标显示比例
    private float handCenterHeightScale;//纵坐标显示比例
    private int minuteHandSize;//分钟长度
    private int hourHandSize;//时针长度
    private Handler hanlder=new Handler();
    public HandClock(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
        //读取属性值
        clockImageResourceId=attrs.getAttributeResourceValue(null, "clockImageSrc", 0);
        if(clockImageResourceId>0)
        {
            bitmap=BitmapFactory.decodeResource(getResources(), clockImageResourceId);
        }
        scale=attrs.getAttributeFloatValue(null, "scale", 1);
        handCenterWidthScale=attrs.getAttributeFloatValue(null, "handCenterWidthScale", bitmap.getWidth()/2);
        handCenterHeightScale=attrs.getAttributeFloatValue(null, "handCenterHeightScale", bitmap.getHeight()/2);
        minuteHandSize=(int)(attrs.getAttributeIntValue(null, "minuteHandSize",0)*scale);
        hourHandSize=(int)(attrs.getAttributeIntValue(null, "hourHandSize", 0)*scale);
        int curentSecond=Calendar.getInstance().get(Calendar.SECOND);
        hanlder.postDelayed(this, (60-curentSecond)*1000);
    }

    protected void onDetachedFromWindow()
    {
        super.onDetachedFromWindow();
        hanlder.removeCallbacks(this);
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        invalidate();
        hanlder.postDelayed(this,60*1000);
    }
    protected void onMeasure(int widthMeasurespc,int heightMeasurespe)
    {
        super.onMeasure(widthMeasurespc, heightMeasurespe);
        setMeasuredDimension((int)(bitmap.getWidth()*scale),(int)(bitmap.getHeight()*scale));
        
    }
    protected void onDraw(Canvas canvas)
    {
        super.onDraw(canvas);
        Paint paint=new Paint();
        Rect src=new Rect();
        Rect target=new Rect();
        src.left=0;
        src.top=0;
        src.right=bitmap.getWidth();
        src.bottom=bitmap.getHeight();
        target.left=0;
        target.top=0;
        target.bottom=(int)(src.bottom*scale);
        target.right=(int)(src.right*scale);
        //画表盘图像
        canvas.drawBitmap(bitmap, src, target,paint);
        //计算表盘中心点的横坐标
        float centerX=bitmap.getWidth()*scale*handCenterWidthScale;
        //计算表盘中心店的纵坐标
        float centerY=bitmap.getHeight()*scale*handCenterHeightScale;
        
        canvas.drawCircle(centerX, centerY, 5, paint);
        paint.setStrokeWidth(3);
        Calendar calendar=Calendar.getInstance();
        int currentMin=calendar.get(Calendar.MINUTE);
        int currentHour=calendar.get(Calendar.HOUR);
        //计算时针和分针角度
        double minuteRadian=Math.toRadians((360-((currentMin*6)-90))%360);
        double hourRadian=Math.toRadians((360-((currentHour*30)-90))%360-(30*currentMin/60));
        //画分针
        canvas.drawLine(centerX, centerY,(int)(centerX+minuteHandSize*Math.cos(minuteRadian)),(int)(centerY-minuteHandSize*Math.sin(minuteRadian)),paint);
        paint.setStrokeWidth(4);
        //画时针
        canvas.drawLine(centerX, centerY,(int)(centerX+hourHandSize*Math.cos(hourRadian)),(int)(centerY-hourHandSize*Math.sin(hourRadian)),paint);
    }

}

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。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    
<com.example.myandroiddemp.HandClock
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    clockImageSrc="@drawable/clock1" 
    scale="0.7"
    handCenterWidthScale="0.5"
    handCenterHeightScale="0.5"
    minuteHandSize="54"
    hourHandSize="40"/>

</LinearLayout>