CustomButton

实现自定义Button有两种方式，
1. 继承View,在里面自己去实现onDraw(), onMeasure(), onClickListener()等方法。这种方式比较灵活，可以实现复杂的需求。
代码样例如下：
package seya.test.comp;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.view.View;

public class CustomButton extends View{

private final static int WIDTH_PADDING = 8;
private final static int HEIGHT_PADDING = 10;
private final String label;
private final int imageResId;
private final Bitmap image;
//private final InternalListener listenerAdapter = new InternalListener();

public CustomButton(Context context, int resImage, String label)
       {
           super(context);
          this.label = label;
          this.imageResId = resImage;
           this.image = BitmapFactory.decodeResource(context.getResources(),
                  imageResId);
 
           setFocusable(true);
           setBackgroundColor(Color.WHITE);

           //setOnClickListener(listenerAdapter);
           setClickable(true);
       }

@Override
protected void onFocusChanged (boolean gainFocus, int direction, Rect previouslyFocusedRect){
this.setBackgroundColor(Color.GREEN);
}

@Override
protected void onDraw(Canvas canvas)
    {
         Paint textPaint = new Paint();
         textPaint.setColor(Color.BLACK);
         canvas.drawBitmap(image, WIDTH_PADDING / 2, HEIGHT_PADDING / 2, null);
          canvas.drawText(label, WIDTH_PADDING / 2, (HEIGHT_PADDING / 2) +
                  image.getHeight() + 8, textPaint);
     }

@Override
       protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
        {
         setMeasuredDimension(measureWidth(widthMeasureSpec),
                 measureHeight(heightMeasureSpec));
         }

private int measureWidth(int measureSpec)
     {
        int preferred = image.getWidth() * 2;
         return getMeasurement(measureSpec, preferred);
     }
    
     private int measureHeight(int measureSpec)
     {
          int preferred = image.getHeight() * 2;
          return getMeasurement(measureSpec, preferred);
     }
     private int getMeasurement(int measureSpec, int preferred)
     {
              int specSize = MeasureSpec.getSize(measureSpec);
              int measurement = 0;
           
              switch(MeasureSpec.getMode(measureSpec))
             {
                  case MeasureSpec.EXACTLY:
                      // This means the width of this view has been given.
                      measurement = specSize;
                      break;
                 case MeasureSpec.AT_MOST:
                     // Take the minimum of the preferred size and what
                      // we were told to be.
                     measurement = Math.min(preferred, specSize);
                     break;
                default:
                     measurement = preferred;
                    break;
             }
      
             return measurement;
         }

    /* public void setOnClickListener(ClickListener newListener)
          {
              listenerAdapter.setListener(newListener);
          }*/

     public String getLabel()
          {
              return label;
          }
        
          /**
           * Returns the resource id of the image.
           */
          public int getImageResId()
          {
              return imageResId;
          }
         /* private class InternalListener implements View.OnClickListener
               {
                   private ClickListener listener = null;
             
                  
                   public void setListener(ClickListener newListener)
                   {
                       listener = newListener;
                   }
                 
                   @Override
                   public void onClick(View v)
                   {
                       if (listener != null)
                       {
                           listener.onClick(CustomImageButton.this);
                       }
                   }
               }*/
  
}

2. 另一种还是保持原来button的基本功能，只需要改变button在不同状态下的样式，那么就可以这样来做：
在res/drawable下面新建mybutton_background.xml文件，内容如下：
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">   
<item android:state_focused="true"      
android:state_pressed="false"    
android:drawable="@drawable/yellow" />  
<item android:state_focused="true"      
android:state_pressed="true"     
android:drawable="@drawable/green" />
<item android:state_focused="false"      
    android:state_pressed="true"
    android:drawable="@drawable/blue" /> 
<item android:drawable="@drawable/grey" />
</selector>
这里面就定义了在不同状态下的显示图片
然后在layout里面定义Button的时候，指定它的background为这个mybutton_background
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <Button android:id="@+id/btn"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/mybtn"
    android:background="@drawable/mybutton_background"/>
</LinearLayout>
这种方式开发比较简单，适合做一些风格一致的Button，设置成同一个background就可以了。