gt: 		badgeBg = getDefaultBackground();
context: package net.oschina.app.widget;
  
  import android.content.Context;
  import android.content.res.Resources;
  import android.graphics.Color;
  import android.graphics.Typeface;
  import android.graphics.drawable.ShapeDrawable;
  import android.graphics.drawable.shapes.RoundRectShape;
  import android.util.AttributeSet;
  import android.util.TypedValue;
  import android.view.Gravity;
  import android.view.View;
  import android.view.ViewGroup;
  import android.view.ViewGroup.LayoutParams;
  import android.view.ViewParent;
  import android.view.animation.AccelerateInterpolator;
  import android.view.animation.AlphaAnimation;
  import android.view.animation.Animation;
  import android.view.animation.DecelerateInterpolator;
  import android.widget.FrameLayout;
  import android.widget.TabWidget;
  import android.widget.TextView;
  
  /**
   * A simple text label view that can be applied as a "badge" to any given {@link android.view.View}. 
   * This class is intended to be instantiated at runtime rather than included in XML layouts.
   * 
   * @author Jeff Gilfelt
   */
  public class BadgeView extends TextView {
  
  	public static final int POSITION_TOP_LEFT = 1;
  	public static final int POSITION_TOP_RIGHT = 2;
  	public static final int POSITION_BOTTOM_LEFT = 3;
  	public static final int POSITION_BOTTOM_RIGHT = 4;
  	public static final int POSITION_CENTER = 5;
  	
  	private static final int DEFAULT_MARGIN_DIP = 5;
  	private static final int DEFAULT_LR_PADDING_DIP = 5;
  	private static final int DEFAULT_CORNER_RADIUS_DIP = 8;
  	private static final int DEFAULT_POSITION = POSITION_TOP_RIGHT;
  	private static final int DEFAULT_BADGE_COLOR = Color.parseColor("#CCFF0000"); //Color.RED;
  	private static final int DEFAULT_TEXT_COLOR = Color.WHITE;
  	
  	private static Animation fadeIn;
  	private static Animation fadeOut;
  	
  	private Context context;
  	private View target;
  	
  	private int badgePosition;
  	private int badgeMarginH;
  	private int badgeMarginV;
  	private int badgeColor;
  	
  	private boolean isShown;
  	
  	private ShapeDrawable badgeBg;
  	
  	private int targetTabIndex;
  	
  	public BadgeView(Context context) {
  		this(context, (AttributeSet) null, android.R.attr.textViewStyle);
  	}
  	
  	public BadgeView(Context context, AttributeSet attrs) {
  		 this(context, attrs, android.R.attr.textViewStyle);
  	}
  	
  	/**
       * Constructor -
       * 
       * create a new BadgeView instance attached to a target {@link android.view.View}.
       *
       * @param context context for this view.
       * @param target the View to attach the badge to.
       */
  	public BadgeView(Context context, View target) {
  		 this(context, null, android.R.attr.textViewStyle, target, 0);
  	}
  	
  	/**
       * Constructor -
       * 
       * create a new BadgeView instance attached to a target {@link android.widget.TabWidget}
       * tab at a given index.
       *
       * @param context context for this view.
       * @param target the TabWidget to attach the badge to.
       * @param index the position of the tab within the target.
       */
  	public BadgeView(Context context, TabWidget target, int index) {
  		this(context, null, android.R.attr.textViewStyle, target, index);
  	}
  	
  	public BadgeView(Context context, AttributeSet attrs, int defStyle) {
  		this(context, attrs, defStyle, null, 0);
  	}
  	
  	public BadgeView(Context context, AttributeSet attrs, int defStyle, View target, int tabIndex) {
  		super(context, attrs, defStyle);
  		init(context, target, tabIndex);
  	}
  
  	private void init(Context context, View target, int tabIndex) {
  		
  		this.context = context;
  		this.target = target;
  		this.targetTabIndex = tabIndex;
  		
  		// apply defaults
  		badgePosition = DEFAULT_POSITION;
  		badgeMarginH = dipToPixels(DEFAULT_MARGIN_DIP);
  		badgeMarginV = badgeMarginH;
  		badgeColor = DEFAULT_BADGE_COLOR;
  		
  		setTypeface(Typeface.DEFAULT_BOLD);
  		int paddingPixels = dipToPixels(DEFAULT_LR_PADDING_DIP);
  		setPadding(paddingPixels, 0, paddingPixels, 0);
  		setTextColor(DEFAULT_TEXT_COLOR);
  		
  		fadeIn = new AlphaAnimation(0, 1);
  		fadeIn.setInterpolator(new DecelerateInterpolator());
  		fadeIn.setDuration(200);
  
  		fadeOut = new AlphaAnimation(1, 0);
  		fadeOut.setInterpolator(new AccelerateInterpolator());
  		fadeOut.setDuration(200);
  		
  		isShown = false;
  		
  		if (this.target != null) {
  			applyTo(this.target);
  		} else {
  			show();
  		}
  		
  	}
  
  	private void applyTo(View target) {
  		
  		LayoutParams lp = target.getLayoutParams();
  		ViewParent parent = target.getParent();
  		FrameLayout container = new FrameLayout(context);
  		
  		if (target instanceof TabWidget) {
  			
  			// set target to the relevant tab child container
  			target = ((TabWidget) target).getChildTabViewAt(targetTabIndex);
  			this.target = target;
  			
  			((ViewGroup) target).addView(container, 
  					new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
  			
  			this.setVisibility(View.GONE);
  			container.addView(this);
  			
  		} else {
  			
  			// TODO verify that parent is indeed a ViewGroup
  			ViewGroup group = (ViewGroup) parent; 
  			int index = group.indexOfChild(target);
  			
  			group.removeView(target);
  			group.addView(container, index, lp);
  			
  			container.addView(target);
  	
  			this.setVisibility(View.GONE);
  			container.addView(this);
  			
  			group.invalidate();
  			
  		}
  		
  	}
  	
  	/**
       * Make the badge visible in the UI.
       * 
       */
  	public void show() {
  		show(false, null);
  	}
  	
  	/**
       * Make the badge visible in the UI.
       *
       * @param animate flag to apply the default fade-in animation.
       */
  	public void show(boolean animate) {
  		show(animate, fadeIn);
  	}
  	
  	/**
       * Make the badge visible in the UI.
       *
       * @param anim Animation to apply to the view when made visible.
       */
  	public void show(Animation anim) {
  		show(true, anim);
  	}
  	
  	/**
       * Make the badge non-visible in the UI.
       * 
       */
  	public void hide() {
  		hide(false, null);
  	}
  	
  	/**
       * Make the badge non-visible in the UI.
       *
       * @param animate flag to apply the default fade-out animation.
       */
  	public void hide(boolean animate) {
  		hide(animate, fadeOut);
  	}
  	
  	/**
       * Make the badge non-visible in the UI.
       *
       * @param anim Animation to apply to the view when made non-visible.
       */
  	public void hide(Animation anim) {
  		hide(true, anim);
  	}
  	
  	/**
       * Toggle the badge visibility in the UI.
       * 
       */
  	public void toggle() {
  		toggle(false, null, null);
  	}
  	
  	/**
       * Toggle the badge visibility in the UI.
       * 
       * @param animate flag to apply the default fade-in/out animation.
       */
  	public void toggle(boolean animate) {
  		toggle(animate, fadeIn, fadeOut);
  	}
  	
  	/**
       * Toggle the badge visibility in the UI.
       *
       * @param animIn Animation to apply to the view when made visible.
       * @param animOut Animation to apply to the view when made non-visible.
       */
  	public void toggle(Animation animIn, Animation animOut) {
  		toggle(true, animIn, animOut);
  	}
  	
  	private void show(boolean animate, Animation anim) {
  		if (getBackground() == null) {
  			if (badgeBg == null) {
  				badgeBg = getDefaultBackground();
  			}
  			setBackgroundDrawable(badgeBg);
  		}
  		applyLayoutParams();
  		
  		if (animate) {
  			this.startAnimation(anim);
  		}
  		this.setVisibility(View.VISIBLE);
  		isShown = true;
  	}
  	
  	private void hide(boolean animate, Animation anim) {
  		this.setVisibility(View.GONE);
  		if (animate) {
  			this.startAnimation(anim);
  		}
  		isShown = false;
  	}
  	
  	private void toggle(boolean animate, Animation animIn, Animation animOut) {
  		if (isShown) {
  			hide(animate && (animOut != null), animOut);	
  		} else {
  			show(animate && (animIn != null), animIn);
  		}
  	}
  	
  	/**
       * Increment the numeric badge label. If the current badge label cannot be converted to
       * an integer value, its label will be set to "0".
       * 
       * @param offset the increment offset.
       */
  	public int increment(int offset) {
  		CharSequence txt = getText();
  		int i;
  		if (txt != null) {
  			try {
  				i = Integer.parseInt(txt.toString());
  			} catch (NumberFormatException e) {
  				i = 0;
  			}
  		} else {
  			i = 0;
  		}
  		i = i + offset;
  		setText(String.valueOf(i));
  		return i;
  	}
  	
  	/**
       * Decrement the numeric badge label. If the current badge label cannot be converted to
       * an integer value, its label will be set to "0".
       * 
       * @param offset the decrement offset.
       */
  	public int decrement(int offset) {
  		return increment(-offset);
  	}
  	
  	private ShapeDrawable getDefaultBackground() {
  		
  		int r = dipToPixels(DEFAULT_CORNER_RADIUS_DIP);
  		float[] outerR = new float[] {r, r, r, r, r, r, r, r};
          
  		RoundRectShape rr = new RoundRectShape(outerR, null, null);
  		ShapeDrawable drawable = new ShapeDrawable(rr);
  		drawable.getPaint().setColor(badgeColor);
  		
  		return drawable;
  		
  	}
  	
  	private void applyLayoutParams() {
  		
  		FrameLayout.LayoutParams lp = new FrameLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
  		
  		switch (badgePosition) {
  		case POSITION_TOP_LEFT:
  			lp.gravity = Gravity.LEFT | Gravity.TOP;
  			lp.setMargins(badgeMarginH, badgeMarginV, 0, 0);
  			break;
  		case POSITION_TOP_RIGHT:
  			lp.gravity = Gravity.RIGHT | Gravity.TOP;
  			lp.setMargins(0, badgeMarginV, badgeMarginH, 0);
  			break;
  		case POSITION_BOTTOM_LEFT:
  			lp.gravity = Gravity.LEFT | Gravity.BOTTOM;
  			lp.setMargins(badgeMarginH, 0, 0, badgeMarginV);
  			break;
  		case POSITION_BOTTOM_RIGHT:
  			lp.gravity = Gravity.RIGHT | Gravity.BOTTOM;
  			lp.setMargins(0, 0, badgeMarginH, badgeMarginV);
  			break;
  		case POSITION_CENTER:
  			lp.gravity = Gravity.CENTER;
  			lp.setMargins(0, 0, 0, 0);
  			break;
  		default:
  			break;
  		}
  		
  		setLayoutParams(lp);
  		
  	}
  
  	/**
       * Returns the target View this badge has been attached to.
       * 
       */
  	public View getTarget() {
  		return target;
  	}
  
  	/**
       * Is this badge currently visible in the UI?
       * 
       */
  	@Override
  	public boolean isShown() {
  		return isShown;
  	}
  
  	/**
       * Returns the positioning of this badge.
       * 
       * one of POSITION_TOP_LEFT, POSITION_TOP_RIGHT, POSITION_BOTTOM_LEFT, POSITION_BOTTOM_RIGHT, POSTION_CENTER.
       * 
       */
  	public int getBadgePosition() {
  		return badgePosition;
  	}
  
  	/**
       * Set the positioning of this badge.
       * 
       * @param layoutPosition one of POSITION_TOP_LEFT, POSITION_TOP_RIGHT, POSITION_BOTTOM_LEFT, POSITION_BOTTOM_RIGHT, POSTION_CENTER.
       * 
       */
  	public void setBadgePosition(int layoutPosition) {
  		this.badgePosition = layoutPosition;
  	}
  
  	/**
       * Returns the horizontal margin from the target View that is applied to this badge.
       * 
       */
  	public int getHorizontalBadgeMargin() {
  		return badgeMarginH;
  	}
  	
  	/**
       * Returns the vertical margin from the target View that is applied to this badge.
       * 
       */
  	public int getVerticalBadgeMargin() {
  		return badgeMarginV;
  	}
  
  	/**
       * Set the horizontal/vertical margin from the target View that is applied to this badge.
       * 
       * @param badgeMargin the margin in pixels.
       */
  	public void setBadgeMargin(int badgeMargin) {
  		this.badgeMarginH = badgeMargin;
  		this.badgeMarginV = badgeMargin;
  	}
  	
  	/**
       * Set the horizontal/vertical margin from the target View that is applied to this badge.
       * 
       * @param horizontal margin in pixels.
       * @param vertical margin in pixels.
       */
  	public void setBadgeMargin(int horizontal, int vertical) {
  		this.badgeMarginH = horizontal;
  		this.badgeMarginV = vertical;
  	}
  	
  	/**
       * Returns the color value of the badge background.
       * 
       */
  	public int getBadgeBackgroundColor() {
  		return badgeColor;
  	}
  
  	/**
       * Set the color value of the badge background.
       * 
       * @param badgeColor the badge background color.
       */
  	public void setBadgeBackgroundColor(int badgeColor) {
  		this.badgeColor = badgeColor;
  