实现购物车中的数字提醒功能

在实现购物车的时候，当用户成功购买某一商品后，我们需要在代表购物车该控件上给出一个数量提示，提醒用户当前购买商品的数量。

例如

               

就我知道的实现该功能的方法有两种，第一种其实就是在购物车那个图标上面再画一个TextView上去，用一张9-path图片做背景图片，这种是最简单的实现该效果的方法。

另一种其实道理也差不多，用别人写好的类BadgeView一样可以实现，该类可以实现不同控件上的提醒，入RadioButton、Button、tabhost也可以用等等。

接下来我先将第一种方法

首先是一个Tabhost和一个RadioGroup布局

<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@android:id/tabhost"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent" >
        <RelativeLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent" >
        <FrameLayout
            android:id="@android:id/tabcontent"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"/>             
        <TabWidget
            android:id="@android:id/tabs"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:visibility="gone"/>         
        <RadioGroup
            android:id="@+id/group"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:orientation="horizontal"
            android:background="@color/black" >
        <RadioButton
            android:id="@+id/show_core"
            android:drawableTop="@drawable/setbuttonbackground_main"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical|center_horizontal"
            android:layout_weight="1"
            android:button="@null"
            android:checked="true"
            android:paddingTop="10dp"
            android:gravity="center"/>
        <FrameLayout 
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:id="@+id/radioFram">
            <RadioButton
                android:drawableTop="@drawable/carta"
                android:gravity="center"
                android:id="@+id/show_student"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_gravity="center_vertical|center_horizontal"
                android:button="@null"
                android:paddingTop="10dp" />
            <TextView 
                android:id="@+id/num"
                android:background="@drawable/del3"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="right"
                android:textColor="@color/white"
                android:textStyle="bold"
                android:gravity="center"
                android:layout_marginBottom="20dp"/>
        </FrameLayout>
        <RadioButton
                android:layout_weight="1"
                android:drawableTop="@drawable/setbuttonbackground_cart"
                android:gravity="center"
                android:id="@+id/show_student_temp"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_vertical|center_horizontal"
                android:button="@null"
                android:paddingTop="10dp"
                android:visibility="gone"
                />
        <RadioButton
            android:drawableTop="@drawable/setbuttonbackground_account"
            android:id="@+id/show_teacher"
            android:layout_weight="1"
            android:button="@null"
            android:gravity="center"
            android:paddingTop="10dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical|center_horizontal"/>
        <RadioButton
            android:drawableTop="@drawable/setbuttonbackground_more"
            android:id="@+id/show_more"            
            android:layout_weight="1"        
            android:button="@null"
            android:gravity="center"
            android:paddingTop="10dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical|center_horizontal" />
        </RadioGroup>
    </RelativeLayout>
</TabHost>

用FrameLayout实现将红色的小圆点一层一层叠上去，就像我上面写的那样会出现一个问题，就是FrameLayout会覆盖RadioButton的点击事件，造成不能切换，解决办法是可以用一个隐藏的RadioButton代替，如上述代码所示，在Activity中只要将查询到的集合大小SetText进去就行了，这样便可实现。当然在Activity中需要重写Onresume（）方法才能够即使更新提醒。

第二种方法，是BadgeView，在这里我给大家提供一个类，当然我也是网上找的，并且实现过，所以推荐给大家

package com.techrare.util;

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.RadioGroup;
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;
    
    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.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 badgeMargin;
    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, RadioGroup group, int index) {
        this(context, null, android.R.attr.textViewStyle, group, 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;
        badgeMargin = dipToPixels(DEFAULT_MARGIN_DIP);
        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(badgeMargin, badgeMargin, 0, 0);
            break;
        case POSITION_TOP_RIGHT:
            lp.gravity = Gravity.RIGHT | Gravity.TOP;
            lp.setMargins(0, badgeMargin, badgeMargin, 0);
            break;
        case POSITION_BOTTOM_LEFT:
            lp.gravity = Gravity.LEFT | Gravity.BOTTOM;
            lp.setMargins(badgeMargin, 0, 0, badgeMargin);
            break;
        case POSITION_BOTTOM_RIGHT:
            lp.gravity = Gravity.RIGHT | Gravity.BOTTOM;
            lp.setMargins(0, 0, badgeMargin, badgeMargin);
            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.
     * 
     */
    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.
     * 
     */
    public void setBadgePosition(int layoutPosition) {
        this.badgePosition = layoutPosition;
    }

    /**
     * Returns the horizontal/vertical margin from the target View that is applied to this badge.
     * 
     */
    public int getBadgeMargin() {
        return badgeMargin;
    }

    /**
     * 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.badgeMargin = badgeMargin;
    }
    
    /**
     * 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;
        badgeBg = getDefaultBackground();
    }
    
    private int dipToPixels(int dip) {
        Resources r = getResources();
        float px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dip, r.getDisplayMetrics());
        return (int) px;
    }

}

里面有多种构造方法，可以为多种控件实现数字提醒，大家可以研究研究

在这里我先讲讲我在项目中用到的方法，Activity中的使用

定义一个全局的BadgeView,在Activity中的OnCreate方法中找到TabWidget该控件，因为我的主界面是用TabHost布局的，在项目中用户购买后的商品是保存在sqlite里面，所以这里的查询到的大小就是购物车中的商品的数量了。

    //數字提醒
    public void getText(){
         //查找本地数据库中的数据
        List<ProductDetailToCart> list=new ArrayList<ProductDetailToCart>();
        list=new ProductDao(MainActivity.this,"product").getProByCart();        
        int mycount=0;
        for (int i = 0; i < list.size(); i++) {
            ProductDetailToCart pro=list.get(i);
            mycount+=pro.getPcount();
        }
        
      System.out.println("输出的数量是==="+mycount);

      if(badge==null||!badge.isShown()){
            badge = new BadgeView(MainActivity.this,tabs,1);//三个参数，1、this,2、当前控件（tab）3、在第几个控件上实现数字提醒
            badge.setText(mycount+"");
            badge.show();
        }else{
            badge.setText(mycount+"");
       }    
    }

好了，基本上就是这样了。。。