Android的开发中，坚持强大的通知栏，用户通知有些地方需依赖数字角标，因此参考资料做些记录；
首先来看以下用法：
public class MainActivity extends Activity {
Button mCloseButton;
Button mOpenButton;
MultiDirectionSlidingDrawer mDrawer;
private ImageView bt;
private BadgeView bg;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_badge_layout);
bt=(ImageView)findViewById(R.id.badge_image_view);
bg=new BadgeView(getApplicationContext(),bt);
bg.setText("12");
bg.setTextColor(Color.WHITE);
bg.setBadgePosition(BadgeView.POSITION_TOP_RIGHT);
bg.setBadgeMargin(0,0);
bg.setAnimation(alphaAnimation);
bg.show();
}
}<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/badge_image_view"
android:layout_width="120dp"
android:layout_height="120dp"
android:text="@string/app_name"
android:src="@drawable/icon"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_marginLeft="98dp"
android:layout_marginTop="126dp" />
</LinearLayout>要实现这个角标，我们一想有以下几种方式：
1、放置一个隐藏的图片在app中，在需要它显示的时候，显示该图片，并以该图片为背景，显示新增消息数；
2、自定义一个控件，用于显示该角标信息。例如，角标相对于控件的位置、底色、数字等；
对比或者使用后，你会发现，自定义一个控件，无疑更符合我们的使用习惯。无需特定的图片，减少了app的大小等，更重要的是，这样方便我们的使用。
在角标实现中，有个开源代码BadgeView写的很符合我们的心理预期。实现了我们常用的所有功能。
BadgeView
这是一个继承TextView控件，自定义而成的一个简单控件。我们通过它，可轻易实现对角标位置、角标底色、角标内容等控制。
package it.sephiroth.demo.slider.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.
*/
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 = 3;
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("#FF3E3D"); //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, -3, paddingPixels, -3);
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;
badgeBg = getDefaultBackground();
}
private int dipToPixels(int dip) {
Resources r = getResources();
float px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dip, r.getDisplayMetrics());
return (int) px;
}
}