Android实现带有指示器的自定义底部导航栏

package com.example.indicatornavigationbar; 
 
import android.app.Activity; 
import android.content.Context; 
import android.support.v4.view.ViewPager; 
import android.support.v4.view.ViewPager.OnPageChangeListener; 
import android.util.DisplayMetrics; 
import android.view.Gravity; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.view.ViewGroup; 
import android.view.animation.Animation; 
import android.view.animation.TranslateAnimation; 
import android.widget.ImageView; 
import android.widget.ImageView.ScaleType; 
import android.widget.LinearLayout; 
import android.widget.TextView; 
 
/** 
 * 
 * @ClassName: com.mengle.activity.IndicatorNavigationBar 
 * @Description: 带有指示器的底部导航栏 
 * @author zhaokaiqiang 
 * @date 2014-10-17 上午11:07:40 
 * 
 */ 
public class IndicatorNavigationBar extends LinearLayout implements 
  OnClickListener, OnPageChangeListener { 
 
 // 导航栏默认高度，不包括指示器高度，单位是dp 
 private static final int HEIGHT_NAVIGATION_BAR = 40; 
 // 指示器默认高度，单位是dp 
 private static final int HEIGHT_INDICATOR = 4; 
 
 private Context context; 
 private ViewPager viewPager; 
 // 指示器 
 private ImageView ivBottomLine; 
 // 当前显示的index 
 private int currIndex = 0; 
 // 存储移动位置 
 private int positions[]; 
 // 标题数量 
 private int titleCount; 
 
 public IndicatorNavigationBar(Context context) { 
  super(context); 
  this.context = context; 
 } 
 
 /** 
  * 
  * @Description: 依附到父布局上 
  * @param viewGroup 
  *   要依附在的父布局 
  * @param titles 
  *   底部显示的导航文字 
  * @param viewPager 
  *   绑定的ViewPager对象 
  * @return void 
  */ 
 public void attachToParent(ViewGroup viewGroup, String[] titles, 
   ViewPager viewPager) { 
 
  this.viewPager = viewPager; 
  titleCount = titles.length; 
 
  // 初始化主布局 
  setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, 
    dip2px(HEIGHT_NAVIGATION_BAR + HEIGHT_INDICATOR))); 
  setBackgroundColor(getResources().getColor(android.R.color.transparent)); 
  setOrientation(VERTICAL); 
 
  // 导航栏布局 
  LinearLayout ll_navigation = new LinearLayout(context); 
  ll_navigation.setLayoutParams(new LayoutParams( 
    LayoutParams.MATCH_PARENT, dip2px(HEIGHT_NAVIGATION_BAR))); 
  ll_navigation.setBackgroundColor(getResources().getColor( 
    android.R.color.holo_blue_light)); 
  ll_navigation.setOrientation(HORIZONTAL); 
 
  // 生成导航按钮(TextView) 
  for (int i = 0; i < titles.length; i++) { 
 
   TextView textView = new TextView(context); 
   textView.setLayoutParams(new LayoutParams(0, 
     dip2px(HEIGHT_NAVIGATION_BAR), 1)); 
   textView.setText(titles[i]); 
   textView.setGravity(Gravity.CENTER); 
   textView.setTextSize(16); 
   textView.setTextColor(getResources() 
     .getColor(android.R.color.white)); 
   textView.setId(i); 
   textView.setOnClickListener(this); 
   ll_navigation.addView(textView); 
  } 
  // 添加导航 
  this.addView(ll_navigation); 
 
  // 指示器布局 
  LinearLayout ll_indicator = new LinearLayout(context); 
  ll_indicator.setLayoutParams(new LayoutParams( 
    LayoutParams.MATCH_PARENT, dip2px(HEIGHT_INDICATOR))); 
  ll_indicator.setBackgroundColor(getResources().getColor( 
    android.R.color.holo_blue_light)); 
  ll_indicator.setOrientation(HORIZONTAL); 
 
  // 指示器 
  ivBottomLine = new ImageView(context); 
  ivBottomLine.setImageResource(android.R.color.holo_orange_light); 
  ivBottomLine.setScaleType(ScaleType.MATRIX); 
  ivBottomLine 
    .setLayoutParams(new LinearLayout.LayoutParams( 
      getScreenWidth(context) / titleCount, 
      dip2px(HEIGHT_INDICATOR))); 
  ll_indicator.addView(ivBottomLine); 
  // 添加指示器 
  this.addView(ll_indicator); 
 
  viewGroup.addView(this); 
  viewPager.setOnPageChangeListener(this); 
 
  // 初始化移动位置 
  positions = new int[titleCount]; 
  positions[0] = 0; 
  int distance = (int) (getScreenWidth(context) / titleCount); 
  for (int i = 1; i < titleCount; i++) { 
   positions[i] = distance * i; 
  } 
 
 } 
 
 @Override 
 public void onClick(View v) { 
  viewPager.setCurrentItem(v.getId()); 
 } 
 
 @Override 
 public void onPageScrollStateChanged(int arg0) { 
 
 } 
 
 @Override 
 public void onPageScrolled(int position, float positionOffset, 
   int positionOffsetPixels) { 
 
 } 
 
 @Override 
 public void onPageSelected(int position) { 
 
  Animation animation = new TranslateAnimation(currIndex * positions[1], 
    positions[position], 0, 0); 
  currIndex = position; 
  animation.setFillAfter(true); 
  animation.setDuration(300); 
  ivBottomLine.startAnimation(animation); 
 } 
 
 private int dip2px(float dpValue) { 
  final float scale = context.getResources().getDisplayMetrics().density; 
  return (int) (dpValue * scale + 0.5f); 
 } 
 
 // 获取屏幕宽度 
 private int getScreenWidth(Context context) { 
  DisplayMetrics dm = new DisplayMetrics(); 
  ((Activity) context).getWindowManager().getDefaultDisplay() 
    .getMetrics(dm); 
  return dm.widthPixels; 
 } 
}