Android实现微信首页左右滑动切换效果

 /**
  * 初始化资源图片bitmap及相关绘制对象
  * @param normal normals
  * @param selected focus
  */
 public final void init(int normal, int selected, int width, int height) {
  this.mNormalIcon = createBitmap(normal);
  this.mSelectedIcon = createBitmap(selected);
  this.mNormalRect = new Rect(0, 0, width, height);
  this.mSelectedRect = new Rect(0, 0, width, height);
  this.mPaint = new Paint(1);
 }

 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  if (this.mPaint == null) {
   return;
  }
  this.mPaint.setAlpha(255 - this.mSelectedAlpha);
  canvas.drawBitmap(this.mNormalIcon, null, this.mNormalRect, this.mPaint);
  this.mPaint.setAlpha(this.mSelectedAlpha);
  canvas.drawBitmap(this.mSelectedIcon, null, this.mSelectedRect, this.mPaint);
 }

public void initContainer (String[] titles, int[][] iconsRes, int[] colors, boolean showTransitionColor) {
  this.mTitles = titles;
  this.mIconRes = iconsRes;
  this.mTextNormalColor = getResources().getColor(colors[0]);
  this.mTextSelectedColor = getResources().getColor(colors[1]);
  this.mShowTransitionColor = showTransitionColor;
 }

/**
  * 设置布局文件及相关控件id
  * @param layout layout布局文件 id
  * @param iconId ImageView 控件 id id <=0 时不显示
  * @param textId TextView 控件 id id <=0 时不显示
  * @param width icon 宽度
  * @param height icon 高度
  */
 public void setContainerLayout (int layout, int iconId, int textId, int width, int height) {
  mLayoutId = layout;
  mTextViewId = textId;
  mIconVIewId = iconId;
  mIconWidth = width;
  mIconHeight = height;
 }

/**
  * <p>添加tab view到当前容器</p>
  */
 private void addTabViewToContainer() {
  final PagerAdapter adapter = mViewPager.getAdapter(); 
  mTabView = new View[adapter.getCount()]; //这里根据adapter判断底部要显示的tab总数

  for (int index = 0, len = adapter.getCount(); index < len; index++) {

   final View tabView = LayoutInflater.from(getContext()).inflate(mLayoutId, this, false); //加载tab布局
   mTabView[index] = tabView;

   /*tabIconView初始化*/
   TabIconView iconView = null;
   if (mIconVIewId > 0) { // 传入的图片资源文件ID不为0时，表示需要显示icon,然后初始化该View
    iconView = (TabIconView) tabView.findViewById(mIconVIewId);
    iconView.init(mIconRes[index][0], mIconRes[index][1], mIconWidth, mIconHeight); //这里调了自定义ImageView的init方法
   }

   /*tabTextView初始化*/
   TextView textView = null;
   if (mTextViewId > 0) {
    textView = (TextView) tabView.findViewById(mTextViewId);
    textView.setText(mTitles[index]);

   }

   /*设置宽度，等分container*/
   LayoutParams lp = (LayoutParams) tabView.getLayoutParams();
   lp.width = 0;
   lp.weight = 1;

   /*添加tab点击事件*/
   addTabOnClickListener(tabView, index);

   /*设置当前状态*/
   if (index == mViewPager.getCurrentItem()) { //当先显示tab，设置初始状态为获得焦点状态
    if (iconView != null) {
     iconView.offsetChanged(0);
    }
    tabView.setSelected(true);
    if (textView != null) {
     textView.setTextColor(mTextSelectedColor);
    }
   }

   addView(tabView);
  }
 }

@Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  final int childCount = getChildCount();
  if (childCount > 0) {
   /*当发生偏移时，绘制渐变区域*/
   if (mSelectionOffset > 0f && mSelectedPosition < (getChildCount() - 1) && mShowTransitionColor) {

    /*获取当前tab和下一tab view */
    View selectedTab = getChildAt(mSelectedPosition);
    View nextTab = getChildAt(mSelectedPosition + 1);

    /*显示tab icon时,刷新各自view 透明度*/
    if (mIconVIewId > 0) {
     View selectedIconView = selectedTab.findViewById(mIconVIewId);
     View nextIconView = nextTab.findViewById(mIconVIewId);

     //draw icon alpha
     if (selectedIconView instanceof TabIconView && nextIconView instanceof TabIconView) {
      ((TabIconView) selectedIconView).offsetChanged(mSelectionOffset);
      ((TabIconView) nextIconView).offsetChanged(1 - mSelectionOffset);
     }
    }

     /*显示tab text,刷新各自view 透明度*/
    if (mTextViewId > 0) {
     View selectedTextView = selectedTab.findViewById(mTextViewId);
     View nextTextView = nextTab.findViewById(mTextViewId);

     //draw text color
     Integer selectedColor = (Integer) evaluate(mSelectionOffset, mTextSelectedColor, mTextNormalColor);
     Integer nextColor = (Integer) evaluate(1 - mSelectionOffset, mTextSelectedColor, mTextNormalColor);

     if (selectedTextView instanceof TextView && nextTextView instanceof TextView) {
      ((TextView) selectedTextView).setTextColor(selectedColor);
      ((TextView) nextTextView).setTextColor(nextColor);
     }
    }

   }
  }
 }

private void initViews() {  //得到apdater
  TabFragmentAdapter mAdapter = new TabFragmentAdapter(getSupportFragmentManager(), fragments);
  ViewPager mPager = (ViewPager) findViewById(R.id.tab_pager);
  mPager.setAdapter(mAdapter);
  //如果当前类需要对viewPager做监听
  TabContainerView mTabLayout = (TabContainerView) findViewById(R.id.ll_tab_container);
  mTabLayout.setOnPageChangeListener(this);

  mTabLayout.initContainer(getResources().getStringArray(R.array.tab_main_title), ICONS_RES, TAB_COLORS, true);

  int width = getResources().getDimensionPixelSize(R.dimen.tab_icon_width);
  int height = getResources().getDimensionPixelSize(R.dimen.tab_icon_height);
  mTabLayout.setContainerLayout(R.layout.tab_container_view, R.id.iv_tab_icon, R.id.tv_tab_text, width, height);
//  mTabLayout.setSingleTextLayout(R.layout.tab_container_view, R.id.tv_tab_text);
//  mTabLayout.setSingleIconLayout(R.layout.tab_container_view, R.id.iv_tab_icon);

  mTabLayout.setViewPager(mPager);
  mPager.setCurrentItem(getIntent().getIntExtra("tab", 0));
 }