Android 微信6.1 tab栏图标和字体颜色渐变的实现

可以看到没有定义我们刚刚自定义的 TabItem，而是使用的 TabView，那 TabView 到底是啥东西？相信大家都想到了，TabView 其实就是我们自定义的线性布局，

[java] view plain copy
package moon.wechat.view; 
import android.content.Context; 
import android.content.res.TypedArray; 
import android.support.v4.view.PagerAdapter; 
import android.support.v4.view.ViewPager; 
import android.util.AttributeSet; 
import android.util.Log; 
import android.util.TypedValue; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.LinearLayout; 
import java.util.ArrayList; 
import java.util.List; 
import moon.wechat.R; 
/** 
 * Created by moon.zhong on 2015/2/4. 
 */ 
public class TabView extends LinearLayout implements View.OnClickListener { 
  private ViewPager mViewPager; 
  private ViewPager.OnPageChangeListener mOnPageChangeListener; 
  private PagerAdapter mPagerAdapter; 
  private int mChildSize; 
  private List<TabItem> mTabItems; 
  private OnItemIconTextSelectListener mListener; 
  private int mTextSize = 12; 
  private int mTextColorSelect = 0xff45c01a; 
  private int mTextColorNormal = 0xff777777; 
  private int mPadding = 10; 
  public TabView(Context context) { 
    this(context, null); 
  } 
  public TabView(Context context, AttributeSet attrs) { 
    this(context, attrs, 0); 
  } 
  public TabView(Context context, AttributeSet attrs, int defStyleAttr) { 
    super(context, attrs, defStyleAttr); 
    TypedArray typedArray = getResources().obtainAttributes(attrs, R.styleable.TabView); 
    int N = typedArray.getIndexCount(); 
    for (int i = 0; i < N; i++) { 
      switch (typedArray.getIndex(i)) { 
        case R.styleable.TabView_text_size: 
          mTextSize = (int) typedArray.getDimension(i, TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 
              mTextSize, getResources().getDisplayMetrics())); 
          break; 
        case R.styleable.TabView_text_normal_color: 
          mTextColorNormal = typedArray.getColor(i, mTextColorNormal); 
          break; 
        case R.styleable.TabView_text_select_color: 
          mTextColorSelect = typedArray.getColor(i, mTextColorSelect); 
          break; 
        case R.styleable.TabView_item_padding: 
          mPadding = (int) typedArray.getDimension(i, TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 
              mPadding, getResources().getDisplayMetrics())); 
          break; 
      } 
    } 
    typedArray.recycle(); 
    mTabItems = new ArrayList<>(); 
  } 
  public void setViewPager(final ViewPager mViewPager) { 
    if (mViewPager == null) { 
      return; 
    } 
    this.mViewPager = mViewPager; 
    this.mPagerAdapter = mViewPager.getAdapter(); 
    if (this.mPagerAdapter == null) { 
      throw new RuntimeException("亲，在您设置TabView的ViewPager时，请先设置ViewPager的PagerAdapter"); 
    } 
    this.mChildSize = this.mPagerAdapter.getCount(); 
    this.mViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() { 
      @Override 
      public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { 
//        Log.v("zgy","=============position="+position+",====positionOffset="+positionOffset) ; 
        View leftView; 
        View rightView; 
        if (positionOffset > 0) { 
          leftView = mViewPager.getChildAt(position); 
          rightView = mViewPager.getChildAt(position + 1); 
          leftView.setAlpha(1 - positionOffset); 
          rightView.setAlpha(positionOffset); 
          mTabItems.get(position).setTabAlpha(1 - positionOffset); 
          mTabItems.get(position + 1).setTabAlpha(positionOffset); 
        } else { 
          mViewPager.getChildAt(position).setAlpha(1); 
          mTabItems.get(position).setTabAlpha(1 - positionOffset); 
        } 
        if (mOnPageChangeListener != null) { 
mOnPageChangeListener.onPageScrolled(position, positionOffset, positionOffsetPixels); 
        } 
      } 
      @Override 
      public void onPageSelected(int position) { 
        if (mOnPageChangeListener != null) { 
mOnPageChangeListener.onPageSelected(position); 
        } 
      } 
      @Override 
      public void onPageScrollStateChanged(int state) { 
        if (mOnPageChangeListener != null) { 
mOnPageChangeListener.onPageScrollStateChanged(state); 
        } 
      } 
    }); 
    if (mPagerAdapter instanceof OnItemIconTextSelectListener) { 
      mListener = (OnItemIconTextSelectListener) mPagerAdapter; 
    }else { 
      throw new RuntimeException("请让你的pageAdapter实现OnItemIconTextSelectListener接口"); 
    } 
    initItem(); 
  } 
  public void setOnPageChangeListener(ViewPager.OnPageChangeListener mOnPageChangeListener) { 
    this.mOnPageChangeListener = mOnPageChangeListener; 
  } 
  private void initItem() { 
    for (int i = 0; i < mChildSize; i++) { 
      TabItem tabItem = new TabItem(getContext()); 
      LayoutParams params = new LayoutParams(0, ViewGroup.LayoutParams.WRAP_CONTENT, 1); 
      tabItem.setPadding(mPadding, mPadding, mPadding, mPadding); 
      tabItem.setIconText(mListener.onIconSelect(i), mListener.onTextSelect(i)); 
      tabItem.setTextSize(mTextSize); 
      tabItem.setTextColorNormal(mTextColorNormal); 
      tabItem.setTextColorSelect(mTextColorSelect); 
      tabItem.setLayoutParams(params); 
      tabItem.setTag(i); 
      tabItem.setOnClickListener(this); 
      mTabItems.add(tabItem); 
      addView(tabItem); 
    } 
  } 
  @Override 
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
    super.onMeasure(widthMeasureSpec, heightMeasureSpec); 
  } 
  @Override 
  public void onClick(View v) { 
    int position = (Integer) v.getTag(); 
    if (mViewPager.getCurrentItem() == position) { 
      return; 
    } 
    for (TabItem tabItem : mTabItems) { 
      tabItem.setTabAlpha(0); 
    } 
    mTabItems.get(position).setTabAlpha(1); 
    mViewPager.setCurrentItem(position, false); 
  } 
  public interface OnItemIconTextSelectListener { 
    int[] onIconSelect(int position); 
    String onTextSelect(int position); 
  } 
} 
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