仿网易新闻栏目滑动TAB效果
? ? 网易新闻这种滑动TAB效果，在android软件中还是比较常见的（是不是原创我不清楚，仅当学习研究之用～～～）。
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? ?比较常见的做法是：在FrameLayout里包装TAB bar,再在FrameLayout加一个虚拟的tab，切换tab时用虚拟tab在之前选中和当前选中的tab距离之间做一个移动动画。
? ?用此种方法的十之八九，但在复杂的布局中FrameLayout不是你想加就能加滴，加了很容易崩溃滴^_^，此法的劣势大家明了吧？不明那就慢慢明吧。
? ?今天我采用一种更加高效、灵活的方法来实现这种大家喜欢的花样--自画控件+Drawable动画。
? ?大体原理跟FrameLayout加虚拟tab类似，以下是基本的实现方法:在切换tab时在之前选中的tab和当前选中的tab，做一个drawable移动动画。这个drawable?就是当前选中tab的画面。
? ?下面是我重载RadioGoup做的tab bar并实现了滑动效果的类
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public class NewsRadioGroup extends RadioGroupimplementsOnCheckedChangeListener {private final Transformation mTransformation = new Transformation();private Animation mAnimation;private OnCheckedChangeListener mOnCheckedChangeListener;private int mLastCheckedId = -1;private Drawable mDummy;private Drawable mDrawableNormal,mDrawableChecked;private boolean mAminDoing=false;public NewsRadioGroup(Context context) {super(context);init();}public NewsRadioGroup(Context context, AttributeSet attrs) {super(context, attrs);init();}private void init() {super.setOnCheckedChangeListener(this);mLastCheckedId = super.getCheckedRadioButtonId();mDummy = getResources().getDrawable(R.drawable.rb_checked);mDrawableNormal = getResources().getDrawable(android.R.color.transparent);}public void onCheckedChanged(RadioGroup group, int checkedId) {if (mLastCheckedId != -1) {doAmin(checkedId);}else{mLastCheckedId = checkedId;}if (mOnCheckedChangeListener != null) {mOnCheckedChangeListener.onCheckedChanged(group, checkedId);}}private void doAmin( int checkedId){RadioButton rbCurChecked = (RadioButton) super.findViewById(checkedId), rbLastChecked = (RadioButton) super.findViewById(mLastCheckedId);if(rbCurChecked==null||rbLastChecked==null){mLastCheckedId=checkedId;return;}int X1=rbLastChecked.getLeft(),X2=rbCurChecked.getLeft();if (X1 <= 0 && X2 <= 0) {mLastCheckedId=checkedId;return;}if (mDrawableChecked == null) {mDrawableChecked = rbCurChecked.getBackground();mDummy.setBounds(0, 0, rbCurChecked.getWidth(), rbCurChecked.getHeight());}rbCurChecked.setBackgroundDrawable(mDrawableNormal);if(mAminDoing && mAnimation!=null){mAnimation.reset();}mAnimation = new TranslateAnimation(X1,X2, rbCurChecked.getTop(), rbCurChecked.getTop());mAnimation.setDuration(300);mAnimation.initialize(0, 0, 0, 0);mAminDoing=true;mAnimation.startNow();invalidate();}public void setOnCheckedChangeListener(OnCheckedChangeListener listener) {mOnCheckedChangeListener = listener;}protected void onDraw(Canvas canvas) {if (mAnimation == null || !mAminDoing) {return;}if (!mAnimation.hasEnded()) {int sc = canvas.save();mAnimation.getTransformation(AnimationUtils.currentAnimationTimeMillis(),mTransformation);canvas.concat(mTransformation.getMatrix());mDummy.draw(canvas);canvas.restoreToCount(sc);invalidate();} else {mAminDoing=false;setReallyCheck();}}private void setReallyCheck() {if (mLastCheckedId != -1) {super.findViewById(mLastCheckedId).setBackgroundDrawable(mDrawableNormal);}mLastCheckedId = super.getCheckedRadioButtonId();if (mLastCheckedId != -1) {super.findViewById(mLastCheckedId).setBackgroundDrawable(mDrawableChecked);}}}// end class NesRadioGroup??
? 之前以为只要重写RadioGroup的check方法就可以拦截选中，没想到RadioGroup把实际的选中执行实现在setCheckxx里面，而这个函数是私有方法，最后绕了不小的圈子。
代码在上，具体的效果请见demo～～