ViewPager 的 PagerIndicator

public class PagerIndicator extends LinearLayout implements OnPageChangeListener, OnClickListener {

private List<String> mTitles;
private int mTabCount;
private int mTitleItemWidth;
private int mLineColor;
private int mSelectedTextColor;
private int mNorTextColor;
private int mTextSize = 17;
private int mLineWidth;
private Paint mLinePaint;
private float mTranslationX;
private ViewPager mViewPager;
private List<TextView> mTextViewList;
private OnViewPagerChangeListener listener;

public interface OnViewPagerChangeListener{
void onPageScrolled(int position, float positionOffset,int positionOffsetPixels);
}

public PagerIndicator(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}

private void init() {
mLineColor = getResources().getColor(R.color.indicator_bottom_line_color);
mSelectedTextColor = getResources().getColor(R.color.indicator_selected_txt_color);
mNorTextColor = getResources().getColor(R.color.indicator_un_selected_txt_color);

mLineWidth = DensityConverter.dp2px(getContext(), 1);
mLinePaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG);
mLinePaint.setColor(mLineColor);
mLinePaint.setStrokeWidth(mLineWidth);
mLinePaint.setStrokeCap(Cap.ROUND);

}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
if(mTitles != null && mTitles.size() > 0 ){
mTitleItemWidth = w / mTitles.size();
}
}

@SuppressWarnings("deprecation")
public void setViewPager(ViewPager viewPager){
mViewPager = viewPager;
initTitles();
initTitleItemView();
mViewPager.setOnPageChangeListener(this);
}

private void initTitleItemView() {
mTextViewList = new ArrayList<TextView>();
if(getChildCount() > 0){
this.removeAllViews();
}
for(int i = 0 ; i < mTabCount; i++){
TextView titleTv  = new TextView(getContext());
LinearLayout.LayoutParams params = new LayoutParams(0, android.view.ViewGroup.LayoutParams.MATCH_PARENT);
params.weight = 1;
titleTv.setText(mTitles.get(i));
titleTv.setId(i);
titleTv.setGravity(Gravity.CENTER);
titleTv.setTextColor(i == 0 ? mSelectedTextColor : mNorTextColor);
titleTv.setTextSize(TypedValue.COMPLEX_UNIT_SP, mTextSize);
titleTv.setLayoutParams(params);
titleTv.setOnClickListener(this);
addView(titleTv);
mTextViewList.add(titleTv);
}
}

private void initTitles(){
PagerAdapter adapter = mViewPager.getAdapter();
mTabCount = adapter.getCount();
mTitles = new ArrayList<String>();
for(int i = 0 ; i < mTabCount ; i++){
String title = (String) adapter.getPageTitle(i);
mTitles.add(title);
}
}

@Override
public void onPageScrollStateChanged(int position) {
}

@Override
public void onPageScrolled(int position, float positionOffset,int positionOffsetPixels) {
if(null != listener){
listener.onPageScrolled(position, positionOffset, positionOffsetPixels);
}
mTranslationX = getWidth() / mTabCount * (position + positionOffset);
for(int i = 0 ; i < mTextViewList.size() ; i++){
TextView textView = mTextViewList.get(i);
if(position == i){
textView.setTextColor(mSelectedTextColor);
}else{
textView.setTextColor(mNorTextColor);
}
}
invalidate();
}

@Override
public void onPageSelected(int state) {}

//绘制下划线
@Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);
canvas.save();
canvas.translate(mTranslationX, getHeight() - mLineWidth / 2);
canvas.drawLine(0, 0, mTitleItemWidth, 0, mLinePaint);
canvas.restore();
}

@Override
public void onClick(View v) {
int id = v.getId();
mViewPager.setCurrentItem(id);
}

public void setOnViewPagerChangeListener(OnViewPagerChangeListener l) {
this.listener = l;
}
}

mTranslationX = getWidth() / mTabCount * (position + positionOffset);
for(int i = 0 ; i < mTextViewList.size() ; i++){
TextView textView = mTextViewList.get(i);
if(position == i){
textView.setTextColor(mSelectedTextColor);
}else{
textView.setTextColor(mNorTextColor);
}
}
invalidate();

@Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);
canvas.save();
canvas.translate(mTranslationX, getHeight() - mLineWidth / 2);
canvas.drawLine(0, 0, mTitleItemWidth, 0, mLinePaint);
canvas.restore();
}