TabPageIndicator.java

package com.viewpagerindicator;

import android.content.Context;
import android.graphics.Typeface;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.TypedValue;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.HorizontalScrollView;
import android.widget.LinearLayout;
import android.widget.TextView;

import org.music.player.R;

/**
 * This widget implements the dynamic action bar tab behavior that can change
 * across different configurations or circumstances.
 */
public class TabPageIndicator extends HorizontalScrollView
	implements ViewPager.OnPageChangeListener
	         , View.OnClickListener
{
	Runnable mTabSelector;

	private final LinearLayout mTabLayout;
	private ViewPager mViewPager;
	private ViewPager.OnPageChangeListener mListener;

	private int mSelectedTabIndex;

	public TabPageIndicator(Context context) {
		this(context, null);
	}

	public TabPageIndicator(Context context, AttributeSet attrs) {
		super(context, attrs);
		setHorizontalScrollBarEnabled(false);

		mTabLayout = new LinearLayout(getContext());
		addView(mTabLayout, new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.MATCH_PARENT));
	}

	@Override
	public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
		final boolean lockedExpanded = widthMode == MeasureSpec.EXACTLY;
		setFillViewport(lockedExpanded);

		final int oldWidth = getMeasuredWidth();
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		final int newWidth = getMeasuredWidth();

		if (lockedExpanded && oldWidth != newWidth) {
			// Recenter the tab display if we're at a new (scrollable) size.
			setCurrentItem(mSelectedTabIndex);
		}
	}

	private void animateToTab(final int position) {
		final View tabView = mTabLayout.getChildAt(position);
		if (mTabSelector != null) {
			removeCallbacks(mTabSelector);
		}
		mTabSelector = new Runnable() {
			@Override
			public void run() {
				final int scrollPos = tabView.getLeft() - (getWidth() - tabView.getWidth()) / 2;
				smoothScrollTo(scrollPos, 0);
				mTabSelector = null;
			}
		};
		post(mTabSelector);
	}

	@Override
	public void onAttachedToWindow() {
		super.onAttachedToWindow();
		if (mTabSelector != null) {
			// Re-post the selector we saved
			post(mTabSelector);
		}
	}

	@Override
	public void onDetachedFromWindow() {
		super.onDetachedFromWindow();
		if (mTabSelector != null) {
			removeCallbacks(mTabSelector);
		}
	}

	private void addTab(CharSequence text, int index) {
		Context context = getContext();
		DisplayMetrics dm = context.getResources().getDisplayMetrics();

		int padX = (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 22, dm);
		int padY = (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 12, dm);

		TextView tabView = new TextView(context);
		tabView.setBackgroundResource(R.drawable.vpi__tab_indicator);
		tabView.setPadding(padX, padY, padX, padY);
		tabView.setGravity(Gravity.CENTER);
		tabView.setTextColor(0xfff3f3f3);
		tabView.setTextSize(TypedValue.COMPLEX_UNIT_SP, 12);
		tabView.setTypeface(tabView.getTypeface(), Typeface.BOLD);
		tabView.setSingleLine();
		tabView.setTag(index);
		tabView.setFocusable(true);
		tabView.setOnClickListener(this);
		tabView.setText(text);

		mTabLayout.addView(tabView, new LinearLayout.LayoutParams(0, LayoutParams.MATCH_PARENT, 1));
	}

	@Override
	public void onPageScrollStateChanged(int arg0) {
		if (mListener != null) {
			mListener.onPageScrollStateChanged(arg0);
		}
	}

	@Override
	public void onPageScrolled(int arg0, float arg1, int arg2) {
		if (mListener != null) {
			mListener.onPageScrolled(arg0, arg1, arg2);
		}
	}

	@Override
	public void onPageSelected(int arg0) {
		setCurrentItem(arg0);
		if (mListener != null) {
			mListener.onPageSelected(arg0);
		}
	}

	public void setViewPager(ViewPager view) {
		final PagerAdapter adapter = view.getAdapter();
		if (adapter == null) {
			throw new IllegalStateException("ViewPager does not have adapter instance.");
		}
		mViewPager = view;
		view.setOnPageChangeListener(this);
		notifyDataSetChanged();
	}

	public void notifyDataSetChanged() {
		mTabLayout.removeAllViews();
		PagerAdapter adapter = mViewPager.getAdapter();
		final int count = adapter.getCount();
		for (int i = 0; i < count; i++) {
			addTab(adapter.getPageTitle(i), i);
		}
		if (mSelectedTabIndex > count) {
			mSelectedTabIndex = count - 1;
		}
		setCurrentItem(mSelectedTabIndex);
		requestLayout();
	}

	public void setCurrentItem(int item) {
		if (mViewPager == null) {
			throw new IllegalStateException("ViewPager has not been bound.");
		}
		mSelectedTabIndex = item;
		final int tabCount = mTabLayout.getChildCount();
		for (int i = 0; i < tabCount; i++) {
			final View child = mTabLayout.getChildAt(i);
			final boolean isSelected = i == item;
			child.setSelected(isSelected);
			if (isSelected) {
				animateToTab(item);
			}
		}
	}

	public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) {
		mListener = listener;
	}

	@Override
	public void onClick(View view) {
		mViewPager.setCurrentItem((Integer)view.getTag());
	}
}