Android Open Source - My-Wallet-Android View Pager Tabs

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License

The source code is released under:
GNU General Public License
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Java Source Code

/*
 * Copyright 2011-2012 the original author or authors.
 *// w  w w .j a v a 2s  .  c om
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package piuk.blockchain.android.util;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Typeface;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.AttributeSet;
import android.view.View;
import piuk.blockchain.R;

/**
 * @author Andreas Schildbach
 */
public class ViewPagerTabs extends View implements OnPageChangeListener
{
  private final List<String> labels = new ArrayList<String>();
  private final Paint paint = new Paint();
  private int maxWidth = 0;
  private int pagePosition = 0;
  private float pageOffset = 0;

  public ViewPagerTabs(final Context context, final AttributeSet attrs)
  {
    super(context, attrs);
    paint.setTextSize(getResources().getDimension(R.dimen.font_size_tiny));
    paint.setColor(Color.BLACK);
    paint.setAntiAlias(true);
    paint.setShadowLayer(2, 0, 0, Color.WHITE);
  }

  public void addTabLabels(final int... labelResId)
  {
    final Context context = getContext();

    paint.setTypeface(Typeface.DEFAULT_BOLD);

    for (final int resId : labelResId)
    {
      final String label = context.getString(resId);

      final int width = (int) paint.measureText(label);

      if (width > maxWidth)
        maxWidth = width;

      labels.add(label);
    }
  }

  @Override
  protected void onDraw(final Canvas canvas)
  {
    super.onDraw(canvas);

    final int viewWidth = getWidth();
    final int viewHalfWidth = viewWidth / 2;
    final int viewBottom = getHeight();

    final float density = getResources().getDisplayMetrics().density;
    final float spacing = 32 * density;

    final Path path = new Path();
    path.moveTo(viewHalfWidth, viewBottom - 5 * density);
    path.lineTo(viewHalfWidth + 5 * density, viewBottom);
    path.lineTo(viewHalfWidth - 5 * density, viewBottom);
    path.close();

    paint.setColor(Color.WHITE);
    canvas.drawPath(path, paint);

    paint.setTypeface(Typeface.DEFAULT_BOLD);
    final float y = getPaddingTop() + -paint.getFontMetrics().top;

    for (int i = 0; i < labels.size(); i++)
    {
      final String label = labels.get(i);

      paint.setTypeface(i == pagePosition ? Typeface.DEFAULT_BOLD : Typeface.DEFAULT);
      paint.setColor(i == pagePosition ? Color.BLACK : Color.DKGRAY);

      final float x = viewHalfWidth + (maxWidth + spacing) * (i - pageOffset);
      final float labelWidth = paint.measureText(label);
      final float labelHalfWidth = labelWidth / 2;

      final float labelLeft = x - labelHalfWidth;
      final float labelVisibleLeft = labelLeft >= 0 ? 1f : 1f - (-labelLeft / labelWidth);

      final float labelRight = x + labelHalfWidth;
      final float labelVisibleRight = labelRight < viewWidth ? 1f : 1f - ((labelRight - viewWidth) / labelWidth);

      final float labelVisible = Math.min(labelVisibleLeft, labelVisibleRight);

      paint.setAlpha((int) (labelVisible * 255));

      canvas.drawText(label, labelLeft, y, paint);
    }
  }

  @Override
  protected void onMeasure(final int widthMeasureSpec, final int heightMeasureSpec)
  {
    final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    final int widthSize = MeasureSpec.getSize(widthMeasureSpec);

    final int width;
    if (widthMode == MeasureSpec.EXACTLY)
      width = widthSize;
    else if (widthMode == MeasureSpec.AT_MOST)
      width = Math.min(getMeasuredWidth(), widthSize);
    else
      width = 0;

    final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
    final int heightSize = MeasureSpec.getSize(heightMeasureSpec);

    final int height;
    if (heightMode == MeasureSpec.EXACTLY)
      height = heightSize;
    else if (heightMode == MeasureSpec.AT_MOST)
      height = Math.min(getSuggestedMinimumHeight(), heightSize);
    else
      height = getSuggestedMinimumHeight();

    setMeasuredDimension(width, height);
  }

  @Override
  protected int getSuggestedMinimumHeight()
  {
    paint.setTypeface(Typeface.DEFAULT_BOLD);
    return (int) (-paint.getFontMetrics().top + paint.getFontMetrics().bottom) + getPaddingTop() + getPaddingBottom();
  }

  public void onPageScrolled(final int position, final float positionOffset, final int positionOffsetPixels)
  {
    pageOffset = position + positionOffset;
    invalidate();
  }

  public void onPageSelected(final int position)
  {
    pagePosition = position;
    invalidate();
  }

  public void onPageScrollStateChanged(final int state)
  {
  }
}
Java Source Code List
