Android Open Source - ParallaxScroll Parallax List View Helper

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Back to project page ParallaxScroll.
License

The source code is released under:
MIT License
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Java Source Code

package com.nirhart.parallaxscroll.views;
//w ww.  ja v  a2s  . co  m
import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.TranslateAnimation;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;

import com.nirhart.parallaxscroll.R;

public class ParallaxListViewHelper implements OnScrollListener {

  private static final float DEFAULT_ALPHA_FACTOR = -1F;
  private static final float DEFAULT_PARALLAX_FACTOR = 1.9F;
  private static final boolean DEFAULT_IS_CIRCULAR = false;
  private float parallaxFactor = DEFAULT_PARALLAX_FACTOR;
  private float alphaFactor = DEFAULT_ALPHA_FACTOR;
  private ParallaxedView parallaxedView;
  private boolean isCircular;
  private OnScrollListener listener = null;
  private ListView listView;

  protected ParallaxListViewHelper(Context context, AttributeSet attrs, ListView listView) {
    init(context, attrs, listView);
  }

  protected void init(Context context, AttributeSet attrs, ListView listView) {
    this.listView = listView;
    TypedArray typeArray = context.obtainStyledAttributes(attrs, R.styleable.ParallaxScroll);
    this.parallaxFactor = typeArray.getFloat(R.styleable.ParallaxScroll_parallax_factor, DEFAULT_PARALLAX_FACTOR);
    this.alphaFactor = typeArray.getFloat(R.styleable.ParallaxScroll_alpha_factor, DEFAULT_ALPHA_FACTOR);
    this.isCircular = typeArray.getBoolean(R.styleable.ParallaxScroll_circular_parallax, DEFAULT_IS_CIRCULAR);
    typeArray.recycle();
  }

  protected void setOnScrollListener(OnScrollListener l) {
    this.listener = l;
  }
  
  protected void addParallaxedHeaderView(View v) {
    addParallaxedView(v);
  }

  protected void addParallaxedHeaderView(View v, Object data, boolean isSelectable) {
    addParallaxedView(v);
  }

  protected void addParallaxedView(View v) {
    this.parallaxedView = new ListViewParallaxedItem(v);
  }

  protected void parallaxScroll() {
    if (isCircular)
      circularParallax();
    else
      headerParallax();
  }

  private void circularParallax() {
    if (listView.getChildCount() > 0) {
      int top = -listView.getChildAt(0).getTop();
      if (top >= 0) {
        fillParallaxedViews();
        setFilters(top);
      }
    }
  }

  private void headerParallax() {
    if (parallaxedView != null) {
      if (listView.getChildCount() > 0) {
        int top = -listView.getChildAt(0).getTop();
        if (top >= 0) {
          setFilters(top);
        }
      }
    }
  }

  private void setFilters(int top) {
    parallaxedView.setOffset((float)top / parallaxFactor);
    if (alphaFactor != DEFAULT_ALPHA_FACTOR) {
      float alpha = (top <= 0) ? 1 : (100 / ((float)top * alphaFactor));
      parallaxedView.setAlpha(alpha);
    }
    parallaxedView.animateNow();
  }

  private void fillParallaxedViews() {
    if (parallaxedView == null || parallaxedView.is(listView.getChildAt(0)) == false) {
      if (parallaxedView != null) {
        resetFilters();
        parallaxedView.setView(listView.getChildAt(0));
      } else {
        parallaxedView = new ListViewParallaxedItem(listView.getChildAt(0));
      }
    }
  }

  private void resetFilters() {
    parallaxedView.setOffset(0);
    if (alphaFactor != DEFAULT_ALPHA_FACTOR)
      parallaxedView.setAlpha(1F);
    parallaxedView.animateNow();
  }
  
  @Override
  public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
    parallaxScroll();
    if (this.listener != null)
      this.listener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
  }

  @Override
  public void onScrollStateChanged(AbsListView view, int scrollState) {
    if (this.listener != null)
      this.listener.onScrollStateChanged(view, scrollState);
  }
  
  protected class ListViewParallaxedItem extends ParallaxedView {

    public ListViewParallaxedItem(View view) {
      super(view);
    }
    
    @Override
    protected void translatePreICS(View view, float offset) {
      addAnimation(new TranslateAnimation(0, 0, offset, offset));
    }
  }
}
Java Source Code List
