AvatarImageBehavior.java

package com.alorma.github.ui.utils;

import android.content.Context;
import android.support.design.widget.CoordinatorLayout;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toolbar;
import com.alorma.github.R;

public class AvatarImageBehavior extends CoordinatorLayout.Behavior<ImageView> {

  private final static float MIN_AVATAR_PERCENTAGE_SIZE = 0.3f;
  private final static int EXTRA_FINAL_AVATAR_PADDING = 80;

  private final static String TAG = "behavior";
  private final Context mContext;
  private float mAvatarMaxSize;

  private float mFinalLeftAvatarPadding;
  private float mStartPosition;
  private int mStartXPosition;
  private float mStartToolbarPosition;
  private int mStartYPosition;
  private int mFinalYPosition;
  private int finalHeight;
  private int mStartHeight;
  private int mFinalXPosition;

  public AvatarImageBehavior(Context context, AttributeSet attrs) {
    mContext = context;
    init();

    mFinalLeftAvatarPadding = context.getResources().getDimension(R.dimen.spacing_normal);
  }

  private void init() {
    bindDimensions();
  }

  private void bindDimensions() {
    mAvatarMaxSize = mContext.getResources().getDimension(R.dimen.avatar_size_profile);
  }

  @Override
  public boolean layoutDependsOn(CoordinatorLayout parent, ImageView child, View dependency) {
    return dependency instanceof Toolbar;
  }

  @Override
  public boolean onDependentViewChanged(CoordinatorLayout parent, ImageView child, View dependency) {
    shouldInitProperties(child, dependency);

    final int maxScrollDistance = (int) (mStartToolbarPosition - getStatusBarHeight());
    float expandedPercentageFactor = dependency.getY() / maxScrollDistance;

    float distanceYToSubtract = ((mStartYPosition - mFinalYPosition) * (1f - expandedPercentageFactor)) + (child.getHeight() / 2);

    float distanceXToSubtract = ((mStartXPosition - mFinalXPosition) * (1f - expandedPercentageFactor)) + (child.getWidth() / 2);

    float heightToSubtract = ((mStartHeight - finalHeight) * (1f - expandedPercentageFactor));

    child.setY(mStartYPosition - distanceYToSubtract);
    child.setX(mStartXPosition - distanceXToSubtract);

    int proportionalAvatarSize = (int) (mAvatarMaxSize * (expandedPercentageFactor));

    CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams) child.getLayoutParams();
    lp.width = (int) (mStartHeight - heightToSubtract);
    lp.height = (int) (mStartHeight - heightToSubtract);
    child.setLayoutParams(lp);
    return true;
  }

  private void shouldInitProperties(ImageView child, View dependency) {
    if (mStartYPosition == 0) mStartYPosition = (int) (child.getY() + (child.getHeight() / 2));

    if (mFinalYPosition == 0) mFinalYPosition = (dependency.getHeight() / 2);

    if (mStartHeight == 0) mStartHeight = child.getHeight();

    if (finalHeight == 0) {
      finalHeight = mContext.getResources().getDimensionPixelOffset(R.dimen.image_final_width);
    }

    if (mStartXPosition == 0) mStartXPosition = (int) (child.getX() + (child.getWidth() / 2));

    if (mFinalXPosition == 0) {
      mFinalXPosition = mContext.getResources().getDimensionPixelOffset(R.dimen.abc_action_bar_content_inset_material) + (finalHeight / 2);
    }

    if (mStartToolbarPosition == 0) {
      mStartToolbarPosition = dependency.getY() + (dependency.getHeight() / 2);
    }
  }

  public int getStatusBarHeight() {
    int result = 0;
    int resourceId = mContext.getResources().getIdentifier("status_bar_height", "dimen", "android");

    if (resourceId > 0) {
      result = mContext.getResources().getDimensionPixelSize(resourceId);
    }
    return result;
  }
}