Tint edges on pre-lollipop

EdgeTint.java

/*
 * Copyright (C) 2015 Jared Rummler <jared.rummler@gmail.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.jrummyapps.android.ui;

import android.app.Activity;
import android.graphics.PorterDuff;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.support.annotation.ColorInt;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.EdgeEffectCompat;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.EdgeEffect;
import android.widget.HorizontalScrollView;
import android.widget.ScrollView;

import java.lang.reflect.Field;

/**
 * <p>Helper class to set the color of an {@link EdgeEffect} on pre-lollipop.</p>
 *
 * <p>Example usage in an {@link Activity}:</p>
 *
 * <pre>
 * &#64;Override public void onStart() {
 *     super.onStart();
 *     if (android.os.Build.VERSION.SDK_INT < android.os.Build.VERSION_CODES.LOLLIPOP) {
 *         EdgeTint.on(this).apply(getResources().getColor(R.color.color_primary));
 *     }
 * }
 * </pre>
 */
public class EdgeTint {

  /**
   * @param activity
   *     the activity to apply the edge effect on.
   * @return A new {@link EdgeTint}. To set the color use {@link #apply(int)}.
   */
  public static EdgeTint on(Activity activity) {
    return new EdgeTint((ViewGroup) activity.findViewById(android.R.id.content).getRootView());
  }

  /**
   * @param view
   *     the ViewGroup to apply the edge effect on.
   * @return A new {@link EdgeTint}. To set the color use {@link #apply(int)}.
   */
  public static EdgeTint on(ViewGroup view) {
    return new EdgeTint(view);
  }

  /**
   * Set the color of an {@link EdgeEffect}. This uses reflection on pre-L.
   *
   * @param edgeEffect
   *     the EdgeEffect to apply the color on.
   * @param color
   *     the color value
   */
  public static void setEdgeEffectColor(EdgeEffect edgeEffect, @ColorInt int color) {
    try {
      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        edgeEffect.setColor(color);
        return;
      }
      for (String name : new String[]{"mEdge", "mGlow"}) {
        Field field = EdgeEffect.class.getDeclaredField(name);
        if (!field.isAccessible()) {
          field.setAccessible(true);
        }
        Drawable drawable = (Drawable) field.get(edgeEffect);
        drawable.setColorFilter(color, PorterDuff.Mode.SRC_IN);
        drawable.setCallback(null); // free up any references
      }
    } catch (Throwable ignored) {
    }
  }

  /**
   * Set the edge-effect color on a ListView or GridView.
   *
   * @param listView
   *     The view (ListView/GridView) to set the edge color
   * @param color
   *     the color value
   */
  public static void setEdgeGlowColor(AbsListView listView, @ColorInt int color) {
    try {
      for (String name : new String[]{"mEdgeGlowTop", "mEdgeGlowBottom"}) {
        Field field = AbsListView.class.getDeclaredField(name);
        if (!field.isAccessible()) {
          field.setAccessible(true);
        }
        setEdgeEffectColor((EdgeEffect) field.get(listView), color);
      }
    } catch (Throwable ignored) {
    }
  }

  /**
   * Set the edge-effect color on a {@link HorizontalScrollView}.
   *
   * @param hsv
   *     the view to set the edge color
   * @param color
   *     the color value
   */
  public static void setEdgeGlowColor(HorizontalScrollView hsv, @ColorInt int color) {
    try {
      for (String name : new String[]{"mEdgeGlowLeft", "mEdgeGlowRight"}) {
        Field field = HorizontalScrollView.class.getDeclaredField(name);
        if (!field.isAccessible()) {
          field.setAccessible(true);
        }
        setEdgeEffectColor((EdgeEffect) field.get(hsv), color);
      }
    } catch (Throwable ignored) {
    }
  }

  /**
   * Set the edge-effect color on a {@link ScrollView}.
   *
   * @param scrollView
   *     the view to set the edge color
   * @param color
   *     the color value
   */
  public static void setEdgeGlowColor(ScrollView scrollView, int color) {
    try {
      for (String name : new String[]{"mEdgeGlowTop", "mEdgeGlowBottom"}) {
        Field field = ScrollView.class.getDeclaredField(name);
        if (!field.isAccessible()) {
          field.setAccessible(true);
        }
        setEdgeEffectColor((EdgeEffect) field.get(scrollView), color);
      }
    } catch (Throwable ignored) {
    }
  }

  /**
   * Set the edge-effect color on a {@link ViewPager}.
   *
   * @param viewPager
   *     the ViewPager
   * @param color
   *     the color value
   */
  public static void setEdgeGlowColor(ViewPager viewPager, int color) {
    try {
      for (String name : new String[]{"mLeftEdge", "mRightEdge"}) {
        Field field = viewPager.getClass().getDeclaredField(name);
        if (!field.isAccessible()) {
          field.setAccessible(true);
        }
        EdgeEffectCompat edge = (EdgeEffectCompat) field.get(viewPager);
        Field fEdgeEffect = edge.getClass().getDeclaredField("mEdgeEffect");
        fEdgeEffect.setAccessible(true);
        setEdgeEffectColor((EdgeEffect) fEdgeEffect.get(edge), color);
      }
    } catch (Throwable ignored) {
    }
  }

  private final ViewGroup view;

  private EdgeTint(ViewGroup view) {
    this.view = view;
  }

  /**
   * Sets the color on all edge effects for the ViewGroup/Activity passed to the constructor.
   *
   * @param color
   *     the color to be applied on the {@link EdgeEffect}
   */
  public void apply(int color) {
    setEdgeTint(view, color);
  }

  private void setEdgeTint(ViewGroup viewGroup, int color) {
    for (int i = 0, count = viewGroup.getChildCount(); i < count; i++) {
      View child = viewGroup.getChildAt(i);
      if (child instanceof AbsListView) {
        setEdgeGlowColor((AbsListView) child, color);
      } else if (child instanceof HorizontalScrollView) {
        setEdgeGlowColor((HorizontalScrollView) child, color);
      } else if (child instanceof ScrollView) {
        setEdgeGlowColor((ScrollView) child, color);
      } else if (child instanceof ViewPager) {
        setEdgeGlowColor((ViewPager) child, color);
      } else if (child instanceof ViewGroup) {
        setEdgeTint((ViewGroup) child, color);
      }
    }
  }

}