EdgeGlowUtil.java

package com.afollestad.aesthetic;

import android.annotation.TargetApi;
import android.graphics.PorterDuff;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.support.annotation.ColorInt;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.annotation.RestrictTo;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.EdgeEffectCompat;
import android.support.v4.widget.NestedScrollView;
import android.support.v7.widget.RecyclerView;
import android.widget.AbsListView;
import android.widget.EdgeEffect;
import android.widget.ScrollView;

import java.lang.reflect.Field;

import static android.support.annotation.RestrictTo.Scope.LIBRARY_GROUP;

/** @author Aidan Follestad (afollestad) */
@RestrictTo(LIBRARY_GROUP)
final class EdgeGlowUtil {

  private static Field EDGE_GLOW_FIELD_EDGE;
  private static Field EDGE_GLOW_FIELD_GLOW;
  private static Field EDGE_EFFECT_COMPAT_FIELD_EDGE_EFFECT;
  private static Field SCROLL_VIEW_FIELD_EDGE_GLOW_TOP;
  private static Field SCROLL_VIEW_FIELD_EDGE_GLOW_BOTTOM;
  private static Field NESTED_SCROLL_VIEW_FIELD_EDGE_GLOW_TOP;
  private static Field NESTED_SCROLL_VIEW_FIELD_EDGE_GLOW_BOTTOM;
  private static Field LIST_VIEW_FIELD_EDGE_GLOW_TOP;
  private static Field LIST_VIEW_FIELD_EDGE_GLOW_BOTTOM;
  private static Field RECYCLER_VIEW_FIELD_EDGE_GLOW_TOP;
  private static Field RECYCLER_VIEW_FIELD_EDGE_GLOW_LEFT;
  private static Field RECYCLER_VIEW_FIELD_EDGE_GLOW_RIGHT;
  private static Field RECYCLER_VIEW_FIELD_EDGE_GLOW_BOTTOM;
  private static Field VIEW_PAGER_FIELD_EDGE_GLOW_LEFT;
  private static Field VIEW_PAGER_FIELD_EDGE_GLOW_RIGHT;

  private static void invalidateEdgeEffectFields() {
    if (EDGE_GLOW_FIELD_EDGE != null
        && EDGE_GLOW_FIELD_GLOW != null
        && EDGE_EFFECT_COMPAT_FIELD_EDGE_EFFECT != null) {
      EDGE_GLOW_FIELD_EDGE.setAccessible(true);
      EDGE_GLOW_FIELD_GLOW.setAccessible(true);
      EDGE_EFFECT_COMPAT_FIELD_EDGE_EFFECT.setAccessible(true);
      return;
    }
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
      Field edge = null;
      Field glow = null;
      for (Field f : EdgeEffect.class.getDeclaredFields()) {
        switch (f.getName()) {
          case "mEdge":
            f.setAccessible(true);
            edge = f;
            break;
          case "mGlow":
            f.setAccessible(true);
            glow = f;
            break;
        }
      }
      EDGE_GLOW_FIELD_EDGE = edge;
      EDGE_GLOW_FIELD_GLOW = glow;
    } else {
      EDGE_GLOW_FIELD_EDGE = null;
      EDGE_GLOW_FIELD_GLOW = null;
    }

    Field efc = null;
    try {
      efc = EdgeEffectCompat.class.getDeclaredField("mEdgeEffect");
    } catch (NoSuchFieldException e) {
      if (BuildConfig.DEBUG) e.printStackTrace();
    }
    EDGE_EFFECT_COMPAT_FIELD_EDGE_EFFECT = efc;
  }

  private static void invalidateScrollViewFields() {
    if (SCROLL_VIEW_FIELD_EDGE_GLOW_TOP != null && SCROLL_VIEW_FIELD_EDGE_GLOW_BOTTOM != null) {
      SCROLL_VIEW_FIELD_EDGE_GLOW_TOP.setAccessible(true);
      SCROLL_VIEW_FIELD_EDGE_GLOW_BOTTOM.setAccessible(true);
      return;
    }
    final Class<?> cls = ScrollView.class;
    for (Field f : cls.getDeclaredFields()) {
      switch (f.getName()) {
        case "mEdgeGlowTop":
          f.setAccessible(true);
          SCROLL_VIEW_FIELD_EDGE_GLOW_TOP = f;
          break;
        case "mEdgeGlowBottom":
          f.setAccessible(true);
          SCROLL_VIEW_FIELD_EDGE_GLOW_BOTTOM = f;
          break;
      }
    }
  }

  private static void invalidateNestedScrollViewFields() {
    if (NESTED_SCROLL_VIEW_FIELD_EDGE_GLOW_TOP != null
        && NESTED_SCROLL_VIEW_FIELD_EDGE_GLOW_BOTTOM != null) {
      NESTED_SCROLL_VIEW_FIELD_EDGE_GLOW_TOP.setAccessible(true);
      NESTED_SCROLL_VIEW_FIELD_EDGE_GLOW_BOTTOM.setAccessible(true);
      return;
    }
    Class cls = NestedScrollView.class;
    for (Field f : cls.getDeclaredFields()) {
      switch (f.getName()) {
        case "mEdgeGlowTop":
          f.setAccessible(true);
          NESTED_SCROLL_VIEW_FIELD_EDGE_GLOW_TOP = f;
          break;
        case "mEdgeGlowBottom":
          f.setAccessible(true);
          NESTED_SCROLL_VIEW_FIELD_EDGE_GLOW_BOTTOM = f;
          break;
      }
    }
  }

  private static void invalidateListViewFields() {
    if (LIST_VIEW_FIELD_EDGE_GLOW_TOP != null && LIST_VIEW_FIELD_EDGE_GLOW_BOTTOM != null) {
      LIST_VIEW_FIELD_EDGE_GLOW_TOP.setAccessible(true);
      LIST_VIEW_FIELD_EDGE_GLOW_BOTTOM.setAccessible(true);
      return;
    }
    final Class<?> cls = AbsListView.class;
    for (Field f : cls.getDeclaredFields()) {
      switch (f.getName()) {
        case "mEdgeGlowTop":
          f.setAccessible(true);
          LIST_VIEW_FIELD_EDGE_GLOW_TOP = f;
          break;
        case "mEdgeGlowBottom":
          f.setAccessible(true);
          LIST_VIEW_FIELD_EDGE_GLOW_BOTTOM = f;
          break;
      }
    }
  }

  private static void invalidateRecyclerViewFields() {
    if (RECYCLER_VIEW_FIELD_EDGE_GLOW_TOP != null
        && RECYCLER_VIEW_FIELD_EDGE_GLOW_LEFT != null
        && RECYCLER_VIEW_FIELD_EDGE_GLOW_RIGHT != null
        && RECYCLER_VIEW_FIELD_EDGE_GLOW_BOTTOM != null) {
      RECYCLER_VIEW_FIELD_EDGE_GLOW_TOP.setAccessible(true);
      RECYCLER_VIEW_FIELD_EDGE_GLOW_LEFT.setAccessible(true);
      RECYCLER_VIEW_FIELD_EDGE_GLOW_RIGHT.setAccessible(true);
      RECYCLER_VIEW_FIELD_EDGE_GLOW_BOTTOM.setAccessible(true);
      return;
    }
    Class cls = RecyclerView.class;
    for (Field f : cls.getDeclaredFields()) {
      switch (f.getName()) {
        case "mTopGlow":
          f.setAccessible(true);
          RECYCLER_VIEW_FIELD_EDGE_GLOW_TOP = f;
          break;
        case "mBottomGlow":
          f.setAccessible(true);
          RECYCLER_VIEW_FIELD_EDGE_GLOW_BOTTOM = f;
          break;
        case "mLeftGlow":
          f.setAccessible(true);
          RECYCLER_VIEW_FIELD_EDGE_GLOW_LEFT = f;
          break;
        case "mRightGlow":
          f.setAccessible(true);
          RECYCLER_VIEW_FIELD_EDGE_GLOW_RIGHT = f;
          break;
      }
    }
  }

  private static void invalidateViewPagerFields() {
    if (VIEW_PAGER_FIELD_EDGE_GLOW_LEFT != null && VIEW_PAGER_FIELD_EDGE_GLOW_RIGHT != null) {
      VIEW_PAGER_FIELD_EDGE_GLOW_LEFT.setAccessible(true);
      VIEW_PAGER_FIELD_EDGE_GLOW_RIGHT.setAccessible(true);
      return;
    }
    Class cls = ViewPager.class;
    for (Field f : cls.getDeclaredFields()) {
      switch (f.getName()) {
        case "mLeftEdge":
          f.setAccessible(true);
          VIEW_PAGER_FIELD_EDGE_GLOW_LEFT = f;
          break;
        case "mRightEdge":
          f.setAccessible(true);
          VIEW_PAGER_FIELD_EDGE_GLOW_RIGHT = f;
          break;
      }
    }
  }

  // Setter methods

  static void setEdgeGlowColor(@NonNull ScrollView scrollView, @ColorInt int color) {
    invalidateScrollViewFields();
    try {
      Object ee;
      ee = SCROLL_VIEW_FIELD_EDGE_GLOW_TOP.get(scrollView);
      setEffectColor(ee, color);
      ee = SCROLL_VIEW_FIELD_EDGE_GLOW_BOTTOM.get(scrollView);
      setEffectColor(ee, color);
    } catch (Exception ex) {
      if (BuildConfig.DEBUG) ex.printStackTrace();
    }
  }

  static void setEdgeGlowColor(@NonNull NestedScrollView scrollView, @ColorInt int color) {
    invalidateNestedScrollViewFields();
    try {
      Object ee = NESTED_SCROLL_VIEW_FIELD_EDGE_GLOW_TOP.get(scrollView);
      setEffectColor(ee, color);
      ee = NESTED_SCROLL_VIEW_FIELD_EDGE_GLOW_BOTTOM.get(scrollView);
      setEffectColor(ee, color);
    } catch (Exception ex) {
      if (BuildConfig.DEBUG) ex.printStackTrace();
    }
  }

  static void setEdgeGlowColor(@NonNull AbsListView listView, @ColorInt int color) {
    invalidateListViewFields();
    try {
      Object ee = LIST_VIEW_FIELD_EDGE_GLOW_TOP.get(listView);
      setEffectColor(ee, color);
      ee = LIST_VIEW_FIELD_EDGE_GLOW_BOTTOM.get(listView);
      setEffectColor(ee, color);
    } catch (Exception ex) {
      if (BuildConfig.DEBUG) ex.printStackTrace();
    }
  }

  static void setEdgeGlowColor(
      @NonNull RecyclerView scrollView,
      final @ColorInt int color,
      @Nullable RecyclerView.OnScrollListener scrollListener) {
    invalidateRecyclerViewFields();
    invalidateRecyclerViewFields();
    if (scrollListener == null) {
      scrollListener =
          new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
              super.onScrollStateChanged(recyclerView, newState);
              EdgeGlowUtil.setEdgeGlowColor(recyclerView, color, this);
            }
          };
      scrollView.addOnScrollListener(scrollListener);
    }
    try {
      Object ee = RECYCLER_VIEW_FIELD_EDGE_GLOW_TOP.get(scrollView);
      setEffectColor(ee, color);
      ee = RECYCLER_VIEW_FIELD_EDGE_GLOW_BOTTOM.get(scrollView);
      setEffectColor(ee, color);
      ee = RECYCLER_VIEW_FIELD_EDGE_GLOW_LEFT.get(scrollView);
      setEffectColor(ee, color);
      ee = RECYCLER_VIEW_FIELD_EDGE_GLOW_RIGHT.get(scrollView);
      setEffectColor(ee, color);
    } catch (Exception ex) {
      if (BuildConfig.DEBUG) ex.printStackTrace();
    }
  }

  static void setEdgeGlowColor(@NonNull ViewPager pager, @ColorInt int color) {
    invalidateViewPagerFields();
    try {
      Object ee = VIEW_PAGER_FIELD_EDGE_GLOW_LEFT.get(pager);
      setEffectColor(ee, color);
      ee = VIEW_PAGER_FIELD_EDGE_GLOW_RIGHT.get(pager);
      setEffectColor(ee, color);
    } catch (Exception ex) {
      if (BuildConfig.DEBUG) ex.printStackTrace();
    }
  }

  // Utilities

  @TargetApi(Build.VERSION_CODES.LOLLIPOP)
  private static void setEffectColor(Object edgeEffect, @ColorInt int color) {
    invalidateEdgeEffectFields();
    if (edgeEffect instanceof EdgeEffectCompat) {
      // EdgeEffectCompat
      try {
        EDGE_EFFECT_COMPAT_FIELD_EDGE_EFFECT.setAccessible(true);
        edgeEffect = EDGE_EFFECT_COMPAT_FIELD_EDGE_EFFECT.get(edgeEffect);
      } catch (IllegalAccessException e) {
        e.printStackTrace();
        return;
      }
    }
    if (edgeEffect == null) {
      return;
    }
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
      // EdgeGlow
      try {
        EDGE_GLOW_FIELD_EDGE.setAccessible(true);
        final Drawable mEdge = (Drawable) EDGE_GLOW_FIELD_EDGE.get(edgeEffect);
        EDGE_GLOW_FIELD_GLOW.setAccessible(true);
        final Drawable mGlow = (Drawable) EDGE_GLOW_FIELD_GLOW.get(edgeEffect);
        mEdge.setColorFilter(color, PorterDuff.Mode.SRC_IN);
        mGlow.setColorFilter(color, PorterDuff.Mode.SRC_IN);
        mEdge.setCallback(null); // free up any references
        mGlow.setCallback(null); // free up any references
      } catch (Exception ex) {
        ex.printStackTrace();
      }
    } else {
      // EdgeEffect
      ((EdgeEffect) edgeEffect).setColor(color);
    }
  }
}