Fix tag picker checkbox tint on Android 4.4

app/src/main/java/org/tasks/tags/CheckBoxTriStates.java

@@ -1,8 +1,16 @@
 package org.tasks.tags;
 
+import static com.todoroo.andlib.utility.AndroidUtilities.atLeastLollipop;
 import static org.tasks.preferences.ResourceResolver.getData;
 
 import android.content.Context;
+import android.graphics.Bitmap;
+import android.graphics.Bitmap.Config;
+import android.graphics.Canvas;
+import android.graphics.Paint;
+import android.graphics.PorterDuff;
+import android.graphics.PorterDuffColorFilter;
+import android.graphics.drawable.BitmapDrawable;
 import android.graphics.drawable.Drawable;
 import android.os.Parcel;
 import android.os.Parcelable;
@@ -118,14 +126,23 @@ public class CheckBoxTriStates extends AppCompatCheckBox {
         break;
     }
     Drawable original = getResources().getDrawable(btnDrawable);
-    Drawable drawable = original.mutate();
+    Drawable drawable;
+    int color = state == State.UNCHECKED
+        ? getResources().getColor(R.color.icon_tint)
+        : getData(getContext(), R.attr.colorAccent);
+    if (atLeastLollipop()) {
+      drawable = original.mutate();
+      DrawableCompat.setTint(drawable, color);
+    } else {
+      Bitmap bitmap = ((BitmapDrawable) original).getBitmap();
+      Paint paint = new Paint();
+      paint.setColorFilter(new PorterDuffColorFilter(color, PorterDuff.Mode.SRC_IN));
+      Bitmap bitmapResult = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888);
+      Canvas canvas = new Canvas(bitmapResult);
+      canvas.drawBitmap(bitmap, 0, 0, paint);
+      drawable = new BitmapDrawable(getContext().getResources(), bitmapResult);
+    }
     drawable.setAlpha(alpha);
-    DrawableCompat.setTint(
-        drawable,
-        state == State.UNCHECKED
-            ? getResources().getColor(R.color.icon_tint)
-            : getData(getContext(), R.attr.colorAccent));
-
     setButtonDrawable(drawable);
   }