CircularReveal.java

/*
 * Copyright 2016 Google Inc.
 *
 * 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 io.plaidapp.ui.transitions;

import android.animation.Animator;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Point;
import android.support.annotation.IdRes;
import android.support.annotation.NonNull;
import android.transition.TransitionValues;
import android.transition.Visibility;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewAnimationUtils;
import android.view.ViewGroup;

import io.plaidapp.R;
import io.plaidapp.util.AnimUtils;

/**
 * A transition which shows/hides a view with a circular clipping mask. Callers should provide the
 * center point of the reveal either {@link #setCenter(Point) directly} or by
 * {@link #centerOn(View) specifying} another view to center on; otherwise the target {@code view}'s
 * pivot point will be used.
 */
public class CircularReveal extends Visibility {

    private Point center;
    private float startRadius;
    private float endRadius;
    private @IdRes int centerOnId = View.NO_ID;
    private View centerOn;

    public CircularReveal() {
        super();
    }

    public CircularReveal(Context context, AttributeSet attrs) {
        super(context, attrs);
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CircularReveal);
        startRadius = a.getDimension(R.styleable.CircularReveal_startRadius, 0f);
        endRadius = a.getDimension(R.styleable.CircularReveal_endRadius, 0f);
        centerOnId = a.getResourceId(R.styleable.CircularReveal_centerOn, View.NO_ID);
        a.recycle();
    }

    /**
     * The center point of the reveal or conceal, relative to the target {@code view}.
     */
    public void setCenter(@NonNull Point center) {
        this.center = center;
    }

    /**
     * Center the reveal or conceal on this view.
     */
    public void centerOn(@NonNull View source) {
        centerOn = source;
    }

    /**
     * Sets the radius that <strong>reveals</strong> start from.
     */
    public void setStartRadius(float startRadius) {
        this.startRadius = startRadius;
    }

    /**
     * Sets the radius that <strong>conceals</strong> end at.
     */
    public void setEndRadius(float endRadius) {
        this.endRadius = endRadius;
    }

    @Override
    public Animator onAppear(ViewGroup sceneRoot, View view,
                             TransitionValues startValues,
                             TransitionValues endValues) {
        if (view == null || view.getHeight() == 0 || view.getWidth() == 0) return null;
        ensureCenterPoint(sceneRoot, view);
        return new AnimUtils.NoPauseAnimator(ViewAnimationUtils.createCircularReveal(
                view,
                center.x,
                center.y,
                startRadius,
                getFullyRevealedRadius(view)));
    }

    @Override
    public Animator onDisappear(ViewGroup sceneRoot, View view,
                                TransitionValues startValues,
                                TransitionValues endValues) {
        if (view == null || view.getHeight() == 0 || view.getWidth() == 0) return null;
        ensureCenterPoint(sceneRoot, view);
        return new AnimUtils.NoPauseAnimator(ViewAnimationUtils.createCircularReveal(
                view,
                center.x,
                center.y,
                getFullyRevealedRadius(view),
                endRadius));
    }

    private void ensureCenterPoint(ViewGroup sceneRoot, View view) {
        if (center != null) return;
        if (centerOn != null || centerOnId != View.NO_ID) {
            View source;
            if (centerOn != null) {
                source = centerOn;
            } else {
                source = sceneRoot.findViewById(centerOnId);
            }
            if (source != null) {
                // use window location to allow views in diff hierarchies
                int[] loc = new int[2];
                source.getLocationInWindow(loc);
                int srcX = loc[0] + (source.getWidth() / 2);
                int srcY = loc[1] + (source.getHeight() / 2);
                view.getLocationInWindow(loc);
                center = new Point(srcX - loc[0], srcY - loc[1]);
            }
        }
        // else use the pivot point
        if (center == null) {
            center = new Point(Math.round(view.getPivotX()), Math.round(view.getPivotY()));
        }
    }

    private float getFullyRevealedRadius(@NonNull View view) {
        return (float) Math.hypot(
                Math.max(center.x, view.getWidth() - center.x),
                Math.max(center.y, view.getHeight() - center.y));
    }
}