quickstep/src/com/android/quickstep/views/ClearAllButton.java

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * 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.android.quickstep.views;

import android.content.Context;
import android.util.AttributeSet;
import android.widget.Button;

import com.android.launcher3.Utilities;
import com.android.quickstep.views.RecentsView.PageCallbacks;
import com.android.quickstep.views.RecentsView.ScrollState;

public class ClearAllButton extends Button implements PageCallbacks {

    private float mScrollAlpha = 1;
    private float mContentAlpha = 1;

    private final boolean mIsRtl;

    private int mScrollOffset;

    public ClearAllButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        mIsRtl = Utilities.isRtl(context.getResources());
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);

        RecentsView parent = (RecentsView) getParent();
        mScrollOffset = mIsRtl ? parent.getPaddingRight() / 2 : - parent.getPaddingLeft() / 2;
    }

    @Override
    public boolean hasOverlappingRendering() {
        return false;
    }

    public void setContentAlpha(float alpha) {
        if (mContentAlpha != alpha) {
            mContentAlpha = alpha;
            setAlpha(mScrollAlpha * mContentAlpha);
        }
    }

    @Override
    public void onPageScroll(ScrollState scrollState) {
        float width = getWidth();
        if (width == 0) {
            return;
        }

        float shift = Math.min(scrollState.scrollFromEdge, width);
        setTranslationX(mIsRtl ? (mScrollOffset - shift) : (mScrollOffset + shift));
        mScrollAlpha = 1 - shift / width;
        setAlpha(mScrollAlpha * mContentAlpha);
    }
}