AlphaTouchInterceptorOverlay.java

/*
 * Copyright (C) 2013 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.tabcarousel;

import android.content.Context;
import android.view.View;
import android.widget.FrameLayout;

/**
 * A {@link View} that other Views can use to create a touch-interceptor layer
 * above their other sub-views. This layer can be enabled and disabled; when
 * enabled, clicks are intercepted and passed to a listener. Also supports an
 * alpha layer to dim the content underneath. By default, the alpha layer is the
 * same View as the touch-interceptor layer. However, for some use-cases, you
 * want a few Views to not be dimmed, but still have touches intercepted (for
 * example, {@link CarouselTab}'s label appears above the alpha layer). In this
 * case, you can specify the View to use as the alpha layer via setAlphaLayer();
 * in this case you are responsible for managing the z-order of the alpha-layer
 * with respect to your other sub-views. Typically, you would not use this class
 * directly, but rather use another class that uses it, for example
 * {@link FrameLayoutWithOverlay}.
 */
public class AlphaTouchInterceptorOverlay extends FrameLayout {

    private final View mInterceptorLayer;
    private float mAlpha = 0.0f;
    private View mAlphaLayer;

    /**
     * @param context The {@link Context} to use
     */
    public AlphaTouchInterceptorOverlay(Context context) {
        super(context);

        mInterceptorLayer = new View(context);
        final int resId = Utils.getSelectableItemBackground(context.getTheme());
        mInterceptorLayer.setBackgroundResource(resId);
        addView(mInterceptorLayer);

        mAlphaLayer = this;
    }

    /**
     * Set the View that the overlay will use as its alpha-layer. If none is set
     * it will use itself. Only necessary to set this if some child views need
     * to appear above the alpha-layer but below the touch-interceptor
     */
    public void setAlphaLayer(View alphaLayer) {
        if (mAlphaLayer == alphaLayer) {
            return;
        }

        // We're no longer the alpha-layer, so make ourself invisible
        if (mAlphaLayer == this) {
            Utils.setAlphaOnViewBackground(this, 0.0f);
        }

        mAlphaLayer = alphaLayer == null ? this : alphaLayer;
        setAlphaLayerValue(mAlpha);
    }

    /** Sets the alpha value on the alpha layer */
    public void setAlphaLayerValue(float alpha) {
        mAlpha = alpha;
        if (mAlphaLayer != null) {
            Utils.setAlphaOnViewBackground(mAlphaLayer, mAlpha);
        }
    }

    /** Delegate to interceptor-layer */
    public void setOverlayOnClickListener(OnClickListener listener) {
        mInterceptorLayer.setOnClickListener(listener);
    }

    /** Delegate to interceptor-layer */
    public void setOverlayClickable(boolean clickable) {
        mInterceptorLayer.setClickable(clickable);
    }
}