src/com/android/contacts/widget/AlphaTouchInterceptorOverlay.java

/*
 * Copyright (C) 2012 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.contacts.widget;

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

import com.android.contacts.detail.ContactDisplayUtils;
import com.android.contacts.util.ThemeUtils;

/**
 * A 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 View mInterceptorLayer;
    private View mAlphaLayer;
    private float mAlpha = 0.0f;

    public AlphaTouchInterceptorOverlay(Context context) {
        super(context);

        mInterceptorLayer = new View(context);
        final int resId = ThemeUtils.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) ContactDisplayUtils.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) {
            ContactDisplayUtils.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);
    }
}