RecyclingImageView.java

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/*
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 * Copyright (C) 2013 The Android Open Source Project
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 *      http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package com.example.android.displayingbitmaps.ui;
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import android.content.Context;
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import android.graphics.drawable.Drawable;
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import android.graphics.drawable.LayerDrawable;
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import android.util.AttributeSet;
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import android.widget.ImageView;
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import com.example.android.displayingbitmaps.util.RecyclingBitmapDrawable;
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/**
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 * Sub-class of ImageView which automatically notifies the drawable when it is
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 * being displayed.
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 */
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public class RecyclingImageView extends ImageView {
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    public RecyclingImageView(Context context) {
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        super(context);
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    }
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    public RecyclingImageView(Context context, AttributeSet attrs) {
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        super(context, attrs);
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    }
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    /**
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     * @see android.widget.ImageView#onDetachedFromWindow()
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     */
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    @Override
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    protected void onDetachedFromWindow() {
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        // This has been detached from Window, so clear the drawable
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        setImageDrawable(null);
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        super.onDetachedFromWindow();
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    }
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    /**
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     * @see android.widget.ImageView#setImageDrawable(android.graphics.drawable.Drawable)
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     */
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    @Override
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    public void setImageDrawable(Drawable drawable) {
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        // Keep hold of previous Drawable
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        final Drawable previousDrawable = getDrawable();
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        // Call super to set new Drawable
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        super.setImageDrawable(drawable);
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        // Notify new Drawable that it is being displayed
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        notifyDrawable(drawable, true);
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        // Notify old Drawable so it is no longer being displayed
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        notifyDrawable(previousDrawable, false);
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    }
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    /**
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     * Notifies the drawable that it's displayed state has changed.
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     *
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     * @param drawable
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     * @param isDisplayed
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     */
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    private static void notifyDrawable(Drawable drawable, final boolean isDisplayed) {
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        if (drawable instanceof RecyclingBitmapDrawable) {
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            // The drawable is a CountingBitmapDrawable, so notify it
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            ((RecyclingBitmapDrawable) drawable).setIsDisplayed(isDisplayed);
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        } else if (drawable instanceof LayerDrawable) {
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            // The drawable is a LayerDrawable, so recurse on each layer
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            LayerDrawable layerDrawable = (LayerDrawable) drawable;
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            for (int i = 0, z = layerDrawable.getNumberOfLayers(); i < z; i++) {
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                notifyDrawable(layerDrawable.getDrawable(i), isDisplayed);
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            }
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        }
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    }
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}