Android Open Source - droidling Bitmap Loader Task

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License

The source code is released under:

Copyright (c) 2012 Keith Trnka Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Softwa...

Java Source Code

package com.github.ktrnka.droidling.helpers;
// w w  w.j ava  2s. com
import java.io.IOException;
import java.lang.ref.WeakReference;

import android.graphics.Bitmap;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.os.AsyncTask;
import android.widget.ImageView;

import com.github.ktrnka.droidling.ExtendedApplication;

/**
 * Helper class load and scale images async. Based on
 * http://developer.android.com/training/displaying-bitmaps/process-bitmap.html
 */
public class BitmapLoaderTask extends AsyncTask<Uri, Void, Bitmap> {
    private static final String RESOURCE_SCHEME = "droidlingresources";
    private final WeakReference<ImageView> imageViewReference;
    private Uri imageUri;
    private int widthPixels;
    private int heightPixels;

    // TODO: Try to remove this circular dep between packages
    private ExtendedApplication application;

    public BitmapLoaderTask(ImageView imageView, int widthPixels, int heightPixels,
            ExtendedApplication application) {
        imageViewReference = new WeakReference<ImageView>(imageView);
        this.widthPixels = widthPixels;
        this.heightPixels = heightPixels;
        this.application = application;
    }

    @Override
    protected Bitmap doInBackground(Uri... params) {
        imageUri = params[0];

        if (imageViewReference != null && application != null) {
            ImageView imageView = imageViewReference.get();
            try {
                if (imageUri.getScheme().equals(RESOURCE_SCHEME)) {
                    return application.loadBitmapFromResources(imageView.getContext(),
                            Integer.parseInt(imageUri.getSchemeSpecificPart()), widthPixels,
                            heightPixels);
                }
                else {
                    return application.loadBitmapFromUri(imageView.getContext(), imageUri,
                            widthPixels, heightPixels);
                }
            } catch (IOException e) {
                return null;
            }
        }

        return null;
    }

    /**
     * Check if we should avoid potential work. This function should be run on
     * the UI thread for synchronization.
     * 
     * @param imageView the ImageView we're going to populate
     * @param imageUri the Uri of the image we're going to populate
     * @return true if the potential work should be avoided, false otherwise
     */
    public static boolean cancelPotentialWork(ImageView imageView, Uri imageUri) {
        if (imageView == null)
            return false;

        AsyncDrawable drawable;
        Drawable plainDrawable = imageView.getDrawable();
        if (plainDrawable instanceof AsyncDrawable)
            drawable = (AsyncDrawable) plainDrawable;
        else
            return false;

        BitmapLoaderTask task = drawable.getBitmapLoaderTask();
        if (task == null)
            return false;

        // already loading this data
        if (task.imageUri != null && task.imageUri.equals(imageUri)) {
            return true;
        }
        // loading something else - kill it
        else {
            task.cancel(true);
            return false;
        }
    }

    public static Uri packIntoUri(int drawableId) {
        return Uri.fromParts(RESOURCE_SCHEME, String.valueOf(drawableId), null);
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
        if (!isCancelled() && imageViewReference != null && bitmap != null) {
            ImageView imageView = imageViewReference.get();
            if (imageView != null)
                imageView.setImageBitmap(bitmap);
        }
    }

}

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