Android Open Source - filelistview Picture Generator

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License

The source code is released under:

MIT License

Java Source Code

package com.jcw.andriod.fileListView;
/*from w  ww .j a  v  a  2s . co  m*/
/*
 * Created by Jackson Woodruff on 12/09/2014
 *
 *
 * This is a protected class that is used
 * in the list view to generate the images
 * for certain types of file.
 */

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.widget.ImageView;

import com.jcw.android.fileListView.R;

import java.io.File;

class PictureGenerator {
  File file;
  FileExtension extension;

  public static final int ICON_SIZE = 64;


  public PictureGenerator(File file) {
    this.file = file;
    extension = FileExtension.createExtension(getExtension());
  }

  /*
   * you should avoid calling this
   * on the main thread -- it will
   * get very expensive very fast
   * because it loads the whole
   * picture into memory then trims
   * it.
   */
  public Bitmap getIcon(Context context) {
    return extension.getIcon(context, this.file);
  }

  /*
   * This MUST be called within a thread
   *
   * This is private because
   * if it is called many times at
   * once then you run into out
   * of memory errors
   *
   * Hence, this SHOULD BE USED WITH
   * EXTREME CAUTION
   */
  protected void addIconAsync(final ImageView view) {
    Thread thread = new Thread(new Runnable() {
      @Override
      public void run() {
        final Bitmap icon = getIcon(view.getContext());
        Runnable setImageRunnable = new Runnable() {
          @Override
          public void run() {
            if (icon == null) {
              //the icon was not loaded here
              view.setImageResource(R.drawable.file_icon);
            } else {
              view.setImageBitmap(icon);
            }
          }
        };

        try {
          view.getHandler().post(setImageRunnable);
        } catch (Exception e) {
          //this is really trying to catch a dead object
          //exception, which means that the view is already destroyed
          view.post(setImageRunnable);
        }
      }
    });
    thread.start();
  }

  /*
   * This adds images to a series of views in
   * async fashion.
   */
  public static void addIconsAsync(final FileListItemView[] items) {
    Thread runnable = new Thread(new Runnable() {
      @Override
      public void run() {
        for (FileListItemView view : items) {
          PictureGenerator generator = new PictureGenerator(view.getFullFile());
          generator.addIconAsync(view.icon);
        }
      }
    });
  }

  private String getExtension() {
    String[] delimited = file.getName().split("\\.");
    if (delimited.length == 0) {
      return "";
    } else {
      return delimited[delimited.length - 1].toLowerCase();
    }
  }

  private enum FileExtension {
    //IMPORTANT NOTE
    //if you add something here, you also have to add it to the
    //getIcon and createExtension methods
    JPG(".jpg"),
    PNG(".png"),
    MP3(".MP3"),
    Other("");

    protected String extension;

    FileExtension(String extension) {
      this.extension = extension;
    }

    /*
     * returns a bitmap in 64x64 format
     * of the passed picture
     */
    public Bitmap getIcon(Context context, File file) {
      switch (this) {
        case PNG:
        case JPG:
          return getPictureIcon(file);
        case MP3:
          return getPictureFromResource(context, R.drawable.mp3_icon);
        case Other:
          return null;
      }
      return null;
    }

    private Bitmap getPictureFromResource(Context context, int resId) {
      return BitmapFactory.decodeResource(context.getResources(), resId);
    }

    private Bitmap getPictureIcon(File file) {
      try {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inPreferredConfig = Bitmap.Config.ARGB_8888;
        Bitmap fullSized = BitmapFactory.decodeFile(file.toString(), options);
        Bitmap resized = Bitmap.createScaledBitmap(fullSized, 64, 64, true);
        fullSized.recycle();
        return resized;
      } catch (Exception e) {
        //This can happen if there is an improperly formatted png/jpg file
        //i.e. if someone changed the extension of a file name by accident
        return null;
      }
    }

    public static FileExtension createExtension(String extension) {
      String s = extension.toLowerCase();
      if (s.equals("jpg")) {
        return JPG;
      } else if (s.equals("png")) {
        return PNG;
      } else if (s.equals("mp3")) {
        return MP3;
      } else {
        return Other;
      }
    }
  }
}

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