Add generated icon for cards in card list

This add a thumbnail of a single letter for each card,
consisting of the first letter of the card and a
pastel background.

This was adapted from the andOTP project.

app/src/main/java/protect/card_locker/LetterBitmap.java

@@ -0,0 +1,141 @@
+package protect.card_locker;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.content.res.TypedArray;
+import android.graphics.Bitmap;
+import android.graphics.BitmapFactory;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+import android.graphics.Rect;
+import android.graphics.Typeface;
+import android.text.TextPaint;
+
+/**
+ * Original from https://github.com/andOTP/andOTP/blob/master/app/src/main/java/org/shadowice/flocke/andotp/Utilities/LetterBitmap.java
+ * which was originally from http://stackoverflow.com/questions/23122088/colored-boxed-with-letters-a-la-gmail
+ * Used to create a {@link Bitmap} that contains a letter used in the English
+ * alphabet or digit, if there is no letter or digit available, a default image
+ * is shown instead.
+ *
+ * Only English language supported.
+ */
+class LetterBitmap
+{
+
+    /**
+     * The number of available tile colors
+     */
+    private static final int NUM_OF_TILE_COLORS = 8;
+
+    /**
+     * The {@link TextPaint} used to draw the letter onto the tile
+     */
+    private final TextPaint mPaint = new TextPaint();
+    /**
+     * The bounds that enclose the letter
+     */
+    private final Rect mBounds = new Rect();
+    /**
+     * The {@link Canvas} to draw on
+     */
+    private final Canvas mCanvas = new Canvas();
+    /**
+     * The first char of the name being displayed
+     */
+    private final char[] mFirstChar = new char[1];
+
+    /**
+     * The background colors of the tile
+     */
+    private final TypedArray mColors;
+    /**
+     * The font size used to display the letter
+     */
+    private final int mTileLetterFontSize;
+    /**
+     * The default image to display
+     */
+    private final Bitmap mDefaultBitmap;
+
+    /**
+     * Constructor for <code>LetterTileProvider</code>
+     *
+     * @param context The {@link Context} to use
+     */
+    public LetterBitmap(Context context)
+    {
+        final Resources res = context.getResources();
+
+        mPaint.setTypeface(Typeface.create("sans-serif-light", Typeface.BOLD));
+        mPaint.setColor(Color.WHITE);
+        mPaint.setTextAlign(Paint.Align.CENTER);
+        mPaint.setAntiAlias(true);
+
+        mColors = res.obtainTypedArray(R.array.letter_tile_colors);
+        mTileLetterFontSize = res.getDimensionPixelSize(R.dimen.tile_letter_font_size);
+
+        mDefaultBitmap = BitmapFactory.decodeResource(res, android.R.drawable.sym_def_app_icon);
+    }
+
+    /**
+     * @param displayName The name used to create the letter for the tile
+     * @param key         The key used to generate the background color for the tile
+     * @param width       The desired width of the tile
+     * @param height      The desired height of the tile
+     * @return A {@link Bitmap} that contains a letter used in the English
+     * alphabet or digit, if there is no letter or digit available, a
+     * default image is shown instead
+     */
+    public Bitmap getLetterTile(String displayName, String key, int width, int height)
+    {
+        final Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+        char firstChar = displayName.charAt(0);
+
+        final Canvas c = mCanvas;
+        c.setBitmap(bitmap);
+        c.drawColor(pickColor(key));
+
+        if (!isEnglishLetterOrDigit(firstChar))
+        {
+            firstChar = 'A';
+        }
+        mFirstChar[0] = Character.toUpperCase(firstChar);
+        mPaint.setTextSize(mTileLetterFontSize);
+        mPaint.getTextBounds(mFirstChar, 0, 1, mBounds);
+        c.drawText(mFirstChar, 0, 1, width / 2, height / 2
+                + (mBounds.bottom - mBounds.top) / 2, mPaint);
+        return bitmap;
+    }
+
+    /**
+     * @param c The char to check
+     * @return True if <code>c</code> is in the English alphabet or is a digit,
+     * false otherwise
+     */
+    private static boolean isEnglishLetterOrDigit(char c)
+    {
+        return 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z' || '0' <= c && c <= '9';
+    }
+
+    /**
+     * @param key The key used to generate the tile color
+     * @return A new or previously chosen color for <code>key</code> used as the
+     * tile background color
+     */
+    private int pickColor(String key)
+    {
+        // String.hashCode() is not supposed to change across java versions, so
+        // this should guarantee the same key always maps to the same color
+        final int color = Math.abs(key.hashCode()) % NUM_OF_TILE_COLORS;
+        try
+        {
+            return mColors.getColor(color, Color.BLACK);
+        }
+        finally
+        {
+            mColors.recycle();
+        }
+    }
+}

app/src/main/java/protect/card_locker/LoyaltyCardCursorAdapter.java

@@ -6,6 +6,7 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.CursorAdapter;
+import android.widget.ImageView;
 import android.widget.TextView;
 
 class LoyaltyCardCursorAdapter extends CursorAdapter
@@ -29,6 +30,7 @@ class LoyaltyCardCursorAdapter extends CursorAdapter
     public void bindView(View view, Context context, Cursor cursor)
     {
         // Find fields to populate in inflated template
+        ImageView thumbnail = view.findViewById(R.id.thumbnail);
         TextView storeField = (TextView) view.findViewById(R.id.store);
         TextView cardIdField = (TextView) view.findViewById(R.id.cardId);
 
@@ -49,5 +51,9 @@ class LoyaltyCardCursorAdapter extends CursorAdapter
         String cardIdLabel = view.getResources().getString(R.string.cardId);
         String cardIdText = String.format(cardIdFormat, cardIdLabel, loyaltyCard.cardId);
         cardIdField.setText(cardIdText);
+
+        LetterBitmap letterBitmap = new LetterBitmap(context);
+        int pixelSize = context.getResources().getDimensionPixelSize(R.dimen.cardThumbnailSize);
+        thumbnail.setImageBitmap(letterBitmap.getLetterTile(loyaltyCard.store, loyaltyCard.store, pixelSize, pixelSize));
     }
 }