Download Sudokuv2/src/org/example/sudoku/PuzzleView.java

Log.d(TAG, "setSelectedTile: invalid: " + tile); startAnimation(AnimationUtils.loadAnimation(game,

R.anim.shake));

This loads and runs a resource called R.anim.shake, defined in res/anim/ shake.xml, that shakes the screen for 1,000 milliseconds (1 second) by 10 pixels from side to side.

Download Sudokuv2/res/anim/shake.xml

<?xml version="1.0" encoding="utf-8"?>

<translate xmlns:android="http://schemas.android.com/apk/res/android" android:fromXDelta="0"

android:toXDelta="10" android:duration="1000" android:interpolator="@anim/cycle_7" />

The number of times to run the animation and the velocity and acceleration of the animation are controlled by an animation interpolator defined in XML.

Download Sudokuv2/res/anim/cycle_7.xml

<?xml version="1.0" encoding="utf-8"?>

<cycleInterpolator xmlns:android="http://schemas.android.com/apk/res/android" android:cycles="7" />

This particular one will cause the animation to be repeated seven times.

4.4The Rest of the Story

Now let’s go back and tie up a few loose ends, starting with the Keypad class. These pieces are necessary for the program to compile and operate but have nothing to do with graphics. Feel free to skip ahead to Section 4.5, Making More Improvements, on page 103 if you like.

Creating the Keypad

The keypad is handy for phones that don’t have keyboards. It displays a grid of the numbers 1 through 9 in an activity that appears on top of the puzzle. The whole purpose of the keypad dialog box is to return a number selected by the player.

Here’s the user interface layout from res/layout/keypad.xml:

Download Sudokuv2/res/layout/keypad.xml

<?xml version="1.0" encoding="utf-8"?>

<TableLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/keypad"

android:orientation="vertical" android:layout_width="wrap_content" android:layout_height="wrap_content" android:stretchColumns="*">

<TableRow>

<Button android:id="@+id/keypad_1" android:text="1">

</Button>

<Button android:id="@+id/keypad_2" android:text="2">

</Button>

<Button android:id="@+id/keypad_3" android:text="3">

</Button>

</TableRow>

<TableRow>

<Button android:id="@+id/keypad_4" android:text="4">

</Button>

<Button android:id="@+id/keypad_5" android:text="5">

</Button>

<Button android:id="@+id/keypad_6" android:text="6">

</Button>

</TableRow>

<TableRow>

<Button android:id="@+id/keypad_7" android:text="7">

</Button>

<Button android:id="@+id/keypad_8" android:text="8">

</Button>

<Button android:id="@+id/keypad_9" android:text="9">

</Button>

</TableRow>

</TableLayout>

Next let’s define the Keypad class.

Here’s the outline:

Download Sudokuv2/src/org/example/sudoku/Keypad.java

package org.example.sudoku;

import android.app.Dialog; import android.content.Context; import android.os.Bundle; import android.view.KeyEvent; import android.view.View;

public class Keypad extends Dialog {

protected static final String TAG = "Sudoku";

private final View keys[] = new View[9]; private View keypad;

private final int useds[];

private final PuzzleView puzzleView;

public Keypad(Context context, int useds[], PuzzleView puzzleView) { super(context);

this.useds = useds; this.puzzleView = puzzleView;

}

@Override

protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);

setTitle(R.string.keypad_title); setContentView(R.layout.keypad); findViews();

for (int element : useds) { if (element != 0)

keys[element - 1].setVisibility(View.INVISIBLE);

}

setListeners();

}

// ...

}

If a particular number is not valid (for example, the same number already appears in that row), then we make the number invisible in the grid so the player can’t select it (see Figure 4.7, on the next page).

Figure 4.7: Invalid values are hidden in the keypad view.

The findViews( ) method fetches and saves the views for all the keypad keys and the main keypad window:

Download Sudokuv2/src/org/example/sudoku/Keypad.java

setListeners( ) loops through all the keypad keys and sets a listener for each one. It also sets a listener for the main keypad window.

Download Sudokuv2/src/org/example/sudoku/Keypad.java

private void setListeners() {

for (int i = 0; i < keys.length; i++) { final int t = i + 1;

keys[i].setOnClickListener(new View.OnClickListener(){ public void onClick(View v) {

returnResult(t);

}});

}

keypad.setOnClickListener(new View.OnClickListener(){ public void onClick(View v) {

returnResult(0);

}});

}

When the player selects one of the buttons on the keypad, it calls the returnResult( ) method with the number for that button. If the player selects a place that doesn’t have a button, then returnResult( ) is called with a zero, indicating the tile should be erased.

onKeyDown( ) is called when the player uses the keyboard to enter a number:

Download Sudokuv2/src/org/example/sudoku/Keypad.java

@Override

public boolean onKeyDown(int keyCode, KeyEvent event) { int tile = 0;

switch (keyCode) {

case KeyEvent.KEYCODE_0:

case KeyEvent.KEYCODE_SPACE: tile = 0; break;

return super.onKeyDown(keyCode, event);

}

if (isValid(tile)) { returnResult(tile);

}

return true;

}

If the number is valid for the current tile, then it calls returnResult( ); otherwise, the keystroke is ignored.

The isValid( ) method checks to see whether the given number is valid for the current position:

Download Sudokuv2/src/org/example/sudoku/Keypad.java

private boolean isValid(int tile) { for (int t : useds) {

if (tile == t) return false;

}

return true;

}

If it appears in the used array, then it’s not valid because the same number is already used in the current row, column, or block.

The returnResult( ) method is called to return the number selected to the calling activity:

Download Sudokuv2/src/org/example/sudoku/Keypad.java

private void returnResult(int tile) { puzzleView.setSelectedTile(tile); dismiss();

}

We call the PuzzleView.setSelectedTile() method to change the puzzle’s current tile. The dismiss call terminates the Keypad dialog box. Now that we have the activity, let’s call it in the Game class and retrieve the result:

Download Sudokuv2/src/org/example/sudoku/Game.java

protected void showKeypadOrError(int x, int y) { int tiles[] = getUsedTiles(x, y);

if (tiles.length == 9) {

Toast toast = Toast.makeText(this, R.string.no_moves_label, Toast.LENGTH_SHORT);

toast.setGravity(Gravity.CENTER, 0, 0); toast.show();

} else {

Log.d(TAG, "showKeypad: used=" + toPuzzleString(tiles)); Dialog v = new Keypad(this, tiles, puzzleView); v.show();

}

}

To decide which numbers are possible, we pass the Keypad a string in the extraData area containing all the numbers that have already been used.

Implementing the Game Logic

The rest of the code in Game.java concerns itself with the logic of the game, in particular with determining which are and aren’t valid moves according to the rules. The setTileIfValid( ) method is a key part of that. Given an x and y position and the new value of a tile, it changes the tile only if the value provided is valid.

Download Sudokuv2/src/org/example/sudoku/Game.java

protected boolean setTileIfValid(int x, int y, int value) { int tiles[] = getUsedTiles(x, y);

if (value != 0) {

for (int tile : tiles) { if (tile == value) return false;

}

}

setTile(x, y, value); calculateUsedTiles(); return true;

}

To detect valid moves, we create an array for every tile in the grid. For each position, it keeps a list of filled-in tiles that are currently visible from that position. If a number appears on the list, then it won’t be valid for the current tile. The getUsedTiles( ) method retrieves that list for a given tile position:

Download Sudokuv2/src/org/example/sudoku/Game.java

private final int used[][][] = new int[9][9][];

protected int[] getUsedTiles(int x, int y) { return used[x][y];

}

The array of used tiles is somewhat expensive to compute, so we cache the array and recalculate it only when necessary by calling calculateUsedTiles( ):

Download Sudokuv2/src/org/example/sudoku/Game.java

private void calculateUsedTiles() { for (int x = 0; x < 9; x++) {

for (int y = 0; y < 9; y++) {

used[x][y] = calculateUsedTiles(x, y);

//Log.d(TAG, "used[" + x + "][" + y + "] = "

//+ toPuzzleString(used[x][y]));

}

}

}