public class MainActivity extends AppCompatActivity $\{$

$5$ usages

private MemoryGame mGame;

$10$ usages

private GridLayout mMemoryGrid;

$6$ usages

private int mTurnNumber;

$5$ usages

private int mFirstBtnNdx;

@override

protected void onCreate$($Bundle savedInstancestate$)\{$

super.oncreate$($savedinstancestate$)$;

setContentView$($R$.$layout.activity$\_$main$)$;

mMemoryGrid $=$ findViewById$($R$.$id$.$memory$\_$grid$)$;

$//$ Add the same click handler to all grid buttons

for $($int buttonIndex $=0$; buttonIndex $<$ mMemoryGrid.getChildCount $()$; buttonIndex $++)$

$\{$

Button gridButton $=($Button$)$ mMemoryGrid.getchildAt$($buttonIndex$)$;

gridButton.setonclickListener$($this: : onTileButtonclick$)$;

$\}$

mGame $=$ new MemoryGame$()$;

startGame$()$;

$\}$

$2$ usages

private void startGame$()\{$

mGame. newGame $()$;

mTurnNumber $=0$;

mFirstBtnNdx $=-1$;

for $($int buttonIndex $=0$; buttonIndex $<$ mMemoryGrid.getChildCount$()$; buttonIndex$++)$

$\{$

Button gridButton Button$)$ mMemoryGrid.getChildAt$($buttonIndex

private void onTileButtonclick$($View view$)\{$

$//$ Try to prevent fast$-$clicking tiles creating errors

if $($mTurnNumber $=2)$

$\{$

return;

$\}$

$//$ Find the button's row and col

int buttonIndex $=$ mMemoryGrid.indexofChild$($view$)$;

$//$ show the color for this tile

Button gridButton $=($Button$)$ mMemoryGrid.getChildAt$($buttonIndex$)$;

gridButton.setBackgroundColor$($ContextCompat$.$getColor$($ context: this, mGame.getTileColor$($buttonIndex$)))$;

if $($mTurnNumber $=0)$

$\{$

mTurnNumber $=1$;

mFirstBtnNdx $=$ buttonIndex;

$//$ Disable the first grid button so we can't click it a second time

gridButton.setEnabled$($false$)$;

$\}$

else

$\{$

mTurnNumber $=2$;

$//$ Is it a match??

if$($mGame$.$getTileColor$($mFirstBtnNdx$)==$ mGame.getTileColor$($buttonIndex$))$

$\{$

$//$ Yes, disable the buttons and leave the colors displayed

Button firstButton Button$)$ mMemoryGrid.getChildAt $($mFirstBtnNdx$)$;

firstButton.setEnabled$($false$)$;

gridButton.setEnabled$($false$)$;

Toast.makeText$($ context: this, "It's a match!", Toast.LENGTH$\_$SHORT$).$show$()$;

$//$ Check if game is over...

checkForGameover$()$;

$\}$

else

$\{$

$//$ No$,$ delay $750$ then hide the tiles

new CountDownTimer $($ millisinFuture: $750,$ countDowninterval: $750)\{$

$5$ usages

public void onTick$($long millisUntilFinished$)\{$

$\}$

public void onFinish$()\{$

Button firstButton $=($Button$)$ mMemoryGrid.getChildAt$($mFirstBtnNdx$)$;

hideTiles$($firstButton$,$ gridButton$)$;

$\}$

$\}.$start$()$;

$\}$

$1$ usage

public void hideTiles$($Button btn$1,$ Button btn$2)$

$\{$

btn$1.$setBackgroundColor $($ContextCompat$.$getColor $($context: this, R$.$color.darkGray$))$;

btn$2.$setBackgroundColor$($ContextCompat$.$getColor$($ context: this, R$.$color.darkGray$))$;

btn$1.$ setEnabled$($true$)$;

btn$2.$ setEnabled$($true$)$;

$\}$

$1$ usage

public void onNewGameClick$($View view$)$ startGame$()$; $\}$

$1$ usage

public void checkForGameover $()$

$\{$

boolean gameover $=$ true;

for $($int buttonIndex $=0$; buttonIndex $<$ mMemoryGrid.getchildCount $()$; buttonIndex$++$

$\{$

$//$ TODO #$3-$ Get a reference to each grid button and call the isEnabled method

$//$ to determine if any grid buttons are enabled. If the enabled property is true

$//$ the gameover variable should be set to false

$\}$

$//$ Congratulate the user if the game is over

if $($gameover$)\{$

Toast.makeText$($ context: this, "Congratulations!", Toast.LENGTH$\_$LONG$).$show$()$;

$\}$

$\}$

Delete the help button from the Main Activity layout and add it to the app bar. The code for Help button will remain the same.