Develop Reference

Showing results for a quiz app (Android Studio)

I have a quiz app that is working properly, but the thing is the user must answer all questions correctly in order to win the game(if the player gets it wrong the game will be over) .
What I wanted to do is have the questions answered and then at the end there will be an activity that will show how many the player has answered then there will be the options to retry and go back to menu
This is the code for the maingameactivity
public class MainGameActivity extends AppCompatActivity {
FButton buttonA, buttonB, buttonC, buttonD;
TextView questionText, triviaQuizText, timeText, resultText, coinText;
TriviaQuizHelper triviaQuizHelper;
TriviaQuestion currentQuestion;
List<TriviaQuestion> list;
int qid = 0;
int timeValue = 20;
int coinValue = 0;
CountDownTimer countDownTimer;
Typeface tb, sb;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_game_main);
//Initializing variables
questionText = (TextView) findViewById(R.id.triviaQuestion);
buttonA = (FButton) findViewById(R.id.buttonA);
buttonB = (FButton) findViewById(R.id.buttonB);
buttonC = (FButton) findViewById(R.id.buttonC);
buttonD = (FButton) findViewById(R.id.buttonD);
triviaQuizText = (TextView) findViewById(R.id.triviaQuizText);
timeText = (TextView) findViewById(R.id.timeText);
resultText = (TextView) findViewById(R.id.resultText);
coinText = (TextView) findViewById(R.id.coinText);
//Setting typefaces for textview and buttons - this will give stylish fonts on textview and button etc
tb = Typeface.createFromAsset(getAssets(), "fonts/TitilliumWeb-Bold.ttf");
sb = Typeface.createFromAsset(getAssets(), "fonts/shablagooital.ttf");
triviaQuizText.setTypeface(sb);
questionText.setTypeface(tb);
buttonA.setTypeface(tb);
buttonB.setTypeface(tb);
buttonC.setTypeface(tb);
buttonD.setTypeface(tb);
timeText.setTypeface(tb);
resultText.setTypeface(sb);
coinText.setTypeface(tb);
//Our database helper class
triviaQuizHelper = new TriviaQuizHelper(this);
//Make db writable
triviaQuizHelper.getWritableDatabase();
//It will check if the ques,options are already added in table or not
//If they are not added then the getAllOfTheQuestions() will return a list of size zero
if (triviaQuizHelper.getAllOfTheQuestions().size() == 0) {
//If not added then add the ques,options in table
triviaQuizHelper.allQuestion();
}
//This will return us a list of data type TriviaQuestion
list = triviaQuizHelper.getAllOfTheQuestions();
//Now we gonna shuffle the elements of the list so that we will get questions randomly
Collections.shuffle(list);
//currentQuestion will hold the que, 4 option and ans for particular id
currentQuestion = list.get(qid);
//countDownTimer
countDownTimer = new CountDownTimer(22000, 1000) {
public void onTick(long millisUntilFinished) {
//here you can have your logic to set text to timeText
timeText.setText(String.valueOf(timeValue) + "\"");
//With each iteration decrement the time by 1 sec
timeValue -= 1;
//This means the user is out of time so onFinished will called after this iteration
if (timeValue == -1) {
//Since user is out of time setText as time up
resultText.setText(getString(R.string.timeup));
//Since user is out of time he won't be able to click any buttons
//therefore we will disable all four options buttons using this method
disableButton();
}
}
//Now user is out of time
public void onFinish() {
//We will navigate him to the time up activity using below method
timeUp();
}
}.start();
//This method will set the que and four options
updateQueAndOptions();
}
public void updateQueAndOptions() {
//This method will setText for que and options
questionText.setText(currentQuestion.getQuestion());
buttonA.setText(currentQuestion.getOptA());
buttonB.setText(currentQuestion.getOptB());
buttonC.setText(currentQuestion.getOptC());
buttonD.setText(currentQuestion.getOptD());
timeValue = 20;
//Now since the user has ans correct just reset timer back for another que- by cancel and start
countDownTimer.cancel();
countDownTimer.start();
//set the value of coin text
coinText.setText(String.valueOf(coinValue));
//Now since user has ans correct increment the coinvalue
coinValue++;
}
//Onclick listener for first button
public void buttonA(View view) {
//compare the option with the ans if yes then make button color green
if (currentQuestion.getOptA().equals(currentQuestion.getAnswer())) {
buttonA.setButtonColor(ContextCompat.getColor(getApplicationContext(),R.color.lightGreen));
//Check if user has not exceeds the que limit
if (qid < list.size() - 1) {
//Now disable all the option button since user ans is correct so
//user won't be able to press another option button after pressing one button
disableButton();
//Show the dialog that ans is correct
correctDialog();
}
//If user has exceeds the que limit just navigate him to GameWon activity
else {
gameWon();
}
}
//User ans is wrong then just navigate him to the PlayAgain activity
else {
gameLostPlayAgain();
}
}
//Onclick listener for sec button
public void buttonB(View view) {
if (currentQuestion.getOptB().equals(currentQuestion.getAnswer())) {
buttonB.setButtonColor(ContextCompat.getColor(getApplicationContext(),R.color.lightGreen));
if (qid < list.size() - 1) {
disableButton();
correctDialog();
} else {
gameWon();
}
} else {
gameLostPlayAgain();
}
}
//Onclick listener for third button
public void buttonC(View view) {
if (currentQuestion.getOptC().equals(currentQuestion.getAnswer())) {
buttonC.setButtonColor(ContextCompat.getColor(getApplicationContext(),R.color.lightGreen));
if (qid < list.size() - 1) {
disableButton();
correctDialog();
} else {
gameWon();
}
} else {
gameLostPlayAgain();
}
}
//Onclick listener for fourth button
public void buttonD(View view) {
if (currentQuestion.getOptD().equals(currentQuestion.getAnswer())) {
buttonD.setButtonColor(ContextCompat.getColor(getApplicationContext(),R.color.lightGreen));
if (qid < list.size() - 1) {
disableButton();
correctDialog();
} else {
gameWon();
}
} else {
gameLostPlayAgain();
}
}
//This method will navigate from current activity to GameWon
public void gameWon() {
Intent intent = new Intent(this, GameWon.class);
startActivity(intent);
finish();
}
//This method is called when user ans is wrong
//this method will navigate user to the activity PlayAgain
public void gameLostPlayAgain() {
Intent intent = new Intent(this, PlayAgain.class);
startActivity(intent);
finish();
}
//This method is called when time is up
//this method will navigate user to the activity Time_Up
public void timeUp() {
Intent intent = new Intent(this, Time_Up.class);
startActivity(intent);
finish();
}
//If user press home button and come in the game from memory then this
//method will continue the timer from the previous time it left
#Override
protected void onRestart() {
super.onRestart();
countDownTimer.start();
}
//When activity is destroyed then this will cancel the timer
#Override
protected void onStop() {
super.onStop();
countDownTimer.cancel();
}
//This will pause the time
#Override
protected void onPause() {
super.onPause();
countDownTimer.cancel();
}
//On BackPressed
#Override
public void onBackPressed() {
Intent intent = new Intent(this, HomeScreen.class);
startActivity(intent);
finish();
}
//This dialog is show to the user after he ans correct
public void correctDialog() {
final Dialog dialogCorrect = new Dialog(MainGameActivity.this);
dialogCorrect.requestWindowFeature(Window.FEATURE_NO_TITLE);
if (dialogCorrect.getWindow() != null) {
ColorDrawable colorDrawable = new ColorDrawable(Color.TRANSPARENT);
dialogCorrect.getWindow().setBackgroundDrawable(colorDrawable);
}
dialogCorrect.setContentView(R.layout.dialog_correct);
dialogCorrect.setCancelable(false);
dialogCorrect.show();
//Since the dialog is show to user just pause the timer in background
onPause();
TextView correctText = (TextView) dialogCorrect.findViewById(R.id.correctText);
FButton buttonNext = (FButton) dialogCorrect.findViewById(R.id.dialogNext);
//Setting type faces
correctText.setTypeface(sb);
buttonNext.setTypeface(sb);
//OnCLick listener to go next que
buttonNext.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//This will dismiss the dialog
dialogCorrect.dismiss();
//it will increment the question number
qid++;
//get the que and 4 option and store in the currentQuestion
currentQuestion = list.get(qid);
//Now this method will set the new que and 4 options
updateQueAndOptions();
//reset the color of buttons back to white
resetColor();
//Enable button - remember we had disable them when user ans was correct in there particular button methods
enableButton();
}
});
}
//This method will make button color white again since our one button color was turned green
public void resetColor() {
buttonA.setButtonColor(ContextCompat.getColor(getApplicationContext(),R.color.white));
buttonB.setButtonColor(ContextCompat.getColor(getApplicationContext(),R.color.white));
buttonC.setButtonColor(ContextCompat.getColor(getApplicationContext(),R.color.white));
buttonD.setButtonColor(ContextCompat.getColor(getApplicationContext(),R.color.white));
}
//This method will disable all the option button
public void disableButton() {
buttonA.setEnabled(false);
buttonB.setEnabled(false);
buttonC.setEnabled(false);
buttonD.setEnabled(false);
}
//This method will all enable the option buttons
public void enableButton() {
buttonA.setEnabled(true);
buttonB.setEnabled(true);
buttonC.setEnabled(true);
buttonD.setEnabled(true);
}
}

Edited
Just remove the wrapper if else inside all the buttons better to keep it as, don't repeat the code. I am assuming the screen that shows result is handled inside gameWon and you have implemented functionality for inCorrectDialog
public void buttonA(View view) {
Button button = (Button) view;
buttonPressed(button);
}
public void buttonB(View view) {
Button button = (Button) view;
buttonPressed(button);
}
public void buttonC(View view) {
Button button = (Button) view;
buttonPressed(button);
}
public void buttonD(View view) {
Button button = (Button) view;
buttonPressed(button);
}
public void buttonPressed(Button button) {
button.setButtonColor(ContextCompat.getColor(getApplicationContext(), R.color.lightGreen));
if (qid < list.size() - 1) {
disableButton();
if (currentQuestion.getOptA().equals(currentQuestion.getAnswer())) {
correctDialog();
} else {
inCorrectDialog();
}
} else {
gameWon();
}
}

Android Calculator Backspace button

Any idea how to illustrate backspace funtion in this code? I try to make some changes but it can't work the backspace function. So, i would like to help me, with the backspace button.
enter code here
public class MainActivity extends AppCompatActivity implements OnClickListener {
private TextView mCalculatorDisplay;
private Boolean userIsInTheMiddleOfTypingANumber = false;
private CalculatorBrain mCalculatorBrain;
private static final String DIGITS = "0123456789.";
DecimalFormat df = new DecimalFormat("############");
#SuppressLint("NewApi")
#Override
protected void onCreate(Bundle savedInstanceState) {
// hide the window title.
requestWindowFeature(Window.FEATURE_NO_TITLE);
// hide the status bar and other OS-level chrome
getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mCalculatorBrain = new CalculatorBrain();
mCalculatorDisplay = (TextView) findViewById(R.id.textView1);
df.setMinimumFractionDigits(0);
df.setMinimumIntegerDigits(1);
df.setMaximumIntegerDigits(8);
findViewById(R.id.button0).setOnClickListener(this);
findViewById(R.id.button1).setOnClickListener(this);
findViewById(R.id.button2).setOnClickListener(this);
findViewById(R.id.button3).setOnClickListener(this);
findViewById(R.id.button4).setOnClickListener(this);
findViewById(R.id.button5).setOnClickListener(this);
findViewById(R.id.button6).setOnClickListener(this);
findViewById(R.id.button7).setOnClickListener(this);
findViewById(R.id.button8).setOnClickListener(this);
findViewById(R.id.button9).setOnClickListener(this);
findViewById(R.id.buttonBackspace).setOnClickListener(this);
findViewById(R.id.buttonAdd).setOnClickListener(this);
findViewById(R.id.buttonSubtract).setOnClickListener(this);
findViewById(R.id.buttonMultiply).setOnClickListener(this);
findViewById(R.id.buttonDivide).setOnClickListener(this);
findViewById(R.id.buttonToggleSign).setOnClickListener(this);
findViewById(R.id.buttonDecimalPoint).setOnClickListener(this);
findViewById(R.id.buttonEquals).setOnClickListener(this);
findViewById(R.id.buttonClear).setOnClickListener(this);
// The following buttons only exist in layout-land (Landscape mode) and require extra attention.
// The messier option is to place the buttons in the regular layout too and set android:visibility="invisible".
if (findViewById(R.id.buttonSquareRoot) != null) {
findViewById(R.id.buttonSquareRoot).setOnClickListener(this);
}
if (findViewById(R.id.buttonSquared) != null) {
findViewById(R.id.buttonSquared).setOnClickListener(this);
}
if (findViewById(R.id.buttonInvert) != null) {
findViewById(R.id.buttonInvert).setOnClickListener(this);
}
if (findViewById(R.id.buttonSine) != null) {
findViewById(R.id.buttonSine).setOnClickListener(this);
}
if (findViewById(R.id.buttonCosine) != null) {
findViewById(R.id.buttonCosine).setOnClickListener(this);
}
if (findViewById(R.id.buttonTangent) != null) {
findViewById(R.id.buttonTangent).setOnClickListener(this);
}
}
#Override
public void onClick (View v) {
String buttonPressed = ((Button) v).getText().toString();
if (DIGITS.contains(buttonPressed)) {
// digit was pressed
if (userIsInTheMiddleOfTypingANumber) {
if (buttonPressed.equals(".") && mCalculatorDisplay.getText().toString().contains(".")) {
// ERROR PREVENTION
// Eliminate entering multiple decimals
} else {
mCalculatorDisplay.append(buttonPressed);
}
} else {
if (buttonPressed.equals(".")) {
// ERROR PREVENTION
// This will avoid error if only the decimal is hit before an operator, by placing a leading zero
// before the decimal
mCalculatorDisplay.setText(0 + buttonPressed);
} else {
mCalculatorDisplay.setText(buttonPressed);
}
}
userIsInTheMiddleOfTypingANumber = true;
}else{
// operation was pressed
if (userIsInTheMiddleOfTypingANumber) {
mCalculatorBrain.setOperand(Double.parseDouble(mCalculatorDisplay.getText().toString()));
userIsInTheMiddleOfTypingANumber = false;
}
mCalculatorBrain.performOperation(buttonPressed);
if (new Double(mCalculatorBrain.getResult()).equals(0.0)) {
mCalculatorDisplay.setText("" + 0);
} else {
mCalculatorDisplay.setText(df.format(mCalculatorBrain.getResult()));
}
}
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// Save variables on screen orientation change
outState.putDouble("OPERAND", mCalculatorBrain.getResult());
outState.putDouble("MEMORY", mCalculatorBrain.getMemory());
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState){
super.onRestoreInstanceState(savedInstanceState);
// Restore variables on screen orientation change
mCalculatorBrain.setOperand(savedInstanceState.getDouble("OPERAND"));
mCalculatorBrain.setMemory(savedInstanceState.getDouble("MEMORY"));
if (new Double(mCalculatorBrain.getResult()).equals(0.0)){
mCalculatorDisplay.setText("" + 0);
} else {
mCalculatorDisplay.setText(df.format(mCalculatorBrain.getResult()));
}
}
}

In your layout you can add a onClick attribute to each button, say onClick="function", and in your activity you just need to implement a method like this:
public void function(View v) {
switch(v.getId()) {
case R.id.buttonBackspace:
// handle the backspace button
break;
case R.id.xxx:
// handle the button
break;
...
}
}
And for digits, I suggest assign a tag to each digit button in the layout, and do your logic in java based on the tag, instead of the text on the button. Because the text is just a UI, it might change in the future due to other possible requirements.

resolve 'called from wrong thread' exception

The purpose of my app is: User enters a number and clicks a button. The button uses the input to calculate the Fibonacci sequence with a timer - with each number in the sequence displaying each second to a textView. But when I try to run the timer I get the CalledFromWrongThreadException. I've posted my code below. As you can tell by my log statements I believe I know which line is causing the problem. I think it's because I'm calling a method which is outside my onclicklistener but when I move that other method around I just cause more problems.
I've read a couple other posts and I'm not really sure what the proper way is to print to a text area using my method. Does anyone know how I can make this work?
public class MainActivity extends Activity {
// primary widgets
private EditText editText;
private TextView textView;
private Button button1;
static int seconds = 0;
static Timer timer;
static ArrayList<Integer> fibList = new ArrayList<Integer>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText = (EditText) findViewById(R.id.editText1);
textView = (TextView) findViewById(R.id.textView2);
button1 = (Button) findViewById(R.id.button1);
final int delay = 1000;
final int period = 1000;
timer = new Timer();
//Attempt to clear TextView
textView.setText("");
button1.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
//Clear Textview
String array = " ";
fibList.clear();
textView.setText(array);
//Log.i("ARRAY", "ATTEMPT to CLEAR"+fibList);
String input = editText.getText().toString();
int number = Integer.parseInt(input);
int tmp = 0;
// confirm input
if (number < 20) {
Toast.makeText(getApplicationContext(),
"You entered: " + number, Toast.LENGTH_LONG).show();
for (int i = 0; i <= number; i++) {
fibList.add(fib(i));
// sum even numbers
if (fib(i) % 2 == 0) {
tmp += fib(i);
}
}
} else {
Toast.makeText(getApplicationContext(),
"Number is too Large: " + number, Toast.LENGTH_LONG)
.show();
}
//I believe error occurs in this method
Log.i("TEST", "START TIMER");
timer.scheduleAtFixedRate(new TimerTask() {
public void run() {
Log.i("TEST", "RUN TIMER");
int nextIndex = setInterval();
Log.i("TEST", "SET INTERVAL");
if (nextIndex < fibList.size()) {
Log.i("TEST", "TRY TO PRINT");
//It looks like error occurs here when I try to print to textView
textView.setText(fibList.get(nextIndex)+ " ");
Log.i("TEST", "NEXT INDEX"+fibList.get(nextIndex));
Log.i("TEST", "DID PRINT");
}
}
}, delay, period);
Log.i("TEST", "END TIMER");
}
});
}
// run fibonacci sequence
public static int fib(int n) {
if (n < 2) {
return n;
} else {
return fib(n - 1) + fib(n - 2);
}
}
//counts up for every element through the array
public static final int setInterval() {
if (seconds >= fibList.size())
timer.cancel();
return seconds++;
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}

You can use
runOnUiThread(new Runnable(){
public void run(){
textView.setText("aaa");
}
});

Have your timer post a message to a Handler. The handler will, by default, run on the main thread. IT can then change the UI as needed, so just put the body of your timer into that handler.

I just had this problem and came on to StackOverflow to check out a solution. Didn't find anything proper but a little more experimenting with lot many Logs and debugging got me my solution.
getActivity().runOnUiThread(new Runnable() {
#Override
public void run() {
textView.setText("Your String");
}
});
In my code, the problem was due to me accessing Two TextViews in seperate threads one after another using TextView.post(new Runnable...). I guess this was due to it not being able to access UI Thread (as it was busy with previous thread changes). Setting both TextViews together in UI Thread solved the problem. So posting here for anyone else who might be perplexed by similar problem. Hope it helps.

can't figure out this null point exception error

making a coin flip option within an app. Here's the part that's killing me:
public ImageView tails;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
.....
}
in the menu is where the issue happens:
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.coin_flip:
final Context cointext = this;
final Dialog flip = new Dialog(cointext);
flip.setContentView(R.layout.coin);
flip.setTitle("Coin Flip");
flip.setCancelable(true);
n = 99;
n = (generator.nextInt(n)) + 1;
tails.findViewById(R.id.tails).setVisibility(1);
if (n % 2 == 0) {
tails.findViewById(R.id.tails).setVisibility(0);
}else {
tails.findViewById(R.id.tails).setVisibility(1);
}
Button flipBtn = (Button)findViewById(R.id.flipBtn);
flipBtn.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
if (n % 2 == 0) {
tails.findViewById(R.id.tails).setVisibility(0);
}else {
tails.findViewById(R.id.tails).setVisibility(1);
}
}
});
flip.show();
}
}
I keep getting a NullPointerException on:
tails.findViewById(R.id.tails).setVisibility(1);
any ideas how to fix this? Thanks in advance

Tails isn't being initialized.
You should say
tails = (ImageView)findViewById(R.id.tails);
tails.setVisibility(View.VISIBLE);

How to set up a countup timer only when the button press?

I am implementing a countup timer and I follow an example from StackoverFlow.
In my version, I will press the Begin button to start counting and the Stop button to stop.
But the problem is that the counting start immediately after i enter the activity.
Any idea how to make it the way i want?
public class StartActivity extends Activity
{
Button beginRecordingButton;
TextView timer;
long startTime;
long countup;
#Override
protected void onCreate(Bundle savedInstanceState)
{super.onCreate(savedInstanceState);
setContentView(R.layout.startactivity);
beginRecordingButton = (Button) findViewById(R.id.BeginRecording);
timer = (TextView) findViewById(R.id.timer);
final Chronometer stopwatch = (Chronometer) findViewById(R.id.chrono);
startTime = SystemClock.elapsedRealtime();
stopwatch.setOnChronometerTickListener(listener);
beginRecordingButton.setOnClickListener(new OnClickListener()
{
int counter = 0;
public void onClick(View v)
{
if (counter % 2 == 0)
{
stopwatch.start();
beginRecordingButton.setText("Stop");
}
if (counter % 2 == 1)
{
stopwatch.stop();
beginRecordingButton.setText("Begin");
}
counter++; //counter is used for knowing it is stop or begin
}
});
}
private OnChronometerTickListener listener = new OnChronometerTickListener()
{
public void onChronometerTick(Chronometer chronometer)
{
String text;
countup = (SystemClock.elapsedRealtime() - chronometer.getBase())/1000;
if(countup%60<10)
{
text = (countup/60) + ":0" + (countup%60);
}
else
{
text = (countup/60) + ":" + (countup%60);
}
timer.setText(text);
}
};
}

I found the solution by doing follow:
long test;
test = (SystemClock.elapsedRealtime() - stopwatch.getBase())/1000;
Log.i(TAG, = (SystemClock.elapsedRealtime() - chronometer.getBase()) / 1000 - test;
basically String.valueOf(test));
stopwatch.start();
countup the idea is to subtract the passing time if i press the start button so it goes from 0