标记测验应用程序（throwIndexOutOfBoundsException）

Question

基本上我所做的是一个标志测验应用程序，可以测试你猜对了多少个标志，并在最后给你一个基于百分比的分数。

问题在于，当我进行测验时，我有时会出现outOfBounds错误，应用程序崩溃而不是显示分数。它是相当随机的，因为有时我可以做3-4次应用程序没有问题，最后正确显示得分。

这些是在最后重置测验时使用的2个类，问题是String nextImage = quizCountriesList.remove(0);内的loadNextFlag()

确切的错误是：

  

在   java.util.ArrayList.throwIndexOutOfBoundsException（ArrayList.java:255）

     

at java.util.ArrayList.remove（ArrayList.java:403）

     

在   com.map524s1a.flagquizdk.MainActivityFragment.loadNextFlag（MainActivityFragment.java:180）

public void resetQuiz() {
    // use AssetManager to get image file names for enabled regions

    AssetManager assets = getActivity().getAssets();
    fileNameList.clear(); // empty list of image file names

    try {
        // loop through each region
        for (String region : regionsSet) {
            // get a list of all flag image files in this region
            String[] paths = assets.list(region);

            for (String path : paths)
                fileNameList.add(path.replace(".png", ""));
        }
    } catch (IOException ex) {
        Log.e(TAG, "Error loading image file names", ex);
    }

    correctAnswers = 0; // reset the number of correct answers made
    questions = 0; // reset the total number of questions
    quizCountriesList.clear(); // clear prior list of quiz countries

    int flagCounter = 1;
    int numberOfFlags = fileNameList.size();

    // add FLAGS_IN_QUIZ random file names to the quizCountriesList
    while (flagCounter <= FLAGS_IN_QUIZ) {
        int randomIndex = random.nextInt(numberOfFlags);

        // get the random file name
        String filename = fileNameList.get(randomIndex);

        // if the region is enabled and it hasn't already been chosen
        if (!quizCountriesList.contains(filename)) {
            quizCountriesList.add(filename); // add the file to the list
            ++flagCounter;
        }
    }

    loadNextFlag(); // start the quiz by loading the first flag
}

// after the user guesses a correct flag, load the next flag
private void loadNextFlag() {
    // get file name of the next flag and remove it from the list
    String nextImage = quizCountriesList.remove(0);

    correctAnswer = nextImage; // update the correct answer

    answerTextView.setText(""); // clear answerTextView

    // display current question number
    questionNumberTextView.setText(getString(R.string.question, (questions + 1), FLAGS_IN_QUIZ));

    // extract the region from the next image's name
    String region = nextImage.substring(0, nextImage.indexOf('-'));

    // use AssetManager to load next image from assets folder
    AssetManager assets = getActivity().getAssets();

    // get an InputStream to the asset representing the next flag
    // and try to use the InputStream
    try (InputStream stream =
                 assets.open(region + "/" + nextImage + ".png")) {
        // load the asset as a Drawable and display on the flagImageView
        Drawable flag = Drawable.createFromStream(stream, nextImage);
        flagImageView.setImageDrawable(flag);

        animate(false); // animate the flag onto the screen
    }
    catch (IOException exception) {
        Log.e(TAG, "Error loading " + nextImage, exception);
    }

    Collections.shuffle(fileNameList); // shuffle file names

    // put the correct answer at the end of fileNameList
    int correct = fileNameList.indexOf(correctAnswer);
    fileNameList.add(fileNameList.remove(correct));

    // add 2, 4, 6 or 8 guess Buttons based on the value of guessRows
    for (int row = 0; row < guessRows; row++) {
        // place Buttons in currentTableRow
        for (int column = 0;
             column < guessLinearLayouts[row].getChildCount();
             column++) {
            // get reference to Button to configure
            Button newGuessButton =
                    (Button) guessLinearLayouts[row].getChildAt(column);
            newGuessButton.setEnabled(true);

            // get country name and set it as newGuessButton's text
            String filename = fileNameList.get((row * 2) + column);
            newGuessButton.setText(getCountryName(filename));
        }
    }

    // randomly replace one Button with the correct answer
    int row = random.nextInt(guessRows); // pick random row
    int column = random.nextInt(2); // pick random column
    LinearLayout randomRow = guessLinearLayouts[row]; // get the row
    String countryName = getCountryName(correctAnswer);
    ((Button) randomRow.getChildAt(column)).setText(countryName);
}