通过按钮调用方法

Question

I'm new to java and I'm trying to run a method once a button is clicked and I am unsure if I'm on the right track. I am selecting 10 questions from a Sqlite database and would like to cycle through each question 0-9 everytime the button is clicked. Once all 10 questions are asked I will move to another activity. I have the app displaying the first question fine but I am having trouble calling the showQuestions method and increasing the questionNum int by one when the button is clicked and passing this onto the method. Any help would be appreciated!

This is the showQuestions method which I am trying to call.

public void showQuestions(Cursor cursor) {
    cursor.moveToPosition(questionNum);
    while (cursor.moveToNext()) {
        // Collect String Values from Query
        StringBuilder questiontxt = new StringBuilder("");
        StringBuilder answertxt1 = new StringBuilder("");
        StringBuilder answertxt2 = new StringBuilder("");
        StringBuilder answertxt3 = new StringBuilder("");
        StringBuilder answertxt4 = new StringBuilder("");
        String question = cursor.getString(2);
        String answer = cursor.getString(3);
        String option1 = cursor.getString(4);
        String option2 = cursor.getString(5);
        String option3 = cursor.getString(6);
        questiontxt.append(question).append("");
        answertxt1.append(answer).append("");
        answertxt2.append(option1).append("");
        answertxt3.append(option2).append("");
        answertxt4.append(option3).append("");
    }
}

This is the code for the button which I am working on. There are 4 buttons.

public void onClick(View v) {
    switch (v.getId()) {

        case R.id.option1_button:
        if (questionNum<9) {
            questionNum ++;
        }
        Questions.this.showQuestions(null);
        break;
    }

And this is the XML code for the buttons.

<Button
    android:id="@+id/option1_button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/option3_button"/>

OnClick Listener for the button

View option1_button = findViewById(R.id.option1_button);
option1_button.setOnClickListener(this);

Database Query and Allocation to Cursor

//Get the questions and allocate them to the Cursor
public Cursor getQuestions() {
//Select Query 
String loadQuestions = "SELECT * FROM questionlist ORDER BY QID LIMIT 10";
SQLiteDatabase db = questions.getReadableDatabase();
Cursor cursor = db.rawQuery(loadQuestions, null);
startManagingCursor(cursor);
return cursor;
}

Thanks in advance.

Answer 1

Questions.this.showQuestions(null);

Why you pass null to the showQuestions method?

Let me guess - it crashes with NullPointerException .

Did you tried showQuestions(getQuestions())

EDIT: Some general suggestions:

• don't load the question every time when the button is clicked.

• make some Question class containing all needed information for a question

• when onCreate is invoked, open the database and load all needed questions in some Collection , like ArrayList<Question>

• Every time when the user clicks a button, get the next Question element from the Collection and show it