Generating a ListView Using ArrayAdapter

Question

I am trying to populate a ListView using an ArrayAdapter that I am filling with input from an EditText. My program seems to compile fine but during app start up it immediately crashes. I suspect that it has something to do with me trying to set-up my list view. I am not sure what I am initializing wrong such that my app instantly crashes. Any and all tips would be greatly appreciated. Thanks in advance!

This is my global declarations for my ArrayList and Adapter.

ArrayList<scoreScreen> savedScores = new ArrayList<>();
ScoreAdapter adapter = new ScoreAdapter(this, savedScores);

ListView listView = (ListView) findViewById(R.id.dispScores);
listView.setAdapter(adapter);

My Adapter Class:

 private class ScoreAdapter extends ArrayAdapter<scoreScreen> {
    private ScoreAdapter(Context context, ArrayList<scoreScreen> scores) {
        super(context, 0, scores);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        scoreScreen score1 = getItem(position);
        if (convertView == null){
            convertView = LayoutInflater.from(getContext()).inflate(R.layout.item_scores, parent, false);
        }
        TextView holeNum = (TextView) convertView.findViewById(R.id.holeNum);
        holeNum.setText(score1.hole);
        return convertView;
    }
}

My ListView inside of my onCreate method.

 ListView listview = (ListView) findViewById(R.id.listView1);
    listview.setAdapter(adapter);

I am assuming my problem is not inside my EditText inputs since they are inside of an OnClickListener method, but just incase I have attached it below.

public View.OnClickListener onClickListener = new View.OnClickListener() {

    @Override
    public void onClick(View view) {
        EditText input1 = (EditText) findViewById(R.id.scorePrompt);
        TextView output1 = (TextView) findViewById(R.id.textTotal);
        String blankCheck = input1.getText().toString(); //CHANGE INPUT IN scorePrompt TO STRING
        switch (view.getId()) {
            case R.id.buttTotal:
                    if (blankCheck.equals("")) {
                        Toast blankError = Toast.makeText(getApplicationContext(), "YOU CANT SKIP HOLES JERK", Toast.LENGTH_LONG);
                        blankError.show();
                        break;
                     } else {
                        int num1 = Integer.parseInt(input1.getText().toString()); //Get input from text box
                        int sum = num1 + score2;
                        score2 = sum;
                        output1.setText("Your score is : " + Integer.toString(sum));
                        //savedScores.add(input1.getText().toString());

                        scoreScreen addScore = new scoreScreen("Score is" + num1);
                        adapter.add(addScore);
                        j++;
                        input1.setText(""); //Clear input text box
                        break;
                    }
            case R.id.allScores: //CHANGE THIS TO AN EDIT BUTTON, ADD A HOLE NUMBER COUNTER AT TOP OF SCREEN!!!!!
                output1.setText("you messed up");
                break;
            case R.id.editScore: //Need to set up Save Array before we can edit
                //CURRENTLY ONLY DISPLAYS THE LAST NUNMBER IN THE TEXTEDIT, NEED TO SET UP LISTVIEW!!!!!!
                for (int i=0; i < j; i++){
                //    output1.setText(savedScores.get(i));
                } break;
        }
    }
};

onCreate method added as requested:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    /*Button scoresAct = (Button) findViewById(R.id.allScores);   //THIS IS TO GO TO ALL SCORES ACTIVITY
    scoresAct.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent scoreScreen = new Intent(MainActivity.this, AllScoresAct.class);
            startActivity(scoreScreen);
        }
    });*/

    Button sumScores = (Button) findViewById(R.id.buttTotal);
    Button saveScores = (Button) findViewById(R.id.allScores);
    Button changeScores = (Button) findViewById(R.id.editScore);
    sumScores.setOnClickListener(onClickListener);
    saveScores.setOnClickListener(onClickListener);
    changeScores.setOnClickListener(onClickListener);

    ListView listview = (ListView) findViewById(R.id.listView1);
    listview.setAdapter(adapter);

}

After moving my adapter and ArrayList into my onCreate, I get a new error. I did some research on null pointers, but I have already initialized both of these. Below is my logcat, any ideas? Thanks

Answer 1

Make sure super.onCreate(savedInstanceState) is the first thing you are calling in your onCreate() and also not trying to access any view from the layout xml before setContentView().

EDIT:

Initialize the adapter in onCreate() method instead of doing it globally.

onCreate() {
   .......
   this.adapter = new ScoreAdapter(this, savedScores);
}

Answer 2

This is my global declarations for my ArrayList and Adapter.

ArrayList<scoreScreen> savedScores = new ArrayList<>();
ScoreAdapter adapter = new ScoreAdapter(this, savedScores);

You can declare those globally, but for the Adapter, the this parameter must be used within/after onCreate, as the error says

System services not available to Activities before onCreate()

For example

private ArrayList<ScoreScreen> savedScores = new ArrayList<>();
private ScoreAdapter adapter;

@Override
protected void onCreate(Bundle b) {
    ...

    adapter = new ScoreAdapter(this, savedScores);
}