How do i refresh Listview after adding new object to associated arraylist?

Question

I am displaying task objects in my listview.There are 2 layout file one is activty_main layout which has a listview textviews a button and inputs.other is for listview elements row.xml.What i am trying to do is refresh list after adding new task. MainActivity:

public class MainActivity extends AppCompatActivity {

    private EditText name, date, desc;
    List<Task> tasklist = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button= (Button) findViewById(R.id.addtask);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                addNewTask();
            }
        });
        name = (EditText) findViewById(R.id.name);
        date = (EditText) findViewById(R.id.date);
        desc = (EditText) findViewById(R.id.desc);

        ListView tasklistview = (ListView)findViewById(R.id.tasks);
        TaskAdapter adapter = new TaskAdapter(this, R.layout.row, tasklist);

        tasklistview.setAdapter(adapter);

        Task sometask = new Task("CS412-Lecture", "","Apr6,2016");
        tasklist.add(sometask);

    }

    public void addNewTask(){
        Toast.makeText(MainActivity.this,
                "TEST", Toast.LENGTH_LONG).show();
        Task task = new Task(name.getText().toString(),desc.getText().toString(),date.getText().toString());
tasklist.add(task);


    }
}

Task Class:

public class Task {

    String name;
    String desc;
    String date;

    public Task(String name,String desc,String date){

this.name = name;
this.desc = desc;
this.date = date;

    }


    public String getName() {
        return name;
    }

    public String getDesc() {
        return desc;
    }

    public String getDate() {
        return date;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public void setDate(String date) {
        this.date = date;
    }
}

TaskAdapter:

public class TaskAdapter extends ArrayAdapter<Task> {

    private int layoutResource;

    public TaskAdapter(Context context, int layoutResource, List<Task> tasks) {
        super(context, layoutResource, tasks);
        this.layoutResource = layoutResource;
    }

    public View getView(int position, View convertView, ViewGroup parent) {

        View view = convertView;

        if (view == null) {
            LayoutInflater layoutInflater = LayoutInflater.from(getContext());
            view = layoutInflater.inflate(layoutResource, null);
        }

        Task tasks = getItem(position);

        if (tasks != null) {
            TextView name = (TextView) view.findViewById(R.id.name);
            TextView date = (TextView) view.findViewById(R.id.date);

            if (name != null) {
                name.setText(tasks.getName());
            }

            if (date != null) {
                date.setText(tasks.getDate());
            }
        }

        return view;
    }



}

This is how layout looks like:

Sagar · Accepted Answer · 2018-04-07 14:51:30Z

1

You are missing call to adapter.notifyDataSetChanged() which needs to be done each time after you modify the adapter contents.

You need to maintain class level reference for adapter.

public class MainActivity extends AppCompatActivity {

    private EditText name, date, desc;
    private List<Task> tasklist = new ArrayList<>();
    private TaskAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
     ...
     tasklist.add(sometask);
     adapter.notifyDataSetChanged();
    }
    ...
    public void addNewTask(){
        Toast.makeText(MainActivity.this,
                "TEST", Toast.LENGTH_LONG).show();
        Task task = new Task(name.getText().toString(),desc.getText().toString(),date.getText().toString());
        tasklist.add(task);
        adapter.notifyDataSetChanged();    
    }
}

edited Apr 7, 2018 at 14:51

answered Apr 7, 2018 at 14:35

Sagar

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3 Comments

dongerpep Over a year ago

where should i exactly call it ?

Sagar Over a year ago

add it after tasklist.add(task) in the method. You need to maintain class level reference to the adapter, just like your tasklist

Sagar Over a year ago

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