Question

我在listview中显示任务对象。有2个布局文件，一个是activty_main布局，其中有一个listview textviews一个按钮，inputs.other用于listview元素row.xml。我想做的是刷新列表添加新任务。 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);


    }
}

任务类：

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;
    }



}

这就是布局的样子：

Answer 1

您缺少对adapter.notifyDataSetChanged()的调用，每次修改适配器内容后都需要这样做。

您需要维护适配器的类级别引用。

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();    
    }
}

将新对象添加到关联的arraylist后，如何刷新Listview？

1 个答案: