使用Timer从Listview android中的SQLite获取和显示数据

Question

我的数据库表包含task，task_time，task_completed等字段。在我的应用程序中，我正在获取task_time字符串并将其与每次在计时器内循环的android系统时间进行比较。如果时间匹配，那么我将根据列表视图中指定的时间显示该任务字符串。我在这里遇到的问题是，每当添加新列表时，之前的列表就会被删除，即它们会被覆盖。

这是代码。

MainAcivity.java

public class MainAcivity extends Activity
{
private int Current_level = 0;
private int tcount = 0;

private Timer t;

private String[] ids;
private String Current_Date = "";
private String Current_Time = "";
private String DB_Date = "";

private ListView listView;
private TaskAdapter adapter;

private TextView timercount;

private ArrayList<String> LoadTaskFromDb = new ArrayList<String>();
private ArrayList<String> LoadTimeFromDb = new ArrayList<String>();

private DatabaseHandler db = new DatabaseHandler(TaskScheduler.this);

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

    listView = (ListView) findViewById(R.id.listview1);
    timercount = (TextView)findViewById(R.id.levelStartedTime);

    Current_level = 1;

    Initialization(Current_level);
}

//Check level and extract task
private void Initialization(int curr_level)
{
    LoadTaskFromDb = db.GetTaskBasedOnLevel(curr_level);
    LoadTimeFromDb = db.getTime(curr_level);

    t = new Timer();
    t.scheduleAtFixedRate(new TimerTask()
    {
        @Override
        public void run()
        {
            runOnUiThread(new Runnable()
            {
                @Override
                public void run()
                {
                    Load(LoadTaskFromDb, LoadTimeFromDb);
                    Log.d("TimerCount", String.valueOf(tcount));
                    tcount++;
                }
            });

        }
    },0,    30000);

}

//HERE IS THE PROBLEM
//CHECKING SYSTEM TIME WITH DB_TIME
private void Load(ArrayList<String> task, ArrayList<String> time)
{
    for(int j = 0; j < time.size(); j++)
    {
        if(CompareTime(time.get(j)))
        {
            LoadTask.LoadTaskFromDB(task, j); //If matches loading task

            ids = new String[LoadTask.Items.size()];

            for (int i = 0; i < ids.length; i++)
            {
                int k = i + 1;
                ids[i] = Integer.toString(k);
            }

            adapter = new TaskAdapter(this,R.layout.task_llist, ids);
            listView.setAdapter(adapter);

            adapter.notifyDataSetChanged();

            listView.setOnItemClickListener(new AdapterView.OnItemClickListener()
            {
                public void onItemClick(AdapterView<?> listView, View view, int position, long id)
                {
                    Log.d("LIST_POS", String.valueOf(position));
                    TextView task = (TextView)view.findViewById(R.id.taskString);
                    Log.d("LIST_POS_TASK", task.getText().toString());
                }
            });
        }
        else
        {
            Log.d("Nomatch", "NO MATCH FOUND");
        }
    }
}

//compare system time with db fetched time
private boolean CompareTime(String db_time)
{
    boolean time_match = true;

    //TODO check time format in database
    SimpleDateFormat sdf = new SimpleDateFormat("HH:mm aa");

    Date systemDate = Calendar.getInstance().getTime();
    String myDate = sdf.format(systemDate);

    Date Date1 = null;
    Date Date2 = null;

    try
    {
        Date1 = sdf.parse(myDate);
    }
    catch (ParseException e)
    {
        e.printStackTrace();
    }

    try
    {
        Date2 = sdf.parse(db_time);
    }
    catch (ParseException e)
    {
        e.printStackTrace();
    }

    if(Date1.compareTo(Date2) == 0)
    {
        time_match = true;
    }
    else
    {
        time_match = false;
    }

    return time_match;
}
}

Task.java

public class Task
{
    public static int Id;
    public static String IconFile;
    public static String Task;
    public static String TimeLeft;

    public Task(int id, String iconFile, String task, String timeleft)
    {
        Id = id;
        IconFile = iconFile;
        Task = task;
        TimeLeft = timeleft;
    }
}

TaskAdapter.java

public class TaskAdapter extends ArrayAdapter<String>
{
public MyCounter timer;
private final Context context;
private final String[] Ids;
private final int rowResourceId;

public TaskAdapter(Context context, int textViewResourceId, String[] objects)
{
    super(context, textViewResourceId, objects);

    this.context = context;
    this.Ids = objects;
    this.rowResourceId = textViewResourceId;
}

@Override
public View getView(int position, View convertView, ViewGroup parent)
{
    LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    View rowView = inflater.inflate(rowResourceId, parent, false);
    ImageView imageView = (ImageView) rowView.findViewById(R.id.taskImage);
    TextView textView = (TextView) rowView.findViewById(R.id.taskString);
    TextView timeleft = (TextView) rowView.findViewById(R.id.timeShow);

    int id = Integer.parseInt(Ids[position]);

    String imageFile = LoadTask.GetId(id).IconFile;

    textView.setText(LoadTask.GetId(id).Task);

    timeleft.setText("2 hr left");

    InputStream ims = null;
    try
    {
        ims = context.getAssets().open(imageFile);
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }

    Drawable d = Drawable.createFromStream(ims, null);

    imageView.setImageDrawable(d);

    return rowView;
}
}

LoadTask.java

public class LoadTask
{
public static ArrayList<Task> Items = null;

public static void LoadTaskFromDB(ArrayList<String> task, int getTimeid)
{
    Items = new ArrayList<Task>();

    for(int i = 0; i < task.size(); i++)
    {
        int j = i + 1;
        Items.add(new Task(j, "news.png", task.get(getTimeid).toString(), ""));
    }
}

public static Task GetId(int id)
{
    for(Task task : task)
    {
        if (task.Id == id)
        {
            return task;
        }
    }
    return null;
}
}