Question

我尝试从Android中的SQLite DB加载数据并将其值设置为ListView。问题是，当我在OnCreate中加载数据时，它并没有显示任何内容，但是当我刷新应用程序时它会显示数据。

请帮我解决这个问题！

加载任务代码：

public void loadTasks() {

    Cursor c = notesDb.rawQuery("SELECT * FROM notes", null);
    int titleIndex = c.getColumnIndex("title");
    int contentIndex = c.getColumnIndex("content");
    int dateIndex = c.getColumnIndex("date");
    int idIndex = c.getColumnIndex("object");
    if (c.moveToFirst()) {
        if (!titles.isEmpty()) {
            titles.clear();
        }
        if (!content.isEmpty()) {
            content.clear();
        }
        if (!dates.isEmpty()) {
            dates.clear();
        }
        if (!objectId.isEmpty()) {
            objectId.clear();
        }

        do {
            titles.add(c.getString(titleIndex));
            content.add(c.getString(contentIndex));
            dates.add(c.getString(dateIndex));
            objectId.add(c.getString(idIndex));

            Log.i("Title", c.getString(titleIndex));
            Log.i("Content", c.getString(contentIndex));
            Log.i("Date", c.getString(dateIndex));
            Log.i("Id", c.getString(idIndex));

        } while (c.moveToNext());

        tasksList.setAdapter(customAdapter);
        loadingBar.setVisibility(View.INVISIBLE);

    } else {

        if (titles.size() > 0 || content.size() > 0) {
            tasksList.setAdapter(customAdapter);
            loadingBar.setVisibility(View.INVISIBLE);
        } else {
            titles.add("Welcome To App !");
            content.add("Start taking notes by clicking the add button below !");

            final Calendar c1 = Calendar.getInstance();
            final String monthName = new SimpleDateFormat("MMMM").format(c1.getTime());
            dates.add(String.valueOf(monthName + " " + c1.get(Calendar.DAY_OF_MONTH)) + " " + c1.get(Calendar.YEAR));
            objectId.add("randomId");
            tasksList.setAdapter(customAdapter);
            loadingBar.setVisibility(View.INVISIBLE);
        }
    }
}

OnCreate代码

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_dolt);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    loadTasks();

在OnCreate中将数据传递给适配器：

customAdapter = new CustomAdapter(DoltActivity.this, titles, content, dates);

自定义适配器代码：

public class CustomAdapter extends BaseAdapter{

ArrayList<String> title;
ArrayList<String> contents;
ArrayList<String> dates;
Context context;
private static LayoutInflater inflater=null;
public CustomAdapter(DoltActivity mainActivity, ArrayList<String> titles, ArrayList<String> content, ArrayList<String> date) {
    // TODO Auto-generated constructor stub
    title=titles;
    contents=content;
    dates=date;
    context=mainActivity;
    inflater = ( LayoutInflater )context.
            getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
    // TODO Auto-generated method stub
    return title.size();
}

@Override
public Object getItem(int position) {
    // TODO Auto-generated method stub
    return position;
}

@Override
public long getItemId(int position) {
    // TODO Auto-generated method stub
    return position;
}

@Override
public int getItemViewType(int position) {
    return CustomAdapter.IGNORE_ITEM_VIEW_TYPE;
}

public static class Holder
{
    TextView tv;
    TextView content;
    TextView date;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub
    Holder holder = new Holder();
    View rowView = null;

    rowView = inflater.inflate(R.layout.custom_row, null);

    holder.tv = (TextView) rowView.findViewById(R.id.textView10);
    holder.content = (TextView) rowView.findViewById(R.id.textView3);
    holder.date = (TextView) rowView.findViewById(R.id.textView4);

    holder.tv.setText(title.get(position));
    holder.content.setText(contents.get(position));
    holder.date.setText(dates.get(position));

    rowView.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {

            DoltActivity.tapped = true;
            DoltActivity.id = position;
            Log.i("Position", String.valueOf(position));

            }
        });

    rowView.setOnLongClickListener(new View.OnLongClickListener() {
        @Override
        public boolean onLongClick(View view) {

            DoltActivity.longTapped = true;
            DoltActivity.id = position;

            Log.i("Long ", "Tapped");

            return true;
        }
    });


    return rowView;
}

}

刷新代码：

swipeRefresh.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
        @Override
        public void onRefresh() {
                loadTasks();               
            swipeRefresh.setRefreshing(false);
        }
    });

提前致谢！

Answer 1

试试这个，

1 - 在将customAdapter设置为ListView之前初始化loadTask()，即

之前

customAdapter = new CustomAdapter(getActivity(), titles, content, dates);
tasksList.setAdapter(customAdapter);

您的代码中出现逻辑数据流错误，您在调用customAdapter后初始化loadTask()但在loadTask()内部使用该对象而未使用更新的标题，内容和日期。

Answer 2

更新阵列后创建适配器。移动你的行：

 customAdapter = new CustomAdapter(DoltActivity.this, titles, content, dates);

以前：

tasksList.setAdapter(customAdapter);

另外，您可以在代码之下移动到if之外，只是为了删除代码重复。你的loadTask函数如下：

public void loadTasks() {

Cursor c = notesDb.rawQuery("SELECT * FROM notes", null);
int titleIndex = c.getColumnIndex("title");
int contentIndex = c.getColumnIndex("content");
int dateIndex = c.getColumnIndex("date");
int idIndex = c.getColumnIndex("object");
if (c.moveToFirst()) {
    if (!titles.isEmpty()) {
        titles.clear();
    }
    if (!content.isEmpty()) {
        content.clear();
    }
    if (!dates.isEmpty()) {
        dates.clear();
    }
    if (!objectId.isEmpty()) {
        objectId.clear();
    }

    do {
        titles.add(c.getString(titleIndex));
        content.add(c.getString(contentIndex));
        dates.add(c.getString(dateIndex));
        objectId.add(c.getString(idIndex));

        Log.i("Title", c.getString(titleIndex));
        Log.i("Content", c.getString(contentIndex));
        Log.i("Date", c.getString(dateIndex));
        Log.i("Id", c.getString(idIndex));

    } while (c.moveToNext());

} else {

    if (titles.size() > 0 || content.size() > 0) {

    } else {
        titles.add("Welcome To App !");
        content.add("Start taking notes by clicking the add button below !");

        final Calendar c1 = Calendar.getInstance();
        final String monthName = new SimpleDateFormat("MMMM").format(c1.getTime());
        dates.add(String.valueOf(monthName + " " + c1.get(Calendar.DAY_OF_MONTH)) + " " + c1.get(Calendar.YEAR));
        objectId.add("randomId");

    }
}

customAdapter = new CustomAdapter(DoltActivity.this, titles, content, dates);
tasksList.setAdapter(customAdapter);
loadingBar.setVisibility(View.INVISIBLE);

}

将SQLite数据库中的数据加载到ListView

2 个答案: