Question

我创建了一个 StatusAdapter 类，用我通过查询Parse.com数据库获取的对象填充 MainActivity 。一切似乎都很好，我没有在Logcat中得到任何错误。当我运行 MainActivity 时，我得到的是一个没有操作栏和项目列表的白色屏幕。我不明白为什么，也许你可以帮助我。我必须提到我是Android的初学者。

下面你可以看到我的适配器列表。

StatusAdapter.java

public class StatusAdapter extends ArrayAdapter<ParseObject> {

protected Context mContext;
protected List<ParseObject> mStatus;


public StatusAdapter(Context context, List<ParseObject> status) {
    super(context, R.layout.homepage_custom_layout);
    mContext = context;
    mStatus = status;
}


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

    ViewHolder holder;

    if (convertView == null) {

        convertView = LayoutInflater.from(mContext).inflate(R.layout.homepage_custom_layout, null);
        holder = new ViewHolder();
        holder.usernameHomepage = (TextView) convertView.findViewById(R.id.usernameHP);


        holder = new ViewHolder();
        holder.statusHomepage = (TextView) convertView.findViewById(R.id.statusHP);


        convertView.setTag(holder);
    } else {

        holder = (ViewHolder) convertView.getTag();
    }

    ParseObject statusObject = mStatus.get(position);

    // username
    String username = statusObject.getString("username");
    holder.usernameHomepage.setText(username);

    // status
    String status = statusObject.getString("newStatus");
    holder.statusHomepage.setText(status);

    return convertView;
}



public static class ViewHolder {

    TextView usernameHomepage;
    TextView statusHomepage;
}

在我的 MainActivity 中，我从Parse数据库获取数据，并使用 StatusAdapter 将信息输入 ListView 。另外我要提一下，我在 activity_main.xml 的布局中定义了 ListView ，它看起来像这样：

activity_main.xml中

<ListView
    android:id="@android:id/list"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

</ListView>

MainActivity.java

public class MainActivity extends ListActivity {

protected List<ParseObject> mStatusObjects;

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

    // Enable Local Datastore.

    Parse.initialize(this, "fLDZVeIkrA39AHPDK9gbujmzIb0bcZUIuaRNIBdk", "pwwZVAJWmzABPPShPB0qiD8764XiwlBJGZZObiqo");


    ParseUser currentUser = ParseUser.getCurrentUser();
    if (currentUser != null) {
        // do stuff with the user

        ParseQuery<ParseObject> query = new ParseQuery<ParseObject>("Status");
        query.findInBackground(new FindCallback<ParseObject>() {
            @Override
            public void done(List<ParseObject> statusList, ParseException e) {
                if(e == null) {

                    mStatusObjects = statusList;

                    StatusAdapter mAdapter = new StatusAdapter(getListView().getContext(),mStatusObjects);
                    setListAdapter(mAdapter);
                }
            }
        });


    } else {
        // there was a problem
    }


}

MainActivity.java 的ActionBar代码也是：

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    switch (id) {
        case R.id.updateStatus:
            // take user to update activity
            Intent toMainActivityIntent = new Intent(MainActivity.this, UpdateStatusActivity.class);
            startActivity(toMainActivityIntent);
            break;

        case R.id.LogoutUser:
            //Log out user
            ParseUser.logOut();
            // take user to login activity
            Intent toLoginActivityIntent = new Intent(MainActivity.this, LoginActivity.class);
            startActivity(toLoginActivityIntent);
            break;
    }

    return super.onOptionsItemSelected(item);
}

为什么空白活动 - 使用ArrayAdapter的ListView，未显示错误

0 个答案: