Question

我有一个片段，可以扩展三个EditText视图的布局。收集用户的输入后，我想将该数据保存到我的SQLite数据库。 “保存”按钮位于选项菜单上，并由调用片段的相同“活动”进行充气。

当我尝试将数据保存到我的数据库时，我得到以下NPE，

NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference

即使单击“保存”时所有三个字段都填充了有效数据。

我也很困惑我的Fragment与Activity中的逻辑应该是什么，目前所有的逻辑都在Activity中，而片段实际上只是夸大了一个布局。

EditActivity

public class EditActivity extends ActionBarActivity implements DatePickerDialog.OnDateSetListener{

    EditText mTitleText;
    EditText mDueDate;
    EditText mTaskNotes;

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


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_edit, menu);
        return true;
    }

    @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.
       switch (item.getItemId()) {
           case R.id.action_settings:
               return true;
           case R.id.action_save:
               insertNewTask(findViewById(R.id.task_title));
               return true;
           case R.id.action_delete:
               startActivity(new Intent(this, MainActivity.class));
               return true;
           default:
               return super.onOptionsItemSelected(item);
       }
    }

    @Override
    public void onDateSet(DatePicker view, int year, int month, int day) {
        //do some stuff for example write on log and update TextField on activity
        String myFormat = "MM/dd/yy"; //In which you need put here
        SimpleDateFormat sdf = new SimpleDateFormat(myFormat, Locale.US);
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month, day);
        ((EditText) findViewById(R.id.task_due_date)).setText(sdf.format(calendar.getTime()));
    }

    public void showDatePickerDialog(View v) {
        DialogFragment newFragment = new DatePickerFragment();
        newFragment.show(getFragmentManager(), "datePicker");
    }

    private void insertNewTask(View view) {
        Task task = new Task();
        //TODO this is horribles and only for test
        task.setId("TaskId" + Math.random());
        mTitleText = ((EditText) view.findViewById(R.id.task_title));
        mDueDate = ((EditText) view.findViewById(R.id.task_due_date));
        mTaskNotes = ((EditText) view.findViewById(R.id.task_notes));

        task.setTitle(mTitleText.getText().toString());

        //Holy Shit do the date dance.
        try {
            SimpleDateFormat sdf = new SimpleDateFormat();
            Date taskDueDate = sdf.parse(mDueDate.getText().toString());
            DateTime googleDate = new DateTime(taskDueDate);
            task.setDue(googleDate);
        } catch (ParseException ex) {
            Logger.getLogger("EDITFRAGMENT").log(Level.SEVERE, null, ex);
        }

        task.setNotes(mTaskNotes.getText().toString());

        boolean insertSuccess = new TaskTableController(this).insertRow(task);
        if(insertSuccess){
            Toast.makeText(this, "Task information was saved.", Toast.LENGTH_SHORT).show();
        }else {
            Toast.makeText(this, "Unable to save task information.", Toast.LENGTH_SHORT).show();
        }
    }

EditFragment

public class EditFragment extends Fragment {

    public EditFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_edit, container, false);
    }

TaskTableController

public class TaskTableController extends TaskDbHelper {

    public TaskTableController(Context context) {
        super(context);
    }

    /***
     *
     * @param task
     * @return
     */
    public boolean insertRow(Task task) {
        ContentValues values = new ContentValues();
        values.put("_id",task.getId());
        values.put("title",task.getTitle());
        values.put("due", task.getDue().toString());
        values.put("notes", task.getNotes());

        SQLiteDatabase db = this.getWritableDatabase();
        boolean createSuccessful = db.insert(TaskContract.TaskEntry.TABLE_NAME, null, values) > 0;
        db.close();
        return createSuccessful;
    }
}

我正在调用insertRow insertNewTask来自OnOptionsItemSelected来自活动中的<add name="Connection" connectionString="Data Source=(LocalDB)\v11.0;Initial Catalog=C:\Users\Public\Desktop\MyDatabase.mdf;persist security info=True;Integrated Security=SSPI;"providerName="System.Data.SqlClient" />，此时NPE被抛出，我的Toast都没有显示出来。为什么即使在所有三个字段都填充了数据后，我也得到一个空对象引用？是否有更好的模式可供遵循？现在我的片段不包含任何逻辑。

Answer 1

而是从Fragment中检索视图，定义活动可以调用的方法。例如：

onCreate（）中的

：

MyFragment myf = (MyFragment) getSupportFragmentManager().findFragmentById(R.id.yourid);

当你需要时：

myf.getValueFoo();
myf.getValueBar();

等等

用户输入后尝试在SQLite数据库中插入数据时的Android NPE

1 个答案: