Question

我有一个数据更新屏幕，用户可以在其中更新/编辑保存在数据库中的数据。我有多个字段，用户可以编辑。数据将使用数据库中保存的先前值进行预填充。我的编辑屏幕如下

@override
  Widget build(BuildContext context) {
    return Scaffold(
        drawer: newdrawer(),
        appBar: newappbar(
          title: 'Edit Task',
        ),
        body: SingleChildScrollView(
          child: ConstrainedBox(
            constraints: BoxConstraints(),
            child: Center(
              child: Column(
                // mainAxisAlignment: MainAxisAlignment.center,
                crossAxisAlignment: CrossAxisAlignment.center,
                children: <Widget>[
                  TextFormField(
                    decoration: InputDecoration(
                    labelText: 'Title',
                    ),
                    initialValue: widget.postid.data['Title'],
                    onChanged: (value){
                      this.Title=value;
                    },
                  ),
                  SizedBox(height: 5.0),
                  Container(
                    height: maxLines * 24.0,
                    child: TextFormField(
                      maxLines: maxLines,
                      decoration: InputDecoration(
                        hintText: 'Enter Summary',
                        contentPadding: new EdgeInsets.symmetric(
                            vertical: 25.0, horizontal: 10.0),
                      ),
                      initialValue: widget.postid.data['Summary'],
                      onChanged: (value) {
                        this.Summary = value;
                      },
                    ),
                  ),
                  SizedBox(height: 5.0),
                  SizedBox(height: 5.0),
                  TextFormField(
                    decoration: InputDecoration(
                      hintText: 'Task to be given to',
                      contentPadding: new EdgeInsets.symmetric(
                          vertical: 25.0, horizontal: 10.0),
                    ),
                    initialValue: widget.postid.data['Taskgivento'],
                    //TODO: use tagging system or search when typed system
                    onChanged: (value) {
                      this.Taskgivento = value;
                    },
                  ),
                  SizedBox(height: 5.0),
                  TextFormField(
                    decoration: InputDecoration(
                      hintText: 'Status',
                      contentPadding: new EdgeInsets.symmetric(
                          vertical: 25.0, horizontal: 10.0),
                    ),
                    initialValue: widget.postid.data['Status'],
                    onChanged: (value) {
                      this.Status = value;
                    },
                  ),
                  DateTimeField(
                    format: dateformat,
                    onShowPicker: (context, currentValue) {
                      return showDatePicker(
                          context: context,
                          firstDate: DateTime(1900),
                          initialDate: currentValue ?? DateTime.now(),
                          lastDate: DateTime(2100));
                    },
                    decoration: InputDecoration(
                      hintText: 'Enter Date to be completed',
                      contentPadding: new EdgeInsets.symmetric(
                          vertical: 25.0, horizontal: 10.0),
                    ),
                    initialValue: widget.postid.data['Completion'].toDate(),
                    onChanged: (value) {
                      this.Completion = value;
                    },
                  ),
                  SizedBox(height: 25.0),
                  SizedBox(
                    width: 90.0,
                    height: 50.0,
                    child: FlatButton(
                      //color: Colors.blue,

                      padding: EdgeInsets.all(8.0),
                      child: Text('Update Task'),
                      onPressed: () {
                        Firestore.instance.collection('Task').document(_postdocid()).updateData({
                          'Title': this.Title,
                          'Summary': this.Summary,
                          'Taskgivento': this.Taskgivento,
                          'Status': this.Status,
                          'Completion': this.Completion,
                        });
                        Navigator.of(context).pop();
                      },
                    ),
                  )
                ],
              ),
            ),
          ),
        ));
  }
}

我有五个可以编辑的字段，但是说用户只编辑“标题”字段并按“更新”按钮，然后其余字段将保存为null，因为它们没有更改。但是我想和他们以前的值（初始值）一样。我试图使用if else语句进行更改，但这不起作用。我该怎么做才能做到这一点？

Answer 1

更新文档时，Firestore会将在该调用中指定的字段设置为指定的值。因此，如果不应更新字段，则应不将其包含在通话中。

这意味着您应该仅构建具有新值的字段的映射，并将该映射传递给Firestore。像这样：

Map<String, Object> data = new HashMap();
if (this.Title) data['Title'] = this.Title;
if (this.Summary) data['Summary'] = this.Summary;
if (this.Taskgivento) data['Taskgivento'] = this.Taskgivento;
if (this.Status) data['Status'] = this.Status;
if (this.Completion) data['Completion'] = this.Completion;

Firestore.instance.collection('Task').document(_postdocid()).updateData(data);

如果在更新数据期间未编辑Firebase数据库，则更新为null的值

1 个答案: