如何在Android中将双向数据绑定用于动态创建的字段 [英] How to use two-way data binding in Android for dynamically created fields

问题描述

我有一个表单，其字段由服务器返回值设置.

I have a form whose fields are set by server return.

这是活动中的代码.

//returned by server
String[] attributes = new String[] {"occupation", "salary", "age"};

LinearLayout dynamicLayout = (LinearLayout) findViewById(R.id.dynamic_layout);
for (String attribute : attributes) {
    EditText text = new EditText(this);
    text.setLayoutParams(new LayoutParams(
        LayoutParams.WRAP_CONTENT,
        LayoutParams.WRAP_CONTENT
    ));
    text.setText(attribute);
    dynamicLayout.addView(text);
}

我有这个模型课

class Person {
    public Map<String, String> attributes;
}

最后，我希望上面的属性将包含属性名称和EditText

In the end I expect the attributes above will contain the map between attribute name and the values input in the EditText

我尝试创建一个双向数据绑定示例，该示例使用布局文件中预定义的EditText.但是我想知道这个动态属性是否可以实现.

I have tried created a two-way data-binding sample that uses EditText that is predefined in the layout file. But I am wondering if this dynamic attribute can be done.

推荐答案

数据绑定实际上不适用于代码生成的布局.就是说，您可以使用数据绑定和绑定适配器来完成此操作.

Data Binding doesn't really work with code-generated layouts. That said, you can use data binding to do this with a Binding Adapter.

本文告诉您如何对列表使用数据绑定:

This article tells you how to use data binding with lists:

https://medium.com/google-developers/android-data-binding-list-tricks-ef3d5630555e#.v2deebpgv

如果要使用数组而不是列表，这是一个很小的调整.如果要使用地图，则必须将地图作为参数传递给绑定布局.本文假定使用一个变量，但是您可以在BindingAdapter中传递多个变量.对于一个简单的绑定适配器:

If you want to use an array instead of a list, it is a small adjustment. If you want to use a map, you'll have to pass the map as a parameter to the bound layout. The article assumes a single variable, but you can pass in multiple in your BindingAdapter. For a simple Binding Adapter:

@BindingAdapter({"entries", "layout", "extra"})
public static <T, V> void setEntries(ViewGroup viewGroup,
                                     T[] entries, int layoutId,
                                     Object extra) {
    viewGroup.removeAllViews();
    if (entries != null) {
        LayoutInflater inflater = (LayoutInflater)
            viewGroup.getContext()      
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        for (int i = 0; i < entries.length; i++) {
            T entry = entries[i];
            ViewDataBinding binding = DataBindingUtil
                .inflate(inflater, layoutId, viewGroup, true);
            binding.setVariable(BR.data, entry);
            binding.setVariable(BR.extra, extra);
        }
    }
}

您将这样绑定条目:(假设entry.xml)

And you would bind the entries like this: (assume entry.xml)

<layout>
    <data>
        <variable name="data" type="String"/>
        <variable name="extra" type="java.util.Map&lt;String, String&gt;"/>
    </data>
    <EditText xmlns:android="..."
        android:text="@={extra[data]}"
        .../>
</layout>

在您的包含布局中，您将使用:

And in your containing layout, you'd use:

<layout>
    <data>
        <variable name="person" type="com.example.Person"/>
        <variable name="attributes" type="String[]"/>
    </data>
    <FrameLayout xmlns:android="..." xmlns:app="...">
        <!-- ... -->
        <LinearLayout ...
            app:layout="@{@layout/entry}"
            app:entries="@{attributes}"
            app:extra="@{person.attributes}"/>
    </FrameLayout>
</layout>

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