How to use two-way data binding in Android for dynamically created fields

问题

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

This is the code in the Activity.

//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);
}

I have this model class

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

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

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.

回答1:

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

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

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

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);
        }
    }
}

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>

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>

来源：https://stackoverflow.com/questions/42414021/how-to-use-two-way-data-binding-in-android-for-dynamically-created-fields

标签

android

android-databinding