在Android上进行双向数据绑定的正确方法是什么? [英] What is the correct way to do two-way data binding on android?

问题描述

我为2种方式的数据绑定和接缝创建了一个简单的hello世界(当在editext上编写时，textview自动更新)，但是在网上找到的所有代码(如官方文档)都具有更多的代码和复杂性，如

i made a simple hello world for 2 way data binding and seams works perfectly (when write on editext, the textview update automatically), but all code found online like official documentation has much more code and complications like https://developer.android.com/topic/libraries/data-binding/two-way

这是我的代码:

public class MainActivity extends AppCompatActivity {
    public String pippo;
    public Boolean visible = true;

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

    }
}



<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">

    <data>

        <variable
            name="pippo"
            type="String" />

        <variable
            name="visible"
            type="Boolean" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@={pippo}" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@{pippo}"
            android:visibility="@{visible ? android.view.View.VISIBLE: android.view.View.GONE}" />

        <CheckBox
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:checked="@={visible}" />
    </LinearLayout>
</layout>

特别是文档使用了这些东西，但是接缝无用:

In particular documentation use this things but seams useless:

• BaseObservable
• @可绑定
• 避免无限循环的代码
• notifyPropertyChanged

那么，我的代码有什么错误或遗漏?

so, what wrong or missing with my code?

推荐答案

在双向数据绑定中，您需要创建从 BaseObservable 扩展的类，并使用 @Bindable ，然后在设置器中调用 notifyPropertyChanged ，如下所示:

In the two-way data binding you need to create class that extends from BaseObservable, annotate getters with @Bindable and call notifyPropertyChanged in your setters as below:

public class Person extends BaseObservable {

    private String name;

    Person(String name) {
        this.name = name;
    }

    @Bindable
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
        notifyPropertyChanged(BR.name);
    }

}

然后将该类作为类型为 Person 的数据绑定布局变量传递.

Then pass this class as a databinding layout variable of type Person.

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">

    <data>

        <variable
            name="person"
            type="com.example.android......Person" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@={person.name}" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@{person.name}" />
    </LinearLayout>
</layout>

注意:更改 type 属性中的类路径.

Note: change the class path in the type attribute.

，然后在您的活动中使用 setPerson()

and then set this layout variable in your activity with setPerson()

public class ExampleActivity extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        DataBindingUtil.setContentView(this, R.layout.activity_example);

        ActivityExampleBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_example);

        mActivityMainBinding.setPerson(new Person(""));
    }
}

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