android数据绑定(bind)不起作用

Question

我是一个新手程序员。

我正在练习android数据绑定(bind)示例..

它是如何工作的，

单击 imageButton 时，用户类的“喜欢值”会增加。

但它不起作用，我不知道，

原因是为什么？

我该如何解决？

如果将 onClickLike() 方法从主类移动到用户类并修复源，它确实工作得很好。

User Class

public class User {
//
public ObservableField<String> name = new ObservableField<>();
public ObservableInt age = new ObservableInt();
public ObservableInt likes = new ObservableInt();

public User(String nameString, int ageInt) {
    name.set(nameString);
    age.set(ageInt);
    likes.set(0);
}

}

MainActivity

public class MainActivity extends AppCompatActivity {
User user;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //setContentView(R.layout.activity_main);
    ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
    user = new User("john", 29);
    binding.setUser(user);

    String date = (String) DateFormat.format("yyyy/MM/dd kk:mm:ss", Calendar.getInstance());
    binding.textTime.setText(date);

}

public void onClickLike(View view) { <------------ doesn't work
    user.likes.set(user.likes.get() + 1);
}

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context="com.example.john.bindingexample.MainActivity">
    <data>
        <variable
            name="user"
            type="com.example.john.bindingexample.User"/>
        <variable
            name="main"
            type="com.example.john.bindingexample.MainActivity"/>
    </data>

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

        <TextView
            android:id="@+id/text_time"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="right"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="8dp"
            android:text="profile"
            android:textAppearance="@style/TextAppearance.AppCompat.Large"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="8dp"
            android:text="name:"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="8dp"
            android:text="@{user.name}"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="8dp"
            android:text="age:"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="8dp"
            android:text="@{String.valueOf(user.age)}"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="8dp"
            android:text="LIKE:"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="8dp"
            android:text="@{String.valueOf(user.likes)}"
            android:textAppearance="@style/TextAppearance.AppCompat.Medium"/>


        <ImageButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="@{main::onClickLike}" <------------ doesn't work
            android:src="@drawable/ic_thumb_up_black_36dp"
            />

    </LinearLayout>

</layout>

Answer 1

我认为您还必须将您的主要绑定(bind)与 onCreate 中的用户相同.

binding.setMain(this);