android中的数据绑定显示为空
我是android新手,正在尝试下面的数据绑定示例。不显示文本,而是显示一个空框 build.gradle:android中的数据绑定显示为空,android,android-databinding,Android,Android Databinding,我是android新手,正在尝试下面的数据绑定示例。不显示文本,而是显示一个空框 build.gradle: databinding { enabled = true } HelloWorld.java: package com.example.android.databinding; public class HelloWorld { public String getText() { return "My Name is "; }
databinding {
enabled = true
}
HelloWorld.java:
package com.example.android.databinding;
public class HelloWorld {
public String getText() {
return "My Name is ";
}
}
MainActivity.java:
package com.example.android.databinding;
import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;
import android.os.Bundle;
import com.example.android.databinding.databinding.ActivityMainBinding;
public class MainActivity extends AppCompatActivity {
HelloWorld mViewModel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ActivityMainBinding activityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main);
activityMainBinding.setViewModel(mViewModel);
activityMainBinding.executePendingBindings();
}
}
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">
<data>
<variable
name="viewModel"
type="com.example.android.databinding.HelloWorld" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@{viewModel.text}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
在通过数据绑定发送之前,您需要实例化HelloWorld
类
mViewModel = new HelloWorld();
activityMainBinding.setViewModel(mViewModel);
另外,在HelloWorld
类中没有一个文件text
,因此android:text=“@{viewModel.text}”
不会被编译
所以您需要添加它,并设置它的值,我在其中使用构造函数:
public class HelloWorld {
String text;
public HelloWorld() {
text = getText();
}
public String getText() {
return "My Name is ";
}
}