Jetpack-DataBinding初体验

DataBinding.png

上一次中的代码：

image.png

利用DataBinding改善

首先再build.gradle中开启dadabinding

image.png

然后转换xml为databing格式，也就是在最外层添加<layout标签>

image.png
完整activity_live_data.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="data"
            type="com.jsecode.qnsmw.ViewModelViewLiveData" />
    </data>

<androidx.constraintlayout.widget.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="77dp"
        android:text="@{data.number.toString()}"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="87dp"
        android:layout_marginTop="61dp"
        android:text="@string/btn_add"
        android:onClick="@{()->data.increase()}"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="46dp"
        android:text="@string/btn_sub"
        android:onClick="@{()->data.decrease()}"
        app:layout_constraintBaseline_toBaselineOf="@+id/button"
        app:layout_constraintStart_toEndOf="@+id/button" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>

LiveDataActivity.java

public class LiveDataActivity extends AppCompatActivity {
    private ViewModelViewLiveData viewModelViewLiveData;
    private ActivityLiveDataBinding binding;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = DataBindingUtil.setContentView(this,R.layout.activity_live_data);
        viewModelViewLiveData = new ViewModelProvider(this, new ViewModelProvider.NewInstanceFactory()).get(ViewModelViewLiveData.class);
        binding.setData(viewModelViewLiveData);
        binding.setLifecycleOwner(this);//这个是这只数据的观察者，同时应用观察者的生命周期
    }
}