JetPack（MVVM架构）数据绑定实例

一、初步尝试JetPack(MVVM架构)

主要用到了 ViewModel、LiveData、DataBinding

1. 写ViewModel，数据存放
2. 使用dataBinding 数据双向绑定
   1. gradle添加dataBinding
   2. xml执行绑定

案例：

ViewModel

public class MyViewModel extends ViewModel {
    private MutableLiveData<Integer> aTeamScore;    // team A score
    private MutableLiveData<Integer> bTeamScore;    // team B score
    private int aBack;  // team A pre score (for undo)
    private int bBack;  // team B pre score (for undo)

    /**
     * get Team A score
     *
     * @return
     */
    public MutableLiveData<Integer> getaTeamScore() {
        if (aTeamScore == null) {
            aTeamScore = new MutableLiveData<>();
            aTeamScore.setValue(0);
        }
        return aTeamScore;
    }

    /**
     * get Team B score
     *
     * @return
     */
    public MutableLiveData<Integer> getbTeamScore() {
        if (bTeamScore == null) {
            bTeamScore = new MutableLiveData<>();
            bTeamScore.setValue(0);
        }
        return bTeamScore;
    }

    /**
     * add Team A score
     *
     * @param p
     */
    public void aTeamAdd(int p) {
        aBack = aTeamScore.getValue();
        bBack = bTeamScore.getValue();
        aTeamScore.setValue(aTeamScore.getValue() + p);
    }

    /**
     * add Team B score
     *
     * @param p
     */
    public void bTeamAdd(int p) {
        aBack = aTeamScore.getValue();
        bBack = bTeamScore.getValue();
        bTeamScore.setValue(bTeamScore.getValue() + p);
    }

    /**
     * set score 0
     */
    public void reset() {
        aBack = aTeamScore.getValue();
        bBack = bTeamScore.getValue();
        aTeamScore.setValue(0);
        bTeamScore.setValue(0);
    }

    /**
     * 撤销操作
     */
    public void undo() {
        aTeamScore.setValue(aBack);
        bTeamScore.setValue(bBack);
    }
}

gradle

testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
dataBinding{
    enabled true
}

implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0'

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="data"
            type="com.dy.scorejetpack.MyViewModel" />
    </data>

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

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

            <TextView
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:text="TeamA"
                android:textSize="30sp" />

            <TextView
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:text="TeamB"
                android:textSize="30sp" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:paddingTop="50dp">

            <TextView
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:text="@{String.valueOf(data.getaTeamScore())}"
                android:textSize="70sp" />

            <TextView
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:text="@{String.valueOf(data.getbTeamScore())}"
                android:textSize="70sp" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:paddingTop="20dp">

            <Button
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:onClick="@{()->data.aTeamAdd(1)}"
                android:text="+1"
                android:textSize="20sp" />

            <Button
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:onClick="@{()->data.bTeamAdd(1)}"
                android:text="+1"
                android:textSize="20sp" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:paddingTop="20dp">

            <Button
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:onClick="@{()->data.aTeamAdd(2)}"
                android:text="+2"
                android:textSize="20sp" />

            <Button
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:onClick="@{()->data.bTeamAdd(2)}"
                android:text="+2"
                android:textSize="20sp" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:paddingTop="20dp">

            <Button
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:onClick="@{()->data.aTeamAdd(3)}"
                android:text="+3"
                android:textSize="20sp" />

            <Button
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:onClick="@{()->data.bTeamAdd(3)}"
                android:text="+3"
                android:textSize="20sp" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:paddingTop="60dp">

            <ImageButton
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:onClick="@{()->data.undo()}"
                android:src="@drawable/ic_reply_black_24dp" />

            <ImageButton
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:onClick="@{()->data.reset()}"
                android:src="@drawable/ic_refresh_black_24dp" />

        </LinearLayout>
    </LinearLayout>
</layout>

MainActivity

public class MainActivity extends AppCompatActivity {

    MyViewModel mMyViewModel;
    ActivityMainBinding mBinding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mBinding = DataBindingUtil.setContentView(this,R.layout.activity_main);
        mMyViewModel = new ViewModelProvider(this).get(MyViewModel.class);
        mBinding.setData(mMyViewModel);
        mBinding.setLifecycleOwner(this);
    }
}

小技巧：
一些小图标，矢量图Android自带的

本文地址：https://blog.csdn.net/wealth_gold/article/details/110149507