【自学 Android】使用 DataBinding,ViewModel,LiveData 完成点赞小功能

2.MyViewModel.java

package com.example.clickzan;

import androidx.lifecycle.MutableLiveData;

import androidx.lifecycle.ViewModel;

public class MyViewModel extends ViewModel {

private MutableLiveData<Integer> mutableLiveData;

public MutableLiveData<Integer> getMutableLiveData() {

if (mutableLiveData==null) {

mutableLiveData = new MutableLiveData<>();

mutableLiveData.setValue(0);

}

return mutableLiveData;

}

public void addCount(){

mutableLiveData.setValue(mutableLiveData.getValue()+1);

}

}

3.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="data"

type="com.example.clickzan.MyViewModel" />

</data>

<androidx.constraintlayout.widget.ConstraintLayout

android:layout_width="match_parent"

android:layout_height="match_parent"

tools:context=".MainActivity">

<TextView

android:id="@+id/textView"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginStart="8dp"

android:layout_marginEnd="8dp"

android:layout_marginBottom="8dp"

android:text="@{String.valueOf(data.mutableLiveData)}"

android:textSize="36sp"

app:layout_constraintBottom_toBottomOf="parent"

app:layout_constraintEnd_toEndOf="parent"

app:layout_constraintHorizontal_bias="0.498"

app:layout_constraintStart_toStartOf="parent"

app:layout_constraintTop_toTopOf="parent"

app:layout_constraintVertical_bias="0.149" />

<ImageView

android:id="@+id/imageView"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_marginStart="8dp"

android:layout_marginTop="8dp"

android:layout_marginEnd="8dp"

android:layout_marginBottom="8dp"

android:contentDescription="@string/img_button_msg"

app:layout_constraintBottom_toBottomOf="parent"

app:layout_constraintEnd_toEndOf="parent"

app:layout_constraintHorizontal_bias="0.498"

app:layout_constraintStart_toStartOf="parent"

app:layout_constraintTop_toTopOf="parent"

app:layout_constraintVertical_bias="0.353"

app:srcCompat="@drawable/ic_thumb_up_black_24dp"

android:onClick="@{()->data.addCount()}"/>

</androidx.constraintlayout.widget.Cons

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traintLayout>

</layout>

4.MainActivity.java

package com.example.clickzan;

import androidx.appcompat.app.AppCompatActivity;

import androidx.databinding.DataBindingUtil;

import androidx.lifecycle.ViewModelProviders;

import android.os.Bundle;

import com.example.clickzan.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {

MyViewModel myViewModel;

ActivityMainBinding activityMainBinding;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

activityMainBinding = DataBindingUtil.setContentView(this,R.layout.activity_main);

myViewModel = ViewModelProviders.of(this).get(MyViewModel.class);

activityMainBinding.setData(myViewModel);

activityMainBinding.setLifecycleOwner(this);

}

}