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

使用DataBinding,ViewModel,LiveData完成点赞小功能

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1.build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.example.clickzan"
        minSdkVersion 19
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        android.defaultConfig.vectorDrawables.useSupportLibrary = true
        dataBinding {
            enabled true
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.0.2'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.2.0'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    implementation 'androidx.lifecycle:lifecycle-extensions:2.0.0'
}

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

<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.ConstraintLayout>
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);
    }
}

5.效果图

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