Android学习进度三

由昨天学习的 ViewModel 以及今天早上学习的 LiveData 和 DataBinding 的相关知识，开发过程中 Controller 类代码变得十分精简。以此为基础，我开发了一款十分简单的篮球比赛计分器，将以前所学的知识串联了起来，作为一次复习参考。

完成实例图：

  

用户可以点击加分按键进行统分，可以进行一次撤销，也可以重置比分。

附上代码

bulid.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.example.score"
        minSdkVersion 19
        targetSdkVersion 29
        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:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    implementation 'androidx.lifecycle:lifecycle-extensions:2.1.0'
}

MyViewModel.java

package com.example.score;

import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;

public class MyViewModel extends ViewModel {
    private MutableLiveData<Integer> aTeamScore;
    private MutableLiveData<Integer> bTeamScore;
    private int aBack,bBack;

    public MutableLiveData<Integer> getaTeamScore() {
        if (aTeamScore == null) {
            aTeamScore = new MutableLiveData<>();
            aTeamScore.setValue(0);
        }
        return aTeamScore;
    }

    public MutableLiveData<Integer> getbTeamScore() {
        if (bTeamScore == null) {
            bTeamScore = new MutableLiveData<>();
            bTeamScore.setValue(0);
        }
        return bTeamScore;
    }

    public void aTeamAdd(int p) {
        aBack = aTeamScore.getValue();
        bBack = bTeamScore.getValue();
        aTeamScore.setValue(aTeamScore.getValue() + p);
    }

    public void bTeamAdd(int p) {
        aBack = aTeamScore.getValue();
        bBack = bTeamScore.getValue();
        bTeamScore.setValue(bTeamScore.getValue() + p);
    }

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

    public void undo() {
        aTeamScore.setValue(aBack);
        bTeamScore.setValue(bBack);
    }

}

MainActivity.java

package com.example.score;

import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.ViewModelProvider;
import androidx.lifecycle.ViewModelProviders;

import android.os.Bundle;

import com.example.score.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {
    MyViewModel myViewModel;
    ActivityMainBinding binding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = DataBindingUtil.setContentView(this,R.layout.activity_main);
        myViewModel = ViewModelProviders.of(this).get(MyViewModel.class);
        binding.setData(myViewModel);
        binding.setLifecycleOwner(this);
    }
}

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.score.MyViewModel" />
    </data>

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

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline6"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            app:layout_constraintGuide_percent="0.8" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline7"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            app:layout_constraintGuide_percent="0.05" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            app:layout_constraintGuide_percent="0.35" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline5"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            app:layout_constraintGuide_percent="0.65" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_percent="0.5" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            app:layout_constraintGuide_percent="0.5" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            app:layout_constraintGuide_percent="0.15" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline9"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            app:layout_constraintGuide_percent="0.9" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline10"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_percent="0.05" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/guideline11"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_percent="0.95" />

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/textview1"
            android:textSize="@dimen/teamTextSize"
            app:layout_constraintBottom_toTopOf="@+id/guideline3"
            app:layout_constraintEnd_toStartOf="@+id/guideline"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="@+id/guideline7" />

        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/textview2"
            android:textSize="@dimen/teamTextSize"
            app:layout_constraintBottom_toTopOf="@+id/guideline3"
            app:layout_constraintEnd_toStartOf="@+id/guideline11"
            app:layout_constraintStart_toStartOf="@+id/guideline"
            app:layout_constraintTop_toTopOf="@+id/guideline7" />

        <TextView
            android:id="@+id/textView3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{String.valueOf(data.getaTeamScore())}"
            android:textColor="@color/colorAccent"
            android:textSize="@dimen/scoreTextSize"
            app:layout_constraintBottom_toTopOf="@+id/guideline4"
            app:layout_constraintEnd_toStartOf="@+id/guideline"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="@+id/guideline3"
            tools:text="120" />

        <TextView
            android:id="@+id/textView4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{String.valueOf(data.getbTeamScore())}"
            android:textColor="@color/colorPrimary"
            android:textSize="@dimen/scoreTextSize"
            app:layout_constraintBottom_toTopOf="@+id/guideline4"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="@+id/guideline"
            app:layout_constraintTop_toTopOf="@+id/guideline3"
            tools:text="50" />

        <Button
            android:id="@+id/button"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginBottom="8dp"
            android:background="@color/colorAccent"
            android:text="@string/button1"
            android:textColor="@android:color/white"
            android:textSize="@dimen/buttonTextSize"
            android:onClick="@{()->data.aTeamAdd(1)}"
            app:layout_constraintBottom_toTopOf="@+id/guideline2"
            app:layout_constraintEnd_toStartOf="@+id/guideline"
            app:layout_constraintStart_toStartOf="@+id/guideline10"
            app:layout_constraintTop_toTopOf="@+id/guideline4"
            app:layout_constraintVertical_bias="0.58" />

        <Button
            android:id="@+id/button2"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginBottom="8dp"
            android:background="@color/colorPrimary"
            android:text="@string/button1"
            android:textColor="@android:color/white"
            android:textSize="@dimen/buttonTextSize"
            android:onClick="@{()->data.bTeamAdd(1)}"
            app:layout_constraintBottom_toTopOf="@+id/guideline2"
            app:layout_constraintEnd_toStartOf="@+id/guideline11"
            app:layout_constraintStart_toStartOf="@+id/guideline"
            app:layout_constraintTop_toTopOf="@+id/guideline4" />

        <Button
            android:id="@+id/button3"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginBottom="8dp"
            android:background="@color/colorAccent"
            android:text="@string/button2"
            android:textColor="@android:color/white"
            android:textSize="@dimen/buttonTextSize"
            android:onClick="@{()->data.aTeamAdd(2)}"
            app:layout_constraintBottom_toTopOf="@+id/guideline5"
            app:layout_constraintEnd_toStartOf="@+id/guideline"
            app:layout_constraintStart_toStartOf="@+id/guideline10"
            app:layout_constraintTop_toTopOf="@+id/guideline2" />

        <Button
            android:id="@+id/button4"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginBottom="8dp"
            android:background="@color/colorPrimary"
            android:text="@string/button2"
            android:textColor="@android:color/white"
            android:textSize="@dimen/buttonTextSize"
            android:onClick="@{()->data.bTeamAdd(2)}"
            app:layout_constraintBottom_toTopOf="@+id/guideline5"
            app:layout_constraintEnd_toStartOf="@+id/guideline11"
            app:layout_constraintStart_toStartOf="@+id/guideline"
            app:layout_constraintTop_toTopOf="@+id/guideline2" />

        <Button
            android:id="@+id/button5"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginBottom="8dp"
            android:background="@color/colorAccent"
            android:text="@string/button3"
            android:textColor="@android:color/white"
            android:textSize="@dimen/buttonTextSize"
            android:onClick="@{()->data.aTeamAdd(3)}"
            app:layout_constraintBottom_toTopOf="@+id/guideline6"
            app:layout_constraintEnd_toStartOf="@+id/guideline"
            app:layout_constraintStart_toStartOf="@+id/guideline10"
            app:layout_constraintTop_toTopOf="@+id/guideline5" />

        <Button
            android:id="@+id/button6"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginBottom="8dp"
            android:background="@color/colorPrimary"
            android:text="@string/button3"
            android:textColor="@android:color/white"
            android:textSize="@dimen/buttonTextSize"
            android:onClick="@{()->data.bTeamAdd(3)}"
            app:layout_constraintBottom_toTopOf="@+id/guideline6"
            app:layout_constraintEnd_toStartOf="@+id/guideline11"
            app:layout_constraintStart_toStartOf="@+id/guideline"
            app:layout_constraintTop_toTopOf="@+id/guideline5" />

        <ImageButton
            android:id="@+id/imageButton"
            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/undoButton"
            android:onClick="@{()->data.undo()}"
            app:layout_constraintBottom_toTopOf="@+id/guideline9"
            app:layout_constraintEnd_toStartOf="@+id/guideline"
            app:layout_constraintHorizontal_bias="0.8"
            app:layout_constraintStart_toStartOf="@+id/guideline10"
            app:layout_constraintTop_toTopOf="@+id/guideline6"
            app:srcCompat="@drawable/ic_undo_black_24dp" />

        <ImageButton
            android:id="@+id/imageButton2"
            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/resetButton"
            android:onClick="@{()->data.reset()}"
            app:layout_constraintBottom_toTopOf="@+id/guideline9"
            app:layout_constraintEnd_toStartOf="@+id/guideline11"
            app:layout_constraintHorizontal_bias="0.20"
            app:layout_constraintStart_toStartOf="@+id/guideline"
            app:layout_constraintTop_toTopOf="@+id/guideline6"
            app:srcCompat="@drawable/ic_loop_black_24dp" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

今天因身体不适便只学了这些内容，明天我会继续学习Android Jetpack的相关知识。