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示例图：
1.导包 在build.gradle 中 加入
// 使用androidx版本库implementation 'androidx.lifecycle:lifecycle-extensions:2.1.0-alpha03'2. 开启dataBinding
android{...// 步骤1.开启data bindingdataBinding {enabled = true}...}3.写个类继承 ViewModel
package com.example.mydatabindingtest;import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;public class MyViewModel extends ViewModel {private MutableLiveData<Integer> redNumb;private MutableLiveData<Integer> greenNumb;//回滚 用于记录前面一次的值private int redBack,greenBack;public MutableLiveData<Integer> getRedNumb() {if (redNumb == null) {redNumb = new MutableLiveData<>();redNumb.setValue(0);}return redNumb;}public MutableLiveData<Integer> getGreenNumb() {if (greenNumb == null) {greenNumb = new MutableLiveData<>();greenNumb.setValue(0);}return greenNumb;}public void redAdd(int num) {//添加之前保留之前的值 都记录下redBack = redNumb.getValue();greenBack = greenNumb.getValue();redNumb.setValue(getRedNumb().getValue() + num);}public void greenAdd(int num) {//添加之前保留之前的值 都记录下redBack = redNumb.getValue();greenBack = greenNumb.getValue();greenNumb.setValue(getGreenNumb().getValue() + num);}//重置public void reset(){//添加之前保留之前的值greenBack = greenNumb.getValue();redBack = redNumb.getValue();redNumb.setValue(0);greenNumb.setValue(0);}//撤销一次public void rollBack(){//把记录的值设置到变量中redNumb.setValue(redBack);greenNumb.setValue(greenBack);}
}
4.更改布局 activity_main.xml
<?xml version="1.0" encoding="utf-8"?><!-- 步骤2. 点击小灯泡生成新的xml 或者自己更改 -->
<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><variablename="data"type="com.example.mydatabindingtest.MyViewModel" /></data><androidx.constraintlayout.widget.ConstraintLayoutandroid:id="@+id/btn_add1"android:layout_width="match_parent"android:layout_height="match_parent"><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline22"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="vertical"app:layout_constraintGuide_percent="0.45" /><Buttonandroid:id="@+id/btn_green_add3"style="@style/Widget.AppCompat.Button"android:layout_width="0dp"android:layout_height="wrap_content"android:background="#00FFE7"android:onClick="@{() -> data.greenAdd(3)}"android:scrollbarThumbHorizontal="@null"android:scrollbarThumbVertical="@null"android:text="@string/text_add3"android:textColor="#0288D1"android:textColorHighlight="@null"android:textColorHint="@null"android:textColorLink="@null"android:textSize="30sp"android:textStyle="bold"app:layout_constraintBottom_toTopOf="@+id/guideline16"app:layout_constraintEnd_toStartOf="@+id/guideline19"app:layout_constraintStart_toStartOf="@+id/guideline9"app:layout_constraintTop_toTopOf="@+id/guideline15"tools:ignore="DuplicateSpeakableTextCheck,VisualLintButtonSize" /><Buttonandroid:id="@+id/btn_red_add1"style="@style/Widget.AppCompat.Button"android:layout_width="0dp"android:layout_height="wrap_content"android:background="#FFff0000"android:onClick="@{() -> data.redAdd(1)}"android:scrollbarThumbHorizontal="@null"android:scrollbarThumbVertical="@null"android:text="@string/text_add1"android:textColor="@color/white"android:textColorHighlight="@null"android:textColorHint="@null"android:textColorLink="@null"android:textSize="30sp"android:textStyle="bold"app:layout_constraintBottom_toTopOf="@+id/guideline14"app:layout_constraintEnd_toStartOf="@+id/guideline22"app:layout_constraintStart_toStartOf="@+id/guideline18"app:layout_constraintTop_toTopOf="@+id/guideline13"app:layout_constraintVertical_bias="0.52"tools:ignore="DuplicateSpeakableTextCheck,VisualLintButtonSize" /><Buttonandroid:id="@+id/btn_green_add1"style="@style/Widget.AppCompat.Button"android:layout_width="0dp"android:layout_height="wrap_content"android:background="#00FFE7"android:onClick="@{() -> data.greenAdd(1)}"android:scrollbarThumbHorizontal="@null"android:scrollbarThumbVertical="@null"android:text="@string/text_add1"android:textColor="#0288D1"android:textColorHighlight="@null"android:textColorHint="@null"android:textColorLink="@null"android:textSize="30sp"android:textStyle="bold"app:layout_constraintBottom_toTopOf="@+id/guideline14"app:layout_constraintEnd_toStartOf="@+id/guideline19"app:layout_constraintStart_toStartOf="@+id/guideline9"app:layout_constraintTop_toTopOf="@+id/guideline13"tools:ignore="VisualLintButtonSize" /><Buttonandroid:id="@+id/btn_green_add2"style="@style/Widget.AppCompat.Button"android:layout_width="0dp"android:layout_height="wrap_content"android:background="#00FFE7"android:onClick="@{() -> data.greenAdd(2)}"android:scrollbarThumbHorizontal="@null"android:scrollbarThumbVertical="@null"android:text="@string/text_add2"android:textColor="#0288D1"android:textColorHighlight="@null"android:textColorHint="@null"android:textColorLink="@null"android:textSize="30sp"android:textStyle="bold"app:layout_constraintBottom_toTopOf="@+id/guideline15"app:layout_constraintEnd_toStartOf="@+id/guideline19"app:layout_constraintStart_toStartOf="@+id/guideline9"app:layout_constraintTop_toTopOf="@+id/guideline14"tools:ignore="DuplicateSpeakableTextCheck,VisualLintButtonSize" /><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline9"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="vertical"app:layout_constraintGuide_percent="0.55" /><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline10"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="horizontal"app:layout_constraintGuide_percent="0.05" /><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline11"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="horizontal"app:layout_constraintGuide_percent="0.1504788" /><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline13"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="horizontal"app:layout_constraintGuide_percent="0.35" /><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline14"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="horizontal"app:layout_constraintGuide_percent="0.45" /><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline15"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="horizontal"app:layout_constraintGuide_percent="0.55" /><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline16"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="horizontal"app:layout_constraintGuide_percent="0.65" /><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline17"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="horizontal"app:layout_constraintGuide_percent="0.75" /><TextViewandroid:textColor="@color/white"android:gravity="center"android:id="@+id/textView"android:layout_width="0dp"android:layout_height="wrap_content"android:background="#FFff0000"android:text="@string/text_A"android:textSize="20sp"app:layout_constraintBottom_toTopOf="@+id/guideline11"app:layout_constraintEnd_toStartOf="@+id/guideline22"app:layout_constraintStart_toStartOf="@+id/guideline18"app:layout_constraintTop_toTopOf="@+id/guideline10" /><TextViewandroid:id="@+id/textView2"android:layout_width="0dp"android:layout_height="wrap_content"android:background="#00FFE7"android:gravity="center"android:text="@string/text_B"android:textColor="#0288D1"android:textSize="20sp"app:layout_constraintBottom_toTopOf="@+id/guideline11"app:layout_constraintEnd_toStartOf="@+id/guideline19"app:layout_constraintStart_toStartOf="@+id/guideline9"app:layout_constraintTop_toTopOf="@+id/guideline10" /><TextViewandroid:id="@+id/text_red"android:layout_width="0dp"android:layout_height="wrap_content"android:gravity="center"android:text="@{String.valueOf(data.redNumb)}"android:textColor="@color/btn_bg"android:textSize="50sp"app:layout_constraintBottom_toTopOf="@+id/guideline13"app:layout_constraintEnd_toStartOf="@+id/guideline22"app:layout_constraintStart_toStartOf="@+id/guideline18"app:layout_constraintTop_toTopOf="@+id/guideline11"app:layout_constraintVertical_bias="0.526" /><TextViewandroid:id="@+id/text_green"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_marginTop="4dp"android:gravity="center"android:text="@{String.valueOf(data.greenNumb)}"android:textColor="#0288D1"android:textColorHighlight="@null"android:textColorHint="@null"android:textColorLink="@null"android:textSize="50sp"app:layout_constraintBottom_toTopOf="@+id/guideline13"app:layout_constraintEnd_toStartOf="@+id/guideline19"app:layout_constraintHorizontal_bias="1.0"app:layout_constraintStart_toStartOf="@+id/guideline9"app:layout_constraintTop_toTopOf="@+id/guideline11" /><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline18"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="vertical"app:layout_constraintGuide_percent="0.05" /><androidx.constraintlayout.widget.Guidelineandroid:id="@+id/guideline19"android:layout_width="wrap_content"android:layout_height="wrap_content"android:orientation="vertical"app:layout_constraintGuide_percent="0.95" /><ImageViewandroid:id="@+id/img_rollback"android:layout_width="wrap_content"android:layout_height="wrap_content"android:contentDescription="@string/img_rollback_alt"android:onClick="@{() -> data.rollBack()}"app:layout_constraintBottom_toTopOf="@+id/guideline17"app:layout_constraintEnd_toStartOf="@+id/guideline9"app:layout_constraintHorizontal_bias="0.38"app:layout_constraintStart_toStartOf="@+id/guideline18"app:layout_constraintTop_toTopOf="@+id/guideline16"app:layout_constraintVertical_bias="0.166"app:srcCompat="@drawable/baseline_reply" /><ImageViewandroid:id="@+id/img_reset"android:layout_width="wrap_content"android:layout_height="wrap_content"android:contentDescription="@string/img_reset_alt"android:onClick="@{() -> data.reset()}"app:layout_constraintBottom_toTopOf="@+id/guideline17"app:layout_constraintEnd_toStartOf="@+id/guideline19"app:layout_constraintHorizontal_bias="0.521"app:layout_constraintStart_toStartOf="@+id/guideline9"app:layout_constraintTop_toTopOf="@+id/guideline16"app:layout_constraintVertical_bias="0.166"app:srcCompat="@drawable/baseline_cached_24" /><Buttonandroid:id="@+id/btn_red_add2"style="@style/Widget.AppCompat.Button"android:layout_width="0dp"android:layout_height="wrap_content"android:background="#FFff0000"android:onClick="@{() -> data.redAdd(2)}"android:scrollbarThumbHorizontal="@null"android:scrollbarThumbVertical="@null"android:text="@string/text_add2"android:textColor="@color/white"android:textColorHighlight="@null"android:textColorHint="@null"android:textColorLink="@null"android:textSize="30sp"android:textStyle="bold"app:layout_constraintBottom_toTopOf="@+id/guideline15"app:layout_constraintEnd_toStartOf="@+id/guideline22"app:layout_constraintHorizontal_bias="0.0"app:layout_constraintStart_toStartOf="@+id/guideline18"app:layout_constraintTop_toTopOf="@+id/guideline14"app:layout_constraintVertical_bias="0.48"tools:ignore="VisualLintButtonSize" /><Buttonandroid:id="@+id/btn_red_add3"style="@style/Widget.AppCompat.Button"android:layout_width="0dp"android:layout_height="wrap_content"android:background="#FFff0000"android:onClick="@{() -> data.redAdd(3)}"android:scrollbarThumbHorizontal="@null"android:scrollbarThumbVertical="@null"android:text="@string/text_add3"android:textColor="@color/white"android:textColorHighlight="@null"android:textColorHint="@null"android:textColorLink="@null"android:textSize="30sp"android:textStyle="bold"app:layout_constraintBottom_toTopOf="@+id/guideline16"app:layout_constraintEnd_toStartOf="@+id/guideline22"app:layout_constraintStart_toStartOf="@+id/guideline18"app:layout_constraintTop_toTopOf="@+id/guideline15"app:layout_constraintVertical_bias="0.56"tools:ignore="VisualLintButtonSize" /></androidx.constraintlayout.widget.ConstraintLayout>
</layout>5.MainActivity.java
package com.example.mydatabindingtest;import androidx.appcompat.app.AppCompatActivity;import android.os.Bundle;
import android.widget.Toast;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.ViewModelProviders;
import com.example.mydatabindingtest.databinding.ActivityMainBinding;public class MainActivity extends AppCompatActivity {MyViewModel myViewModel;ActivityMainBinding binding;private long exitTime;@Overrideprotected 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);}//返回@Overridepublic void onBackPressed() {if ((System.currentTimeMillis() - exitTime) > 2000) {Toast.makeText(getApplicationContext(), "再按一次退出程序",Toast.LENGTH_SHORT).show();exitTime = System.currentTimeMillis();} else {super.onBackPressed();}}}这篇关于Android : 篮球记分器app _简单应用的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！
