Android开发应用案例——简易计算器（附完整源码）
Android开发-AS学习（一）
Android开发-AS学习（二）
使用android studio开发简易计算器app（完整源码可在博主资源中自行下载）
最终效果：
开发步骤：
创建一个名为calculator的新项目
编写代码
项目目录
MyTextView文件
package com.example.calculator.my_control;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
/*
自定义组件：带有边框的标签
*/
public class MyTextView extends androidx.appcompat.widget.AppCompatTextView {
Paint paint = new Paint();//创建一个paint对象
public MyTextView(@NonNull Context context, @Nullable AttributeSet attrs) {
super(context, attrs);//构造函数
}
@Override//重写方法
protected void onDraw(Canvas canvas){
super.onDraw(canvas);
paint.setColor(Color.BLACK);//设置paint的颜色
//绘制边框
canvas.drawLine(0,0,this.getWidth(),0,paint);//绘制上方的边框
canvas.drawLine(0,this.getHeight()-1,this.getWidth(),this.getHeight()-1,paint);//绘制下方的边框(因为会被遮挡，所以需要-1）
canvas.drawLine(0,0,0,this.getHeight(),paint);//绘制左边的边框
canvas.drawLine(this.getWidth()-1,0,this.getWidth()-1,this.getHeight(),paint);//绘制右边的边框(因为会被遮挡，所以需要-1）
}
}
MainActivity文件
package com.example.calculator;
import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProvider;
import android.database.DatabaseUtils;
import android.os.Bundle;
import android.view.View;
import com.example.calculator.databinding.ActivityMainBinding;
public class MainActivity extends AppCompatActivity {
private ActivityMainBinding binding;//组件存储类
private MyViewModel myViewModel;//数据模型
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = DataBindingUtil.setContentView(this,R.layout.activity_main);//获取所有控件
myViewModel = new ViewModelProvider(this,new ViewModelProvider.NewInstanceFactory()).get(MyViewModel.class);//获取数据模型
//事件监听
myViewModel.getMainNum().observe(this, new Observer() {
@Override
public void onChanged(String s) {//监听 mainNum数据发生改变的监听
binding.myTextView.setText(myViewModel.getMainNum().getValue());//让 myTextView显示mainNum的数值，也就是计算器中的输入框显示数值
if (myViewModel.sign2.equals("")){
if (myViewModel.sign1.equals("")){
binding.textView2.setText(myViewModel.getMainNum().getValue());//让 textView显示式子，也就是输入框上面的小框显示计算式
}
else {//如果是像a + b这种形式的式子时
binding.textView2.setText(myViewModel.num[0] + myViewModel.sign1 + myViewModel.getMainNum().getValue());
}
}
else {//如果是像a+b*c这种形式的式子的时候
binding.textView2.setText(myViewModel.num[0] + myViewModel.sign1 + myViewModel.num[1] + myViewModel.sign2 + myViewModel.getMainNum().getValue());
}
}
});
binding.button0.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.setMainNum("0");
}
});
binding.button1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.setMainNum("1");
}
});
binding.button2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.setMainNum("2");
}
});
binding.button3.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.setMainNum("3");
}
});
binding.button4.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.setMainNum("4");
}
});
binding.button5.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.setMainNum("5");
}
});
binding.button6.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.setMainNum("6");
}
});
binding.button7.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.setMainNum("7");
}
});
binding.button8.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.setMainNum("8");
}
});
binding.button9.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.setMainNum("9");
}
});
//给小数点按钮的监听
binding.button15.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (!myViewModel.havePoint){
myViewModel.getMainNum().setValue(myViewModel.getMainNum().getValue()+".");
myViewModel.havePoint=true;
}
}
});
//给加号按钮的监听
binding.button11.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (myViewModel.sign1.equals("")){
myViewModel.sign1="+";
myViewModel.num[0] = myViewModel.getMainNum().getValue();
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint=false;
}
else if (myViewModel.sign2.equals("")){//如果是像a+b这种形式的式子时
myViewModel.num[0] = myViewModel.mainNumWithNum_0_Tocal();
myViewModel.sign1="+";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
else {//如果是像a+b*c这种形式的式子时
myViewModel.getMainNum().setValue(myViewModel.mainNumWith_Num_1_Tocal());
myViewModel.sign2="";
myViewModel.num[1] = "";
myViewModel.num[0] = myViewModel.mainNumWithNum_0_Tocal();
myViewModel.sign1 = "+";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
}
});
//给减号设置监听
binding.button12.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (myViewModel.sign1.equals("")){
myViewModel.sign1="-";
myViewModel.num[0] = myViewModel.getMainNum().getValue();
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint=false;
}
else if (myViewModel.sign2.equals("")){//如果是像a-b这种形式的式子时
myViewModel.num[0] = myViewModel.mainNumWithNum_0_Tocal();
myViewModel.sign1="-";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
else {//如果是像a-b*c这种形式的式子时
myViewModel.getMainNum().setValue(myViewModel.mainNumWith_Num_1_Tocal());
myViewModel.sign2="";
myViewModel.num[1] = "";
myViewModel.num[0] = myViewModel.mainNumWithNum_0_Tocal();
myViewModel.sign1 = "-";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
}
});
//给乘号设置监听
binding.button13.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (myViewModel.sign1.equals("")){
myViewModel.sign1 = "*";
myViewModel.num[0] = myViewModel.getMainNum().getValue();
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
else if (myViewModel.sign2.equals("")){
if (myViewModel.sign1.equals("*") || myViewModel.sign1.equals("/")){//按顺序进行计算
myViewModel.num[0] = myViewModel.mainNumWithNum_0_Tocal();
myViewModel.sign1="*";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
else {//如果sign1是减号或者加号时
myViewModel.num[1] = myViewModel.getMainNum().getValue();
myViewModel.sign2 = "*";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
}
else {//如果像a+b*c形式的式子时
myViewModel.num[1] = myViewModel.mainNumWith_Num_1_Tocal();
myViewModel.sign2 = "*";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
}
});
//给除号设置监听
binding.button14.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (myViewModel.sign1.equals("")){
myViewModel.sign1 = "/";
myViewModel.num[0] = myViewModel.getMainNum().getValue();
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
else if (myViewModel.sign2.equals("")){
if (myViewModel.sign1.equals("*") || myViewModel.sign1.equals("/")){//按顺序进行计算
myViewModel.num[0] = myViewModel.mainNumWithNum_0_Tocal();
myViewModel.sign1="/";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
else {//如果sign1是减号或者加号时
myViewModel.num[1] = myViewModel.getMainNum().getValue();
myViewModel.sign2 = "/";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
}
else {//如果像a+b/c形式的式子时
myViewModel.num[1] = myViewModel.mainNumWith_Num_1_Tocal();
myViewModel.sign2 = "/";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
}
});
//给 清空 设置监听
binding.button17.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myViewModel.sign2 = "";
myViewModel.num[1] = "";
myViewModel.sign1 = "";
myViewModel.num[0] = "";
myViewModel.getMainNum().setValue("0");
myViewModel.havePoint = false;
}
});
//给 计算按钮 设置监听
binding.button16.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (myViewModel.sign2.equals("")){
if (!myViewModel.sign1.equals("")){
myViewModel.getMainNum().setValue(myViewModel.mainNumWithNum_0_Tocal());
if (myViewModel.getMainNum().getValue().contains(".")){//判断是否包含小数点
myViewModel.havePoint = true;
}
else myViewModel.havePoint = false;
myViewModel.num[0]="";
myViewModel.sign1 = "";
}
}
else {//如果是像 a+b*c 这种形式的式子时
myViewModel.getMainNum().setValue(myViewModel.mainNumWith_Num_1_Tocal());
myViewModel.num[1] = "";
myViewModel.sign2 = "";
myViewModel.getMainNum().setValue(myViewModel.mainNumWithNum_0_Tocal());
if (myViewModel.getMainNum().getValue().contains(".")){//判断是否包含小数点
myViewModel.havePoint = true;
}
else myViewModel.havePoint = false;
myViewModel.num[0]="";
myViewModel.sign1 = "";
}
binding.textView2.setText(myViewModel.num[0] + myViewModel.sign1 + myViewModel.getMainNum().getValue());
}
});
//给 退格按钮 设置监听
binding.imageButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (!myViewModel.getMainNum().getValue().equals("0")){
myViewModel.getMainNum().setValue(myViewModel.getMainNum().getValue().substring(0,myViewModel.getMainNum().getValue().length()-1));//不为空，长度减1
if (myViewModel.getMainNum().getValue().equals("")){
myViewModel.getMainNum().setValue("0");//如果为空，将其设为0
}
}
}
});
}
} MyViewModel
package com.example.calculator;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;
//用来存储一些数据模型
public class MyViewModel extends ViewModel {
private MutableLiveData mainNum;//主数值（用户正在操作的数）
public boolean havePoint =false;//用于记录主数值中是否包含小数点
public String sign1 = "",sign2 = "";//用于存储运算符号
public String num[]={"",""};//用于存储参与计算的数值
public MutableLiveData getMainNum(){
if (mainNum == null){
mainNum = new MutableLiveData<>();
mainNum.setValue("0");
}
return mainNum;
}
public void setMainNum(String n ){
if (mainNum.getValue().equals("0")){
mainNum.setValue(n);
}
else {
mainNum.setValue(mainNum.getValue() + n);
}
}
public String mainNumWithNum_0_Tocal(){
String value = "0";
if (mainNum.getValue().contains(".") || num[0].contains(".")) {//如果两个数的其中一个有小数点的运算
switch (sign1){
case "+":
value = String.valueOf(Double.valueOf(num[0]) + Double.valueOf(mainNum.getValue()));
break;
case "-":
value = String.valueOf(Double.valueOf(num[0]) - Double.valueOf(mainNum.getValue()));
break;
case "*":
value = String.valueOf(Double.valueOf(num[0]) * Double.valueOf(mainNum.getValue()));
break;
case "/":
if (mainNum.getValue().equals("0")){
mainNum.setValue("1");
}
value = String.valueOf(Double.valueOf(num[0]) / Double.valueOf(mainNum.getValue()));
}
}
else {
switch (sign1){//如果没有小数点则为整数运算
case "+":
value = String.valueOf(Integer.valueOf(num[0]) + Integer.valueOf(mainNum.getValue()));
break;
case "-":
value = String.valueOf(Integer.valueOf(num[0]) - Integer.valueOf(mainNum.getValue()));
break;
case "*":
value = String.valueOf(Integer.valueOf(num[0]) * Integer.valueOf(mainNum.getValue()));
break;
case "/"://除号依旧为小数运算方式
if (mainNum.getValue().equals("0")){
mainNum.setValue("1");
}
value = String.valueOf(Double.valueOf(num[0]) / Double.valueOf(mainNum.getValue()));
}
}
return value;
}
public String mainNumWith_Num_1_Tocal(){
String value = "0";
if (mainNum.getValue().contains(".") || num[0].contains(".")) {//如果两个数的其中一个有小数点的运算
switch (sign2){
case "*":
value = String.valueOf(Double.valueOf(num[1]) * Double.valueOf(mainNum.getValue()));
break;
case "/":
if (mainNum.getValue().equals("0")){
mainNum.setValue("1");
}
value = String.valueOf(Double.valueOf(num[1]) / Double.valueOf(mainNum.getValue()));
}
}
else {
switch (sign2){//如果没有小数点则为整数运算
case "*":
value = String.valueOf(Integer.valueOf(num[1]) * Integer.valueOf(mainNum.getValue()));
break;
case "/"://除号依旧为小数运算方式
if (mainNum.getValue().equals("0")){
mainNum.setValue("1");
}
value = String.valueOf(Double.valueOf(num[1]) / Double.valueOf(mainNum.getValue()));
}
}
return value;
}
}
activity_main.xml
补充：
1、在drawable中引入backspace矢量图
2、在build.gradle文件中添加dataBinding{enabled true}代码
