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:

Android开发应用案例——简易计算器(附完整源码)_第1张图片

开发步骤:

  1. 创建一个名为calculator的新项目

Android开发应用案例——简易计算器(附完整源码)_第2张图片
Android开发应用案例——简易计算器(附完整源码)_第3张图片
  1. 编写代码

项目目录

Android开发应用案例——简易计算器(附完整源码)_第4张图片

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

Android开发应用案例——简易计算器(附完整源码)_第5张图片

2、在build.gradle文件中添加dataBinding{enabled true}代码

Android开发应用案例——简易计算器(附完整源码)_第6张图片

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