简单计算器安卓 Android 作业

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作者:知亦行

Android老师布置的课程作业——简单计算器

功能要求实现四则运算，参考界面见下图：

首先给各位老铁提供apk安装包以及项目压缩包，略表诚意~

github地址：https://github.com/wonke/Calculator

使用GirdLayout比较适合计算器这种规则的布局，每行有几个按钮几乎都是固定的，遇到一个按钮需要占两个常规按钮空间时，使用android:layout_columnSpan="2"属性即可解决。

Layout布局代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView

        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:height="30dp"
        android:gravity="center"
        android:text="@string/title"
        android:textAppearance="@style/TextAppearance.AppCompat.Large" />

    <GridLayout
        android:id="@+id/grid_layout"
        android:layout_width="match_parent"
        android:layout_height="500sp"
        android:background="#ece7e7"
        android:alignmentMode="alignBounds"
        android:columnCount="4"
        android:orientation="horizontal"
        android:rowCount="10"
        android:useDefaultMargins="false">

        <TextView
            android:id="@+id/contentText"
            android:background="@drawable/textview_border"
            android:gravity="end"
            android:textSize="50sp"

            android:layout_columnSpan="4"
            android:layout_columnWeight="1"
            android:layout_rowWeight="5"
            />

        <Button
            android:id="@+id/allClear"
            android:textSize="30sp"
            android:background="@drawable/button_border"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:text="CE" />

        <Button
            android:id="@+id/divide"
            android:textSize="30sp"
            android:background="@drawable/button_border"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:text="÷" />

        <Button
            android:id="@+id/multiply"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="×"
            android:textSize="30sp" />

        <Button
            android:id="@+id/clear"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="C"
            android:textSize="30sp" />

        <Button
            android:id="@+id/b7"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="7"
            android:textSize="30sp" />

        <Button
            android:id="@+id/b8"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="8"
            android:textSize="30sp" />

        <Button
            android:id="@+id/b9"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="9"
            android:textSize="30sp" />

        <Button
            android:id="@+id/add"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="+"
            android:textSize="30sp" />

        <Button
            android:id="@+id/b4"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="4"
            android:textSize="30sp" />

        <Button
            android:id="@+id/b5"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="5"
            android:textSize="30sp" />

        <Button
            android:id="@+id/b6"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="6"
            android:textSize="30sp" />

        <Button
            android:id="@+id/subtract"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="-"
            android:textSize="30sp" />

        <Button
            android:id="@+id/b1"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="1"
            android:textSize="30sp" />

        <Button
            android:id="@+id/b2"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="2"
            android:textSize="30sp" />

        <Button
            android:id="@+id/b3"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="3"
            android:textSize="30sp" />

        <Button
            android:id="@+id/root"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="√￣"
            android:textSize="30sp" />

        <Button
            android:id="@+id/b0"
            android:layout_rowWeight="1"
            android:layout_columnSpan="2"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="0"
            android:textSize="30sp" />

        <Button
            android:id="@+id/point"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="."
            android:textSize="30sp" />

        <Button
            android:id="@+id/equal"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:background="@drawable/button_border"
            android:text="="
            android:textSize="30sp" />
    </GridLayout>

</LinearLayout>

MainActivity逻辑处理代码：

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private Button[] buttons = new Button[18];
    private int[] ids = new int[]{R.id.allClear,R.id.divide,R.id.multiply,R.id.clear,R.id.b0,R.id.b1,
            R.id.b2,R.id.b3,R.id.b4,R.id.b5,R.id.b6,R.id.b7,R.id.b8,R.id.b9,R.id.add,R.id.subtract,
            R.id.equal,R.id.point};

    private TextView textView;
    private String expression = "";
    private boolean end = false;
    private int countOperate=2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

       for (int i=0; i<ids.length;i++){
           buttons[i] = findViewById(ids[i]);
           buttons[i].setOnClickListener(this);
       }
        textView = (TextView)findViewById(R.id.contentText);
    }
    public void onClick(View view) {
        int id = view.getId();
        Button button = (Button)view.findViewById(id);
        String current = button.getText().toString();
        if(end){ //如果上一次算式已经结束，则先清零
            expression = "";
            end = false;
        }
        if(current.equals("CE")){ //如果为CE则清零
            expression = "";
            countOperate=0;
        }else if(current.equals("C")){ //如果点击退格
            if(expression.length()>1){ //算式长度大于1
                expression = expression.substring(0,expression.length()-1);//退一格
                int i = expression.length()-1;
                char tmp = expression.charAt(i); //获得最后一个字符
                char tmpFront = tmp;
                for(;i>=0;i--){ //向前搜索最近的 +-*/和.，并退出
                    tmpFront = expression.charAt(i);
                    if(tmpFront=='.'||tmpFront=='+'||tmpFront=='-'||tmpFront=='×'||tmpFront=='÷'){
                        break;
                    }
                }
                if(tmp>='0'&&tmp<='9'){ //最后一个字符为数字，则识别数赋值为0
                    countOperate=0;
                }else if(tmp==tmpFront&&tmpFront!='.') countOperate=2; //如果为+-*/，赋值为2
                else if(tmpFront=='.') countOperate=1; //如果前面有小数点赋值为1
            }else if(expression.length()==1){
                expression = "";
            }
        }else if(current.equals(".")){
            if(expression.equals("")||countOperate==2){
                expression+="0"+current;
                countOperate = 1;  //小数点按过之后赋值为1
            }
            if(countOperate==0){
                expression+=".";
                countOperate = 1;
            }
        }else if(current.equals("+")||current.equals("-")||current.equals("×")||current.equals("÷")){
            if(countOperate==0){
                expression+=current;
                countOperate = 2;  //  +-*/按过之后赋值为2
            }
        }else if(current.equals("=")){ //按下=时，计算结果并显示
            double result = (double) Math.round(count()*100)/100;
            expression+="="+result;
            end = true; //此次计算结束
        }
        else{//此处是当退格出现2+0时，用current的值替代0
            if(expression.length()>=1){
                char tmp1 = expression.charAt(expression.length()-1);
                if(tmp1=='0'&&expression.length()==1){
                    expression = expression.substring(0,expression.length()-1);
                }
                else if(tmp1=='0'&&expression.length()>1){
                    char tmp2 = expression.charAt(expression.length()-2);
                    if(tmp2=='+'||tmp2=='-'||tmp2=='×'||tmp2=='÷'){
                        expression = expression.substring(0,expression.length()-1);
                    }
                }
            }
            expression+=current;
            if(countOperate==2||countOperate==1) countOperate=0;
        }
        //    Toast.makeText(this, "countOperate:"+countOperate, Toast.LENGTH_SHORT).show();
        textView.setText(expression); //显示出来
    }
    //计算逻辑，求expression表达式的值
    private double count(){
        double result=0;
        double tNum=1,lowNum=0.1,num=0;
        char tmp=0;
        int operate = 1; //识别+-*/，为+时为正数，为-时为负数，为×时为-2/2,为/时为3/-3;
        boolean point = false;
        for(int i=0;i<expression.length();i++){ //遍历表达式
            tmp = expression.charAt(i);
            if(tmp=='.'){ //因为可能出现小数，此处进行判断是否有小数出现
                point = true;
                lowNum = 0.1;
            }else if(tmp=='+'||tmp=='-'){
                if(operate!=3&&operate!=-3){ //此处判断通用，适用于+-*
                    tNum *= num;
                }else{ //计算/
                    tNum /= num;
                }
                //    Toast.makeText(this, "tNum = "+tNum, Toast.LENGTH_SHORT).show();
                if(operate<0){ //累加入最终的结果
                    result -= tNum;
                }else{
                    result += tNum;
                }
                operate = tmp=='+'?1:-1;
                num = 0;
                tNum = 1;
                point = false;
            }else if(tmp=='×'){
                if(operate!=3&&operate!=-3){
                    tNum *= num;
                }else{
                    tNum /= num;
                }
                operate = operate<0?-2:2;
                point = false;
                num = 0;
            }else if(tmp=='÷'){
                if(operate!=3&&operate!=-3){
                    tNum *= num;
                }else{
                    tNum /= num;
                }
                operate = operate<0?-3:3;
                point = false;
                num = 0;
            }else{
                //读取expression中的每个数字，doube型
                if(!point){
                    num = num*10+tmp-'0';
                }else{
                    num += (tmp-'0')*lowNum;
                    lowNum*=0.1;
                }
            }
        }
        //循环遍历结束，计算最后一个运算符后面的数
        if(operate!=3&&operate!=-3){
            tNum *= num;
        }else{
            tNum /= num;
        }
        //    Toast.makeText(this, "tNum = "+tNum, Toast.LENGTH_SHORT).show();
        if(operate<0){
            result -= tNum;
        }else{
            result += tNum;
        }
        //返回最后的结果
        return result;
    }

}

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