机智的简单计算器

用Android写出的简单计算器

首先是布局:用GridLayout写的布局

<?xml version="1.0" encoding="utf-8"?><android.support.v7.widget.GridLayout 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:background="#ccc"    android:id="@+id/layout_cal"    app:columnCount="4"    app:rowCount="6">    <TextView        android:id="@+id/edit_text"        android:layout_margin="10dp"        android:layout_marginTop="20dp"        android:background="@drawable/edit_bg"        android:gravity="right"        android:padding="10dp"        android:textSize="30dp"        app:layout_columnSpan="4"        app:layout_columnWeight="1"       android:maxLength="14"        tools:text="0" />    <TextView        style="@style/operatorStyle"        android:text="c"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/operatorStyle"        android:text="+/-"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/operatorStyle"        android:text="/"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/operatorStyle"        android:text="*"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="7"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="8"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="9"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/operatorStyle"        android:text="-"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="4"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="5"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="6"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/operatorStyle"        android:text="+"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="1"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="2"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="3"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/operatorStyle"        android:text="="        android:background="@drawable/equals_bg"        app:layout_columnWeight="1"        app:layout_rowSpan="2"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="0"        app:layout_columnSpan="2"        app:layout_columnWeight="1"        app:layout_rowWeight="1" />    <TextView        style="@style/numbersStyle"        android:text="."        app:layout_columnWeight="1"        app:layout_rowWeight="1" /></android.support.v7.widget.GridLayout>

Android代码:

package com.example.xiaohong.calculatordemo;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.support.v7.widget.GridLayout;import android.view.View;import android.widget.TextView;import java.util.Locale;public class MainActivity extends AppCompatActivity implements View.OnClickListener {    private TextView editView;    private String operator = "";    private float result = 0.0f;    private boolean flag = false;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.cal_activity);        editView = (TextView) findViewById(R.id.edit_text);        // 对于一个布局,如果想对布局中的控件进行监听,而不想为每一个设置id.可以通过下面这个方法做到.        GridLayout grid = (GridLayout) findViewById(R.id.layout_cal);        for (int i = 0; i < grid.getChildCount(); i++) {            TextView text = (TextView) grid.getChildAt(i);            if (!text.equals(editView)) {                text.setOnClickListener(this);            }        }    }    @Override    public void onClick(View view) {        TextView text = (TextView) view;        StringBuilder builder = new StringBuilder(editView.getText().toString());        String str = text.getText().toString();        switch (str) {            case "c":                builder.delete(0, builder.length());                builder.append("0");                break;            case "+/-":                result = Float.valueOf(builder.toString());                result = -result;                builder.delete(0, builder.length());                builder.append(String.format(Locale.CANADA, result % 1 == 0 ? "%.0f" : "%.2f", result));                break;           // 这里去掉了break,这是我绝对想不出来的啊.            case "/":            case "*":            case "+":            case "-":            case "=":                float temp;                if (builder.length() > 0) {                    temp = Float.parseFloat(builder.toString());                } else {                    temp = 0;                }                if (!flag) {                    builder.delete(0, builder.length());                    try {                        switch (operator) {                            case "+":                                result += temp;                                break;                            case "-":                                result -= temp;                                break;                            case "*":                                result *= temp;                                break;                            case "/":                                result /= temp;                                break;                            default:                            // 如果一直点"=",或者在第一次记录第一个运算数                                result = temp;                                break;                        }                        builder.append(String.format(Locale.CANADA, result % 1 == 0 ? "%.0f" : "%.2f", result));                    } catch (Exception e) {                        e.printStackTrace();                        builder.append("erro");                    }                }                operator = str;                flag = true;                break;            case ".":                if (!builder.toString().contains(".")) {                    if (builder.length() == 0) {                        builder.append("0");                    }                    builder.append(".");                }                break;            default:            // 在输入第二个运算符之前,将flag设为false,这样就可以保证在输入运算符时只记录最后一个运算符.棒棒哒...                if (flag) {                    flag = false;                    builder.delete(0, builder.length());                }                if ("0".equals(builder.toString())) {                    builder.delete(0, builder.length());                    builder.append(str);                } else {                    builder.append(str);                }                break;        }        if (builder.length() > 14) {            editView.setText(String.format(Locale.CANADA, "%e", Float.valueOf(builder.toString())));        } else {            editView.setText(builder.toString());        }    }}

效果: