android中实现一个简单的计算器，实现连续的加减乘除运算。
首先，让我们看下布局：
最上边是一个edittext 用来显示用户输入的运算数字和运算符，下面是一个TableLayout显示数字和运算符按钮。
话不多说,主要代码如下：
package com.easygoing.androidcalculator;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListAdapter;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private Button bt_num0;
private Button bt_num1;
private Button bt_num2;
private Button bt_num3;
private Button bt_num4;
private Button bt_num5;
private Button bt_num6;
private Button bt_num7;
private Button bt_num8;
private Button bt_num9;
private Button bt_clear;
private Button bt_percent;
private Button bt_delete;
private Button bt_div;
private Button bt_mult;
private Button bt_minus;
private Button bt_plus;
private Button bt_equal;
private Button bt_dot;
private EditText et_calc;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initViewAndListener();
}
private void initViewAndListener() {
bt_num0 = findViewById(R.id.bt_num0);
bt_num0.setOnClickListener(this);
bt_num1 = findViewById(R.id.bt_num1);
bt_num1.setOnClickListener(this);
bt_num2 = findViewById(R.id.bt_num2);
bt_num2.setOnClickListener(this);
bt_num3 = findViewById(R.id.bt_num3);
bt_num3.setOnClickListener(this);
bt_num4 = findViewById(R.id.bt_num4);
bt_num4.setOnClickListener(this);
bt_num5 = findViewById(R.id.bt_num5);
bt_num5.setOnClickListener(this);
bt_num6 = findViewById(R.id.bt_num6);
bt_num6.setOnClickListener(this);
bt_num7 = findViewById(R.id.bt_num7);
bt_num7.setOnClickListener(this);
bt_num8 = findViewById(R.id.bt_num8);
bt_num8.setOnClickListener(this);
bt_num9 = findViewById(R.id.bt_num9);
bt_num9.setOnClickListener(this);
bt_clear = findViewById(R.id.bt_clear);
bt_clear.setOnClickListener(this);
bt_percent = findViewById(R.id.bt_percent);
bt_percent.setOnClickListener(this);
bt_delete = findViewById(R.id.bt_delete);
bt_delete.setOnClickListener(this);
bt_div = findViewById(R.id.bt_div);
bt_div.setOnClickListener(this);
bt_mult = findViewById(R.id.bt_mult);
bt_mult.setOnClickListener(this);
bt_minus = findViewById(R.id.bt_minus);
bt_minus.setOnClickListener(this);
bt_plus = findViewById(R.id.bt_plus);
bt_plus.setOnClickListener(this);
bt_equal = findViewById(R.id.bt_equal);
bt_equal.setOnClickListener(this);
et_calc = findViewById(R.id.et_calc);
bt_dot = findViewById(R.id.bt_dot);
bt_dot.setOnClickListener(this);
}
private boolean lastIsOperator;
private String lastOperators = "";
private List<String> operatorNumbers = new ArrayList<>();
private List<String> operators = new ArrayList<>();;
private double firstNumber = 0D;
private double sencondNumber = 0D;
@Override
public void onClick(View v) {
String currentText = et_calc.getText().toString();
String operatorNumber = "";
if (currentText.equals("0")) {
et_calc.setText("");
}
operatorNumber = et_calc.getText().toString();
if(!lastOperators.equals(""))
{
int index = operatorNumber.lastIndexOf(lastOperators);
operatorNumber = operatorNumber.substring(index+1);
}
switch (v.getId()) {
case R.id.bt_num0:
et_calc.setText(et_calc.getText() + "0");
lastIsOperator = false;
break;
case R.id.bt_num1:
et_calc.setText(et_calc.getText() + "1");
lastIsOperator = false;
break;
case R.id.bt_num2:
et_calc.setText(et_calc.getText() + "2");
lastIsOperator = false;
break;
case R.id.bt_num3:
et_calc.setText(et_calc.getText() + "3");
lastIsOperator = false;
break;
case R.id.bt_num4:
et_calc.setText(et_calc.getText() + "4");
lastIsOperator = false;
break;
case R.id.bt_num5:
et_calc.setText(et_calc.getText() + "5");
lastIsOperator = false;
break;
case R.id.bt_num6:
et_calc.setText(et_calc.getText() + "6");
lastIsOperator = false;
break;
case R.id.bt_num7:
et_calc.setText(et_calc.getText() + "7");
lastIsOperator = false;
break;
case R.id.bt_num8:
et_calc.setText(et_calc.getText() + "8");
lastIsOperator = false;
break;
case R.id.bt_num9:
et_calc.setText(et_calc.getText() + "9");
lastIsOperator = false;
break;
case R.id.bt_dot:
et_calc.setText(et_calc.getText() + ".");
lastIsOperator = false;
break;
case R.id.bt_clear:
et_calc.setText("");
lastIsOperator = false;
firstNumber = 0D;
sencondNumber = 0D;
lastOperators ="=";
break;
case R.id.bt_percent:
lastIsOperator = true;
break;
case R.id.bt_delete:
if (TextUtils.isEmpty(et_calc.getText())) {
return;
}
lastIsOperator = false;
et_calc.setText(currentText.substring(0, currentText.length() - 1).length() > 0 ? currentText.substring(0, currentText.length() - 1) : "0");
break;
case R.id.bt_div:
if ((TextUtils.isEmpty(et_calc.getText())
|| lastIsOperator) && !lastOperators.equals("=")) {
return;
}
opratorCalc(operatorNumber,"÷");
lastIsOperator = true;
et_calc.setText(et_calc.getText() + "÷");
lastOperators = "÷";
break;
case R.id.bt_mult:
if ((TextUtils.isEmpty(et_calc.getText())
|| lastIsOperator) && !lastOperators.equals("=")) {
return;
}
opratorCalc(operatorNumber,"*");
lastIsOperator = true;
et_calc.setText(et_calc.getText() + "*");
lastOperators = "*";
break;
case R.id.bt_minus:
if ((TextUtils.isEmpty(et_calc.getText())
|| lastIsOperator) && !lastOperators.equals("=")) {
return;
}
opratorCalc(operatorNumber,"-");
lastIsOperator = true;
et_calc.setText(et_calc.getText() + "-");
lastOperators = "-";
break;
case R.id.bt_plus:
if ((TextUtils.isEmpty(et_calc.getText())
|| lastIsOperator) && !lastOperators.equals("=")) {
return;
}
opratorCalc(operatorNumber,"+");
lastIsOperator = true;
et_calc.setText(et_calc.getText() + "+");
lastOperators = "+";
break;
case R.id.bt_equal:
double result = 0D;
if(TextUtils.isEmpty(lastOperators))
{
return;
}
opratorResult(operatorNumber);
sencondNumber = 0D;
lastOperators ="=";
lastIsOperator = true;
et_calc.setText(et_calc.getText() + "\n=" + String.valueOf(firstNumber));
break;
}
}
private void operate(String operatorNumber)
{
if(sencondNumber != 0D)
{
if(lastOperators.equals("÷"))
{
sencondNumber = sencondNumber / Double.parseDouble(operatorNumber);
firstNumber = firstNumber / sencondNumber;
}
else if(lastOperators.equals("*"))
{
sencondNumber = sencondNumber * Double.parseDouble(operatorNumber);
firstNumber = firstNumber * sencondNumber;
}
else if(lastOperators.equals("+"))
{
sencondNumber = Double.parseDouble(operatorNumber);
firstNumber = firstNumber + sencondNumber;
}
else if(lastOperators.equals("-"))
{
sencondNumber = Double.parseDouble(operatorNumber);
firstNumber = firstNumber - sencondNumber;
}
}
else
{
if(lastOperators.equals("÷"))
{
firstNumber = firstNumber / Double.parseDouble(operatorNumber);
}
else if(lastOperators.equals("*"))
{
firstNumber = firstNumber * Double.parseDouble(operatorNumber);
}
else if(lastOperators.equals("+"))
{
firstNumber = firstNumber + Double.parseDouble(operatorNumber);
}
else if(lastOperators.equals("-"))
{
firstNumber= firstNumber - Double.parseDouble(operatorNumber);
}
}
}
public void opratorResult(String operatorNumber)
{
operate(operatorNumber);
}
public void opratorCalc(String operatorNumber,String currentOprator)
{
if(TextUtils.isEmpty(lastOperators))
{
firstNumber = Double.parseDouble(operatorNumber);
return;
}
if(lastOperators.equals(currentOprator))
{
if(lastOperators.equals("÷"))
{
firstNumber = firstNumber / Double.parseDouble(operatorNumber);
}
else if(lastOperators.equals("*"))
{
firstNumber = firstNumber * Double.parseDouble(operatorNumber);
}
else if(lastOperators.equals("+"))
{
firstNumber = firstNumber + Double.parseDouble(operatorNumber);
}
else if(lastOperators.equals("-"))
{
firstNumber = firstNumber - Double.parseDouble(operatorNumber);
}
return;
}
operate(operatorNumber);
}
}
```**重点内容**
至于button的selector样式比较简单，这里简单贴出来两个：、
<div class="se-preview-section-delimiter"></div>
普通button样式
<?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="com.easygoing.androidcalculator.MainActivity">
<EditText android:id="@+id/et_calc" style="@style/et_calc_style" />
<TableLayout android:layout_width="match_parent" android:layout_height="wrap_content">
<TableRow>
<Button android:id="@+id/bt_clear" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="C"/>
<Button android:id="@+id/bt_percent" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="+/-"/>
<Button android:id="@+id/bt_delete" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="Del" />
<Button android:id="@+id/bt_div" style="@style/bt_styles_common" android:background="@drawable/btn_operate_background" android:textColor="#FFFFFF" android:text="÷"/>
</TableRow>
<TableRow>
<Button android:id="@+id/bt_num7" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="7"/>
<Button android:id="@+id/bt_num8" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="8"/>
<Button android:id="@+id/bt_num9" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="9"/>
<Button android:id="@+id/bt_mult" style="@style/bt_styles_common" android:background="@drawable/btn_operate_background" android:textColor="#FFFFFF" android:text="×"/>
</TableRow>
<TableRow>
<Button android:id="@+id/bt_num4" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="4"/>
<Button android:id="@+id/bt_num5" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="5"/>
<Button android:id="@+id/bt_num6" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="6"/>
<Button android:id="@+id/bt_minus" style="@style/bt_styles_common" android:background="@drawable/btn_operate_background" android:textColor="#FFFFFF" android:text="－"/>
</TableRow>
<TableRow>
<Button android:id="@+id/bt_num1" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="1"/>
<Button android:id="@+id/bt_num2" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="2"/>
<Button android:id="@+id/bt_num3" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="3"/>
<Button android:id="@+id/bt_plus" style="@style/bt_styles_common" android:background="@drawable/btn_operate_background" android:textColor="#FFFFFF" android:text="＋"/>
</TableRow>
<TableRow>
<Button android:id="@+id/bt_num0" style="@style/bt_styles_common" android:background="@drawable/btn_background" android:text="0"/>
<Button android:id="@+id/bt_dot" style="@style/bt_styles_common" android:layout_weight="0.5" android:background="@drawable/btn_background" android:text="·"/>
<Button android:id="@+id/bt_equal" style="@style/bt_styles_common" android:layout_weight="0.5" android:background="@drawable/btn_operate_background" android:textColor="#FFFFFF" android:text="＝"/>
</TableRow>
</TableLayout>
</LinearLayout>
这里需要注意的一点就是再按钮0的布局那里，需要设置一样权重，让按钮0能够占两个按钮的长度，
代码的逻辑比较简单，主要是记录三个操作数和两个运算符，当有两个运算符的时候，比较运算符的优先级，先行运算，然后保存计算结果，详细的可以看下代码。
当然了，这个计算器的功能不是很完善，这里只不过是进行一个简单的示例，有兴趣的可以自己做一个。。
源代码下载地址：http://download.csdn.net/download/qingyulove/10181313