Android开发之简易计算器
使用GridLayout对计算器按键进行布局，大致代码如下：
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="/apk/res/android"xmlns:app="/apk/res-auto"xmlns:tools="/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"android:padding="5dp"tools:context=".MainActivity"><ScrollViewandroid:layout_width="match_parent"android:layout_height="wrap_content"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="vertical"><TextViewandroid:layout_width="match_parent"android:layout_height="wrap_content"android:text="计算器"android:gravity="center"android:textColor="@color/colorPrimaryDark"android:textSize="30sp"/><TextViewandroid:id="@+id/tv_result"android:layout_width="match_parent"android:layout_height="wrap_content"android:background="#FFFF"android:text="0"android:textSize="25sp"android:lines="7"android:gravity="bottom|right"/><GridLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:columnCount="4"android:rowCount="5"><Buttonandroid:id="@+id/btn_cancel"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="C"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_percentage"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="%"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><ImageButtonandroid:id="@+id/btn_backspace"android:width="0dp"android:layout_height="75dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:scaleType="centerInside"android:src="@drawable/backspace"/><Buttonandroid:id="@+id/btn_divider"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="/"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_seven"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="7"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_eight"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="8"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_nine"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="9"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_multiply"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="*"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_four"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="4"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_five"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="5"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_six"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="6"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_minus"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="-"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_one"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="1"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_two"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="2"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_three"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="3"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_plus"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="+"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_doublezero"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="00"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_zero"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="0"android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_point"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="."android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/><Buttonandroid:id="@+id/btn_equal"android:width="0dp"android:height="@dimen/button_height_size"android:layout_columnWeight="1"android:gravity="center"android:text="="android:textColor="@color/colorPrimaryDark"android:textSize="@dimen/button_font_size"/></GridLayout></LinearLayout></ScrollView></LinearLayout>
主要逻辑代码如下：
package com.njyd.calculatoractivity;import androidx.appcompat.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.TextView;public class MainActivity extends AppCompatActivity implements View.OnClickListener {private TextView tv_result;//第一个操作数private String firstNum = "";//运算符private String operator = "";//第二个操作数private String secondNum = "";//当前的计算结果private String result = "";//显示的文本内容private String showText = "";@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);initView();}private void initView() {//获取布局文件中的组件tv_result = findViewById(R.id.tv_result);findViewById(R.id.btn_cancel).setOnClickListener(this);findViewById(R.id.btn_percentage).setOnClickListener(this);findViewById(R.id.btn_backspace).setOnClickListener(this);findViewById(R.id.btn_divider).setOnClickListener(this);findViewById(R.id.btn_seven).setOnClickListener(this);findViewById(R.id.btn_eight).setOnClickListener(this);findViewById(R.id.btn_nine).setOnClickListener(this);findViewById(R.id.btn_multiply).setOnClickListener(this);findViewById(R.id.btn_four).setOnClickListener(this);findViewById(R.id.btn_five).setOnClickListener(this);findViewById(R.id.btn_six).setOnClickListener(this);findViewById(R.id.btn_minus).setOnClickListener(this);findViewById(R.id.btn_one).setOnClickListener(this);findViewById(R.id.btn_two).setOnClickListener(this);findViewById(R.id.btn_three).setOnClickListener(this);findViewById(R.id.btn_plus).setOnClickListener(this);findViewById(R.id.btn_doublezero).setOnClickListener(this);findViewById(R.id.btn_zero).setOnClickListener(this);findViewById(R.id.btn_point).setOnClickListener(this);findViewById(R.id.btn_equal).setOnClickListener(this);}@Overridepublic void onClick(View v) {String inputText;if (v.getId() == R.id.btn_backspace){inputText = "X";}else{inputText = ((TextView) v).getText().toString();}switch (v.getId()) {//点击了退格按钮case R.id.btn_backspace:if (operator.equals("")) {firstNum = String.valueOf((int)(Double.parseDouble(firstNum) / 10));updateText(firstNum);}else if(secondNum ==""){operator = "";updateText(firstNum + operator + secondNum);}else {secondNum = String.valueOf((int)(Double.parseDouble(firstNum) / 10));updateText(firstNum + operator + secondNum);}break;//点击了清除按钮case R.id.btn_cancel:clear();break;//点击了加减乘除case R.id.btn_plus:case R.id.btn_minus:case R.id.btn_multiply:case R.id.btn_divider:operator = inputText;//运算符updateText(showText + operator);break;//点击了等号按钮case R.id.btn_equal://加减乘除四则运算double calculate_result = calculate();updateOperate(String.valueOf(calculate_result));updateText(showText + "=" + result);break;//点击了百分号按钮case R.id.btn_percentage:if (operator.equals("")) {firstNum = String.valueOf(Double.parseDouble(firstNum) * 0.01);updateText(firstNum);} else {//有运算符，则继续拼接第二个操作数secondNum = String.valueOf(Double.parseDouble(secondNum) * 0.01);updateText(firstNum + operator + secondNum);}break;//点击了其他按钮default://上次的运算结果已经出来了if (result.length() > 0 && operator.equals("")){clear();}//无运算符，则继续拼接第一个操作数if (operator.equals("")) {firstNum = firstNum + inputText;} else {//有运算符，则继续拼接第二个操作数secondNum = secondNum + inputText;}//整数前不需要0if (showText.equals("0") && !inputText.equals(".")){updateText(inputText);}else {updateText(showText + inputText);}break;}}private double calculate() {switch (operator){case "+":return Double.parseDouble(firstNum) + Double.parseDouble(secondNum);case "-":return Double.parseDouble(firstNum) - Double.parseDouble(secondNum);case "*":return Double.parseDouble(firstNum) * Double.parseDouble(secondNum);case "/":return Double.parseDouble(firstNum) / Double.parseDouble(secondNum);}return 0;}private void clear() {updateOperate("");updateText("");}//刷新运算结果private void updateOperate(String new_result){result = new_result;firstNum = result;secondNum = "";operator = "";}//刷新文本显示private void updateText(String text){showText = text;tv_result.setText(showText);}}
运行效果如下：
clear() {
updateOperate(“”);
updateText(“”);
}
//刷新运算结果
private void updateOperate(String new_result){
result = new_result;
firstNum = result;
secondNum = “”;
operator = “”;
}
//刷新文本显示
private void updateText(String text){
showText = text;
tv_result.setText(showText);
}
}
运行效果如下：
