Android 一个简单的计算器APP
16lz
2021-01-23
apk下载地址：
http://pan.baidu.com/s/1dD3513j
MainActivity.java文件内容：
package netpythontojavaviewmodecontents.csdn.blog.calculator0;import android.app.Activity;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.Toast;//import android.view.View.OnClickListener;public class MainActivity extends Activity implements View.OnClickListener { private Button add; //按钮+ private Button subtract; //按钮- private Button multiply; //按钮* private Button divide; //按钮/ private Button equal; //按钮= private Button delete; //按钮删除一个输入的符号 private Button clear; //按钮用来清除输入框 private Button point; //按钮小数点 private Button one; //按钮1 private Button two; private Button three; private Button four; private Button five; private Button six; private Button seven; private Button eight; private Button nine; private Button zero; private EditText showtext;//用来显示输入的符号和数字 private String OperateSum="";//字符串用来保存输入的数字和符号 private char Operator; //用来记录运算符号 private double num1=0,num2=0,sum=0; //num1,num2记录输入的数字，sum保存运算的结果 //private boolean NewCalculate=true; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initView();//对按钮和事件进行初始化 } private void initView() { one=(Button) findViewById(R.id.one); two=(Button) findViewById(R.id.two); three=(Button) findViewById(R.id.three); four=(Button) findViewById(R.id.four); five=(Button) findViewById(R.id.five); six=(Button) findViewById(R.id.six); seven=(Button) findViewById(R.id.seven); eight=(Button) findViewById(R.id.eight); nine=(Button) findViewById(R.id.nine); zero=(Button) findViewById(R.id.zero); add=(Button) findViewById(R.id.add); subtract=(Button) findViewById(R.id.subtract); multiply=(Button) findViewById(R.id.multiply); divide=(Button) findViewById(R.id.divide); delete=(Button) findViewById(R.id.delete); clear=(Button) findViewById(R.id.clear); equal=(Button) findViewById(R.id.equal); point=(Button) findViewById(R.id.point); //about=(Button) findViewById(R.id.about); showtext=(EditText) findViewById(R.id.text); showtext.setCursorVisible(false); zero.setOnClickListener(this);//添加按钮事件 one.setOnClickListener(this); two.setOnClickListener(this); three.setOnClickListener(this); four.setOnClickListener(this); five.setOnClickListener(this); six.setOnClickListener(this); seven.setOnClickListener(this); eight.setOnClickListener(this); nine.setOnClickListener(this); add.setOnClickListener(this); subtract.setOnClickListener(this); multiply.setOnClickListener(this); divide.setOnClickListener(this); equal.setOnClickListener(this); delete.setOnClickListener(this); clear.setOnClickListener(this); point.setOnClickListener(this); //about.setOnClickListener(this); showtext.setOnClickListener(this); } @Override public void onClick(View v) { switch (v.getId()) { case R.id.one: //记录输入的数字1 OperateSum=AddSum('1');//把数字添加进OperateSum showtext.setText(OperateSum); //把输入的数字显示在EditText break; case R.id.two: //记录输入的数字2 OperateSum=AddSum('2'); showtext.setText(OperateSum); break; case R.id.three: OperateSum=AddSum('3'); showtext.setText(OperateSum); break; case R.id.four: OperateSum=AddSum('4'); showtext.setText(OperateSum); break; case R.id.five: OperateSum=AddSum('5'); showtext.setText(OperateSum); break; case R.id.six: OperateSum=AddSum('6'); showtext.setText(OperateSum); break; case R.id.seven: OperateSum=AddSum('7'); showtext.setText(OperateSum); break; case R.id.eight: OperateSum=AddSum('8'); showtext.setText(OperateSum); break; case R.id.nine: OperateSum=AddSum('9'); showtext.setText(OperateSum); break; case R.id.zero: OperateSum=AddSum('0'); showtext.setText(OperateSum); break; case R.id.add: //记录+号 OperateSum=AddSum('+'); Operator='+'; //记录加法 showtext.setText(OperateSum); //把输入的+号显示在EditText break; case R.id.subtract: OperateSum=AddSum('-'); Operator='-'; showtext.setText(OperateSum); break; case R.id.multiply: OperateSum=AddSum('*'); Operator='*'; showtext.setText(OperateSum); break; case R.id.divide: OperateSum=AddSum('/'); Operator='/'; showtext.setText(OperateSum); break; case R.id.point: OperateSum=AddSum('.'); showtext.setText(OperateSum); break; case R.id.delete: //删除刚刚输入的一个符号 if(OperateSum.length()>=1)//当至少已经输入了一个符号才执行 { OperateSum=OperateSum.substring(0,OperateSum.length()-1); } showtext.setText(OperateSum); break; case R.id.clear: //清除整个显示框 OperateSum=""; //变量全部初始化 num1=0; num2=0; sum=0; Operator=' '; showtext.setText(OperateSum); break; case R.id.equal: if(CheckInput(OperateSum))//当输入的数字和运算符都正确，才进行计算 { OperateSum=OperateSum+"="+String.valueOf(equals(OperateSum)); showtext.setText(OperateSum);//显示数字运算符和结果 OperateSum=String.valueOf(sum); //保存运算结果，以便再直接输入一个运算符和一个数字进行下一次运算 } else //输入不合理弹出警告 { Toast.makeText(this,"Error", Toast.LENGTH_SHORT).show(); } break; default: break; } } public String AddSum(char c)//添加并记录一个输入的数字或符号 { OperateSum=OperateSum+String.valueOf(c); return OperateSum; } public boolean CheckInput(String OperateSum) //这个方法用来检查用户输入的数字是否合理，比如用户输入了"9/3"这是合理的，加入输入了 " 8/*",这部合理 { if(OperateSum.length()<=2)//至少要分别输入了一个数字和一个运算符和一个数字，输入长度<=2肯定不合理，如输入 99 按下=按钮肯定不计算 { return false; } if(OperateSum.indexOf(Operator, 1)==-1) //如果没有输入运算符，肯定不合理 { return false; } if(OperateSum.endsWith(String.valueOf(Operator))) //最后以运算符结尾而不是数字，肯定不合理 如输入 9** ，不进行计算 { return false; } return true; } public double equals(String OperateSum) //计算结果 { int indexOfOperator=0; indexOfOperator=OperateSum.indexOf(Operator,1); //计算运算符在从输入的OperateSum字符串里的位置 if(OperateSum.length()>=3) { num1=Double.parseDouble(OperateSum.substring(0, indexOfOperator)); //从输入的OperateSum字符串里得到第一个运算数 num2=Double.parseDouble(OperateSum.substring(indexOfOperator + 1, OperateSum.length())); //从输入的OperateSum字符串里得到第二个运算数 } switch (Operator) //根据运算符进行计算 { case '+': //加法运算 sum=num1+num2; break; case '-': //减法运算 sum=num1-num2; break; case '*': //乘法运算 sum=num1*num2; break; case '/': //除法运算 if(num2!=0) //除数不应该为0 { sum=num1/num2; } else { sum=0; Toast.makeText(this,"Error", Toast.LENGTH_LONG).show();//若除数是0，弹出警告 } break; default: break; } return sum; //返回结果 } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.menu_main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); //noinspection SimplifiableIfStatement if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); }} /> 
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