                        课程
                    
                        /移动开发
                        
                            /Android
                        
                        /Android攻城狮的第一门课（入门篇）

用的android studio做的，加减乘除都等于0

package com.example.administrator.calculater;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import java.util.ArrayList;
import java.util.Arrays;

public class MainActivity extends Activity implements View.OnClickListener {
Button btn_0;
Button btn_1;
Button btn_2;
Button btn_3;
Button btn_4;
Button btn_5;
Button btn_6;
Button btn_7;
Button btn_8;
Button btn_9;
Button btn_point;
Button btn_clear;
Button btn_del;
Button btn_plus;
Button btn_minus;
Button btn_multiply;
Button btn_divide;
Button btn_equal;
EditText et_input;
Boolean clear_flag = true; //清空标识

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn_0 = (Button) findViewById(R.id.btn_0);
btn_1 = (Button) findViewById(R.id.btn_1);
btn_2 = (Button) findViewById(R.id.btn_2);
btn_3 = (Button) findViewById(R.id.btn_3);
btn_4 = (Button) findViewById(R.id.btn_4);
btn_5 = (Button) findViewById(R.id.btn_5);
btn_6 = (Button) findViewById(R.id.btn_6);
btn_7 = (Button) findViewById(R.id.btn_7);
btn_8 = (Button) findViewById(R.id.btn_8);
btn_9 = (Button) findViewById(R.id.btn_9);
btn_point = (Button) findViewById(R.id.btn_point);
btn_del = (Button) findViewById(R.id.btn_del);
btn_plus = (Button) findViewById(R.id.btn_plus);
btn_clear = (Button) findViewById(R.id.btn_clear);
btn_minus = (Button) findViewById(R.id.btn_minus);
btn_multiply = (Button) findViewById(R.id.btn_multiply);
btn_divide = (Button) findViewById(R.id.btn_divide);
btn_equal = (Button) findViewById(R.id.btn_equal);
et_input = (EditText) findViewById(R.id.et_input);

btn_0.setOnClickListener(this);
btn_1.setOnClickListener(this);
btn_2.setOnClickListener(this);
btn_3.setOnClickListener(this);
btn_4.setOnClickListener(this);
btn_5.setOnClickListener(this);
btn_6.setOnClickListener(this);
btn_7.setOnClickListener(this);
btn_8.setOnClickListener(this);
btn_9.setOnClickListener(this);
btn_point.setOnClickListener(this);
btn_clear.setOnClickListener(this);
btn_del.setOnClickListener(this);
btn_plus.setOnClickListener(this);
btn_minus.setOnClickListener(this);
btn_multiply.setOnClickListener(this);
btn_divide.setOnClickListener(this);
btn_equal.setOnClickListener(this);
et_input.setOnClickListener(this);
}

@Override
public void onClick(View view) {
String str = et_input.getText().toString();
switch (view.getId()) {
case R.id.btn_0:
case R.id.btn_1:
case R.id.btn_2:
case R.id.btn_3:
case R.id.btn_4:
case R.id.btn_5:
case R.id.btn_6:
case R.id.btn_7:
case R.id.btn_8:
case R.id.btn_9:
case R.id.btn_point:
if (clear_flag) {
clear_flag = false;
str = "";
et_input.setText("");

}

et_input.setText(str + ((Button) view).getText());
break;
case R.id.btn_plus:
case R.id.btn_minus:
case R.id.btn_multiply:
case R.id.btn_divide:

et_input.setText(str + " " + ((Button) view).getText() + " ");

break;
case R.id.btn_del:
// if(clear_flag){
// clear_flag=false;
// str="";
// et_input.setText("");
// }else
if (str != null && !str.equals("")) {
et_input.setText(str.substring(0, str.length() - 1));
}
break;
case R.id.btn_clear:
// clear_flag = false;
// str="";

et_input.setText("");
break;
case R.id.btn_equal:

getResult();
break;

}
}

private void getResult() {

String exp = et_input.getText().toString();
// if (exp == null || exp.equals("")) {
// return;
// }
// if (!exp.contains(" ")) {
// return;
// }
// if(clear_flag){
// clear_flag = false;
// return;
// }
clear_flag = true;
double result = 0;
String s1 = exp.substring(0, exp.indexOf(" "));//运算符前面得字符串
String op = exp.substring(exp.indexOf(" ") + 1, exp.indexOf(" ") + 2);//截取到得运算符
String s2 = exp.substring(exp.indexOf(" ") + 3);
if (!s1.equals("") && !s2.equals("")) {
double d1 = Double.parseDouble(s1);
double d2 = Double.parseDouble(s2);
if (op.equals("＋")) {
result = d1 + d2;
Log.d("aaaa","aaaaaaaaaaaaaaaaa");
} else if (op.equals("-")) {
result = d1 - d2;

} else if (op.equals("×")) {
result = d1 * d2;
} else if (op.equals("÷")) {
if (d2 == 0) {
result = 0;
} else {
result = d1 / d2;
}
}
if (!s1.contains(".") && !s2.contains(".") && !op.equals("÷")) {
int r = (int) result;
et_input.setText(r + "");
} else {
et_input.setText(result + "");
}
} else if (!s1.equals("") && s2.equals("")) {
et_input.setText(exp);
} else if (s1.equals("") && !s2.equals("")) {
double d2 = Double.parseDouble(s2);
if (op.equals("+")) {
result = 0 + d2;

} else if (op.equals("-")) {
result = 0 - d2;

} else if (op.equals("×")) {
result = 0;
} else if (op.equals("÷")) {
if (d2 == 0) {
result = 0;
} else {
result = 0;
}
}
if (!s2.contains(".")) {
int r = (int) result;
et_input.setText(r + "");
} else {
et_input.setText(result + "");
}
} else {
et_input.setText("");
}
}
}