android容易的计算器有错，求好心人帮忙（80分）

package com.example.calcultor;import android.os.Bundle;import android.app.Activity;import android.view.Menu;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;public class MainActivity extends Activity implements OnClickListener{    static String number1=null;    static String number2=null;    static String number3=null;//实现连等功能    static double result=0;    static Boolean checkNum=false;    static Boolean check_ls=false;//实现连等功能    static int op=0;    private Button btn0,btn1,btn2,btn3,btn4,btn5,btn6,btn7,btn8,btn9;    private Button btn_multiply,btn_divide,btn_dot,btn_clear,btn_plus,btn_reduce,btn_result;    private EditText et;        @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        btn0=(Button)findViewById(R.id.zero);        btn1=(Button)findViewById(R.id.one);        btn2=(Button)findViewById(R.id.two);        btn3=(Button)findViewById(R.id.three);        btn4=(Button)findViewById(R.id.four);        btn5=(Button)findViewById(R.id.five);        btn6=(Button)findViewById(R.id.six);        btn7=(Button)findViewById(R.id.seven);        btn8=(Button)findViewById(R.id.eight);        btn9=(Button)findViewById(R.id.nine);        btn_reduce=(Button)findViewById(R.id.reduce);        btn_multiply=(Button)findViewById(R.id.multiply);        btn_divide=(Button)findViewById(R.id.divide);        btn_dot=(Button)findViewById(R.id.dot);        btn_clear=(Button)findViewById(R.id.clear);        btn_plus=(Button)findViewById(R.id.plus);        btn_result=(Button)findViewById(R.id.result);        et=(EditText)findViewById(R.id.et);        btn1.setOnClickListener(this);        btn2.setOnClickListener(this);        btn3.setOnClickListener(this);        btn4.setOnClickListener(this);        btn5.setOnClickListener(this);        btn6.setOnClickListener(this);        btn7.setOnClickListener(this);        btn8.setOnClickListener(this);        btn9.setOnClickListener(this);        btn0.setOnClickListener(this);        btn_reduce.setOnClickListener(this);        btn_multiply.setOnClickListener(this);        btn_divide.setOnClickListener(this);        btn_dot.setOnClickListener(this);        btn_clear.setOnClickListener(this);        btn_plus.setOnClickListener(this);        btn_result.setOnClickListener(this);            }   @Override    public boolean onCreateOptionsMenu(Menu menu) {        getMenuInflater().inflate(R.menu.activity_main, menu);        return true;    }    @Override    public void onClick(View v) {        switch(v.getId()){          default:              break;          case R.id.one:setTextValue(String.valueOf(R.id.one));               break;          case R.id.two:setTextValue(String.valueOf(R.id.two));            break;          case R.id.three:setTextValue(String.valueOf(R.id.three));            break;          case R.id.four:setTextValue(String.valueOf(R.id.four));            break;          case R.id.five:setTextValue(String.valueOf(R.id.five));              break;          case R.id.six:setTextValue(String.valueOf(R.id.six));              break;          case R.id.seven:setTextValue(String.valueOf(R.id.seven));              break;          case R.id.eight:setTextValue(String.valueOf(R.id.eight));              break;          case R.id.nine:setTextValue(String.valueOf(R.id.nine));              break;          case R.id.zero:            if(et.getText().toString()!=null)                setTextValue(String.valueOf(R.id.zero));             else            break;          case R.id.plus:{op=1;get_number();             break;}        case R.id.reduce:{op=2;get_number();              break;}          case R.id.multiply:{op=3;get_number();              break;}          case R.id.divide:{op=4;get_number();              break;}          case R.id.dot:            if(et.getText().toString()!=null)                setTextValue(String.valueOf(R.id.dot));             else            break;          case R.id.clear:All_clear();            break;        case R.id.result:print_result();             break;        }             }    private void setTextValue(String str){          et.append(str);      }             private void get_number(){        checkNum=!checkNum;        if(checkNum){            number1=et.getText().toString();            et.setText("");        }                else  number2=et.getText().toString();         }    private void All_clear(){      number1="";      number2="";      number3="";//实现连等功能      result=0;      checkNum=false;      check_ls=false;//实现连等功能      op=0;            }    private void print_result(){    if(!check_ls){        switch(op){        case 1:result=Double.valueOf(number1)+Double.valueOf(number2);break;        case 2:result=Double.valueOf(number1)-Double.valueOf(number2);break;        case 3:result=Double.valueOf(number1)*Double.valueOf(number2);break;        case 4:result=Double.valueOf(number1)/Double.valueOf(number2);break;        }        check_ls=true;    }    else {        switch(op){        case 1:result+=Double.valueOf(number3);break;        case 2:result-=Double.valueOf(number3);break;        case 3:result*=Double.valueOf(number3);break;        case 4:result/=Double.valueOf(number3);break;        }                et.setText(String.valueOf(result));    }                }    }