android开发【六】（基于android studio3.2）计算器

package com.example.calculator;import android.app.Activity;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.TextView;import java.text.NumberFormat;public class MainActivity extends Activity {    double firstNum = 0;    char currentSign = '+';    StringBuffer currentNum = new StringBuffer();    boolean isFirstPoint = false;    TextView txtResult;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        txtResult = (TextView) findViewById(R.id.txtResult);    }    public void init() {        currentNum.delete(0, currentNum.length());        isFirstPoint = false;    }    public double stringToDouble() {        if (currentNum.length() == 0) {            return 0;        }        double result = Double.parseDouble(currentNum.toString());        return result;    }    public double calcu() {        double result = 0;        switch (currentSign) {            case '+':                result = firstNum + stringToDouble();                break;            case '-':                result = firstNum - stringToDouble();                break;            case '*':                result = firstNum * stringToDouble();                break;            case '/':                result = firstNum / stringToDouble();                break;        }        NumberFormat format = NumberFormat.getInstance();        format.setMaximumFractionDigits(2);        result = Double.parseDouble(format.format(result));        return result;    }    public void display(){        txtResult.setText(currentNum.toString());    }    public void digital_click(View view){        Button btnDigital = (Button)view;        char text = btnDigital.getText().charAt(0);        currentNum.append(text);        display();    }    public void add(View view){        double result = calcu();        txtResult.setText(String.valueOf(result));        firstNum=result;        currentSign='+';        init();    }    public void sub(View view){        double result = calcu();        txtResult.setText(String.valueOf(result));        firstNum=result;        currentSign='-';        init();    }    public void mul(View view){        double result = calcu();        txtResult.setText(String.valueOf(result));        firstNum=result;        currentSign='*';        init();    }    public void div(View view){        double result = calcu();        txtResult.setText(String.valueOf(result));        firstNum=result;        currentSign='/';        init();    }    public void equ(View view){        double result = calcu();        txtResult.setText(String.valueOf(result));        firstNum=result;        currentSign='+';        init();    }    public void point_click(View view){        if(isFirstPoint){            return;        }        if(currentNum.length()==0){            return;        }        Button btnPoint=(Button)view;        char text = btnPoint.getText().charAt(0);        isFirstPoint=true;        display();    }    public void del(View view){        if(currentNum.length()>=1){            currentNum.delete(currentNum.length()-1,currentNum.length());        }        if(currentNum.length()==0){            init();            display();        }        txtResult.setText(currentNum);    }}
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