我的代码为单个5+10=15中的两个输入即editText提供了答案，但是对于两个以上的输入，即5+10*2=20，如果我在显示1+的某个值后第二次点击运算符++ 2。如何在值之后仅显示一次以及如何计算editText
我的代码如下：
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
Button reset,root,div,mul,del,four,five,six,seven,eight,nine,one,two,three,minus,plus,zero,deci,eql,percent;
int op1,op2;
String first,second;
String str ="";
Character op ='q';
String displayStr="";
double num,numtemp,temp;
EditText mCalculatorDisplay1;
DecimalFormat df = new DecimalFormat("@###########");
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// mCalculatorBrain = new CalculatorBrain();
mCalculatorDisplay1 = (EditText) findViewById(R.id.edittext1);
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);
plus = (Button) findViewById(R.id.plus);
minus = (Button) findViewById(R.id.minus);
mul = (Button) findViewById(R.id.multi);
div = (Button) findViewById(R.id.div);
del = (Button) findViewById(R.id.delete);
eql = (Button) findViewById(R.id.equalTo);
deci = (Button) findViewById(R.id.decimal);
root = (Button) findViewById(R.id.root);
reset = (Button) findViewById(R.id.cancel);
percent = (Button) findViewById(R.id.percent);
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);
zero.setOnClickListener(this);
plus.setOnClickListener(this);
minus.setOnClickListener(this);
mul.setOnClickListener(this);
div.setOnClickListener(this);
del.setOnClickListener(this);
eql.setOnClickListener(this);
deci.setOnClickListener(this);
root.setOnClickListener(this);
reset.setOnClickListener(this);
percent.setOnClickListener(this);
// mCalculatorDisplay1.setKeyListener(DigitsKeyListener.getInstance(true, true));
}
private void perform() {
// TODO Auto-generated method stub
str = "";
numtemp = num;
}
private void insert(int j) {
// TODO Auto-generated method stub
str = str + Integer.toString(j);
num = Double.valueOf(str);
displayStr += Integer.toString(j);
mCalculatorDisplay1.setText(displayStr);
}
private void calculate() {
// TODO Auto-generated method stub
first=String.valueOf(numtemp);
second=String.valueOf(num);
if(op == '+'){
num = numtemp+num;
}
else if(op == '-')
num = numtemp-num;
else if(op == '/')
num = numtemp/num;
else if(op == '*')
num = numtemp*num;
else if (op=='%')
num = numtemp*num/100;
else if (op=='√') {
num = Math.sqrt(num);
}
mCalculatorDisplay1.setText(first + op + second + "\n"+ "=" + num );
}
private void insert(String j) {
//Insert the values by clicking button
str = str+String.valueOf(j);
String num = String.valueOf(str);
displayStr += String.valueOf(j);
mCalculatorDisplay1.setText(displayStr);
}
@Override
public void onClick(View view) {
switch (view.getId()){
case R.id.one:
insert(1);
break;
case R.id.two:
insert(2);
break;
case R.id.three:
insert(3);
break;
case R.id.four:
insert(4);
break;
case R.id.five:
insert(5);
break;
case R.id.six:
insert(6);
break;
case R.id.seven:
insert(7);
break;
case R.id.eight:
insert(8);
break;
case R.id.nine:
insert(9);
break;
case R.id.decimal:
insert(".");
break;
case R.id.percent:
perform();
op = '%';
displayStr += "%";
break;
case R.id.zero:
insert(0);
break;
case R.id.plus:
// if (displayStr.contains("+")){
// op = '+';
// displayStr+="";
// perform();
// mCalculatorDisplay1.setText(displayStr);
// }
// else
perform();
op = '+';
displayStr+= "+";
mCalculatorDisplay1.setText(displayStr);
break;
case R.id.minus:
perform();
op = '-';
displayStr += "-";
mCalculatorDisplay1.setText(displayStr);
break;
case R.id.multi:
perform();
op = '*';
displayStr += "*";
mCalculatorDisplay1.setText(displayStr);
break;
case R.id.div:
perform();
op = '/';
displayStr += "/";
mCalculatorDisplay1.setText(displayStr);
break;
case R.id.cancel:
str="";
displayStr = "";
mCalculatorDisplay1.setText(displayStr);
break;
case R.id.root:
perform();
op = '√';
displayStr += "√";
mCalculatorDisplay1.setText(displayStr);
break;
case R.id.delete:
str="";
displayStr ="";
displayStr=mCalculatorDisplay1.getText().toString();
if (displayStr.length() >1 ) {
displayStr = displayStr.substring(0, displayStr.length() - 1);
mCalculatorDisplay1.setText(displayStr);
}
else if (displayStr.length() <=1 ) {
displayStr ="";
mCalculatorDisplay1.setText( displayStr);
}
// mCalculatorDisplay1.setText(displayStr.substring(0,displayStr.length()-1));
break;
case R.id.equalTo:
calculate();
break;
}
}
}
答案 0 :(得分：0)
您应该使用exp4j。它是java的表达式求值程序。
为了您的目的
从editText
将字符串传递给以下段
Calculable calc = new ExpressionBuilder("5+10*2").build()
double result=calc.calculate();