我为Android制作了这个计算器应用程序。它接收一个数字，运算符然后是另一个数字。我已经尝试添加一个平方根函数，但它要么不起作用，要么崩溃。主要问题是在数字之前不能输入运算符，并且平方根运算符需要后面的数字，所以我现在删除了平方根。我怎样才能解决这个问题？我在下面添加了我的代码.public class Calculator扩展了AppCompatActivity {
private TextView _screen;
private String display = "";
private String currentOperator = "";
private String result = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_calculator);
_screen = (TextView) findViewById(R.id.textView);
_screen.setText(display);
}
private void updateScreen() {
_screen.setText(display);
}
public void onClickNumber(View view) {
if (result != "") {
clear();
updateScreen();
}
Button b = (Button) view;
display += b.getText();
updateScreen();
}
public void onClickDecimal(View view) {
if (result != "") {
clear();
updateScreen();
}
Button b = (Button) view;
display += b.getText();
updateScreen();
}
public void onClickBackspace(View view) {
int length = display.length();
if (length >= 1) {
display = display.substring(0, length - 1);
updateScreen();
}
else {
Toast toast = Toast.makeText(this, "Please enter some numbers first", Toast.LENGTH_SHORT);
toast.show();
}
}
private boolean isOperator(char op) {
switch (op) {
case '+':
return true;
case '-':
return true;
case 'x':
return true;
case '÷':
return true;
case '%':
return true;
case '^':
return true;
case '√':
return true;
default:
return false;
}
}
public void onClickOperator(View view) {
if (display == "") return;
Button b = (Button) view;
if (result != "") {
String _display = result;
clear();
display = _display;
}
if (currentOperator != "") {
if (isOperator(display.charAt(display.length() - 1))) {
display = display.replace(display.charAt(display.length() - 1), b.getText().charAt(0));
updateScreen();
return;
}
else {
getResult();
display = result;
result = "";
}
currentOperator = b.getText().toString();
}
display += b.getText();
currentOperator = b.getText().toString();
updateScreen();
}
private void clear() {
display = "";
currentOperator = "";
result = "";
}
public void onClickClear(View view) {
clear();
updateScreen();
}
private double operate(String a, String b, String op) {
switch (op) {
case "+":
return Double.valueOf(a) + Double.valueOf(b);
case "-":
return Double.valueOf(a) - Double.valueOf(b);
case "x":
return Double.valueOf(a) * Double.valueOf(b);
case "÷":
return Double.valueOf(a) / Double.valueOf(b);
case "%":
return Double.valueOf(a) % Double.valueOf(b);
case "^":
return Math.pow(Double.valueOf(a), Double.valueOf(b));
case "√":
return Math.sqrt(Double.valueOf(a));
default:
return -1;
}
}
private boolean getResult() {
DecimalFormat res = new DecimalFormat("#,###,###,###.######");
if (currentOperator == "") return false;
String[] operation = display.split(Pattern.quote(currentOperator));
if (operation.length < 2) return false;
result = String.valueOf(res.format(operate(operation[0], operation[1], currentOperator)));
return true;
}
public void onClickEquals(View view) {
int length = result.length();
if (display == "") return;
if(!getResult()) return;
if (length <= 10) {
_screen.setText(String.valueOf(result));
}
else {
result = result.substring(0, 9);
_screen.setText(String.valueOf(result));
}
}`
答案 0 :(得分：0)
您可以使用： -
double x = 2.45;
System.out.printf("sqrt(%.3f) is %.3f%n", x, Math.sqrt(x));
结果： -
sqrt(2.45) is 1.565