Eclipse中的数字平方不起作用
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【中文标题】Eclipse中的数字平方不起作用【英文标题】：Square of a number in Eclipse not working 【发布时间】：2015-06-29 13:27:58 【问题描述】：这是我正在制作的 android 计算器应用程序的代码：
package com.example.calculator;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Iterator;
import java.util.Stack;
import java.lang.Math;
import android.app.Activity;
import android.os.Bundle;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.TextView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.GridView;
import android.view.View;
import android.view.View.OnClickListener;
public class main extends Activity
GridView mKeypadGrid;
TextView userInputText;
TextView memoryStatText;
Stack<String> mInputStack;
Stack<String> mOperationStack;
KeypadAdapter mKeypadAdapter;
TextView mStackText;
boolean resetInput = false;
boolean hasFinalResult = false;
String mDecimalSeperator;
double memoryValue = Double.NaN;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
DecimalFormat currencyFormatter = (DecimalFormat) NumberFormat
.getInstance();
char decimalSeperator = currencyFormatter.getDecimalFormatSymbols()
.getDecimalSeparator();
mDecimalSeperator = Character.toString(decimalSeperator);
setContentView(R.layout.main);
// Create the stack
mInputStack = new Stack<String>();
mOperationStack = new Stack<String>();
// Get reference to the keypad button GridView
mKeypadGrid = (GridView) findViewById(R.id.grdButtons);
// Get reference to the user input TextView
userInputText = (TextView) findViewById(R.id.txtInput);
userInputText.setText("0");
memoryStatText = (TextView) findViewById(R.id.txtMemory);
memoryStatText.setText("");
mStackText = (TextView) findViewById(R.id.txtStack);
// Create Keypad Adapter
mKeypadAdapter = new KeypadAdapter(this);
// Set adapter of the keypad grid
mKeypadGrid.setAdapter(mKeypadAdapter);
// Set button click listener of the keypad adapter
mKeypadAdapter.setOnButtonClickListener(new OnClickListener()
@Override
public void onClick(View v)
Button btn = (Button) v;
// Get the KeypadButton value which is used to identify the
// keypad button from the Button's tag
KeypadButton keypadButton = (KeypadButton) btn.getTag();
// Process keypad button
ProcessKeypadInput(keypadButton);
);
mKeypadGrid.setOnItemClickListener(new OnItemClickListener()
public void onItemClick(AdapterView<?> parent, View v,
int position, long id)
);
private void ProcessKeypadInput(KeypadButton keypadButton)
//Toast.makeText(this, keypadButton.getText(), Toast.LENGTH_SHORT).show();
String text = keypadButton.getText().toString();
String currentInput = userInputText.getText().toString();
int currentInputLen = currentInput.length();
String evalResult = null;
double userInputValue = Double.NaN;
switch (keypadButton)
case BACKSPACE: // Handle backspace
// If has operand skip backspace
if (resetInput)
return;
int endIndex = currentInputLen - 1;
// There is one character at input so reset input to 0
if (endIndex < 1)
userInputText.setText("0");
// Trim last character of the input text
else
userInputText.setText(currentInput.subSequence(0, endIndex));
break;
case SIGN: // Handle -/+ sign
// input has text and is different than initial value 0
if (currentInputLen > 0 && currentInput != "0")
// Already has (-) sign. Remove that sign
if (currentInput.charAt(0) == '-')
userInputText.setText(currentInput.subSequence(1,
currentInputLen));
// Prepend (-) sign
else
userInputText.setText("-" + currentInput.toString());
break;
case CE: // Handle clear input
userInputText.setText("0");
break;
case SQUARE:
double squareInput = Double.valueOf(currentInput);
userInputText.setText(squareInput+"*"+squareInput);
break;
case C: // Handle clear input and stack
userInputText.setText("0");
clearStacks();
break;
case DECIMAL_SEP: // Handle decimal separator
if (hasFinalResult || resetInput)
userInputText.setText("0" + mDecimalSeperator);
hasFinalResult = false;
resetInput = false;
else if (currentInput.contains("."))
return;
else
userInputText.append(mDecimalSeperator);
break;
case DIV:
case PLUS:
case MINUS:
case MULTIPLY:
if (resetInput)
mInputStack.pop();
mOperationStack.pop();
else
if (currentInput.charAt(0) == '-')
mInputStack.add("(" + currentInput + ")");
else
mInputStack.add(currentInput);
mOperationStack.add(currentInput);
mInputStack.add(text);
mOperationStack.add(text);
dumpInputStack();
evalResult = evaluateResult(false);
if (evalResult != null)
userInputText.setText(evalResult);
resetInput = true;
break;
case CALCULATE:
if (mOperationStack.size() == 0)
break;
mOperationStack.add(currentInput);
evalResult = evaluateResult(true);
if (evalResult != null)
clearStacks();
userInputText.setText(evalResult);
resetInput = false;
hasFinalResult = true;
break;
case M_ADD: // Add user input value to memory buffer
userInputValue = tryParseUserInput();
if (Double.isNaN(userInputValue))
return;
if (Double.isNaN(memoryValue))
memoryValue = 0;
memoryValue += userInputValue;
displayMemoryStat();
hasFinalResult = true;
break;
case M_REMOVE: // Subtract user input value to memory buffer
userInputValue = tryParseUserInput();
if (Double.isNaN(userInputValue))
return;
if (Double.isNaN(memoryValue))
memoryValue = 0;
memoryValue -= userInputValue;
displayMemoryStat();
hasFinalResult = true;
break;
case MC: // Reset memory buffer to 0
memoryValue = Double.NaN;
displayMemoryStat();
break;
case MR: // Read memoryBuffer value
if (Double.isNaN(memoryValue))
return;
userInputText.setText(doubleToString(memoryValue));
displayMemoryStat();
break;
case MS: // Set memoryBuffer value to user input
userInputValue = tryParseUserInput();
if (Double.isNaN(userInputValue))
return;
memoryValue = userInputValue;
displayMemoryStat();
hasFinalResult = true;
break;
default:
if (Character.isDigit(text.charAt(0)))
if (currentInput.equals("0") || resetInput || hasFinalResult)
userInputText.setText(text);
resetInput = false;
hasFinalResult = false;
else
userInputText.append(text);
resetInput = false;
break;
private void clearStacks()
mInputStack.clear();
mOperationStack.clear();
mStackText.setText("");
private void dumpInputStack()
Iterator<String> it = mInputStack.iterator();
StringBuilder sb = new StringBuilder();
while (it.hasNext())
CharSequence iValue = it.next();
sb.append(iValue);
mStackText.setText(sb.toString());
private String evaluateResult(boolean requestedByUser)
if ((!requestedByUser && mOperationStack.size() != 4)
|| (requestedByUser && mOperationStack.size() != 3))
return null;
String left = mOperationStack.get(0);
String operator = mOperationStack.get(1);
String right = mOperationStack.get(2);
String tmp = null;
if (!requestedByUser)
tmp = mOperationStack.get(3);
double leftVal = Double.parseDouble(left.toString());
double rightVal = Double.parseDouble(right.toString());
double result = Double.NaN;
if (operator.equals(KeypadButton.DIV.getText()))
result = leftVal / rightVal;
else if (operator.equals(KeypadButton.MULTIPLY.getText()))
result = leftVal * rightVal;
else if (operator.equals(KeypadButton.PLUS.getText()))
result = leftVal + rightVal;
else if (operator.equals(KeypadButton.MINUS.getText()))
result = leftVal - rightVal;
String resultStr = doubleToString(result);
if (resultStr == null)
return null;
mOperationStack.clear();
if (!requestedByUser)
mOperationStack.add(resultStr);
mOperationStack.add(tmp);
return resultStr;
private String doubleToString(double value)
if (Double.isNaN(value))
return null;
long longVal = (long) value;
if (longVal == value)
return Long.toString(longVal);
else
return Double.toString(value);
private double tryParseUserInput()
String inputStr = userInputText.getText().toString();
double result = Double.NaN;
try
result = Double.parseDouble(inputStr);
catch (NumberFormatException nfe)
return result;
private void displayMemoryStat()
if (Double.isNaN(memoryValue))
memoryStatText.setText("");
else
memoryStatText.setText("M = " + doubleToString(memoryValue));
要找到输入数字的平方，我使用以下代码：
case SQUARE:
double squareInput = Double.valueOf(currentInput);
userInputText.setText(squareInput+"*"+squareInput);
break;
但是当输入数字 9 和 9 时，它只显示 *9*9.* 它不显示输出为 81。
这是为什么，有人可以帮我解决吗？
【问题讨论】：
【参考方案1】：您通过添加“*”将数字转换为字符串。相反，您需要的是：
userInputText.setText(String.valueOf(squareInput*squareInput));
它的工作方式是：
首先它看到 9 然后你附加一个返回 9 的字符串 "" 现在你将另一个双精度附加到现有字符串中，将 9 附加到现有字符串中，因此你得到 "9*9"
【讨论】：
【参考方案2】：您的公式不正确。 试试这个。
double squareInput = Double.valueOf(currentInput);
userInputText.setText(String.format("%f", squareInput * squareInput));
【讨论】：
【参考方案3】：您正在设置字符串值而不是平方计算值。
这样做：
userInputText.setText(String.valueOf(squareInput*squareInput));
【讨论】：
【参考方案4】：您只需将值连接为字符串。如果您需要计算什么平方并将其添加到文本字段中：
userInputText.setText(squareInput+"*"+squareInput+"="+(squareInput*squareInput) );
【讨论】：
【参考方案5】：使用下面的代码...可能对你有帮助..
case SQUARE:
double squareInput = Double.valueOf(currentInput);
userInputText.setText(String.valueOf(squareInput*squareInput));
break;
【讨论】：
【参考方案6】：把你的代码改成这个
case SQUARE:
double squareInput = Double.valueOf(currentInput);
userInputText.setText(""+squareInput*squareInput);
break;
【讨论】：
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