Question

我收到以下错误（在logcat中），当我尝试在我的设备上启动时从EditText中删除数字0.0（双数据类型值）时，我的应用程序在我的Android设备上崩溃..

以下是错误消息：

LogCat

以下是代码：

  /*
   * variables prefixed by 'v' are variables of primitive data type
   * variables prefixed by 'et' are edit text
   * variables prefixed by 'cl' are changeListeners of watcher data type 
   * 
   */

   public class MhrSolankiTipCalc extends Activity {

private static final String BILL_BEFORE_TIP = "BILL_BEFORE_TIP";
private static final String CURRENT_TIP = "CURRENT_TIP";
private static final String FINAL_BILL = "FINAL_AMOUNT";

double vBillAmount, vTipAmount, vFinalBillAmount;

EditText etBillAmount, etTipAmount, etFinalBillAmount;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_mhr_solanki_tip_calc);

    if (savedInstanceState == null) {
        vBillAmount = 0.0;
        vTipAmount = 0.0;
        vFinalBillAmount = 0.0;
    } else {
        vBillAmount = savedInstanceState.getDouble(BILL_BEFORE_TIP);
        vTipAmount = savedInstanceState.getDouble(CURRENT_TIP);
        vFinalBillAmount = savedInstanceState.getDouble(FINAL_BILL);

    }

    etBillAmount = (EditText) findViewById(R.id.billBlankEditView);
    etTipAmount = (EditText) findViewById(R.id.tipBlankEditView);
    etFinalBillAmount = (EditText) findViewById(R.id.finalEditView);

    etBillAmount.addTextChangedListener(clBillAmount);
    etTipAmount.addTextChangedListener(clTipAmount);

}

private TextWatcher clBillAmount = new TextWatcher() {

    @Override
    public void onTextChanged(CharSequence s, int start, int before,
            int count) {
        try {
            vBillAmount = Double.parseDouble(s.toString());
        } catch (NumberFormatException e) {
            vBillAmount = 0.0;

        }
        catch(NullPointerException e)
        {
            vBillAmount=0.0;
        }
        updateBillAndFinalAmount();

    }

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count,
            int after) {
        // TODO Auto-generated method stub

    }

    @Override
    public void afterTextChanged(Editable s) {
        // TODO Auto-generated method stub

    }
};

private TextWatcher clTipAmount = new TextWatcher() {

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        try{
            vTipAmount = Double.parseDouble(s.toString());
        }
        catch(NumberFormatException e){
            vTipAmount = 0.0;
        }
        updateBillAndFinalAmount();
    }

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count,
            int after) {
        // TODO Auto-generated method stub

    }

    @Override
    public void afterTextChanged(Editable s) {
        // TODO Auto-generated method stub

    }
};

public void updateBillAndFinalAmount() {
    double vTipAmount = Double
            .parseDouble(etTipAmount.getText().toString());
    double vBillAmount = Double.parseDouble(etBillAmount.getText()
            .toString());
    double vFinalBillAmount = vBillAmount + (vBillAmount * vTipAmount);
    etFinalBillAmount.setText(String.format("%.02f", vFinalBillAmount));
}

Answer 1

在updateBillAndFinalAmount()中，您使用EditTexts的值为空字符串调用Double.parseDouble。您应该像在文本观察者中那样检查它们

    double vTipAmount; 
    double vBillAmount;
    try {
        vTipAmount = Double.parseDouble(etTipAmount.getText().toString());
    } catch (NumberFormatException e) {
        vTipAmount = 0.0;
    }
    try {
        vBillAmount = Double.parseDouble(etBillAmount.getText().toString());
    } catch (NumberFormatException e) {
        vBillAmount = 0.0;
    }

而不是复制/粘贴整个块，你可以简单地编写一个按特定规则返回双精度的函数

public static double getDoubleFromString(String s)
{
    double d;
    try {
        d = Double.parseDouble(s);
    } catch (NumberFormatException e) {
        d = 0.0;
    }
    return d;
}

，您的代码看起来像

 double vTipAmount = getDoubleFromString(etTipAmount.getText().toString()); 
 double vBillAmount = getDoubleFromString(etBillAmount.getText().toString());

Answer 2

在提供从EditText到parseDouble()的字符串值之前，请确保它不为空：

vTipAmount = (s.toString().length > 0 && s.toString() != null)
             ? Double.parseDouble(s.toString())
             : 0.0;

另一种方法是捕获所有异常而不仅仅是NumberFormatException（虽然它增加了一点点开销）：

    try {
        vBillAmount = Double.parseDouble(s.toString());
    } catch (Exception e) {
        vBillAmount = 0.0;

    }

Answer 3

由于您已经在TextWatchers中解析vBillAmount和vTipAmount以及捕获NumberFormatException，因此您无需在updateBillAndFinalAmount()方法中再次执行此操作。这也将修复您在此方法中获得的NumberFormatException。将其更改为：

public void updateBillAndFinalAmount()
{
    double vFinalBillAmount = vBillAmount + (vBillAmount * vTipAmount);
    etFinalBillAmount.setText(String.format("%.02f", vFinalBillAmount));
}

应用程序崩溃由于空值“双”数据类型（android）

3 个答案: