android - 两个 TextWatcher 创建一个无限循环

Question

我的 Android 应用程序中有 3 个 EditText 字段，我试图让它们相互通信。它们是订单总额、收到的金额和小费。用户在第一个 EditText 中输入订单价格。另外两个 EditTexts 是我想要根据每个 EditTexts 的值修改的。如果用户在订单总额中输入 20.00，在收到的金额中输入 25.00，我希望小费显示 5.00。同样，如果他们在订单总额中输入 20.00，在小费中输入 5.00，我希望收到的金额显示 25.00。我的所有计算都是正确的，只要另一个被注释掉，我的每个 TextWatcher 就可以工作，但是对于它们两个，它只会创建一个无限循环。有没有好的方法可以做到这一点，或者有人可以为我指明正确的方向以获得一些有用的链接吗？我似乎找不到任何适合我正在尝试做的事情。

我的代码如下:

eTotalCost = (EditText) findViewById(R.id.orderTotal);
eAmountReceived = (EditText) findViewById(R.id.amountReceived);
eTip = (EditText) findViewById(R.id.tip);
eMileage = (EditText) findViewById(R.id.mileage);
eGrandTotal = (EditText) findViewById(R.id.grandTotal);

eAmountReceived.addTextChangedListener(new TextWatcher()
{
    @Override
    public void beforeTextChanged(CharSequence s, int start,
                                      int count, int after){}

    @Override
    public void onTextChanged(CharSequence s, int start,
                                  int before, int count){}

    @Override
    public void afterTextChanged(Editable s)
    {
        eAmountReceived = (EditText) findViewById(R.id.amountReceived);
        eTotalCost = (EditText) findViewById(R.id.orderTotal);
        eTip = (EditText) findViewById(R.id.tip);
        eMileage = (EditText) findViewById(R.id.mileage);
        eGrandTotal = (EditText) findViewById(R.id.grandTotal);

        sAmountReceived = eAmountReceived.getText().toString();
        sTotalCost = eTotalCost.getText().toString();
        sMileage = eMileage.getText().toString();
        sTip = eTip.getText().toString();

        try
        {
            dAmountReceived = Double.parseDouble(sAmountReceived);
            dTotalCost = Double.parseDouble(sTotalCost);

            dSubtract = dAmountReceived - dTotalCost;
            dMileage = Double.parseDouble(sMileage);
            dGrandTotal = dSubtract + dMileage;
        } catch(NumberFormatException e){}

        sTip = String.valueOf(dSubtract);

        DecimalFormat df = new DecimalFormat("0.00");
        sTip = df.format(dSubtract);

        eTip.setText(sTip);

        sGrandTotal = String.valueOf(dGrandTotal);
        sGrandTotal = df.format(dGrandTotal);
        eGrandTotal.setText(sGrandTotal);
    }
});


eTip.addTextChangedListener(new TextWatcher()
{
    @Override
    public void beforeTextChanged(CharSequence s, int start,
                                      int count, int after){}

    @Override
    public void onTextChanged(CharSequence s, int start,
                                  int before, int count){}

    @Override
    public void afterTextChanged(Editable s) {
        eAmountReceived = (EditText) findViewById(R.id.amountReceived);
        eTotalCost = (EditText) findViewById(R.id.orderTotal);
        eTip = (EditText) findViewById(R.id.tip);
        eMileage = (EditText) findViewById(R.id.mileage);
        eGrandTotal = (EditText) findViewById(R.id.grandTotal);

        sAmountReceived = eAmountReceived.getText().toString();
        sTotalCost = eTotalCost.getText().toString();
        sMileage = eMileage.getText().toString();
        sTip = eTip.getText().toString();

        try 
        {
            dTip = Double.parseDouble(sTip);
            dTotalCost = Double.parseDouble(sTotalCost);

            dAdd = dTotalCost + dTip;
            dMileage = Double.parseDouble(sMileage);
            dGrandTotal = dTip + dMileage;
        } catch (NumberFormatException e) {}

        sAmountReceived = String.valueOf(dAdd);

        DecimalFormat df = new DecimalFormat("0.00");
        sAmountReceived = df.format(dAdd);

        eAmountReceived.setText(sAmountReceived);

        sGrandTotal = String.valueOf(dGrandTotal);
        sGrandTotal = df.format(dGrandTotal);
        eGrandTotal.setText(sGrandTotal);
    }
});

Answer 1

您正在使用 afterTextChanged 回调循环 setText 方法

发生了什么:

您有 2 个 textWatcher:一个用于 eTip，一个用于 eAmountReceived

当您在任何这些字段上调用 ​​setText() 时，它将开始循环，因为 setText 将触发 afterTextChanged 并且在您调用的两个文本观察器中 setText() 用于相反的字段，这将再次触发 afterTextChanged

为了避免这种情况，引入一些 bool 标志，指示是否已为相应的 edittext 设置值，或者仅当新值与已设置的先前值不同时才调用 setText