Android计算器小数点功能异常求助：重复输入引发NaN值问题

Hey there! Let's sort out that annoying duplicate decimal point issue you're facing—totally normal for someone new to app development, so don't stress about it.

What's Causing the Problem? #

Looking at your current code, the issue is that every time you tap the decimal button, you're always adding a decimal point without checking if one already exists. The try block tries to parse the current text to a double first (which works even if there's already a decimal), but then you immediately append another "."—that's why you end up with strings like "1.2." or "1..2" later on, which can't be parsed to a number (hence the NaN errors).

The Fix #

We need to add simple checks before adding the decimal point. Here's how to adjust your code:

b_dot.setOnClickListener(new View.OnClickListener() { 
    @Override 
    public void onClick(View v) { 
        String currentDisplay = show.getText().toString();
        
        // If the display is empty, start with "0." instead of just "."
        if (currentDisplay.isEmpty()) {
            show.setText("0.");
        } 
        // Only add a decimal if there isn't one already
        else if (!currentDisplay.contains(".")) {
            show.setText(currentDisplay + ".");
        }
        // Do nothing if a decimal already exists—no more duplicates!
    } 
});

Why This Works #

• Empty display check: Prevents users from entering a standalone "." (which would cause parsing errors later). Instead, we start with "0." which is a valid partial number.
• Duplicate decimal check: Using contains(".") ensures we only add a decimal point if the current number doesn't have one already. This eliminates those invalid double-decimal strings entirely.

You can also remove that try-catch block from the decimal button click handler now—since we're preventing invalid inputs before they happen, there's no need to handle parsing exceptions here anymore.

内容的提问来源于stack exchange，提问作者Chris