如何实现点击时更新字符串格式当前日期时间？Firebase子元素填充问题

Let's break down how to handle both of your technical requirements step by step:

1. Update Formatted Date/Time String on Click #

First, we'll create a reusable way to generate the formatted date/time string, then update your target string (or UI element) every time the button is clicked.

Step 1: Create a helper method for date formatting #

This method will generate your desired "yyyy-MM-dd HH:mm:ss" string whenever you need it:

private String getCurrentDateTime() {
    // For Java 7 and older
    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.getDefault());
    return dateFormat.format(new Date());
    
    // If you're using Java 8+ (recommended for thread safety), use this instead:
    // DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    // return LocalDateTime.now().format(formatter);
}

Step 2: Trigger update on button click #

In your button's click listener, call the helper method and update your string (or UI):

// Example: If you're displaying the date in a TextView
TextView dateDisplay = findViewById(R.id.date_display_text);

btn_send_msg.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        String currentDateTime = getCurrentDateTime();
        
        // Update your string variable (if needed)
        // yourStringVariable = currentDateTime;
        
        // Or update the UI directly
        dateDisplay.setText(currentDateTime);
    }
});

2. Write Date/Time to Firebase Child Elements #

Let's fix and complete your incomplete Firebase code. The core idea is to add the formatted date string to your data map before pushing it to Firebase.

Step 1: Ensure Firebase reference is set up #

First, make sure you have your Firebase Database reference initialized (usually in your activity's onCreate):

FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference root = database.getReference("your_root_collection"); // Replace with your actual root node name
String temp_key;

Step 2: Complete the click listener for Firebase #

Update your button's click logic to include the date/time in the data sent to Firebase:

btn_send_msg.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        // Get the formatted date/time string
        String currentDateTime = getCurrentDateTime();
        
        // Create a map to hold your message data (add other fields as needed)
        Map<String, Object> messageData = new HashMap<>();
        messageData.put("timestamp", currentDateTime);
        // Add other fields like message content, sender info, etc.
        // messageData.put("message", yourMessageEditText.getText().toString());
        
        // Generate a unique key for the new child element
        temp_key = root.push().getKey();
        
        // Write the data to Firebase
        root.child(temp_key).setValue(messageData)
            .addOnSuccessListener(unused -> {
                // Optional: Show success feedback
                Toast.makeText(getApplicationContext(), "Data saved!", Toast.LENGTH_SHORT).show();
            })
            .addOnFailureListener(e -> {
                // Optional: Handle errors
                Toast.makeText(getApplicationContext(), "Failed to save data: " + e.getMessage(), Toast.LENGTH_SHORT).show();
            });
    }
});

Quick Note: Firebase Server Timestamp #

If you want more accurate timestamps (avoiding device time discrepancies), you can use Firebase's built-in server timestamp instead of formatting a local date:

// Replace the timestamp line with this
messageData.put("timestamp", ServerValue.TIMESTAMP);

This stores the timestamp as a long (milliseconds since epoch), which you can format into your desired string when retrieving the data later.

内容的提问来源于stack exchange，提问作者Hrithik Rawal