FutureBuilder snapshot has no data

Why This Happens

In Flutter, FutureBuilder goes through multiple ConnectionStates: none, waiting, active, done. If you only handle the done state and return the data widget, the waiting state returns null which cannot be used as a Widget. Always handle all snapshot states.

The Problem

FutureBuilder<String>(
  future: fetchData(),
  builder: (context, snapshot) {
    if (snapshot.hasData) {
      return Text(snapshot.data!);
    }
    // Returns null implicitly when loading!
  },
)

The Fix

FutureBuilder<String>(
  future: fetchData(),
  builder: (context, snapshot) {
    if (snapshot.connectionState == ConnectionState.waiting) {
      return CircularProgressIndicator();
    }
    if (snapshot.hasError) {
      return Text('Error: ${snapshot.error}');
    }
    return Text(snapshot.data ?? 'No data');
  },
)

Step-by-Step Fix

1. 1

   Identify the error

   Look for null widget errors or blank screens from FutureBuilder. The builder must return a non-null Widget for every state.

2. 2

   Find the cause

   Check if the FutureBuilder builder handles ConnectionState.waiting and error states, not just the data case.

3. 3

   Apply the fix

   Handle all snapshot states: show a loader for waiting, an error widget for errors, and the data widget when complete.