我想从一个Stateful Widget广播事件到另一个Widget,但似乎找不到实现的方法。我安装了这个插件:event: ^1.1.4,但它没有响应。我想要像下面这样的效果:
Stateful Widget 1:
SomeEventClass.broadcastEvent();
Stateful Widget 2:
SomeEventClass.subscribe();
我想从一个Stateful Widget广播事件到另一个Widget,但似乎找不到实现的方法。我安装了这个插件:event: ^1.1.4,但它没有响应。我想要像下面这样的效果:
Stateful Widget 1:
SomeEventClass.broadcastEvent();
Stateful Widget 2:
SomeEventClass.subscribe();
通过使用像这样的东西。
class ContinuousStream {
_DataStore _mStorage = _DataStore.getInstance();
/// Sets a new value [value] to the data stream [stream].
/// If there are active subscribers, the value will be dispatched to them.
void emit(String stream, var value) {
_mStorage?.setValue(stream, value);
}
/// Subscribes to the given stream [stream].
/// If stream already has data set, it will be delivered to the [callback] function.
void on(String stream, void Function(Object) callback) {
_mStorage?.setCallback(stream, callback);
}
/// Returns the current value of a given data [stream].
Object getValue(String stream) {
return _mStorage?.getValue(stream);
}
}
// Storage class for ContinuousStream.
class _DataStore {
// Singleton Instance for DataStore
static _DataStore _instance;
// Map instance to store data values with data stream.
HashMap<String, _DataItem> _mDataItemsMap = HashMap();
// Sets/Adds the new value to the given key.
void setValue(String key, var value) {
// Retrieve existing data item from map.
_DataItem item = _mDataItemsMap[key];
item ??= _DataItem();
// Set new value to new/existing item.
item.value = value;
// Reset item to the map.
_mDataItemsMap[key] = item;
// Dispatch new value to all callbacks.
item.callbacks?.forEach((callback) {
callback(value);
});
}
// Sets/Adds the new callback to the given data stream.
void setCallback(String key, Function(Object) callback) {
if (callback != null) {
// Retrieve existing data item from the map.
_DataItem item = _mDataItemsMap[key];
item ??= _DataItem();
// Retrieve callback functions from data item.
List<Function(Object)> callbacks = item.callbacks;
// Check if callback functions exists or not.
if (callbacks == null) {
// If it's null then create new List.
callbacks = List();
// Set callback functions list to data item.
item.callbacks = callbacks;
// Set the data item to the map.
_mDataItemsMap[key] = item;
}
// Add the given callback into List of callback functions.
callbacks.add(callback);
// Dispatch value to the callback function if value already exists.
if (item.value != null) {
callback(item.value);
}
}
}
// Returns current value of the data stream.
Object getValue(String key) {
return _mDataItemsMap[key].value;
}
// Returns singleton instance of _DataStore
static _DataStore getInstance() {
_instance ??= _DataStore();
return _instance;
}
}
// Data class to hold value and callback functions of a data stream.
class _DataItem {
var value;
List<Function(Object)> callbacks;
}
创建这个类之后,您可以初始化并访问流。例如,在StateFulWidget 1和StateFulWidget 2中都需要执行此操作。
ContinuousStream continuousStream = new ContinuousStream();
然后从StateFulWidget1开始:
void send() {
String message = "Hello";
continuousStream.emit("chat-message", message);
}
这对应于您的广播事件。
来自StatefulWidget2:
continuousStream.on("chat-message", (message) {
print("Message Received: $message");
});
这对应于您的订阅事件。 这应该解决您的问题。