demo fix

App.tsx

@@ -67,6 +67,12 @@ export default class App extends Component<AppProps, WalletmanAppState> {
     async componentDidMount() {
         await this.setupPermissions();
 
+        this.echoSub = onProxyMessage((msg) => {
+            if (msg.type === 'echo') {
+                Alert.alert('Echo 回来了', JSON.stringify(msg.data));
+            }
+        });
+
         // Login with auto-retry every 3s until success (setTimeout, non-blocking)
         const doLogin = () => {
             Api.instance.login('test123', '123456')
@@ -93,13 +99,6 @@ export default class App extends Component<AppProps, WalletmanAppState> {
 
     sendEcho = () => {
         const text = `hello_${Date.now()}`;
-        this.echoSub?.remove();
-        this.echoSub = onProxyMessage((msg) => {
-            if (msg.type === 'echo') {
-                Alert.alert('Echo 回来了', JSON.stringify(msg.data));
-                this.echoSub?.remove();
-            }
-        });
         proxySendMessage({ type: 'echo', messageId: `echo_${Date.now()}`, data: { text } });
     };