Refine battery reading

src/InfoScreen.tsx

@@ -218,9 +218,13 @@ export default function InfoScreen({ route, navigation }: Props) {
   };
 
   const readBatteryCharacteristic = async () => {
-    let lastValidBattery: number | null = null;
+    const validSamples: number[] = [];
 
-    for (let attempt = 0; attempt < 4; attempt += 1) {
+    // Some devices briefly report a default battery value right after the first
+    // connection. Read a few samples and prefer the later stable value.
+    await sleep(250);
+
+    for (let attempt = 0; attempt < 5; attempt += 1) {
       try {
         const bytes = await readCharacteristicWithRetry("180f", "2a19", 1);
         const batteryValue = bytes[0];
@@ -230,22 +234,36 @@ export default function InfoScreen({ route, navigation }: Props) {
           batteryValue >= 0 &&
           batteryValue <= 100
         ) {
-          if (lastValidBattery !== null && lastValidBattery === batteryValue) {
-            return `${batteryValue}%`;
-          }
-
-          lastValidBattery = batteryValue;
+          validSamples.push(batteryValue);
+          console.log(
+            `🔋 battery sample ${attempt + 1}: ${batteryValue}%`
+          );
         }
       } catch {
         // Continue retrying with a short gap below.
       }
 
-      if (attempt < 3) {
-        await sleep(220);
+      if (attempt < 4) {
+        await sleep(260);
       }
     }
 
-    return lastValidBattery !== null ? `${lastValidBattery}%` : "未知";
+    if (validSamples.length === 0) {
+      return "未知";
+    }
+
+    const lastSample = validSamples[validSamples.length - 1];
+    const previousSample = validSamples[validSamples.length - 2];
+
+    if (previousSample !== undefined && previousSample === lastSample) {
+      return `${lastSample}%`;
+    }
+
+    const lastNonHundredSample = [...validSamples]
+      .reverse()
+      .find((value) => value !== 100);
+
+    return `${lastNonHundredSample ?? lastSample}%`;
   };
 
   const subscribePowerDataIfNeeded = async () => {
@@ -1108,4 +1126,4 @@ const styles = StyleSheet.create({
 
 
 
-});
+});