Fix ADB bug where app interception wouldn't start from background

Only relevant when the app was already installed, and had been running,
but had been disconnected for a while. App moved into background, and
wasn't allowed to start the VPN, so just opened instead. Worked after
2nd usage, but it's much nicer if it works OOTB.

Author: pimterry

src/interceptors/android/adb-commands.ts

@@ -177,3 +177,12 @@ export async function injectSystemCertificate(
     await run(adbClient, deviceId, rootCmd.concat('sh', injectionScriptPath));
 }
 
+export function bringToFront(
+    adbClient: adb.AdbClient,
+    deviceId: string,
+    activityName: string // Of the form: com.package/com.package.YourActivity
+) {
+    return adbClient.shell(deviceId, [
+        "am", "start", "--activity-single-top", activityName
+    ]);
+}

src/interceptors/android/android-adb-interceptor.ts

@@ -16,7 +16,8 @@ import {
     pushFile,
     injectSystemCertificate,
     stringAsStream,
-    hasCertInstalled
+    hasCertInstalled,
+    bringToFront
 } from './adb-commands';
 import { streamLatestApk } from './fetch-apk';
 
@@ -82,6 +83,14 @@ export class AndroidAdbInterceptor implements Interceptor {
             console.log("App installed successfully");
         }
 
+        // Now that the app is installed, bring it to the front (avoids issues with starting a
+        // service for the VPN when in the foreground).
+        await bringToFront(
+            this.adbClient,
+            options.deviceId,
+            'tech.httptoolkit.android.v1/tech.httptoolkit.android.MainActivity'
+        ).catch(reportError); // Not that important, so we continue if this fails somehow
+
         // Build a trigger URL to activate the proxy on the device:
         const setupParams = {
             addresses: [