WifiManager.setWifiEnabled() return 究竟是什么？

Question

你们中有人有 return 值 setWifiEnabled() 的经验吗？

文档不清楚，它说：

Returns true if the operation succeeds (or if the existing state is the same as the requested state).

运行失败怎么办？它会抛出异常还是 return false?

是否可以这样做：

if (!WifiManager.setWifiEnabled(true)) {
    Log.i(LOG_TAG, "Wifi switch failed.");
} else {
    Log.i(LOG_TAG, "Wifi switch succeeded.")
}

非常感谢。

Answer 1

查看 WifiService#setWifiEnabled(boolean) 的实现：

    /**
     * see {@link android.net.wifi.WifiManager#setWifiEnabled(boolean)}
     * @param enable {@code true} to enable, {@code false} to disable.
     * @return {@code true} if the enable/disable operation was
     *         started or is already in the queue.
     */
    public synchronized boolean setWifiEnabled(boolean enable) {
        enforceChangePermission();
        Slog.d(TAG, "setWifiEnabled: " + enable + " pid=" + Binder.getCallingPid()
                    + ", uid=" + Binder.getCallingUid());
        if (DBG) {
            Slog.e(TAG, "Invoking mWifiStateMachine.setWifiEnabled\n");
        }
        if (enable) {
            reportStartWorkSource();
        }
        mWifiStateMachine.setWifiEnabled(enable);
        /*
         * Caller might not have WRITE_SECURE_SETTINGS,
         * only CHANGE_WIFI_STATE is enforced
         */
        long ident = Binder.clearCallingIdentity();
        try {
            handleWifiToggled(enable);
        } finally {
            Binder.restoreCallingIdentity(ident);
        }
        if (enable) {
            if (!mIsReceiverRegistered) {
                registerForBroadcasts();
                mIsReceiverRegistered = true;
            }
        } else if (mIsReceiverRegistered) {
            mContext.unregisterReceiver(mReceiver);
            mIsReceiverRegistered = false;
        }
        return true;
    }

所以，它永远不会 returns false。如果由于某种原因所需的操作无法成功，则会抛出异常，请参阅 WifiManager.setWifiEnabled(boolean):

    /**
     * Enable or disable Wi-Fi.
     * @param enabled {@code true} to enable, {@code false} to disable.
     * @return {@code true} if the operation succeeds (or if the existing state
     *         is the same as the requested state).
     */
    public boolean setWifiEnabled(boolean enabled) {
        try {
            return mService.setWifiEnabled(enabled);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

Answer 2

已接受的答案已过时（来源来自 android 4.2，其中当前 android 现在是 10，11 很快就会出来）。这个方法可以return false。 WifiServiceImpl.java is the current source for handling WifiManager#setWifiEnabled(boolean):

代码：

 /**
 * see {@link android.net.wifi.WifiManager#setWifiEnabled(boolean)}
 * @param enable {@code true} to enable, {@code false} to disable.
 * @return {@code true} if the enable/disable operation was
 *         started or is already in the queue.
 */
@Override
public synchronized boolean setWifiEnabled(String packageName, boolean enable) {
    if (enforceChangePermission(packageName) != MODE_ALLOWED) {
        return false;
    }
    boolean isPrivileged = isPrivileged(Binder.getCallingPid(), Binder.getCallingUid());
    if (!isPrivileged && !isDeviceOrProfileOwner(Binder.getCallingUid())
            && !mWifiPermissionsUtil.isTargetSdkLessThan(packageName, Build.VERSION_CODES.Q,
              Binder.getCallingUid())
            && !isSystem(packageName, Binder.getCallingUid())) {
        mLog.info("setWifiEnabled not allowed for uid=%")
                .c(Binder.getCallingUid()).flush();
        return false;
    }
    // If Airplane mode is enabled, only privileged apps are allowed to toggle Wifi
    if (mSettingsStore.isAirplaneModeOn() && !isPrivileged) {
        mLog.err("setWifiEnabled in Airplane mode: only Settings can toggle wifi").flush();
        return false;
    }
    // If SoftAp is enabled, only privileged apps are allowed to toggle wifi
    boolean apEnabled = mWifiApState == WifiManager.WIFI_AP_STATE_ENABLED;
    if (apEnabled && !isPrivileged) {
        mLog.err("setWifiEnabled SoftAp enabled: only Settings can toggle wifi").flush();
        return false;
    }
    // If we're in crypt debounce, ignore any wifi state change APIs.
    if (mFrameworkFacade.inStorageManagerCryptKeeperBounce()) {
        return false;
    }
    mLog.info("setWifiEnabled package=% uid=% enable=%").c(packageName)
            .c(Binder.getCallingUid()).c(enable).flush();
    long ident = Binder.clearCallingIdentity();
    try {
        if (!mSettingsStore.handleWifiToggled(enable)) {
            // Nothing to do if wifi cannot be toggled
            return true;
        }
    } finally {
        Binder.restoreCallingIdentity(ident);
    }
    mWifiMetrics.incrementNumWifiToggles(isPrivileged, enable);
    mWifiController.sendMessage(CMD_WIFI_TOGGLED);
    return true;
}

WifiManager.setWifiEnabled() return 究竟是什么？

What exactly does WifiManager.setWifiEnabled() return?

java

android

wifi

wifimanager

android-wifi