1.亮屏情况下,在Wifi settings界面,固定扫描,扫描时间为10s。
2.亮屏情况下,在非Wifi settings界面,二进制指数退避扫描,退避:interval*(2^n), 最小间隔min=20s, 最大间隔max=160s.
3.灭屏情况下,有保存网络时,若已连接,不扫描,否则,PNO扫描,即只扫描已保存的网络。最小间隔min=20s,最大间隔max=20s*3=60s。
4.无保存网络情况下,固定扫描,间隔为5分钟,用于通知用户周围存在可用开放网络。
1.亮屏情况下,在Wifi settings界面,固定扫描,扫描时间为10s。
从 wifi扫描流程梳理 可以看到wifi扫描流程会走到WifiTracker的handleMessage函数中,我们看sendEmptyMessageDelayed,会发送一条扫描的信息,其中包含了WIFI_RESCAN_INTERVAL_MS,WIFI_RESCAN_INTERVAL_MS就是默认的扫描周期,可以看到系统设置的默认周期是10 * 1000,也就是10秒。
public void handleMessage(Message message) {
if (message.what != MSG_SCAN) return;
if (mWifiManager.startScan()) {
mRetry = 0;
} else if (++mRetry >= 3) {
mRetry = 0;
if (mContext != null) {
Toast.makeText(mContext, R.string.wifi_fail_to_scan, Toast.LENGTH_LONG).show();
}
return;
}
sendEmptyMessageDelayed(MSG_SCAN, WIFI_RESCAN_INTERVAL_MS);
}
2.亮屏情况下,在非Wifi settings界面,二进制指数退避扫描,退避:interval*(2^n), 最小间隔min=20s, 最大间隔max=160s.
startConnectivityScan –> startPeriodicScan –> startPeriodicSingleScan
private void startConnectivityScan(boolean scanImmediately) {
// Always stop outstanding connecivity scan if there is any
stopConnectivityScan();
if (mWifiState != WIFI_STATE_CONNECTED && mWifiState != WIFI_STATE_DISCONNECTED) {
return;
}
if (mScreenOn) {
startPeriodicScan(scanImmediately);
} else {
if (mWifiState == WIFI_STATE_DISCONNECTED && !mPnoScanStarted) {
startDisconnectedPnoScan();
}
}
}
private void startPeriodicScan(boolean scanImmediately) {
mPnoScanListener.resetLowRssiNetworkRetryDelay();
if (scanImmediately) {
resetLastPeriodicSingleScanTimeStamp();
}
mPeriodicSingleScanInterval = PERIODIC_SCAN_INTERVAL_MS;
startPeriodicSingleScan();
}
// Start a single scan and set up the interval for next single scan.
private void startPeriodicSingleScan() {
long currentTimeStamp = mClock.getElapsedSinceBootMillis();
if (mLastPeriodicSingleScanTimeStamp != RESET_TIME_STAMP) {
long msSinceLastScan = currentTimeStamp - mLastPeriodicSingleScanTimeStamp;
if (msSinceLastScan < PERIODIC_SCAN_INTERVAL_MS) {
localLog("Last periodic single scan started " + msSinceLastScan
+ "ms ago, defer this new scan request.");
schedulePeriodicScanTimer(PERIODIC_SCAN_INTERVAL_MS - (int) msSinceLastScan);
return;
}
...............
if (isScanNeeded) {
mLastPeriodicSingleScanTimeStamp = currentTimeStamp;
startSingleScan(isFullBandScan, WIFI_WORK_SOURCE);
schedulePeriodicScanTimer(mPeriodicSingleScanInterval);
// Set up the next scan interval in an exponential backoff fashion.
mPeriodicSingleScanInterval *= 2;
if (mPeriodicSingleScanInterval > MAX_PERIODIC_SCAN_INTERVAL_MS) {
mPeriodicSingleScanInterval = MAX_PERIODIC_SCAN_INTERVAL_MS;
}
} else {
// Since we already skipped this scan, keep the same scan interval for next scan.
schedulePeriodicScanTimer(mPeriodicSingleScanInterval);
}
}
对于扫描间隔的设置
// Periodic scan interval in milli-seconds. This is the scan
// performed when screen is on.
public static final int PERIODIC_SCAN_INTERVAL_MS = 20 * 1000; // 20 seconds
// When screen is on and WiFi traffic is heavy, exponential backoff
// connectivity scans are scheduled. This constant defines the maximum
// scan interval in this scenario.
@VisibleForTesting
public static final int MAX_PERIODIC_SCAN_INTERVAL_MS = 160 * 1000; // 160 seconds
3.灭屏情况下,有保存网络时,若已连接,不扫描,否则,PNO扫描,即只扫描已保存的网络。最小间隔min=20s,最大间隔max=20s*3=60s。
待续
4.无保存网络情况下,固定扫描,间隔为5分钟,用于通知用户周围存在可用开放网络。
(注:第四种情况属于Android O的逻辑,因为在P的代码里还没有找到关于这个扫描的代码,也可能取消了)
class DisconnectedState extends State {
@Override
public void enter() {
Log.i(TAG, "disconnectedstate enter");
// We dont scan frequently if this is a temporary disconnect
// due to p2p
if (mTemporarilyDisconnectWifi) {
p2pSendMessage(WifiP2pServiceImpl.DISCONNECT_WIFI_RESPONSE);
return;
}
/** clear the roaming state, if we were roaming, we failed */
mIsAutoRoaming = false;
mWifiConnectivityManager.handleConnectionStateChanged(
WifiConnectivityManager.WIFI_STATE_DISCONNECTED);
/**
* If we have no networks saved, the supplicant stops doing the periodic scan.
* The scans are useful to notify the user of the presence of an open network.
* Note that these are not wake up scans.
*/
if (mNoNetworksPeriodicScan != 0 && !mP2pConnected.get()
&& mWifiConfigManager.getSavedNetworks().size() == 0) {
sendMessageDelayed(obtainMessage(CMD_NO_NETWORKS_PERIODIC_SCAN,
++mPeriodicScanToken, 0), mNoNetworksPeriodicScan);
}
mDisconnectedTimeStamp = mClock.getWallClockMillis();
mWifiStateTracker.updateState(WifiStateTracker.DISCONNECTED);
}
mNoNetworksPeriodicScan = mContext.getResources().getInteger(
R.integer.config_wifi_no_network_periodic_scan_interval);
/frameworks/base/core/res/res/values/config.xml
mNoNetworksPeriodicScan在config.xml中注册,周期为5分钟。
<!-- Integer indicating the framework no networks periodic scan interval in milliseconds. -->
<integer translatable="false" name="config_wifi_no_network_periodic_scan_interval">300000</integer>
原文地址:https://blog.csdn.net/sdkdlwk/article/details/134759654
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