What's the meaning of new @SystemApi annotation, any difference from @hide?

Question

Android introduced @SystemApi in its SDK source code recently. Seems like same in effect as the @hide annotation before, since they also got stripped from SDK jar classes.

Answer 1

@SystemApi, @PrivateApi and @hide

According to this commit, @SystemApi is a rename of the old @PrivateApi. APIs marked @hide are not necessarily @SystemApi, but @SystemApi requires @hide.

For more information about @hide javadoc annotation, this post gives a good answer.

Based on my own experiments, one (non-system application) can still access @hide APIs and fields using Java reflection like (from this post):

WifiManager manager = (WifiManager) getSystemService(Context.WIFI_SERVICE);

WifiConfiguration config = new WifiConfiguration();
config.SSID = "AccessPointSSID";

Method method = manager.getClass().getMethod("setWifiApEnabled", WifiConfiguration.class, boolean.class);
method.invoke(manager, config, true);

But trying to access @SystemApi things using Java reflection is impossible (following code will trigger invocationTargetException):

WifiManager manager = (WifiManager) getSystemService(Context.WIFI_SERVICE);

Method method = manager.getClass().getMethod("getPrivilegedConfiguredNetworks");
List configs = (List)method.invoke(manager);

P.S.

In the WifiManager java code, the setWifiApEnabled and getPrivilegedConfiguredNetworks APIs are defined as:

/**
 * Start AccessPoint mode with the specified
 * configuration. If the radio is already running in
 * AP mode, update the new configuration
 * Note that starting in access point mode disables station
 * mode operation
 * @param wifiConfig SSID, security and channel details as
 *        part of WifiConfiguration
 * @return {@code true} if the operation succeeds, {@code false} otherwise
 *
 * @hide Dont open up yet
 */
public boolean setWifiApEnabled(WifiConfiguration wifiConfig, boolean enabled) {
    try {
        mService.setWifiApEnabled(wifiConfig, enabled);
        return true;
    } catch (RemoteException e) {
        return false;
    }
}

and

/** @hide */
@SystemApi
public List getPrivilegedConfiguredNetworks() {
    try {
        return mService.getPrivilegedConfiguredNetworks();
    } catch (RemoteException e) {
        return null;
    }
}