android P 锁屏初探 ——2 开机显示锁屏界面的流程

第一次做流程图，做的不太规范，见谅，见谅。

具体的流程介绍，可以参看这篇文章。 Android8.1 SystemUI Keyguard之启动流程

有一点需要补充一下，系统首次开机是不显示锁屏界面的。
原因应该是下面部分：（KeyguardViewMediator.java）
中文是我自己的备注，结合源码的英文备注，应该没错。 =)

    private void handleSystemReady() {
        synchronized (this) {
            if (DEBUG) Log.d(TAG, "onSystemReady");
            mSystemReady = true;
            doKeyguardLocked(null);
            mUpdateMonitor.registerCallback(mUpdateCallback);
        }
        // Most services aren't available until the system reaches the ready state, so we
        // send it here when the device first boots.
        //第一次开机，跳过锁屏
        maybeSendUserPresentBroadcast();
    }

    private void maybeSendUserPresentBroadcast() {
        if (mSystemReady && mLockPatternUtils.isLockScreenDisabled(
                KeyguardUpdateMonitor.getCurrentUser())) {
            // Lock screen is disabled because the user has set the preference to "None".
            // In this case, send out ACTION_USER_PRESENT here instead of in
            // handleKeyguardDone()
            sendUserPresentBroadcast();
        } else if (mSystemReady && shouldWaitForProvisioning()) {
            //这里跳过了锁屏
            // Skipping the lockscreen because we're not yet provisioned, but we still need to
            // notify the StrongAuthTracker that it's now safe to run trust agents, in case the
            // user sets a credential later.
            getLockPatternUtils().userPresent(KeyguardUpdateMonitor.getCurrentUser());
        }
    }

/**
     * Enable the keyguard if the settings are appropriate.
     */
    private void doKeyguardLocked(Bundle options) {
        if (KeyguardUpdateMonitor.CORE_APPS_ONLY) {
            // Don't show keyguard during half-booted cryptkeeper stage.
            if (DEBUG) Log.d(TAG, "doKeyguard: not showing because booting to cryptkeeper");
            return;
        }

        // if another app is disabling us, don't show
        if (!mExternallyEnabled) {
            if (DEBUG) Log.d(TAG, "doKeyguard: not showing because externally disabled");

            // note: we *should* set mNeedToReshowWhenReenabled=true here, but that makes
            // for an occasional ugly flicker in this situation:
            // 1) receive a call with the screen on (no keyguard) or make a call
            // 2) screen times out
            // 3) user hits key to turn screen back on
            // instead, we reenable the keyguard when we know the screen is off and the call
            // ends (see the broadcast receiver below)
            // TODO: clean this up when we have better support at the window manager level
            // for apps that wish to be on top of the keyguard
            return;
        }

        // if the keyguard is already showing, don't bother
        if (mStatusBarKeyguardViewManager.isShowing()) {
            if (DEBUG) Log.d(TAG, "doKeyguard: not showing because it is already showing");
            resetStateLocked();
            return;
        }

        // In split system user mode, we never unlock system user.
        if (!mustNotUnlockCurrentUser()
                || !mUpdateMonitor.isDeviceProvisioned()) {

            // if the setup wizard hasn't run yet, don't show
            final boolean requireSim = !SystemProperties.getBoolean("keyguard.no_require_sim", false);
            final boolean absent = SubscriptionManager.isValidSubscriptionId(
                    mUpdateMonitor.getNextSubIdForState(ABSENT));
            final boolean disabled = SubscriptionManager.isValidSubscriptionId(
                    mUpdateMonitor.getNextSubIdForState(IccCardConstants.State.PERM_DISABLED));
            final boolean lockedOrMissing = mUpdateMonitor.isSimPinSecure()
                    || ((absent || disabled) && requireSim);

            if (!lockedOrMissing && shouldWaitForProvisioning()) {
                //开机向导还没有运行，设备还没有配置好且sim卡也没有上锁或者没有sim卡。
                if (DEBUG) Log.d(TAG, "doKeyguard: not showing because device isn't provisioned"
                        + " and the sim is not locked or missing");
                return;
            }

            boolean forceShow = options != null && options.getBoolean(OPTION_FORCE_SHOW, false);
            if (mLockPatternUtils.isLockScreenDisabled(KeyguardUpdateMonitor.getCurrentUser())
                    && !lockedOrMissing && !forceShow) {
                //用户关闭了锁屏功能
                if (DEBUG) Log.d(TAG, "doKeyguard: not showing because lockscreen is off");
                return;
            }

            if (mLockPatternUtils.checkVoldPassword(KeyguardUpdateMonitor.getCurrentUser())) {
                //Vold 相关的。外部设备加密解密相关
                if (DEBUG) Log.d(TAG, "Not showing lock screen since just decrypted");
                // Without this, settings is not enabled until the lock screen first appears
                setShowingLocked(false, mAodShowing);
                hideLocked();
                return;
            }
        }

        if (DEBUG) Log.d(TAG, "doKeyguard: showing the lock screen");
        showLocked(options);
    }