Improve scrim handling

Bug: 15163546
Change-Id: I0d2c05b035f832f4b4e6a2fc34113fe9d5677525
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/phone/UnlockMethodCache.java b/packages/SystemUI/src/com/android/systemui/statusbar/phone/UnlockMethodCache.java
new file mode 100644
index 0000000..bfd657b
--- /dev/null
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/phone/UnlockMethodCache.java
@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+package com.android.systemui.statusbar.phone;
+
+import android.content.Context;
+
+import com.android.internal.widget.LockPatternUtils;
+import com.android.keyguard.KeyguardUpdateMonitor;
+import com.android.keyguard.KeyguardUpdateMonitorCallback;
+
+import java.util.ArrayList;
+
+/**
+ * Caches whether the current unlock method is insecure, taking trust into account. This information
+ * might be a little bit out of date and should not be used for actual security decisions; it should
+ * be only used for visual indications.
+ */
+public class UnlockMethodCache {
+
+    private static UnlockMethodCache sInstance;
+
+    private final LockPatternUtils mLockPatternUtils;
+    private final KeyguardUpdateMonitor mKeyguardUpdateMonitor;
+    private final ArrayList<OnUnlockMethodChangedListener> mListeners = new ArrayList<>();
+    private boolean mMethodInsecure;
+
+    private UnlockMethodCache(Context ctx) {
+        mLockPatternUtils = new LockPatternUtils(ctx);
+        mKeyguardUpdateMonitor = KeyguardUpdateMonitor.getInstance(ctx);
+        KeyguardUpdateMonitor.getInstance(ctx).registerCallback(mCallback);
+        updateMethodSecure(true /* updateAlways */);
+    }
+
+    public static UnlockMethodCache getInstance(Context context) {
+        if (sInstance == null) {
+            sInstance = new UnlockMethodCache(context);
+        }
+        return sInstance;
+    }
+
+    /**
+     * @return whether the current security method is secure, i. e. the bouncer will be shown
+     */
+    public boolean isMethodInsecure() {
+        return mMethodInsecure;
+    }
+
+    public void addListener(OnUnlockMethodChangedListener listener) {
+        mListeners.add(listener);
+    }
+
+    public void removeListener(OnUnlockMethodChangedListener listener) {
+        mListeners.remove(listener);
+    }
+
+    private void updateMethodSecure(boolean updateAlways) {
+        int user = mLockPatternUtils.getCurrentUser();
+        boolean methodInsecure = !mLockPatternUtils.isSecure() ||
+                mKeyguardUpdateMonitor.getUserHasTrust(user);
+        boolean changed = methodInsecure != mMethodInsecure;
+        if (changed || updateAlways) {
+            mMethodInsecure = methodInsecure;
+            notifyListeners(mMethodInsecure);
+        }
+    }
+
+    private void notifyListeners(boolean secure) {
+        for (OnUnlockMethodChangedListener listener : mListeners) {
+            listener.onMethodSecureChanged(secure);
+        }
+    }
+
+    private final KeyguardUpdateMonitorCallback mCallback = new KeyguardUpdateMonitorCallback() {
+        @Override
+        public void onUserSwitchComplete(int userId) {
+            updateMethodSecure(false /* updateAlways */);
+        }
+
+        @Override
+        public void onTrustChanged(int userId) {
+            updateMethodSecure(false /* updateAlways */);
+        }
+
+        @Override
+        public void onScreenTurnedOn() {
+            updateMethodSecure(false /* updateAlways */);
+        }
+    };
+
+    public static interface OnUnlockMethodChangedListener {
+        void onMethodSecureChanged(boolean methodSecure);
+    }
+}