Fix issue where pin field doesn't have focus (issue 7348937)

Change-Id: Ia926765271251248701416c001e2e73131cdf4ad

Author: Adam Cohen

policy/src/com/android/internal/policy/impl/keyguard/KeyguardPasswordView.java

@@ -86,6 +86,13 @@ public void setLockPatternUtils(LockPatternUtils utils) {
         mLockPatternUtils = utils;
     }
 
+    @Override
+    public void onWindowFocusChanged(boolean hasWindowFocus) {
+        if (hasWindowFocus) {
+            reset();
+        }
+    }
+
     public void reset() {
         // start fresh
         mPasswordEntry.setText("");
@@ -191,7 +198,9 @@ public void beforeTextChanged(CharSequence s, int start, int count, int after) {
             }
 
             public void afterTextChanged(Editable s) {
-                mCallback.userActivity(0);
+                if (mCallback != null) {
+                    mCallback.userActivity(0);
+                }
             }
         });