Channel settings updates

- Update master switch preference to store enabled state in case
it's set before the view holder is bound
- Update master switch preference to prevent disabled switches
from being toggled
- Show an importance summary for max importance
- properly handle null notification sounds

Change-Id: I395b95b76d2a3c1c94b41d1c2720bb0cf1cae917
Fixes: 36920159
Fixes: 37421928
Fixes: 36939825
Test: RunSettingsRoboTests & manual

src/com/android/settings/widget/MasterSwitchPreference.java

@@ -36,6 +36,7 @@ public class MasterSwitchPreference extends TwoTargetPreference {
 
     private Switch mSwitch;
     private boolean mChecked;
+    private boolean mEnableSwitch = true;
 
     public MasterSwitchPreference(Context context, AttributeSet attrs,
             int defStyleAttr, int defStyleRes) {
@@ -67,6 +68,9 @@ public class MasterSwitchPreference extends TwoTargetPreference {
             widgetView.setOnClickListener(new OnClickListener() {
                 @Override
                 public void onClick(View v) {
+                    if (mSwitch != null && !mSwitch.isEnabled()) {
+                        return;
+                    }
                     setChecked(!mChecked);
                     if (!callChangeListener(mChecked)) {
                         setChecked(!mChecked);
@@ -76,9 +80,11 @@ public class MasterSwitchPreference extends TwoTargetPreference {
                 }
             });
         }
+
         mSwitch = (Switch) holder.findViewById(R.id.switchWidget);
         if (mSwitch != null) {
             mSwitch.setChecked(mChecked);
+            mSwitch.setEnabled(mEnableSwitch);
         }
     }
 
@@ -94,6 +100,7 @@ public class MasterSwitchPreference extends TwoTargetPreference {
     }
 
     public void setSwitchEnabled(boolean enabled) {
+        mEnableSwitch = enabled;
         if (mSwitch != null) {
             mSwitch.setEnabled(enabled);
         }