Add ability to set onShowListener to custom dialog pref

Currently there is no way to ensure something happens when the
dialog first shows since the getter for it is best effort. This CL
makes it so that a preference can provide an onShowListener so we
can do things right when the dialog becomes available.

Test: robotests in sister CL
Bug: 73102003
Change-Id: I269c3d89dc2323f5d0163cc12208eb8df5ace6f6
diff --git a/packages/SettingsLib/src/com/android/settingslib/CustomDialogPreference.java b/packages/SettingsLib/src/com/android/settingslib/CustomDialogPreference.java
index 9554e81..95a8f1d 100644
--- a/packages/SettingsLib/src/com/android/settingslib/CustomDialogPreference.java
+++ b/packages/SettingsLib/src/com/android/settingslib/CustomDialogPreference.java
@@ -28,6 +28,7 @@
 public class CustomDialogPreference extends DialogPreference {
 
     private CustomPreferenceDialogFragment mFragment;
+    private DialogInterface.OnShowListener mOnShowListener;
 
     public CustomDialogPreference(Context context, AttributeSet attrs, int defStyleAttr,
             int defStyleRes) {
@@ -54,6 +55,10 @@
         return mFragment != null ? mFragment.getDialog() : null;
     }
 
+    public void setOnShowListener(DialogInterface.OnShowListener listner) {
+        mOnShowListener = listner;
+    }
+
     protected void onPrepareDialogBuilder(AlertDialog.Builder builder,
             DialogInterface.OnClickListener listener) {
     }
@@ -71,6 +76,10 @@
         mFragment = fragment;
     }
 
+    private DialogInterface.OnShowListener getOnShowListener() {
+        return mOnShowListener;
+    }
+
     public static class CustomPreferenceDialogFragment extends PreferenceDialogFragment {
 
         public static CustomPreferenceDialogFragment newInstance(String key) {
@@ -104,6 +113,13 @@
         }
 
         @Override
+        public Dialog onCreateDialog(Bundle savedInstanceState) {
+            final Dialog dialog = super.onCreateDialog(savedInstanceState);
+            dialog.setOnShowListener(getCustomizablePreference().getOnShowListener());
+            return dialog;
+        }
+
+        @Override
         public void onClick(DialogInterface dialog, int which) {
             super.onClick(dialog, which);
             getCustomizablePreference().onClick(dialog, which);