Implement receiver flow of WiFi sharing feature

1.Add a button to launch QR code scanner when add a network.
2.Scan button added in AddNetworkFragment / WifiDialog / WifiSettings.

Bug: 120630683
Test: make RunSettingsRoboTests
Change-Id: I340bfa2247e092f586dd90dfea37c355e681ffee

src/com/android/settings/wifi/ButtonPreference.java

@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2018 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.settings.wifi;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.graphics.drawable.Drawable;
+import android.util.AttributeSet;
+import android.util.Log;
+import android.view.View;
+import android.widget.ImageButton;
+
+import com.android.settings.R;
+
+import androidx.annotation.VisibleForTesting;
+import androidx.annotation.DrawableRes;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceViewHolder;
+
+/**
+ * This preference provides one button layout with Settings style.
+ * It looks like below
+ *
+ * --------------------------------------------------------------
+ * | icon | title                                    |  button  |
+ * --------------------------------------------------------------
+ *
+ * User can set icon / click listener for button.
+ * By default, the button is invisible.
+ */
+public class ButtonPreference extends Preference {
+
+    private static final String TAG = "ButtonPreference";
+
+    private ImageButton mImageButton;
+    private Drawable mButtonIcon;
+    private View.OnClickListener mClickListener;
+
+    // Used for dummy pref.
+    public ButtonPreference(Context context, AttributeSet attrs) {
+        super(context, attrs);
+        setWidgetLayoutResource(R.layout.wifi_button_preference_widget);
+        mImageButton = null;
+        mButtonIcon = null;
+        mClickListener = null;
+    }
+
+    public ButtonPreference(Context context) {
+        this(context, /* attrs */ null);
+    }
+
+    @Override
+    public void onBindViewHolder(final PreferenceViewHolder view) {
+        super.onBindViewHolder(view);
+        initButton(view);
+    }
+
+    @Override
+    public void setOrder(int order) {
+        super.setOrder(order);
+        setButtonVisibility();
+    }
+
+    @VisibleForTesting
+    protected void initButton(final PreferenceViewHolder view) {
+        if (mImageButton == null) {
+            mImageButton = (ImageButton) view.findViewById(R.id.button_icon);
+        }
+        if (mImageButton != null) {
+            mImageButton.setImageDrawable(mButtonIcon);
+            mImageButton.setOnClickListener(mClickListener);
+        }
+        setButtonVisibility();
+    }
+
+    private void setButtonVisibility() {
+        if(mImageButton != null) {
+            mImageButton.setVisibility(mButtonIcon == null ? View.GONE : View.VISIBLE);
+        }
+    }
+
+    /**
+     * Sets the drawable to be displayed in button.
+     */
+    public ButtonPreference setButtonIcon(@DrawableRes int iconResId) {
+        if (iconResId == 0) {
+            return this;
+        }
+
+        try {
+            mButtonIcon = getContext().getDrawable(iconResId);
+            notifyChanged();
+        } catch (Resources.NotFoundException exception) {
+            Log.e(TAG, "Resource does not exist: " + iconResId);
+        }
+        return this;
+    }
+
+    /**
+     * Register a callback to be invoked when button is clicked.
+     */
+    public ButtonPreference setButtonOnClickListener(View.OnClickListener listener) {
+        if (listener != mClickListener) {
+            mClickListener = listener;
+            notifyChanged();
+        }
+        return this;
+    }
+}