Create preference controller for each tethering option

These controllers are responsible for persisting preference values and
managing the visibility and switch state. TetherEnabler will be
listening to changes of shared prefernce values and turn on/off
corresponding type of tethering when tethering is on at that time.

Bug: 146582865
Test: tests are created for each controller class.
Change-Id: I7e601b2bd693da59269517d2988bade7475e7f12

src/com/android/settings/network/UsbTetherPreferenceController.java

@@ -0,0 +1,144 @@
+/*
+ * Copyright (C) 2019 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.network;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.content.SharedPreferences;
+import android.hardware.usb.UsbManager;
+import android.net.ConnectivityManager;
+import android.os.Environment;
+import android.text.TextUtils;
+import android.util.Log;
+
+import androidx.lifecycle.Lifecycle;
+import androidx.lifecycle.LifecycleObserver;
+import androidx.lifecycle.OnLifecycleEvent;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceScreen;
+import androidx.preference.SwitchPreference;
+
+import com.android.internal.annotations.VisibleForTesting;
+import com.android.settings.Utils;
+import com.android.settingslib.core.AbstractPreferenceController;
+
+/**
+ * This controller helps to manage the switch state and visibility of USB tether switch
+ * preference. It stores preference values when preference changed.
+ * TODO(b/147272749): Extend BasePreferenceController.java instead.
+ *
+ */
+public final class UsbTetherPreferenceController extends AbstractPreferenceController implements
+        LifecycleObserver, Preference.OnPreferenceChangeListener {
+
+    private static final String TAG = "UsbTetherPrefController";
+    private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
+    @VisibleForTesting
+    static final String PREF_KEY = "enable_usb_tethering";
+
+    private final ConnectivityManager mCm;
+    private boolean mUsbConnected;
+    private boolean mMassStorageActive;
+    private Preference mPreference;
+    private final SharedPreferences mSharedPreferences;
+
+    public UsbTetherPreferenceController(Context context, Lifecycle lifecycle) {
+        super(context);
+        mCm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
+        mSharedPreferences =
+                context.getSharedPreferences(TetherEnabler.SHARED_PREF, Context.MODE_PRIVATE);
+        if (lifecycle != null) {
+            lifecycle.addObserver(this);
+        }
+    }
+
+    @OnLifecycleEvent(Lifecycle.Event.ON_START)
+    public void onStart() {
+        mMassStorageActive = Environment.MEDIA_SHARED.equals(Environment.getExternalStorageState());
+        IntentFilter filter = new IntentFilter(UsbManager.ACTION_USB_STATE);
+        filter.addAction(Intent.ACTION_MEDIA_SHARED);
+        filter.addAction(Intent.ACTION_MEDIA_UNSHARED);
+        mContext.registerReceiver(mUsbChangeReceiver, filter);
+    }
+
+    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
+    public void onStop() {
+        mContext.unregisterReceiver(mUsbChangeReceiver);
+    }
+
+    @Override
+    public boolean isAvailable() {
+        String[] usbRegexs = mCm.getTetherableUsbRegexs();
+        return usbRegexs != null && usbRegexs.length > 0 && !Utils.isMonkeyRunning();
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return PREF_KEY;
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+        mPreference = screen.findPreference(PREF_KEY);
+        if (mPreference != null && mPreference instanceof SwitchPreference) {
+            ((SwitchPreference) mPreference)
+                    .setChecked(mSharedPreferences.getBoolean(PREF_KEY, false));
+        }
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        super.updateState(preference);
+        if (preference != null) {
+            if (mUsbConnected && !mMassStorageActive) {
+                preference.setEnabled(true);
+            } else {
+                preference.setEnabled(false);
+            }
+        }
+    }
+
+    @VisibleForTesting
+    final BroadcastReceiver mUsbChangeReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            String action = intent.getAction();
+            if (TextUtils.equals(Intent.ACTION_MEDIA_SHARED, action)) {
+                mMassStorageActive = true;
+            } else if (TextUtils.equals(Intent.ACTION_MEDIA_UNSHARED, action)) {
+                mMassStorageActive = false;
+            } else if (TextUtils.equals(UsbManager.ACTION_USB_STATE, action)) {
+                mUsbConnected = intent.getBooleanExtra(UsbManager.USB_CONNECTED, false);
+            }
+            updateState(mPreference);
+        }
+    };
+
+    @Override
+    public boolean onPreferenceChange(Preference preference, Object o) {
+        if (DEBUG) {
+            Log.d(TAG, "preference changing to " + o);
+        }
+        final SharedPreferences.Editor editor = mSharedPreferences.edit();
+        editor.putBoolean(PREF_KEY, (Boolean) o);
+        editor.apply();
+        return true;
+    }
+}