src/com/android/settings/display/ScreenResolutionFragment.java - LeafOS-Project/android_packages_apps_Settings - Gitiles

 /*
  * Copyright (C) 2022 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.display;

 import android.annotation.Nullable;
 import android.app.settings.SettingsEnums;
 import android.content.Context;
 import android.content.res.Resources;
 import android.graphics.Point;
 import android.graphics.drawable.Drawable;
 import android.hardware.display.DisplayManager;
 import android.provider.Settings;
 import android.text.TextUtils;
 import android.util.Log;
 import android.view.Display;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityManager;

 import androidx.annotation.VisibleForTesting;
 import androidx.preference.PreferenceScreen;

 import com.android.settings.R;
 import com.android.settings.core.instrumentation.SettingsStatsLog;
 import com.android.settings.search.BaseSearchIndexProvider;
 import com.android.settings.widget.RadioButtonPickerFragment;
 import com.android.settingslib.display.DisplayDensityUtils;
 import com.android.settingslib.search.SearchIndexable;
 import com.android.settingslib.widget.CandidateInfo;
 import com.android.settingslib.widget.FooterPreference;
 import com.android.settingslib.widget.IllustrationPreference;
 import com.android.settingslib.widget.SelectorWithWidgetPreference;

 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;

 /** Preference fragment used for switch screen resolution */
 @SearchIndexable
 public class ScreenResolutionFragment extends RadioButtonPickerFragment {
     private static final String TAG = "ScreenResolution";

     private Resources mResources;
     private static final String SCREEN_RESOLUTION = "user_selected_resolution";
     private static final String SCREEN_RESOLUTION_KEY = "screen_resolution";
     private Display mDefaultDisplay;
     private String[] mScreenResolutionOptions;
     private Set<Point> mResolutions;
     private String[] mScreenResolutionSummaries;

     private IllustrationPreference mImagePreference;
     private DisplayObserver mDisplayObserver;
     private AccessibilityManager mAccessibilityManager;

     private int mHighWidth;
     private int mFullWidth;

     @Override
     public void onAttach(Context context) {
         super.onAttach(context);

         mDefaultDisplay =
                 context.getSystemService(DisplayManager.class).getDisplay(Display.DEFAULT_DISPLAY);
         mAccessibilityManager = context.getSystemService(AccessibilityManager.class);
         mResources = context.getResources();
         mScreenResolutionOptions =
                 mResources.getStringArray(R.array.config_screen_resolution_options_strings);
         mImagePreference = new IllustrationPreference(context);
         mDisplayObserver = new DisplayObserver(context);
         ScreenResolutionController controller =
                 new ScreenResolutionController(context, SCREEN_RESOLUTION_KEY);
         mResolutions = controller.getAllSupportedResolutions();
         mHighWidth = controller.getHighWidth();
         mFullWidth = controller.getFullWidth();
         Log.i(TAG, "mHighWidth:" + mHighWidth + "mFullWidth:" + mFullWidth);
         mScreenResolutionSummaries =
                 new String[] {
                     mHighWidth + " x " + controller.getHighHeight(),
                     mFullWidth + " x " + controller.getFullHeight()
                 };
     }

     @Override
     protected int getPreferenceScreenResId() {
         return R.xml.screen_resolution_settings;
     }

     @Override
     protected void addStaticPreferences(PreferenceScreen screen) {
         updateIllustrationImage(mImagePreference);
         screen.addPreference(mImagePreference);

         final FooterPreference footerPreference = new FooterPreference(screen.getContext());
         footerPreference.setTitle(R.string.screen_resolution_footer);
         footerPreference.setSelectable(false);
         footerPreference.setLayoutResource(
                 com.android.settingslib.widget.preference.footer.R.layout.preference_footer);
         screen.addPreference(footerPreference);
     }

     @Override
     public void bindPreferenceExtra(
             SelectorWithWidgetPreference pref,
             String key,
             CandidateInfo info,
             String defaultKey,
             String systemDefaultKey) {
         final ScreenResolutionCandidateInfo candidateInfo = (ScreenResolutionCandidateInfo) info;
         final CharSequence summary = candidateInfo.loadSummary();
         if (summary != null) pref.setSummary(summary);
     }

     @Override
     protected List<? extends CandidateInfo> getCandidates() {
         final List<ScreenResolutionCandidateInfo> candidates = new ArrayList<>();

         for (int i = 0; i < mScreenResolutionOptions.length; i++) {
             candidates.add(
                     new ScreenResolutionCandidateInfo(
                             mScreenResolutionOptions[i],
                             mScreenResolutionSummaries[i],
                             mScreenResolutionOptions[i],
                             true /* enabled */));
         }

         return candidates;
     }

     /** Get prefer display mode. */
     private Display.Mode getPreferMode(int width) {
         for (Point resolution : mResolutions) {
             if (resolution.x == width) {
                 return new Display.Mode(
                         resolution.x, resolution.y, getDisplayMode().getRefreshRate());
             }
         }

         return getDisplayMode();
     }

     /** Get current display mode. */
     @VisibleForTesting
     public Display.Mode getDisplayMode() {
         return mDefaultDisplay.getMode();
     }

     /** Using display manager to set the display mode. */
     @VisibleForTesting
     public void setDisplayMode(final int width) {
         Display.Mode mode = getPreferMode(width);

         mDisplayObserver.startObserve();

         /** For store settings globally. */
         /** TODO(b/259797244): Remove this once the atom is fully populated. */
         Settings.System.putString(
                 getContext().getContentResolver(),
                 SCREEN_RESOLUTION,
                 mode.getPhysicalWidth() + "x" + mode.getPhysicalHeight());

         try {
             /** Apply the resolution change. */
             Log.i(TAG, "setUserPreferredDisplayMode: " + mode);
             mDefaultDisplay.setUserPreferredDisplayMode(mode);
         } catch (Exception e) {
             Log.e(TAG, "setUserPreferredDisplayMode() failed", e);
             return;
         }

         /** Send the atom after resolution changed successfully. */
         SettingsStatsLog.write(
                 SettingsStatsLog.USER_SELECTED_RESOLUTION,
                 mDefaultDisplay.getUniqueId().hashCode(),
                 mode.getPhysicalWidth(),
                 mode.getPhysicalHeight());
     }

     /** Get the key corresponding to the resolution. */
     @VisibleForTesting
     String getKeyForResolution(int width) {
         return width == mHighWidth
                 ? mScreenResolutionOptions[ScreenResolutionController.HIGHRESOLUTION_IDX]
                 : width == mFullWidth
                         ? mScreenResolutionOptions[ScreenResolutionController.FULLRESOLUTION_IDX]
                         : null;
     }

     /** Get the width corresponding to the resolution key. */
     int getWidthForResoluitonKey(String key) {
         return mScreenResolutionOptions[ScreenResolutionController.HIGHRESOLUTION_IDX].equals(key)
                 ? mHighWidth
                 : mScreenResolutionOptions[ScreenResolutionController.FULLRESOLUTION_IDX].equals(
                     key)
                 ? mFullWidth : -1;
     }

     @Override
     protected String getDefaultKey() {
         int physicalWidth = getDisplayMode().getPhysicalWidth();

         return getKeyForResolution(physicalWidth);
     }

     @Override
     protected boolean setDefaultKey(final String key) {
         int width = getWidthForResoluitonKey(key);
         if (width < 0) {
             return false;
         }

         setDisplayMode(width);
         updateIllustrationImage(mImagePreference);

         return true;
     }

     @Override
     public void onRadioButtonClicked(SelectorWithWidgetPreference selected) {
         String selectedKey = selected.getKey();
         int selectedWidth = getWidthForResoluitonKey(selectedKey);
         if (!mDisplayObserver.setPendingResolutionChange(selectedWidth)) {
             return;
         }

         if (mAccessibilityManager.isEnabled()) {
             AccessibilityEvent event = AccessibilityEvent.obtain();
             event.setEventType(AccessibilityEvent.TYPE_ANNOUNCEMENT);
             event.getText().add(mResources.getString(R.string.screen_resolution_selected_a11y));
             mAccessibilityManager.sendAccessibilityEvent(event);
         }

         super.onRadioButtonClicked(selected);
     }

     /** Update the resolution image according display mode. */
     private void updateIllustrationImage(IllustrationPreference preference) {
         String key = getDefaultKey();

         if (TextUtils.equals(
                 mScreenResolutionOptions[ScreenResolutionController.HIGHRESOLUTION_IDX], key)) {
             preference.setLottieAnimationResId(R.drawable.screen_resolution_high);
         } else if (TextUtils.equals(
                 mScreenResolutionOptions[ScreenResolutionController.FULLRESOLUTION_IDX], key)) {
             preference.setLottieAnimationResId(R.drawable.screen_resolution_full);
         }
     }

     @Override
     public int getMetricsCategory() {
         return SettingsEnums.SCREEN_RESOLUTION;
     }

     /** This is an extension of the CandidateInfo class, which adds summary information. */
     public static class ScreenResolutionCandidateInfo extends CandidateInfo {
         private final CharSequence mLabel;
         private final CharSequence mSummary;
         private final String mKey;

         ScreenResolutionCandidateInfo(
                 CharSequence label, CharSequence summary, String key, boolean enabled) {
             super(enabled);
             mLabel = label;
             mSummary = summary;
             mKey = key;
         }

         @Override
         public CharSequence loadLabel() {
             return mLabel;
         }

         /** It is the summary for radio options. */
         public CharSequence loadSummary() {
             return mSummary;
         }

         @Override
         public Drawable loadIcon() {
             return null;
         }

         @Override
         public String getKey() {
             return mKey;
         }
     }

     public static final BaseSearchIndexProvider SEARCH_INDEX_DATA_PROVIDER =
             new BaseSearchIndexProvider(R.xml.screen_resolution_settings) {
                 @Override
                 protected boolean isPageSearchEnabled(Context context) {
                     ScreenResolutionController mController =
                             new ScreenResolutionController(context, SCREEN_RESOLUTION_KEY);
                     return mController.checkSupportedResolutions();
                 }
             };

     private static final class DisplayObserver implements DisplayManager.DisplayListener {
         private final @Nullable Context mContext;
         private int mDefaultDensity;
         private int mCurrentIndex;
         private AtomicInteger mPreviousWidth = new AtomicInteger(-1);

         DisplayObserver(Context context) {
             mContext = context;
         }

         public void startObserve() {
             if (mContext == null) {
                 return;
             }

             final DisplayDensityUtils density = new DisplayDensityUtils(mContext);
             final int currentIndex = density.getCurrentIndexForDefaultDisplay();
             final int defaultDensity = density.getDefaultDensityForDefaultDisplay();

             if (density.getDefaultDisplayDensityValues()[mCurrentIndex]
                     == density.getDefaultDensityForDefaultDisplay()) {
                 return;
             }

             mDefaultDensity = defaultDensity;
             mCurrentIndex = currentIndex;
             final DisplayManager dm = mContext.getSystemService(DisplayManager.class);
             dm.registerDisplayListener(this, null);
         }

         public void stopObserve() {
             if (mContext == null) {
                 return;
             }

             final DisplayManager dm = mContext.getSystemService(DisplayManager.class);
             dm.unregisterDisplayListener(this);
         }

         @Override
         public void onDisplayAdded(int displayId) {}

         @Override
         public void onDisplayRemoved(int displayId) {}

         @Override
         public void onDisplayChanged(int displayId) {
             if (displayId != Display.DEFAULT_DISPLAY) {
                 return;
             }

             if (!isDensityChanged() || !isResolutionChangeApplied()) {
                 return;
             }

             restoreDensity();
             stopObserve();
         }

         private void restoreDensity() {
             final DisplayDensityUtils density = new DisplayDensityUtils(mContext);
             /* If current density is the same as a default density of other resolutions,
              * then mCurrentIndex may be out of boundary.
              */
             if (density.getDefaultDisplayDensityValues().length <= mCurrentIndex) {
                 mCurrentIndex = density.getCurrentIndexForDefaultDisplay();
             }
             if (density.getDefaultDisplayDensityValues()[mCurrentIndex]
                     != density.getDefaultDensityForDefaultDisplay()) {
                 density.setForcedDisplayDensity(mCurrentIndex);
             }

             mDefaultDensity = density.getDefaultDensityForDefaultDisplay();
         }

         private boolean isDensityChanged() {
             final DisplayDensityUtils density = new DisplayDensityUtils(mContext);
             if (density.getDefaultDensityForDefaultDisplay() == mDefaultDensity) {
                 return false;
             }

             return true;
         }

         private int getCurrentWidth() {
             final DisplayManager dm = mContext.getSystemService(DisplayManager.class);
             return dm.getDisplay(Display.DEFAULT_DISPLAY).getMode().getPhysicalWidth();
         }

         private boolean setPendingResolutionChange(int selectedWidth) {
             int currentWidth = getCurrentWidth();

             if (selectedWidth == currentWidth) {
                 return false;
             }
             if (mPreviousWidth.get() != -1 && !isResolutionChangeApplied()) {
                 return false;
             }

             mPreviousWidth.set(currentWidth);

             return true;
         }

         private boolean isResolutionChangeApplied() {
             if (mPreviousWidth.get() == getCurrentWidth()) {
                 return false;
             }

             Log.i(TAG,
                     "resolution changed from " + mPreviousWidth.get() + " to " + getCurrentWidth());
             return true;
         }
     }
 }
	/*
	* Copyright (C) 2022 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.display;

	import android.annotation.Nullable;
	import android.app.settings.SettingsEnums;
	import android.content.Context;
	import android.content.res.Resources;
	import android.graphics.Point;
	import android.graphics.drawable.Drawable;
	import android.hardware.display.DisplayManager;
	import android.provider.Settings;
	import android.text.TextUtils;
	import android.util.Log;
	import android.view.Display;
	import android.view.accessibility.AccessibilityEvent;
	import android.view.accessibility.AccessibilityManager;

	import androidx.annotation.VisibleForTesting;
	import androidx.preference.PreferenceScreen;

	import com.android.settings.R;
	import com.android.settings.core.instrumentation.SettingsStatsLog;
	import com.android.settings.search.BaseSearchIndexProvider;
	import com.android.settings.widget.RadioButtonPickerFragment;
	import com.android.settingslib.display.DisplayDensityUtils;
	import com.android.settingslib.search.SearchIndexable;
	import com.android.settingslib.widget.CandidateInfo;
	import com.android.settingslib.widget.FooterPreference;
	import com.android.settingslib.widget.IllustrationPreference;
	import com.android.settingslib.widget.SelectorWithWidgetPreference;

	import java.util.ArrayList;
	import java.util.List;
	import java.util.Set;
	import java.util.concurrent.atomic.AtomicInteger;

	/** Preference fragment used for switch screen resolution */
	@SearchIndexable
	public class ScreenResolutionFragment extends RadioButtonPickerFragment {
	private static final String TAG = "ScreenResolution";

	private Resources mResources;
	private static final String SCREEN_RESOLUTION = "user_selected_resolution";
	private static final String SCREEN_RESOLUTION_KEY = "screen_resolution";
	private Display mDefaultDisplay;
	private String[] mScreenResolutionOptions;
	private Set<Point> mResolutions;
	private String[] mScreenResolutionSummaries;

	private IllustrationPreference mImagePreference;
	private DisplayObserver mDisplayObserver;
	private AccessibilityManager mAccessibilityManager;

	private int mHighWidth;
	private int mFullWidth;

	@Override
	public void onAttach(Context context) {
	super.onAttach(context);

	mDefaultDisplay =
	context.getSystemService(DisplayManager.class).getDisplay(Display.DEFAULT_DISPLAY);
	mAccessibilityManager = context.getSystemService(AccessibilityManager.class);
	mResources = context.getResources();
	mScreenResolutionOptions =
	mResources.getStringArray(R.array.config_screen_resolution_options_strings);
	mImagePreference = new IllustrationPreference(context);
	mDisplayObserver = new DisplayObserver(context);
	ScreenResolutionController controller =
	new ScreenResolutionController(context, SCREEN_RESOLUTION_KEY);
	mResolutions = controller.getAllSupportedResolutions();
	mHighWidth = controller.getHighWidth();
	mFullWidth = controller.getFullWidth();
	Log.i(TAG, "mHighWidth:" + mHighWidth + "mFullWidth:" + mFullWidth);
	mScreenResolutionSummaries =
	new String[] {
	mHighWidth + " x " + controller.getHighHeight(),
	mFullWidth + " x " + controller.getFullHeight()
	};
	}

	@Override
	protected int getPreferenceScreenResId() {
	return R.xml.screen_resolution_settings;
	}

	@Override
	protected void addStaticPreferences(PreferenceScreen screen) {
	updateIllustrationImage(mImagePreference);
	screen.addPreference(mImagePreference);

	final FooterPreference footerPreference = new FooterPreference(screen.getContext());
	footerPreference.setTitle(R.string.screen_resolution_footer);
	footerPreference.setSelectable(false);
	footerPreference.setLayoutResource(
	com.android.settingslib.widget.preference.footer.R.layout.preference_footer);
	screen.addPreference(footerPreference);
	}

	@Override
	public void bindPreferenceExtra(
	SelectorWithWidgetPreference pref,
	String key,
	CandidateInfo info,
	String defaultKey,
	String systemDefaultKey) {
	final ScreenResolutionCandidateInfo candidateInfo = (ScreenResolutionCandidateInfo) info;
	final CharSequence summary = candidateInfo.loadSummary();
	if (summary != null) pref.setSummary(summary);
	}

	@Override
	protected List<? extends CandidateInfo> getCandidates() {
	final List<ScreenResolutionCandidateInfo> candidates = new ArrayList<>();

	for (int i = 0; i < mScreenResolutionOptions.length; i++) {
	candidates.add(
	new ScreenResolutionCandidateInfo(
	mScreenResolutionOptions[i],
	mScreenResolutionSummaries[i],
	mScreenResolutionOptions[i],
	true /* enabled */));
	}

	return candidates;
	}

	/** Get prefer display mode. */
	private Display.Mode getPreferMode(int width) {
	for (Point resolution : mResolutions) {
	if (resolution.x == width) {
	return new Display.Mode(
	resolution.x, resolution.y, getDisplayMode().getRefreshRate());
	}
	}

	return getDisplayMode();
	}

	/** Get current display mode. */
	@VisibleForTesting
	public Display.Mode getDisplayMode() {
	return mDefaultDisplay.getMode();
	}

	/** Using display manager to set the display mode. */
	@VisibleForTesting
	public void setDisplayMode(final int width) {
	Display.Mode mode = getPreferMode(width);

	mDisplayObserver.startObserve();

	/** For store settings globally. */
	/** TODO(b/259797244): Remove this once the atom is fully populated. */
	Settings.System.putString(
	getContext().getContentResolver(),
	SCREEN_RESOLUTION,
	mode.getPhysicalWidth() + "x" + mode.getPhysicalHeight());

	try {
	/** Apply the resolution change. */
	Log.i(TAG, "setUserPreferredDisplayMode: " + mode);
	mDefaultDisplay.setUserPreferredDisplayMode(mode);
	} catch (Exception e) {
	Log.e(TAG, "setUserPreferredDisplayMode() failed", e);
	return;
	}

	/** Send the atom after resolution changed successfully. */
	SettingsStatsLog.write(
	SettingsStatsLog.USER_SELECTED_RESOLUTION,
	mDefaultDisplay.getUniqueId().hashCode(),
	mode.getPhysicalWidth(),
	mode.getPhysicalHeight());
	}

	/** Get the key corresponding to the resolution. */
	@VisibleForTesting
	String getKeyForResolution(int width) {
	return width == mHighWidth
	? mScreenResolutionOptions[ScreenResolutionController.HIGHRESOLUTION_IDX]
	: width == mFullWidth
	? mScreenResolutionOptions[ScreenResolutionController.FULLRESOLUTION_IDX]
	: null;
	}

	/** Get the width corresponding to the resolution key. */
	int getWidthForResoluitonKey(String key) {
	return mScreenResolutionOptions[ScreenResolutionController.HIGHRESOLUTION_IDX].equals(key)
	? mHighWidth
	: mScreenResolutionOptions[ScreenResolutionController.FULLRESOLUTION_IDX].equals(
	key)
	? mFullWidth : -1;
	}

	@Override
	protected String getDefaultKey() {
	int physicalWidth = getDisplayMode().getPhysicalWidth();

	return getKeyForResolution(physicalWidth);
	}

	@Override
	protected boolean setDefaultKey(final String key) {
	int width = getWidthForResoluitonKey(key);
	if (width < 0) {
	return false;
	}

	setDisplayMode(width);
	updateIllustrationImage(mImagePreference);

	return true;
	}

	@Override
	public void onRadioButtonClicked(SelectorWithWidgetPreference selected) {
	String selectedKey = selected.getKey();
	int selectedWidth = getWidthForResoluitonKey(selectedKey);
	if (!mDisplayObserver.setPendingResolutionChange(selectedWidth)) {
	return;
	}

	if (mAccessibilityManager.isEnabled()) {
	AccessibilityEvent event = AccessibilityEvent.obtain();
	event.setEventType(AccessibilityEvent.TYPE_ANNOUNCEMENT);
	event.getText().add(mResources.getString(R.string.screen_resolution_selected_a11y));
	mAccessibilityManager.sendAccessibilityEvent(event);
	}

	super.onRadioButtonClicked(selected);
	}

	/** Update the resolution image according display mode. */
	private void updateIllustrationImage(IllustrationPreference preference) {
	String key = getDefaultKey();

	if (TextUtils.equals(
	mScreenResolutionOptions[ScreenResolutionController.HIGHRESOLUTION_IDX], key)) {
	preference.setLottieAnimationResId(R.drawable.screen_resolution_high);
	} else if (TextUtils.equals(
	mScreenResolutionOptions[ScreenResolutionController.FULLRESOLUTION_IDX], key)) {
	preference.setLottieAnimationResId(R.drawable.screen_resolution_full);
	}
	}

	@Override
	public int getMetricsCategory() {
	return SettingsEnums.SCREEN_RESOLUTION;
	}

	/** This is an extension of the CandidateInfo class, which adds summary information. */
	public static class ScreenResolutionCandidateInfo extends CandidateInfo {
	private final CharSequence mLabel;
	private final CharSequence mSummary;
	private final String mKey;

	ScreenResolutionCandidateInfo(
	CharSequence label, CharSequence summary, String key, boolean enabled) {
	super(enabled);
	mLabel = label;
	mSummary = summary;
	mKey = key;
	}

	@Override
	public CharSequence loadLabel() {
	return mLabel;
	}

	/** It is the summary for radio options. */
	public CharSequence loadSummary() {
	return mSummary;
	}

	@Override
	public Drawable loadIcon() {
	return null;
	}

	@Override
	public String getKey() {
	return mKey;
	}
	}

	public static final BaseSearchIndexProvider SEARCH_INDEX_DATA_PROVIDER =
	new BaseSearchIndexProvider(R.xml.screen_resolution_settings) {
	@Override
	protected boolean isPageSearchEnabled(Context context) {
	ScreenResolutionController mController =
	new ScreenResolutionController(context, SCREEN_RESOLUTION_KEY);
	return mController.checkSupportedResolutions();
	}
	};

	private static final class DisplayObserver implements DisplayManager.DisplayListener {
	private final @Nullable Context mContext;
	private int mDefaultDensity;
	private int mCurrentIndex;
	private AtomicInteger mPreviousWidth = new AtomicInteger(-1);

	DisplayObserver(Context context) {
	mContext = context;
	}

	public void startObserve() {
	if (mContext == null) {
	return;
	}

	final DisplayDensityUtils density = new DisplayDensityUtils(mContext);
	final int currentIndex = density.getCurrentIndexForDefaultDisplay();
	final int defaultDensity = density.getDefaultDensityForDefaultDisplay();

	if (density.getDefaultDisplayDensityValues()[mCurrentIndex]
	== density.getDefaultDensityForDefaultDisplay()) {
	return;
	}

	mDefaultDensity = defaultDensity;
	mCurrentIndex = currentIndex;
	final DisplayManager dm = mContext.getSystemService(DisplayManager.class);
	dm.registerDisplayListener(this, null);
	}

	public void stopObserve() {
	if (mContext == null) {
	return;
	}

	final DisplayManager dm = mContext.getSystemService(DisplayManager.class);
	dm.unregisterDisplayListener(this);
	}

	@Override
	public void onDisplayAdded(int displayId) {}

	@Override
	public void onDisplayRemoved(int displayId) {}

	@Override
	public void onDisplayChanged(int displayId) {
	if (displayId != Display.DEFAULT_DISPLAY) {
	return;
	}

	if (!isDensityChanged() \|\| !isResolutionChangeApplied()) {
	return;
	}

	restoreDensity();
	stopObserve();
	}

	private void restoreDensity() {
	final DisplayDensityUtils density = new DisplayDensityUtils(mContext);
	/* If current density is the same as a default density of other resolutions,
	* then mCurrentIndex may be out of boundary.
	*/
	if (density.getDefaultDisplayDensityValues().length <= mCurrentIndex) {
	mCurrentIndex = density.getCurrentIndexForDefaultDisplay();
	}
	if (density.getDefaultDisplayDensityValues()[mCurrentIndex]
	!= density.getDefaultDensityForDefaultDisplay()) {
	density.setForcedDisplayDensity(mCurrentIndex);
	}

	mDefaultDensity = density.getDefaultDensityForDefaultDisplay();
	}

	private boolean isDensityChanged() {
	final DisplayDensityUtils density = new DisplayDensityUtils(mContext);
	if (density.getDefaultDensityForDefaultDisplay() == mDefaultDensity) {
	return false;
	}

	return true;
	}

	private int getCurrentWidth() {
	final DisplayManager dm = mContext.getSystemService(DisplayManager.class);
	return dm.getDisplay(Display.DEFAULT_DISPLAY).getMode().getPhysicalWidth();
	}

	private boolean setPendingResolutionChange(int selectedWidth) {
	int currentWidth = getCurrentWidth();

	if (selectedWidth == currentWidth) {
	return false;
	}
	if (mPreviousWidth.get() != -1 && !isResolutionChangeApplied()) {
	return false;
	}

	mPreviousWidth.set(currentWidth);

	return true;
	}

	private boolean isResolutionChangeApplied() {
	if (mPreviousWidth.get() == getCurrentWidth()) {
	return false;
	}

	Log.i(TAG,
	"resolution changed from " + mPreviousWidth.get() + " to " + getCurrentWidth());
	return true;
	}
	}
	}