Android系统apps之Setting的修改和设置

由于接到了一个修改系统app---Settings条目是需求，接着也看到了一个博主的文章http://blog.csdn.net/wangjinyu501/article/details/22077803 这篇文章写的很好，基本满足了需求，我这里再做下整理，作为对知识的总结和梳理。

首先我们下载源码，可以从https://android.googlesource.com/上下载，接着我们找到AndroidManifest,xml文件。找到入口，代码如下

<activity android:name="Settings"                android:label="@string/settings_label_launcher"                android:taskAffinity="com.android.settings"                android:launchMode="singleTask">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <action android:name="android.settings.SETTINGS" />                <category android:name="android.intent.category.DEFAULT" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter></activity>

接着我们找到Settings.java。代码如下

/* * Copyright (C) 2008 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;import com.android.internal.util.ArrayUtils;import com.android.settings.ChooseLockGeneric.ChooseLockGenericFragment;import com.android.settings.accounts.AccountSyncSettings;import com.android.settings.accounts.AuthenticatorHelper;import com.android.settings.accounts.ManageAccountsSettings;import com.android.settings.applications.InstalledAppDetails;import com.android.settings.applications.ManageApplications;import com.android.settings.bluetooth.BluetoothEnabler;import com.android.settings.deviceinfo.Memory;import com.android.settings.fuelgauge.PowerUsageSummary;import com.android.settings.vpn2.VpnSettings;import com.android.settings.wifi.WifiEnabler;import android.accounts.Account;import android.accounts.AccountManager;import android.accounts.OnAccountsUpdateListener;import android.content.ComponentName;import android.content.Context;import android.content.Intent;import android.content.SharedPreferences;import android.content.pm.ActivityInfo;import android.content.pm.PackageManager;import android.content.pm.PackageManager.NameNotFoundException;import android.graphics.drawable.Drawable;import android.os.Bundle;import android.os.INetworkManagementService;import android.os.RemoteException;import android.os.ServiceManager;import android.os.UserHandle;import android.os.UserManager;import android.preference.Preference;import android.preference.PreferenceActivity;import android.preference.PreferenceFragment;import android.text.TextUtils;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.View.OnClickListener;import android.view.ViewGroup;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.ImageView;import android.widget.ListAdapter;import android.widget.Switch;import android.widget.TextView;import java.util.ArrayList;import java.util.Collections;import java.util.Comparator;import java.util.HashMap;import java.util.List;/** * Top-level settings activity to handle single pane and double pane UI layout. */public class Settings extends PreferenceActivity        implements ButtonBarHandler, OnAccountsUpdateListener {    private static final String LOG_TAG = "Settings";    private static final String META_DATA_KEY_HEADER_ID =        "com.android.settings.TOP_LEVEL_HEADER_ID";    private static final String META_DATA_KEY_FRAGMENT_CLASS =        "com.android.settings.FRAGMENT_CLASS";    private static final String META_DATA_KEY_PARENT_TITLE =        "com.android.settings.PARENT_FRAGMENT_TITLE";    private static final String META_DATA_KEY_PARENT_FRAGMENT_CLASS =        "com.android.settings.PARENT_FRAGMENT_CLASS";    private static final String EXTRA_CLEAR_UI_OPTIONS = "settings:remove_ui_options";    private static final String SAVE_KEY_CURRENT_HEADER = "com.android.settings.CURRENT_HEADER";    private static final String SAVE_KEY_PARENT_HEADER = "com.android.settings.PARENT_HEADER";    private String mFragmentClass;    private int mTopLevelHeaderId;    private Header mFirstHeader;    private Header mCurrentHeader;    private Header mParentHeader;    private boolean mInLocalHeaderSwitch;    // Show only these settings for restricted users    private int[] SETTINGS_FOR_RESTRICTED = {            R.id.wireless_section,            R.id.wifi_settings,            R.id.bluetooth_settings,            R.id.data_usage_settings,            R.id.wireless_settings,            R.id.device_section,            R.id.sound_settings,            R.id.display_settings,            R.id.storage_settings,            R.id.application_settings,            R.id.battery_settings,            R.id.personal_section,            R.id.location_settings,            R.id.security_settings,            R.id.language_settings,            R.id.user_settings,            R.id.account_settings,            R.id.account_add,            R.id.system_section,            R.id.date_time_settings,            R.id.about_settings,            R.id.accessibility_settings    };    private SharedPreferences mDevelopmentPreferences;    private SharedPreferences.OnSharedPreferenceChangeListener mDevelopmentPreferencesListener;    // TODO: Update Call Settings based on airplane mode state.    protected HashMap<Integer, Integer> mHeaderIndexMap = new HashMap<Integer, Integer>();    private AuthenticatorHelper mAuthenticatorHelper;    private Header mLastHeader;    private boolean mListeningToAccountUpdates;    @Override    protected void onCreate(Bundle savedInstanceState) {        if (getIntent().getBooleanExtra(EXTRA_CLEAR_UI_OPTIONS, false)) {            getWindow().setUiOptions(0);        }        mAuthenticatorHelper = new AuthenticatorHelper();        mAuthenticatorHelper.updateAuthDescriptions(this);        mAuthenticatorHelper.onAccountsUpdated(this, null);        mDevelopmentPreferences = getSharedPreferences(DevelopmentSettings.PREF_FILE,                Context.MODE_PRIVATE);        getMetaData();        mInLocalHeaderSwitch = true;        super.onCreate(savedInstanceState);        mInLocalHeaderSwitch = false;        if (!onIsHidingHeaders() && onIsMultiPane()) {            highlightHeader(mTopLevelHeaderId);            // Force the title so that it doesn't get overridden by a direct launch of            // a specific settings screen.            setTitle(R.string.settings_label);        }        // Retrieve any saved state        if (savedInstanceState != null) {            mCurrentHeader = savedInstanceState.getParcelable(SAVE_KEY_CURRENT_HEADER);            mParentHeader = savedInstanceState.getParcelable(SAVE_KEY_PARENT_HEADER);        }        // If the current header was saved, switch to it        if (savedInstanceState != null && mCurrentHeader != null) {            //switchToHeaderLocal(mCurrentHeader);            showBreadCrumbs(mCurrentHeader.title, null);        }        if (mParentHeader != null) {            setParentTitle(mParentHeader.title, null, new OnClickListener() {                public void onClick(View v) {                    switchToParent(mParentHeader.fragment);                }            });        }        // Override up navigation for multi-pane, since we handle it in the fragment breadcrumbs        if (onIsMultiPane()) {            getActionBar().setDisplayHomeAsUpEnabled(false);            getActionBar().setHomeButtonEnabled(false);        }    }    @Override    protected void onSaveInstanceState(Bundle outState) {        super.onSaveInstanceState(outState);        // Save the current fragment, if it is the same as originally launched        if (mCurrentHeader != null) {            outState.putParcelable(SAVE_KEY_CURRENT_HEADER, mCurrentHeader);        }        if (mParentHeader != null) {            outState.putParcelable(SAVE_KEY_PARENT_HEADER, mParentHeader);        }    }    @Override    public void onResume() {        super.onResume();        mDevelopmentPreferencesListener = new SharedPreferences.OnSharedPreferenceChangeListener() {            @Override            public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {                invalidateHeaders();            }        };        mDevelopmentPreferences.registerOnSharedPreferenceChangeListener(                mDevelopmentPreferencesListener);        ListAdapter listAdapter = getListAdapter();        if (listAdapter instanceof HeaderAdapter) {            ((HeaderAdapter) listAdapter).resume();        }        invalidateHeaders();    }    @Override    public void onPause() {        super.onPause();        ListAdapter listAdapter = getListAdapter();        if (listAdapter instanceof HeaderAdapter) {            ((HeaderAdapter) listAdapter).pause();        }        mDevelopmentPreferences.unregisterOnSharedPreferenceChangeListener(                mDevelopmentPreferencesListener);        mDevelopmentPreferencesListener = null;    }    @Override    public void onDestroy() {        super.onDestroy();        if (mListeningToAccountUpdates) {            AccountManager.get(this).removeOnAccountsUpdatedListener(this);        }    }    private void switchToHeaderLocal(Header header) {        mInLocalHeaderSwitch = true;        switchToHeader(header);        mInLocalHeaderSwitch = false;    }    @Override    public void switchToHeader(Header header) {        if (!mInLocalHeaderSwitch) {            mCurrentHeader = null;            mParentHeader = null;        }        super.switchToHeader(header);    }    /**     * Switch to parent fragment and store the grand parent's info     * @param className name of the activity wrapper for the parent fragment.     */    private void switchToParent(String className) {        final ComponentName cn = new ComponentName(this, className);        try {            final PackageManager pm = getPackageManager();            final ActivityInfo parentInfo = pm.getActivityInfo(cn, PackageManager.GET_META_DATA);            if (parentInfo != null && parentInfo.metaData != null) {                String fragmentClass = parentInfo.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);                CharSequence fragmentTitle = parentInfo.loadLabel(pm);                Header parentHeader = new Header();                parentHeader.fragment = fragmentClass;                parentHeader.title = fragmentTitle;                mCurrentHeader = parentHeader;                switchToHeaderLocal(parentHeader);                highlightHeader(mTopLevelHeaderId);                mParentHeader = new Header();                mParentHeader.fragment                        = parentInfo.metaData.getString(META_DATA_KEY_PARENT_FRAGMENT_CLASS);                mParentHeader.title = parentInfo.metaData.getString(META_DATA_KEY_PARENT_TITLE);            }        } catch (NameNotFoundException nnfe) {            Log.w(LOG_TAG, "Could not find parent activity : " + className);        }    }    @Override    public void onNewIntent(Intent intent) {        super.onNewIntent(intent);        // If it is not launched from history, then reset to top-level        if ((intent.getFlags() & Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY) == 0) {            if (mFirstHeader != null && !onIsHidingHeaders() && onIsMultiPane()) {                switchToHeaderLocal(mFirstHeader);            }            getListView().setSelectionFromTop(0, 0);        }    }    private void highlightHeader(int id) {        if (id != 0) {            Integer index = mHeaderIndexMap.get(id);            if (index != null) {                getListView().setItemChecked(index, true);                if (isMultiPane()) {                    getListView().smoothScrollToPosition(index);                }            }        }    }    @Override    public Intent getIntent() {        Intent superIntent = super.getIntent();        String startingFragment = getStartingFragmentClass(superIntent);        // This is called from super.onCreate, isMultiPane() is not yet reliable        // Do not use onIsHidingHeaders either, which relies itself on this method        if (startingFragment != null && !onIsMultiPane()) {            Intent modIntent = new Intent(superIntent);            modIntent.putExtra(EXTRA_SHOW_FRAGMENT, startingFragment);            Bundle args = superIntent.getExtras();            if (args != null) {                args = new Bundle(args);            } else {                args = new Bundle();            }            args.putParcelable("intent", superIntent);            modIntent.putExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS, superIntent.getExtras());            return modIntent;        }        return superIntent;    }    /**     * Checks if the component name in the intent is different from the Settings class and     * returns the class name to load as a fragment.     */    protected String getStartingFragmentClass(Intent intent) {        if (mFragmentClass != null) return mFragmentClass;        String intentClass = intent.getComponent().getClassName();        if (intentClass.equals(getClass().getName())) return null;        if ("com.android.settings.ManageApplications".equals(intentClass)                || "com.android.settings.RunningServices".equals(intentClass)                || "com.android.settings.applications.StorageUse".equals(intentClass)) {            // Old names of manage apps.            intentClass = com.android.settings.applications.ManageApplications.class.getName();        }        return intentClass;    }    /**     * Override initial header when an activity-alias is causing Settings to be launched     * for a specific fragment encoded in the android:name parameter.     */    @Override    public Header onGetInitialHeader() {        String fragmentClass = getStartingFragmentClass(super.getIntent());        if (fragmentClass != null) {            Header header = new Header();            header.fragment = fragmentClass;            header.title = getTitle();            header.fragmentArguments = getIntent().getExtras();            mCurrentHeader = header;            return header;        }        return mFirstHeader;    }    @Override    public Intent onBuildStartFragmentIntent(String fragmentName, Bundle args,            int titleRes, int shortTitleRes) {        Intent intent = super.onBuildStartFragmentIntent(fragmentName, args,                titleRes, shortTitleRes);        // some fragments want to avoid split actionbar        if (DataUsageSummary.class.getName().equals(fragmentName) ||                PowerUsageSummary.class.getName().equals(fragmentName) ||                AccountSyncSettings.class.getName().equals(fragmentName) ||                UserDictionarySettings.class.getName().equals(fragmentName) ||                Memory.class.getName().equals(fragmentName) ||                ManageApplications.class.getName().equals(fragmentName) ||                WirelessSettings.class.getName().equals(fragmentName) ||                SoundSettings.class.getName().equals(fragmentName) ||                PrivacySettings.class.getName().equals(fragmentName) ||                ManageAccountsSettings.class.getName().equals(fragmentName) ||                VpnSettings.class.getName().equals(fragmentName) ||                SecuritySettings.class.getName().equals(fragmentName) ||                InstalledAppDetails.class.getName().equals(fragmentName) ||                ChooseLockGenericFragment.class.getName().equals(fragmentName) ||                TetherSettings.class.getName().equals(fragmentName) ||                ApnSettings.class.getName().equals(fragmentName) ||                LocationSettings.class.getName().equals(fragmentName) ||                ZonePicker.class.getName().equals(fragmentName)) {            intent.putExtra(EXTRA_CLEAR_UI_OPTIONS, true);        }        intent.setClass(this, SubSettings.class);        return intent;    }    /**     * Populate the activity with the top-level headers.     */    @Override    public void onBuildHeaders(List<Header> headers) {        loadHeadersFromResource(R.xml.settings_headers, headers);        updateHeaderList(headers);    }    private void updateHeaderList(List<Header> target) {        final boolean showDev = mDevelopmentPreferences.getBoolean(                DevelopmentSettings.PREF_SHOW,                android.os.Build.TYPE.equals("eng"));        int i = 0;        mHeaderIndexMap.clear();        while (i < target.size()) {            Header header = target.get(i);            // Ids are integers, so downcasting            int id = (int) header.id;            if (id == R.id.operator_settings || id == R.id.manufacturer_settings) {                Utils.updateHeaderToSpecificActivityFromMetaDataOrRemove(this, target, header);            } else if (id == R.id.wifi_settings) {                // Remove WiFi Settings if WiFi service is not available.                if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_WIFI)) {                    target.remove(i);                }            } else if (id == R.id.bluetooth_settings) {                // Remove Bluetooth Settings if Bluetooth service is not available.                if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH)) {                    target.remove(i);                }            } else if (id == R.id.data_usage_settings) {                // Remove data usage when kernel module not enabled                final INetworkManagementService netManager = INetworkManagementService.Stub                        .asInterface(ServiceManager.getService(Context.NETWORKMANAGEMENT_SERVICE));                try {                    if (!netManager.isBandwidthControlEnabled()) {                        target.remove(i);                    }                } catch (RemoteException e) {                    // ignored                }            } else if (id == R.id.account_settings) {                int headerIndex = i + 1;                i = insertAccountsHeaders(target, headerIndex);            } else if (id == R.id.user_settings) {                if (!UserHandle.MU_ENABLED                        || !UserManager.supportsMultipleUsers()                        || Utils.isMonkeyRunning()) {                    target.remove(i);                }            } else if (id == R.id.development_settings) {                if (!showDev) {                    target.remove(i);                }            }            if (target.get(i) == header                    && UserHandle.MU_ENABLED && UserHandle.myUserId() != 0                    && !ArrayUtils.contains(SETTINGS_FOR_RESTRICTED, id)) {                target.remove(i);            }            // Increment if the current one wasn't removed by the Utils code.            if (target.get(i) == header) {                // Hold on to the first header, when we need to reset to the top-level                if (mFirstHeader == null &&                        HeaderAdapter.getHeaderType(header) != HeaderAdapter.HEADER_TYPE_CATEGORY) {                    mFirstHeader = header;                }                mHeaderIndexMap.put(id, i);                i++;            }        }    }    private int insertAccountsHeaders(List<Header> target, int headerIndex) {        String[] accountTypes = mAuthenticatorHelper.getEnabledAccountTypes();        List<Header> accountHeaders = new ArrayList<Header>(accountTypes.length);        for (String accountType : accountTypes) {            CharSequence label = mAuthenticatorHelper.getLabelForType(this, accountType);            if (label == null) {                continue;            }            Account[] accounts = AccountManager.get(this).getAccountsByType(accountType);            boolean skipToAccount = accounts.length == 1                    && !mAuthenticatorHelper.hasAccountPreferences(accountType);            Header accHeader = new Header();            accHeader.title = label;            if (accHeader.extras == null) {                accHeader.extras = new Bundle();            }            if (skipToAccount) {                accHeader.breadCrumbTitleRes = R.string.account_sync_settings_title;                accHeader.breadCrumbShortTitleRes = R.string.account_sync_settings_title;                accHeader.fragment = AccountSyncSettings.class.getName();                accHeader.fragmentArguments = new Bundle();                // Need this for the icon                accHeader.extras.putString(ManageAccountsSettings.KEY_ACCOUNT_TYPE, accountType);                accHeader.extras.putParcelable(AccountSyncSettings.ACCOUNT_KEY, accounts[0]);                accHeader.fragmentArguments.putParcelable(AccountSyncSettings.ACCOUNT_KEY,                        accounts[0]);            } else {                accHeader.breadCrumbTitle = label;                accHeader.breadCrumbShortTitle = label;                accHeader.fragment = ManageAccountsSettings.class.getName();                accHeader.fragmentArguments = new Bundle();                accHeader.extras.putString(ManageAccountsSettings.KEY_ACCOUNT_TYPE, accountType);                accHeader.fragmentArguments.putString(ManageAccountsSettings.KEY_ACCOUNT_TYPE,                        accountType);                if (!isMultiPane()) {                    accHeader.fragmentArguments.putString(ManageAccountsSettings.KEY_ACCOUNT_LABEL,                            label.toString());                }            }            accountHeaders.add(accHeader);        }        // Sort by label        Collections.sort(accountHeaders, new Comparator<Header>() {            @Override            public int compare(Header h1, Header h2) {                return h1.title.toString().compareTo(h2.title.toString());            }        });        for (Header header : accountHeaders) {            target.add(headerIndex++, header);        }        if (!mListeningToAccountUpdates) {            AccountManager.get(this).addOnAccountsUpdatedListener(this, null, true);            mListeningToAccountUpdates = true;        }        return headerIndex;    }    private void getMetaData() {        try {            ActivityInfo ai = getPackageManager().getActivityInfo(getComponentName(),                    PackageManager.GET_META_DATA);            if (ai == null || ai.metaData == null) return;            mTopLevelHeaderId = ai.metaData.getInt(META_DATA_KEY_HEADER_ID);            mFragmentClass = ai.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);            // Check if it has a parent specified and create a Header object            final int parentHeaderTitleRes = ai.metaData.getInt(META_DATA_KEY_PARENT_TITLE);            String parentFragmentClass = ai.metaData.getString(META_DATA_KEY_PARENT_FRAGMENT_CLASS);            if (parentFragmentClass != null) {                mParentHeader = new Header();                mParentHeader.fragment = parentFragmentClass;                if (parentHeaderTitleRes != 0) {                    mParentHeader.title = getResources().getString(parentHeaderTitleRes);                }            }        } catch (NameNotFoundException nnfe) {            // No recovery        }    }    @Override    public boolean hasNextButton() {        return super.hasNextButton();    }    @Override    public Button getNextButton() {        return super.getNextButton();    }    private static class HeaderAdapter extends ArrayAdapter<Header> {        static final int HEADER_TYPE_CATEGORY = 0;        static final int HEADER_TYPE_NORMAL = 1;        static final int HEADER_TYPE_SWITCH = 2;        private static final int HEADER_TYPE_COUNT = HEADER_TYPE_SWITCH + 1;        private final WifiEnabler mWifiEnabler;        private final BluetoothEnabler mBluetoothEnabler;        private AuthenticatorHelper mAuthHelper;        private static class HeaderViewHolder {            ImageView icon;            TextView title;            TextView summary;            Switch switch_;        }        private LayoutInflater mInflater;        static int getHeaderType(Header header) {            if (header.fragment == null && header.intent == null) {                return HEADER_TYPE_CATEGORY;            } else if (header.id == R.id.wifi_settings || header.id == R.id.bluetooth_settings) {                return HEADER_TYPE_SWITCH;            } else {                return HEADER_TYPE_NORMAL;            }        }        @Override        public int getItemViewType(int position) {            Header header = getItem(position);            return getHeaderType(header);        }        @Override        public boolean areAllItemsEnabled() {            return false; // because of categories        }        @Override        public boolean isEnabled(int position) {            return getItemViewType(position) != HEADER_TYPE_CATEGORY;        }        @Override        public int getViewTypeCount() {            return HEADER_TYPE_COUNT;        }        @Override        public boolean hasStableIds() {            return true;        }        public HeaderAdapter(Context context, List<Header> objects,                AuthenticatorHelper authenticatorHelper) {            super(context, 0, objects);            mAuthHelper = authenticatorHelper;            mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);            // Temp Switches provided as placeholder until the adapter replaces these with actual            // Switches inflated from their layouts. Must be done before adapter is set in super            mWifiEnabler = new WifiEnabler(context, new Switch(context));            mBluetoothEnabler = new BluetoothEnabler(context, new Switch(context));        }        @Override        public View getView(int position, View convertView, ViewGroup parent) {            HeaderViewHolder holder;            Header header = getItem(position);            int headerType = getHeaderType(header);            View view = null;            if (convertView == null) {                holder = new HeaderViewHolder();                switch (headerType) {                    case HEADER_TYPE_CATEGORY:                        view = new TextView(getContext(), null,                                android.R.attr.listSeparatorTextViewStyle);                        holder.title = (TextView) view;                        break;                    case HEADER_TYPE_SWITCH:                        view = mInflater.inflate(R.layout.preference_header_switch_item, parent,                                false);                        holder.icon = (ImageView) view.findViewById(R.id.icon);                        holder.title = (TextView)                                view.findViewById(com.android.internal.R.id.title);                        holder.summary = (TextView)                                view.findViewById(com.android.internal.R.id.summary);                        holder.switch_ = (Switch) view.findViewById(R.id.switchWidget);                        break;                    case HEADER_TYPE_NORMAL:                        view = mInflater.inflate(                                R.layout.preference_header_item, parent,                                false);                        holder.icon = (ImageView) view.findViewById(R.id.icon);                        holder.title = (TextView)                                view.findViewById(com.android.internal.R.id.title);                        holder.summary = (TextView)                                view.findViewById(com.android.internal.R.id.summary);                        break;                }                view.setTag(holder);            } else {                view = convertView;                holder = (HeaderViewHolder) view.getTag();            }            // All view fields must be updated every time, because the view may be recycled            switch (headerType) {                case HEADER_TYPE_CATEGORY:                    holder.title.setText(header.getTitle(getContext().getResources()));                    break;                case HEADER_TYPE_SWITCH:                    // Would need a different treatment if the main menu had more switches                    if (header.id == R.id.wifi_settings) {                        mWifiEnabler.setSwitch(holder.switch_);                    } else {                        mBluetoothEnabler.setSwitch(holder.switch_);                    }                    // No break, fall through on purpose to update common fields                    //$FALL-THROUGH$                case HEADER_TYPE_NORMAL:                    if (header.extras != null                            && header.extras.containsKey(ManageAccountsSettings.KEY_ACCOUNT_TYPE)) {                        String accType = header.extras.getString(                                ManageAccountsSettings.KEY_ACCOUNT_TYPE);                        ViewGroup.LayoutParams lp = holder.icon.getLayoutParams();                        lp.width = getContext().getResources().getDimensionPixelSize(                                R.dimen.header_icon_width);                        lp.height = lp.width;                        holder.icon.setLayoutParams(lp);                        Drawable icon = mAuthHelper.getDrawableForType(getContext(), accType);                        holder.icon.setImageDrawable(icon);                    } else {                        holder.icon.setImageResource(header.iconRes);                    }                    holder.title.setText(header.getTitle(getContext().getResources()));                    CharSequence summary = header.getSummary(getContext().getResources());                    if (!TextUtils.isEmpty(summary)) {                        holder.summary.setVisibility(View.VISIBLE);                        holder.summary.setText(summary);                    } else {                        holder.summary.setVisibility(View.GONE);                    }                    break;            }            return view;        }        public void resume() {            mWifiEnabler.resume();            mBluetoothEnabler.resume();        }        public void pause() {            mWifiEnabler.pause();            mBluetoothEnabler.pause();        }    }    @Override    public void onHeaderClick(Header header, int position) {        boolean revert = false;        if (header.id == R.id.account_add) {            revert = true;        }        super.onHeaderClick(header, position);        if (revert && mLastHeader != null) {            highlightHeader((int) mLastHeader.id);        } else {            mLastHeader = header;        }    }    @Override    public boolean onPreferenceStartFragment(PreferenceFragment caller, Preference pref) {        // Override the fragment title for Wallpaper settings        int titleRes = pref.getTitleRes();        if (pref.getFragment().equals(WallpaperTypeSettings.class.getName())) {            titleRes = R.string.wallpaper_settings_fragment_title;        } else if (pref.getFragment().equals(OwnerInfoSettings.class.getName())                && UserHandle.myUserId() != UserHandle.USER_OWNER) {            titleRes = R.string.user_info_settings_title;        }        startPreferencePanel(pref.getFragment(), pref.getExtras(), titleRes, pref.getTitle(),                null, 0);        return true;    }    public boolean shouldUpRecreateTask(Intent targetIntent) {        return super.shouldUpRecreateTask(new Intent(this, Settings.class));    }    @Override    public void setListAdapter(ListAdapter adapter) {        if (adapter == null) {            super.setListAdapter(null);        } else {            super.setListAdapter(new HeaderAdapter(this, getHeaders(), mAuthenticatorHelper));        }    }    @Override    public void onAccountsUpdated(Account[] accounts) {        // TODO: watch for package upgrades to invalidate cache; see 7206643        mAuthenticatorHelper.updateAuthDescriptions(this);        mAuthenticatorHelper.onAccountsUpdated(this, accounts);        invalidateHeaders();    }    /*     * Settings subclasses for launching independently.     */    public static class BluetoothSettingsActivity extends Settings { /* empty */ }    public static class WirelessSettingsActivity extends Settings { /* empty */ }    public static class TetherSettingsActivity extends Settings { /* empty */ }    public static class VpnSettingsActivity extends Settings { /* empty */ }    public static class DateTimeSettingsActivity extends Settings { /* empty */ }    public static class StorageSettingsActivity extends Settings { /* empty */ }    public static class WifiSettingsActivity extends Settings { /* empty */ }    public static class WifiP2pSettingsActivity extends Settings { /* empty */ }    public static class InputMethodAndLanguageSettingsActivity extends Settings { /* empty */ }    public static class KeyboardLayoutPickerActivity extends Settings { /* empty */ }    public static class InputMethodAndSubtypeEnablerActivity extends Settings { /* empty */ }    public static class SpellCheckersSettingsActivity extends Settings { /* empty */ }    public static class LocalePickerActivity extends Settings { /* empty */ }    public static class UserDictionarySettingsActivity extends Settings { /* empty */ }    public static class SoundSettingsActivity extends Settings { /* empty */ }    public static class DisplaySettingsActivity extends Settings { /* empty */ }    public static class DeviceInfoSettingsActivity extends Settings { /* empty */ }    public static class ApplicationSettingsActivity extends Settings { /* empty */ }    public static class ManageApplicationsActivity extends Settings { /* empty */ }    public static class StorageUseActivity extends Settings { /* empty */ }    public static class DevelopmentSettingsActivity extends Settings { /* empty */ }    public static class AccessibilitySettingsActivity extends Settings { /* empty */ }    public static class SecuritySettingsActivity extends Settings { /* empty */ }    public static class LocationSettingsActivity extends Settings { /* empty */ }    public static class PrivacySettingsActivity extends Settings { /* empty */ }    public static class RunningServicesActivity extends Settings { /* empty */ }    public static class ManageAccountsSettingsActivity extends Settings { /* empty */ }    public static class PowerUsageSummaryActivity extends Settings { /* empty */ }    public static class AccountSyncSettingsActivity extends Settings { /* empty */ }    public static class AccountSyncSettingsInAddAccountActivity extends Settings { /* empty */ }    public static class CryptKeeperSettingsActivity extends Settings { /* empty */ }    public static class DeviceAdminSettingsActivity extends Settings { /* empty */ }    public static class DataUsageSummaryActivity extends Settings { /* empty */ }    public static class AdvancedWifiSettingsActivity extends Settings { /* empty */ }    public static class TextToSpeechSettingsActivity extends Settings { /* empty */ }    public static class AndroidBeamSettingsActivity extends Settings { /* empty */ }    public static class WifiDisplaySettingsActivity extends Settings { /* empty */ }    public static class DreamSettingsActivity extends Settings { /* empty */ }}

到了这里我们一般都会去onCreat()去寻找setContentView(LayoutId)。并且根据LayoutId我们就可以找到布局文件，并且去寻找ListView.可是我们并没有发现setContentView。那布局中的文件在哪里呢？，我们就可以考虑去找一下Settings的父类，根据代码可以发现他的父类有三个 PreferenceActivity   ，ButtonBarHandler   , OnAccountsUpdateListener

PreferenceActivity: 是ListActivity的子类（你应该懂了点什么）

ButtonBarHandler：根据类名我们暂时理解为ButtonBar的处理者

OnAccountsUpdateListener: 监听器

根据分析，我们就可以去看看PreferenceActivity，而发现在Settings中复写了PreferenceActivity的OnBuildHeaders(List<PreferenceActivity.target> target)

@Override  ublic void onBuildHeaders(List<Header> target) {    loadHeadersFromResource(R.xml.preference_headers, target);  }

发现原来条目是根据R.xml.preference_headers来配置列表条目的

所以我们这里根据删除，增加R.xml.preference_headers里面的条目配置就可以实现Settings的增加和删除条目的效果