Android PreferenceActivity点击Header是如何处理的？

最新推荐文章于 2024-04-06 17:39:46 发布

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最新推荐文章于 2024-04-06 17:39:46 发布

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分类专栏： Preference Android 设置解析文章标签：设置源代码 Settings PreferenceActivity Header

本文链接：https://blog.youkuaiyun.com/droyon/article/details/18009373

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转载请注明出处：http://blog.youkuaiyun.com/droyon/article/details/18009373

本文讲述PreferenceActivity中单击事件的处理，重点记述mCurrentHeader以及设置源代码Settings中的mLastHeader、mCurrentHeader、mParentHeader的作用。主要以多屏幕为例。

在PreferenceActivity中，当我们点击Header时，其处理流程分为单屏幕和双屏幕两套流程。

1、单屏幕（SinglePane）

1.1、点击每一项，执行如下代码.

public void onHeaderClick(Header header, int position) {
    	Log.d(LOG_TAG, "Settings onHeaderClick Header is:"+header.title+",position is:"+position+",mLastHeader is:"+mLastHeader);
    	
        boolean revert = false;
        if (header.id == R.id.account_add) {
            revert = true;
        }
        Log.d(LOG_TAG, "Settings onHeaderClick Header id is:"+header.id+", R.id.account_add is:"+R.id.account_add+",revert is:"+revert);
        super.onHeaderClick(header, position);

        if (revert && mLastHeader != null) {
            highlightHeader((int) mLastHeader.id);
        } else {
            mLastHeader = header;
        }
    }

关于hightlightHeader下面有详细介绍，这里就不介绍了。

主要执行父类的onHeaderClick方法。

1.2、

public void onHeaderClick(Header header, int position) {
        if (header.fragment != null) {
            if (mSinglePane) {
                int titleRes = header.breadCrumbTitleRes;
                int shortTitleRes = header.breadCrumbShortTitleRes;
                if (titleRes == 0) {
                    titleRes = header.titleRes;
                    shortTitleRes = 0;
                }
                startWithFragment(header.fragment, header.fragmentArguments, null, 0,
                        titleRes, shortTitleRes);
            } else {
                switchToHeader(header);
            }
        } else if (header.intent != null) {
            startActivity(header.intent);
        }
    }

因为mSinglePane为true，故执行startWithFragment。

1.3、

Intent intent = onBuildStartFragmentIntent(fragmentName, args, titleRes, shortTitleRes);
        if (resultTo == null) {
            startActivity(intent);
        } else {
            resultTo.startActivityForResult(intent, resultRequestCode);
        }

我们看到这里会执行onBuildStartFragmentIntent。
1.4、

public Intent onBuildStartFragmentIntent(String fragmentName, Bundle args,
            int titleRes, int shortTitleRes) {
        Intent intent = new Intent(Intent.ACTION_MAIN);
        intent.setClass(this, getClass());
        intent.putExtra(EXTRA_SHOW_FRAGMENT, fragmentName);
        intent.putExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS, args);
        intent.putExtra(EXTRA_SHOW_FRAGMENT_TITLE, titleRes);
        intent.putExtra(EXTRA_SHOW_FRAGMENT_SHORT_TITLE, shortTitleRes);
        intent.putExtra(EXTRA_NO_HEADERS, true);
        return intent;
    }

这个方法在子类中有重写。

Settings.java

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)) {
            intent.putExtra(EXTRA_CLEAR_UI_OPTIONS, true);
        }

        intent.setClass(this, SubSettings.class);
        return intent;
    }

这里主要是为intent增加了SubSettings.class，因为Header中的fragment，需要有个Activity依附。

ps：//******log信息

01-08 21:55:05.857: D/Hlwang_Settings(25569): Settings onBuildStartFragmentIntent fragmentName is:com.android.settings.wifi.WifiSettings

//*************************

1.5、由1.3可知，这个intent会被startActivity(intent)发送出去。

Intent会被SubSettings接收，由于SubSettings继承自Settigns.java，因此，这个Intent还会被Settings.java执行。

public class SubSettings extends Settings {
}

1.6、在Settings.java的onCreate中：

在onCreate中会执行getMeteData以及getIntent。这两个方法共同作用得到了mFragmentClass。然后执行super.onCreate

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
        }
    }

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;
    }

ps：//****log信息

01-08 21:55:05.897: D/Hlwang_Settings(25569): Settings getStartingFragmentClass intentClass is:com.android.settings.SubSettingsgetClassName is:com.android.settings.SubSettings

//***********

PreferenceActivity.java

String initialFragment = getIntent().getStringExtra(EXTRA_SHOW_FRAGMENT);
        Bundle initialArguments = getIntent().getBundleExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS);
        int initialTitle = getIntent().getIntExtra(EXTRA_SHOW_FRAGMENT_TITLE, 0);
        int initialShortTitle = getIntent().getIntExtra(EXTRA_SHOW_FRAGMENT_SHORT_TITLE, 0);

这样initialFragment得到了初始化，并且。

if (initialFragment != null && mSinglePane) {
                // If we are just showing a fragment, we want to run in
                // new fragment mode, but don't need to compute and show
                // the headers.
                switchToHeader(initialFragment, initialArguments);
                if (initialTitle != 0) {
                    CharSequence initialTitleStr = getText(initialTitle);
                    CharSequence initialShortTitleStr = initialShortTitle != 0
                            ? getText(initialShortTitle) : null;
                    showBreadCrumbs(initialTitleStr, initialShortTitleStr);
                }

            }

这里跳用switchToHeader将Fragment切换到右边窗体中。

if (initialFragment != null && mSinglePane) {
            // Single pane, showing just a prefs fragment.
            findViewById(com.android.internal.R.id.headers).setVisibility(View.GONE);
            mPrefsContainer.setVisibility(View.VISIBLE);
            if (initialTitle != 0) {
                CharSequence initialTitleStr = getText(initialTitle);
                CharSequence initialShortTitleStr = initialShortTitle != 0
                        ? getText(initialShortTitle) : null;
                showBreadCrumbs(initialTitleStr, initialShortTitleStr);
            }
        }

这里，将左边窗体的Header 列表隐藏。

2、双屏幕（平板）

2.1、首先执行单击事件

public void onHeaderClick(Header header, int position) {
        if (header.fragment != null) {
            if (mSinglePane) {
                int titleRes = header.breadCrumbTitleRes;
                int shortTitleRes = header.breadCrumbShortTitleRes;
                if (titleRes == 0) {
                    titleRes = header.titleRes;
                    shortTitleRes = 0;
                }
                startWithFragment(header.fragment, header.fragmentArguments, null, 0,
                        titleRes, shortTitleRes);
            } else {
                switchToHeader(header);
            }
        } else if (header.intent != null) {
            startActivity(header.intent);
        }
    }

我们在这个方法内看到，首先判断fragment以及intent，然后会根据mSinglePane来判断进入那个逻辑里。mSinglePane是单屏幕或者双屏幕，此处为false。

在双屏幕中，此处会执行switchToHeader（header）方法。

2.2、

if (mCurHeader == header) {
            // This is the header we are currently displaying.  Just make sure
            // to pop the stack up to its root state.
            getFragmentManager().popBackStack(BACK_STACK_PREFS,
                    FragmentManager.POP_BACK_STACK_INCLUSIVE);
        } else {
            int direction = mHeaders.indexOf(header) - mHeaders.indexOf(mCurHeader);
            switchToHeaderInner(header.fragment, header.fragmentArguments, direction);
            setSelectedHeader(header);
        }

这里首先会判断mCurrentHeader是否为要切换的header。如果mCurrentHeader == header，那么执行：

getFragmentManager().popBackStack(BACK_STACK_PREFS,
                    FragmentManager.POP_BACK_STACK_INCLUSIVE);

否则：

int direction = mHeaders.indexOf(header) - mHeaders.indexOf(mCurHeader);
            switchToHeaderInner(header.fragment, header.fragmentArguments, direction);
            setSelectedHeader(header);

在这里，direction没有发挥作用。这里应该是判断ListView是向上滚动还是向下滚动。

我们看switchToHeaderInnr方法。

2.3、

getFragmentManager().popBackStack(BACK_STACK_PREFS,
                FragmentManager.POP_BACK_STACK_INCLUSIVE);
        Fragment f = Fragment.instantiate(this, fragmentName, args);
        FragmentTransaction transaction = getFragmentManager().beginTransaction();
        transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
        transaction.replace(com.android.internal.R.id.prefs, f);
        transaction.commitAllowingStateLoss();

这个方法处理fragment的切换。例如：我们在左边，点击了Bluetooth的设置项，那么其fragment会在右边显示。

2.4,最后执行setSelectedHeader方法。

void setSelectedHeader(Header header) {
        mCurHeader = header;
        int index = mHeaders.indexOf(header);
        if (index >= 0) {
            getListView().setItemChecked(index, true);
        } else {
            getListView().clearChoices();
        }
        showBreadCrumbs(header);
    }

在这个方法中主要处理ListView的setItemChecked状态。如上图中蓝牙设置项的选中底色。并且设置Breadcrumb（标题）

2.5、

void showBreadCrumbs(Header header) {
        if (header != null) {
            CharSequence title = header.getBreadCrumbTitle(getResources());
            if (title == null) title = header.getTitle(getResources());
            if (title == null) title = getTitle();
            showBreadCrumbs(title, header.getBreadCrumbShortTitle(getResources()));
        } else {
            showBreadCrumbs(getTitle(), null);
        }
    }

 if (mFragmentBreadCrumbs == null) {
            View crumbs = findViewById(android.R.id.title);
            // For screens with a different kind of title, don't create breadcrumbs.
            try {
                mFragmentBreadCrumbs = (FragmentBreadCrumbs)crumbs;
            } catch (ClassCastException e) {
                return;
            }
            if (mFragmentBreadCrumbs == null) {
                if (title != null) {
                    setTitle(title);
                }
                return;
            }
            mFragmentBreadCrumbs.setMaxVisible(2);
            mFragmentBreadCrumbs.setActivity(this);
        }
        mFragmentBreadCrumbs.setTitle(title, shortTitle);
        mFragmentBreadCrumbs.setParentTitle(null, null, null);

//*****************************************************************************************

2.6、在设置应用的源代码中，Settings.java类中。上述的处理存在如下差别。

Settings.java重新了switchHeader方法：

public void switchToHeader(Header header) {
        if (!mInLocalHeaderSwitch) {
            mCurrentHeader = null;
            mParentHeader = null;
        }
        super.switchToHeader(header);
    }

mInLocalHeaderSwitch在我们点击条目的时候为false，故，Settings.java中定义的mCurrentHeader以及mParentHeader会赋值null。然后执行super.switchToHeader（）。

二、外部通过Action进入设置应用的流程。（多屏幕的状态下）

Intent intent=new Intent();
//		intent.setClassName(this, "c");
//		intent.setAction("android.intent.action.PICK_ACTIVITY");
		intent.setAction("android.settings.WIFI_IP_SETTINGS");
		startActivity(intent);

通过上述代码，会进入如下界面。

启动这个界面会经历如下流程，

首先Settigns.java的onCreate方法。

1、

protected void onCreate(Bundle savedInstanceState) {
        if (getIntent().getBooleanExtra(EXTRA_CLEAR_UI_OPTIONS, false)) {
            getWindow().setUiOptions(0);
        }

        getMetaData();
        mInLocalHeaderSwitch = true;
        super.onCreate(savedInstanceState);
        mInLocalHeaderSwitch = false;

        if (!onIsHidingHeaders() && onIsMultiPane()) {
            highlightHeader();
            // 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);
                }
            });
        }

        // TODO Add support for android.R.id.home in all Setting's onOptionsItemSelected
        // getActionBar().setDisplayOptions(ActionBar.DISPLAY_HOME_AS_UP,
        // ActionBar.DISPLAY_HOME_AS_UP);
    }

在这个方法内，首先执行getIntent方法，Settings重新了这个方法。

2、

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;
    }

在这个方法内，会调用getStartingFragmentClass方法。

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;
    }

这个方法中，intentClass为：com.android.settings.Settings$AdvancedWifiSettingsActivity

ps：//****************************************************************log信息

01-08 21:10:06.737: D/Hlwang_Settings(15602): Settings getStartingFragmentClass mFragmentClass is:null
01-08 21:10:06.737: D/Hlwang_Settings(15602): Settings getStartingFragmentClass intentClass is:com.android.settings.Settings$AdvancedWifiSettingsActivity

//************************************************

3、我们继续看onCreate方法。在往下会执行getMeteData方法。

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
        }
    }

这里，AdvancedWifiSettingsActivity在AndroidManifest.xml中的配置：

<activity android:name="Settings$AdvancedWifiSettingsActivity"
                android:label="@string/wifi_advanced_settings_label"
                android:configChanges="orientation|keyboardHidden|screenSize"
                android:clearTaskOnLaunch="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <action android:name="android.settings.WIFI_IP_SETTINGS" />
                <category android:name="android.intent.category.VOICE_LAUNCH" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
            <meta-data android:name="com.android.settings.FRAGMENT_CLASS"
                android:value="com.android.settings.wifi.AdvancedWifiSettings" />
            <meta-data android:name="com.android.settings.TOP_LEVEL_HEADER_ID"
                android:resource="@id/wifi_settings" />
            <meta-data android:name="com.android.settings.PARENT_FRAGMENT_TITLE"
                android:resource="@string/wifi_settings" />
            <meta-data android:name="com.android.settings.PARENT_FRAGMENT_CLASS"
                android:value="com.android.settings.Settings$WifiSettingsActivity" />
        </activity>

故而：mTopLevelId = @+id/wifi_settigns，mFragmentClass为：com.android.settings.wifi.AdvancedWifiSettings，mParentClass为：com.android.settings.Settings$WifiSettingsActivity

ps：//************************log信息

01-08 21:10:06.747: D/Hlwang_Settings(15602): Settings getMetaData
01-08 21:10:06.747: D/Hlwang_Settings(15602): Settings getMetaData mFragmentClass is:com.android.settings.wifi.AdvancedWifiSettings
01-08 21:10:06.747: D/Hlwang_Settings(15602): Settings getMetaData parentFragmentClass is:com.android.settings.Settings$WifiSettingsActivity

//******************************
4、继续onCreate执行，接下来会执行：

mInLocalHeaderSwitch = true;
        super.onCreate(savedInstanceState);
        mInLocalHeaderSwitch = false;

这里会执行super.onCreate方法。之所以用mInLocalHeaderSwitch包裹，主要是因为super.onCreate方法，会执行到PreferenceActitivity.java中的：

if (!mSinglePane) {
                        if (initialFragment == null) {
                            Header h = onGetInitialHeader();
                            switchToHeader(h);
                        } else {
                            switchToHeader(initialFragment, initialArguments);
                        }
                    }

Settings.java重写了switchToHeader方法。

public void switchToHeader(Header header) {
        if (!mInLocalHeaderSwitch) {
            mCurrentHeader = null;
            mParentHeader = null;
        }
        super.switchToHeader(header);
    }

这样mInLocalHeaderSwitch为true，不会清楚mCurrentHeader以及mParentHeader。

最后会执行super.switchToHeader方法，这个方法的执行，会将AdvancedWifiSettings加载到如上图所示的右边的区域内。

Settings.java还重新了onGetInitialHeader方法，这个方法为Header赋了正确的值。

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;
    }

5、最后一步，给上图左边的部分加上setItemChecked效果。也即是上图中的选中状态底纹。

if (!onIsHidingHeaders() && onIsMultiPane()) {
            highlightHeader();
            // Force the title so that it doesn't get overridden by a direct launch of
            // a specific settings screen.
            setTitle(R.string.settings_label);
        }

private void highlightHeader() {
        if (mTopLevelHeaderId != 0) {
            Integer index = mHeaderIndexMap.get(mTopLevelHeaderId);
            if (index != null) {
                getListView().setItemChecked(index, true);
                getListView().smoothScrollToPosition(index);
            }
        }
    }

mTopLevelHeaderId，我们在getMeteData方法中得到。

一、在多屏幕中，mFirstHeader的作用主要是为了正确的切换第一个Header。

mFirstHeader的初始化

if (mFirstHeader == null &&
                        HeaderAdapter.getHeaderType(header) != HeaderAdapter.HEADER_TYPE_CATEGORY) {
                    mFirstHeader = header;
                }

如果为空，那么mFirstHeader为最靠前的第一个category。

mFirstHeader的使用：

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;
    }

如果getStarttingFragmentClass为null，那么返回mFirstHeader。

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
                && mFirstHeader != null && !onIsHidingHeaders() && onIsMultiPane()) {
            switchToHeaderLocal(mFirstHeader);
        }
    }

二、mCurrentHeader的作用，显示当前Header的title。

初始化：

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;
    }

外部跳转得到了fragmentClass，那么会初始化mCurrentHeader。

另外的一处初始化：

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();

                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);
        }
    }

使用：

在onCreate中。

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);
        }

三、mParentHeader，

初始化：

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
        }
    }

使用如上面的mCurrentHeader。