• Preference深度解析

    在阅读Android系统应用Settings源码的时候，我们会发现它的布局文件有一大批Preference控件，这个是什么东西呢？其实Preference是android原生为了持久化数据的一种"控件"，注意它并不是真正意义上的View。

    一、初识Preference

    Preference家族代码被定义在frameworks/base/core/java/android/preference，改目录下的代码用来实现偏好设置相关的界面。即Preference是android原生为了持久化数据的一种"控件"。要使用Preference就必须建立在PreferenceActivity或PreferenceFragment的载体上面。具体用法可以参考《Android之PreferenceFragment详解》

    • Preference家族

    Preference被定义在frameworks/base/core下面，其中Preference作为视图控件在整个家族中的地位类似于View，PreferenceGroup就类似于ViewGroup，XXXPreference则继承于Preference并扩展了不同功能样式。除此之外Preference并不能直接使用在Activity和Fragment上面，因此多了PreferenceActivity和PreferenceFragment他们分别继承Activity和Fragment并在此基础上实现了数据持久化、控件解析等功能。除此之外还有两个比较重要的类： PreferenceScreen和PreferenceGroupAdapter

    • Preference是"控件"？

    Preference并不是控件，它没有继承View，但是为什么我们的布局文件中可以使用他呢？其实只有继承了PreferenceFragment或者PreferenceActivity的才能使用上面以PreferenceScreen标签开头的xml文件，因为他们内部作了一系列解析，同时Preference有方法返回一个View对象，如下代码：

    1. //android/frameworks/base/core/java/android/preference/Preference.java
    2. @Deprecated
    3. public class Preference implements Comparable {
    4.     private boolean mShouldDisableView = true;
    5.     @UnsupportedAppUsage
    6.     private int mLayoutResId = com.android.internal.R.layout.preference;
    7.     @UnsupportedAppUsage
    8.     private int mWidgetLayoutResId;
    9.     public void setLayoutResource(@LayoutRes int layoutResId) {
    10.         if (layoutResId != mLayoutResId)   mRecycleEnabled = false;
    11.         mLayoutResId = layoutResId;
    12.     }
    13.     @LayoutRes
    14.     public int getLayoutResource() {
    15.         return mLayoutResId;
    16.     }
    17.     //返回一个视图控件View
    18.     public View getView(View convertView, ViewGroup parent) {
    19.         //如果第一次就创建视图View
    20.         if (convertView == null)  convertView = onCreateView(parent);
    21.         //给视图View填充数据和更新ui
    22.         onBindView(convertView);
    23.         return convertView;
    24.     }
    25.     //创建视图控件View，实际上还是inflate对应的资源ID文件
    26.     @CallSuper
    27.     protected View onCreateView(ViewGroup parent) {
    28.         final LayoutInflater layoutInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    29.         final View layout = layoutInflater.inflate(mLayoutResId, parent, false);
    30.         final ViewGroup widgetFrame = (ViewGroup) layout.findViewById(com.android.internal.R.id.widget_frame);
    31.        if (widgetFrame != null) {
    32.             if (mWidgetLayoutResId != 0) layoutInflater.inflate(mWidgetLayoutResId, widgetFrame);
    33.             else widgetFrame.setVisibility(View.GONE);
    34.         }
    35.         return layout;
    36.     }
    37.     //主要是给上面创建的视图View设置数据
    38.     @CallSuper
    39.     protected void onBindView(View view) {
    40.         final TextView titleView = (TextView) view.findViewById(com.android.internal.R.id.title);
    41.         if (titleView != null) {
    42.             final CharSequence title = getTitle();
    43.             if (!TextUtils.isEmpty(title)) {
    44.                 titleView.setText(title);
    45.                 titleView.setVisibility(View.VISIBLE);
    46.                 if (mHasSingleLineTitleAttr) titleView.setSingleLine(mSingleLineTitle);
    47.             } else {
    48.                 titleView.setVisibility(View.GONE);
    49.             }
    50.         }
    51.         final TextView summaryView = (TextView) view.findViewById( com.android.internal.R.id.summary);
    52.         if (summaryView != null) {
    53.             final CharSequence summary = getSummary();
    54.             if (!TextUtils.isEmpty(summary)) {
    55.                 summaryView.setText(summary);
    56.                 summaryView.setVisibility(View.VISIBLE);
    57.             } else {
    58.                 summaryView.setVisibility(View.GONE);
    59.             }
    60.         }
    61.         final ImageView imageView = (ImageView) view.findViewById(com.android.internal.R.id.icon);
    62.         if (imageView != null) {
    63.             if (mIconResId != 0 || mIcon != null) {
    64.                 if (mIcon == null)  mIcon = getContext().getDrawable(mIconResId);
    65.                 if (mIcon != null) imageView.setImageDrawable(mIcon);
    66.             }
    67.             if (mIcon != null) imageView.setVisibility(View.VISIBLE);
    68.             else imageView.setVisibility(mIconSpaceReserved ? View.INVISIBLE : View.GONE);
    69.         }
    70.         final View imageFrame = view.findViewById(com.android.internal.R.id.icon_frame);
    71.         if (imageFrame != null) {
    72.             if (mIcon != null) imageFrame.setVisibility(View.VISIBLE);
    73.             else imageFrame.setVisibility(mIconSpaceReserved ? View.INVISIBLE : View.GONE);
    74.         }
    75.         if (mShouldDisableView) setEnabledStateOnViews(view, isEnabled());
    76.     }
    77.     //界面更改条目栏
    78.     public void setTitle(CharSequence title) {
    79.         if (title == null && mTitle != null || title != null && !title.equals(mTitle)) {
    80.             mTitleRes = 0;
    81.             mTitle = title;
    82.             notifyChanged();
    83.         }
    84.     }
    85.     //界面更改图标
    86.     public void setIcon(Drawable icon) {
    87.         if ((icon == null && mIcon != null) || (icon != null && mIcon != icon)) {
    88.             mIcon = icon;
    89.             notifyChanged();
    90.         }
    91.     }
    92.     //界面有改变回调监听器
    93.     protected void notifyChanged() {
    94.         if (mListener != null)  mListener.onPreferenceChange(this);
    95.     }
    96. }
    • Preference如何持久化？

    Settings为什么大量使用了Preference，而没有使用到我们常见的View和TextView呢，因为这里逻辑功能上主要是为了给系统进行一些设置，所有就涉及到了设置参数持久化（即断电后还继续生效），如下代码它内部已经通过PreferenceManager来进行对数据的持久化，实际上还是使用了四大存储方式之一

    1. //android/frameworks/base/core/java/android/preference/Preference.java
    2. @Deprecated
    3. public class Preference implements Comparable {
    4.     @Nullable
    5.     private PreferenceManager mPreferenceManager;
    6.     public SharedPreferences getSharedPreferences() {
    7.         if (mPreferenceManager == null || getPreferenceDataStore() != null)   return null;
    8.         return mPreferenceManager.getSharedPreferences();
    9.     }
    10.     public SharedPreferences.Editor getEditor() {
    11.         if (mPreferenceManager == null || getPreferenceDataStore() != null)  return null;
    12.         return mPreferenceManager.getEditor();
    13.     }
    14.     public boolean shouldCommit() {
    15.         if (mPreferenceManager == null)  return false;
    16.         return mPreferenceManager.shouldCommit();
    17.     }
    18.     public PreferenceManager getPreferenceManager() {
    19.         return mPreferenceManager;
    20.     }
    21. }
    • Preference唯一标识
    • Preference跳转到Fragment

    二、深度剖析

    第一章初步介绍了Preference的基本用法和一些特点，想使用Preference必须建立在PreferenceActivity或者PreferenceFragment的基础之上，除此之外布局文件最外层必须使用一个PreferenceScreen嵌套所有的Preference。

    1、剖析PreferenceActivity

    1.1、布局文件加载

    PreferenceActivity的布局跟主流布局类似，即通常由三部分组成：标题栏、内容、最底层的bar。这里我们关注标题栏和内容，因为PreferenceActivity在设计的时候就考虑到了公用同一个activity进行页面跳转，即替换内容区域的fragment。

    1. //frameworks/base/core/java/android/preference/PreferenceActivity.java
    2. /*继承ListActivity,即其布局文件中必须有一个ListView控件且id必须为list*/
    3. @Deprecated public abstract class PreferenceActivity extends ListActivity implements
    4.         /*Preference树结构下所有视图控件点击回调事件*/
    5.         PreferenceManager.OnPreferenceTreeClickListener,
    6.         /*Preference被点击后如果有设置fragment就直接替换fragment回调*/
    7.         PreferenceFragment.OnPreferenceStartFragmentCallback {
    8.     //通过android:fragment属性进行跳转不同fragment页面，可能共用同一个PreferenceActivity，但是标题栏不一样，mHeaders 存储了所有的标题
    9.     private final ArrayList
       mHeaders = new ArrayList
      ();
    10.     private FrameLayout mListFooter;
    11.     private ViewGroup mPrefsContainer;
    12.     private CharSequence mActivityTitle;
    13.     private ViewGroup mHeadersContainer;
    14.     //当前对应的标题，Header表示一个标题
    15.     private Header mCurHeader;
    16.     //管理器
    17.     private PreferenceManager mPreferenceManager;
    18.     //数据持久化
    19.     private Bundle mSavedInstanceState;
    20.     @Override
    21.     protected void onCreate(@Nullable Bundle savedInstanceState) {
    22.         super.onCreate(savedInstanceState);
    23.         //布局文件加载的是preference_list_content.xml
    24.         final int layoutResId = sa.getResourceId(
    25.                 com.android.internal.R.styleable.PreferenceActivity_layout,
    26.                 com.android.internal.R.layout.preference_list_content);
    27.         setContentView(layoutResId);
    28.         mListFooter = (FrameLayout)findViewById(com.android.internal.R.id.list_footer);
    29.         mPrefsContainer = (ViewGroup) findViewById(com.android.internal.R.id.prefs_frame);
    30.         mHeadersContainer = (ViewGroup) findViewById(com.android.internal.R.id.headers);
    31.         //......
    32.     }
    33. }
    1. //frameworks/base/core/res/res/layout/preference_list_content.xml
    2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    3.     android:orientation="vertical"
    4.     android:layout_height="match_parent"
    5.     android:layout_width="match_parent">
    6.     <LinearLayout
    7.         android:id="@+id/prefs_container"
    8.         android:orientation="horizontal"
    9.         android:layout_width="match_parent"
    10.         android:layout_height="0px"
    11.         android:layout_weight="1">
    12.         
    13.         <LinearLayout
    14.             style="?attr/preferenceHeaderPanelStyle"
    15.             android:id="@+id/headers"
    16.             android:orientation="vertical"
    17.             android:layout_width="0px"
    18.             android:layout_height="match_parent"
    19.             android:layout_weight="@integer/preferences_left_pane_weight">
    20.             <ListView android:id="@android:id/list"
    21.                 style="?attr/preferenceListStyle"
    22.                 android:layout_width="match_parent"
    23.                 android:layout_height="0px"
    24.                 android:layout_weight="1"
    25.                 android:clipToPadding="false"
    26.                 android:drawSelectorOnTop="false"
    27.                 android:cacheColorHint="@android:color/transparent"
    28.                 android:listPreferredItemHeight="48dp"
    29.                 android:scrollbarAlwaysDrawVerticalTrack="true" />
    30.             <FrameLayout android:id="@+id/list_footer"
    31.                     android:layout_width="match_parent"
    32.                     android:layout_height="wrap_content"
    33.                     android:layout_weight="0" />
    34.         LinearLayout>
    35.         
    36.         <LinearLayout
    37.                 android:id="@+id/prefs_frame"
    38.                 style="?attr/preferencePanelStyle"
    39.                 android:layout_width="0px"
    40.                 android:layout_height="match_parent"
    41.                 android:layout_weight="@integer/preferences_right_pane_weight"
    42.                 android:orientation="vertical">
    43.             <include layout="@layout/breadcrumbs_in_fragment" />
    44.             <android.preference.PreferenceFrameLayout android:id="@+id/prefs"
    45.                     android:layout_width="match_parent"
    46.                     android:layout_height="0dip"
    47.                     android:layout_weight="1"
    48.                 />
    49.         LinearLayout>
    50.     LinearLayout>
    51.     
    52. LinearLayout>

    1.2、Header对应fragment的标题

    1. //frameworks/base/core/java/android/preference/PreferenceActivity.java
    2. @Deprecated public abstract class PreferenceActivity extends ListActivity{
    3.     //Header对应当前界面，即存储了当前界面的基本信息：
    4.     //                   titleRes和title为标题栏
    5.     //                   summaryRes和summary为概述
    6.     @Deprecated public static final class Header implements Parcelable {
    7.         @StringRes
    8.         public int titleRes;
    9.         public CharSequence title;
    10.         @StringRes
    11.         public int summaryRes;
    12.         public CharSequence summary;
    13.         //对应的ICON图标
    14.         public int iconRes;
    15.         //存储了对应的fragment的类名，点击Preference会自动跳转到android:fragment属性的值对应的类（通过反射进行实例化）
    16.         public String fragment;
    17.         //需要传递到fragment的参数
    18.         public Bundle fragmentArguments;
    19.         public Intent intent;
    20.         public Bundle extras;
    21.         //序列化上面的内容，包括fragment的类名
    22.         @Override public void writeToParcel(Parcel dest, int flags) {
    23.             dest.writeLong(id);
    24.             dest.writeInt(titleRes);
    25.             TextUtils.writeToParcel(title, dest, flags);
    26.             dest.writeInt(summaryRes);
    27.             TextUtils.writeToParcel(summary, dest, flags);
    28.             dest.writeInt(breadCrumbTitleRes);
    29.             TextUtils.writeToParcel(breadCrumbTitle, dest, flags);
    30.             dest.writeInt(breadCrumbShortTitleRes);
    31.             TextUtils.writeToParcel(breadCrumbShortTitle, dest, flags);
    32.             dest.writeInt(iconRes);
    33.             dest.writeString(fragment);
    34.             dest.writeBundle(fragmentArguments);
    35.             if (intent != null) {
    36.                 dest.writeInt(1);
    37.                 intent.writeToParcel(dest, flags);
    38.             } else dest.writeInt(0);
    39.             dest.writeBundle(extras);
    40.         }
    41.         //反序列化上面的内容，包括fragment的类名
    42.         public void readFromParcel(Parcel in) {
    43.             id = in.readLong();
    44.             titleRes = in.readInt();
    45.             title = TextUtils.CHAR_SEQUENCE_CREATOR.createFromParcel(in);
    46.             summaryRes = in.readInt();
    47.             summary = TextUtils.CHAR_SEQUENCE_CREATOR.createFromParcel(in);
    48.             breadCrumbTitleRes = in.readInt();
    49.             breadCrumbTitle = TextUtils.CHAR_SEQUENCE_CREATOR.createFromParcel(in);
    50.             breadCrumbShortTitleRes = in.readInt();
    51.             breadCrumbShortTitle = TextUtils.CHAR_SEQUENCE_CREATOR.createFromParcel(in);
    52.             iconRes = in.readInt();
    53.             fragment = in.readString();
    54.             fragmentArguments = in.readBundle();
    55.             if (in.readInt() != 0)  intent = Intent.CREATOR.createFromParcel(in);
    56.             extras = in.readBundle();
    57.         }
    58.         Header(Parcel in) {
    59.             readFromParcel(in);
    60.         }
    61.         public static final @android.annotation.NonNull Creator
       CREATOR = new Creator
      () {
    62.             public Header createFromParcel(Parcel source) {
    63.                 return new Header(source);
    64.             }
    65.             public Header[] newArray(int size) {
    66.                 return new Header[size];
    67.             }
    68.         };
    69.     }
    70.     private static class HeaderAdapter extends ArrayAdapter
       {
    71.         private static class HeaderViewHolder {
    72.             ImageView icon;
    73.             TextView title;
    74.             TextView summary;
    75.         }
    76.         private LayoutInflater mInflater;
    77.         private int mLayoutResId;
    78.         private boolean mRemoveIconIfEmpty;
    79.         public HeaderAdapter(Context context, List
       objects, int layoutResId, boolean removeIconBehavior) {
    80.             super(context, 0, objects);
    81.             mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    82.             mLayoutResId = layoutResId;
    83.             mRemoveIconIfEmpty = removeIconBehavior;
    84.         }
    85.         @Override
    86.         public View getView(int position, View convertView, ViewGroup parent) {
    87.             HeaderViewHolder holder;
    88.             View view;
    89.             if (convertView == null) {
    90.                 view = mInflater.inflate(mLayoutResId, parent, false);
    91.                 holder = new HeaderViewHolder();
    92.                 holder.icon = (ImageView) view.findViewById(com.android.internal.R.id.icon);
    93.                 holder.title = (TextView) view.findViewById(com.android.internal.R.id.title);
    94.                 holder.summary = (TextView) view.findViewById(com.android.internal.R.id.summary);
    95.                 view.setTag(holder);
    96.             } else {
    97.                 view = convertView;
    98.                 holder = (HeaderViewHolder) view.getTag();
    99.             }
    100.         }
    101.     }
    102. }

    1.3、切换fragment

    1. //frameworks/base/core/java/android/preference/PreferenceActivity.java
    2. @Deprecated public abstract class PreferenceActivity extends ListActivity{
    3.     //该方法很多地方被调用，例如创建或者点击需要切换fragment或者当前header的时候
    4.     public void switchToHeader(Header header) {
    5.         //判断是否当前header，是不切换
    6.         if (mCurHeader == header) {
    7.             getFragmentManager().popBackStack(BACK_STACK_PREFS,  FragmentManager.POP_BACK_STACK_INCLUSIVE);
    8.         } else {
    9.             if (header.fragment == null)   throw new IllegalStateException("can't switch to header that has no fragment");
    10.             //切换对应的fragment
    11.             switchToHeaderInner(header.fragment, header.fragmentArguments);
    12.             //切换header布局里面的字符串和图标等信息
    13.             setSelectedHeader(header);
    14.         }
    15.     }
    16.     //还是使用了FragmentTransaction 方式进行切换
    17.     private void switchToHeaderInner(String fragmentName, Bundle args) {
    18.         getFragmentManager().popBackStack(BACK_STACK_PREFS, FragmentManager.POP_BACK_STACK_INCLUSIVE);
    19.         if (!isValidFragment(fragmentName))  throw new IllegalArgumentException("Invalid fragment for this activity: " + fragmentName); 
    20.         Fragment f = Fragment.instantiate(this, fragmentName, args);
    21.         FragmentTransaction transaction = getFragmentManager().beginTransaction();
    22.         transaction.setTransition(mSinglePane
    23.                 ? FragmentTransaction.TRANSIT_NONE
    24.                 : FragmentTransaction.TRANSIT_FRAGMENT_FADE);
    25.         transaction.replace(com.android.internal.R.id.prefs, f);
    26.         transaction.commitAllowingStateLoss();
    27.         if (mSinglePane && mPrefsContainer.getVisibility() == View.GONE) {
    28.             mPrefsContainer.setVisibility(View.VISIBLE);
    29.             mHeadersContainer.setVisibility(View.GONE);
    30.         }
    31.     }
    32.     //切换header的内容，通过触发点击事件
    33.     void setSelectedHeader(Header header) {
    34.         mCurHeader = header;
    35.         int index = mHeaders.indexOf(header);
    36.         if (index >= 0)  getListView().setItemChecked(index, true);
    37.         else  getListView().clearChoices();
    38.         showBreadCrumbs(header);
    39.     }
    40. }

    2、剖析PreferenceFragment

    2.1、布局文件加载

    PreferenceFragment的布局跟PreferenceActivity类似，如下代码：

    1. //frameworks/base/core/java/android/preference/PreferenceFragment.java
    2. @Deprecated public abstract class PreferenceFragment extends Fragment implements
    3.         /*Preference树结构下所有视图控件点击回调事件*/
    4.         PreferenceManager.OnPreferenceTreeClickListener {
    5.     @UnsupportedAppUsage
    6.     private PreferenceManager mPreferenceManager;
    7.     private ListView mList;
    8.     //PreferenceFragment的布局文件，与PreferenceActivity使用了同样的布局
    9.     private int mLayoutResId = com.android.internal.R.layout.preference_list_fragment;
    10.     private static final int MSG_BIND_PREFERENCES = 1;
    11.     private Handler mHandler = new Handler() {
    12.         @Override public void handleMessage(Message msg) {
    13.             switch (msg.what) {
    14.                 case MSG_BIND_PREFERENCES:
    15.                     bindPreferences();
    16.                     break;
    17.             }
    18.         }
    19.     };
    20.     @Override
    21.     public void onCreate(@Nullable Bundle savedInstanceState) {
    22.         super.onCreate(savedInstanceState);
    23.         mPreferenceManager = new PreferenceManager(getActivity(), FIRST_REQUEST_CODE);
    24.         mPreferenceManager.setFragment(this);
    25.     }
    26.     @Override
    27.     public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    28.         //加载preference_list_fragment.xml,如果有acitivity沿用
    29.         mLayoutResId = a.getResourceId(com.android.internal.R.styleable.PreferenceFragment_layout, mLayoutResId);
    30.         return inflater.inflate(mLayoutResId, container, false);
    31.     }
    32.     //从布局文件中找到list
    33.     @Override public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    34.         super.onViewCreated(view, savedInstanceState);
    35.         ListView lv = (ListView) view.findViewById(android.R.id.list);
    36.         if (lv != null && a.hasValueOrEmpty(com.android.internal.R.styleable.PreferenceFragment_divider)) {
    37.             lv.setDivider( a.getDrawable(com.android.internal.R.styleable.PreferenceFragment_divider));
    38.         }
    39.     }
    40.     //这里很重要
    41.     @Override public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    42.         super.onActivityCreated(savedInstanceState);
    43.         //bindPreferences方法是用来绑定加载所有的Preference类的
    44.         if (mHavePrefs)  bindPreferences(); 
    45.         mInitDone = true;
    46.         if (savedInstanceState != null) {
    47.             Bundle container = savedInstanceState.getBundle(PREFERENCES_TAG);
    48.             if (container != null) {
    49.                 //如果有缓存PreferenceScreen，直接获取出来
    50.                 final PreferenceScreen preferenceScreen = getPreferenceScreen();
    51.                 if (preferenceScreen != null)   preferenceScreen.restoreHierarchyState(container); 
    52.             }
    53.         }
    54.     }
    55.     //设置Preference点击事件
    56.     @Override public void onStart() {
    57.         super.onStart();
    58.         mPreferenceManager.setOnPreferenceTreeClickListener(this);
    59.     }
    60.     @Override public void onStop() {
    61.         super.onStop();
    62.         mPreferenceManager.dispatchActivityStop();
    63.         mPreferenceManager.setOnPreferenceTreeClickListener(null);
    64.     }
    65. }

    2.2、什么时候回调onBindPreferences方法？

    1. public abstract class PreferenceFragment{
    2.     private static final int MSG_BIND_PREFERENCES = 1;
    3.     private Handler mHandler = new Handler() {
    4.         @Override public void handleMessage(Message msg) {
    5.             switch (msg.what) {
    6.                 case MSG_BIND_PREFERENCES:
    7.                     bindPreferences();
    8.                     break;
    9.             }
    10.         }
    11.     };
    12.     private void bindPreferences() {
    13.         //获取当前对应的PreferenceScreen
    14.         final PreferenceScreen preferenceScreen = getPreferenceScreen();
    15.         if (preferenceScreen != null) {
    16.             View root = getView();
    17.             if (root != null) {
    18.                 View titleView = root.findViewById(android.R.id.title);
    19.                 if (titleView instanceof TextView) {
    20.                     CharSequence title = preferenceScreen.getTitle();
    21.                     if (TextUtils.isEmpty(title)) {
    22.                         titleView.setVisibility(View.GONE);
    23.                     } else {
    24.                         ((TextView) titleView).setText(title);
    25.                         titleView.setVisibility(View.VISIBLE);
    26.                     }
    27.                 }
    28.             }
    29.             preferenceScreen.bind(getListView());
    30.         }
    31.         //回调子类（继承于PreferenceFragment中的onBindPreferences方法，通常在子类该方法钟回调所有需要显示的Preference控件）
    32.         onBindPreferences();
    33.     }
    34.     //通过mPreferenceManager获取当前的PreferenceScreen 
    35.     public PreferenceScreen getPreferenceScreen() {
    36.         return mPreferenceManager.getPreferenceScreen();
    37.     }
    38.     //通过mPreferenceManager设置当前的PreferenceScreen 
    39.     public void setPreferenceScreen(PreferenceScreen preferenceScreen) {
    40.         if (mPreferenceManager.setPreferences(preferenceScreen) && preferenceScreen != null) {
    41.             onUnbindPreferences();
    42.             mHavePrefs = true;
    43.             if (mInitDone)  postBindPreferences();
    44.         }
    45.     }
    46.     //这个PreferenceScreen怎么来的呢，最终还是用户调用该接口设置进去的
    47.     public void addPreferencesFromResource(@XmlRes int preferencesResId) {
    48.         requirePreferenceManager();
    49.         setPreferenceScreen(mPreferenceManager.inflateFromResource(getActivity(), preferencesResId, getPreferenceScreen()));
    50.     }
    51. }

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  • 原文地址：https://blog.csdn.net/qq_27672101/article/details/117304561