所以，我有这个用于 PreferenceScreen 的 xml。

<?xml version="1.0" encoding="utf-8"?>

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >

    <EditTextPreference
        android:dialogMessage="@string/w_common_display_name_desc"
        android:key="display_name"
        android:summary="@string/w_common_display_name_desc"
        android:title="@string/w_common_display_name" />
    <EditTextPreference
        android:dialogMessage="@string/w_basic_username_desc"
        android:inputType="textVisiblePassword"
        android:key="username"
        android:summary="@string/w_basic_username_desc"
        android:title="@string/w_basic_username" />
    <EditTextPreference
        android:dialogMessage="@string/w_common_server_desc"
        android:inputType="textVisiblePassword"
        android:key="server"
        android:summary="@string/w_common_server_desc"
        android:title="@string/w_common_server" />

    <com.csipsimple.widgets.PasswordPreference
        android:dialogMessage="@string/w_basic_password_desc"
        android:key="password"
        android:password="true"
        android:summary="@string/w_basic_password_desc"
        android:title="@string/w_basic_password" />

</PreferenceScreen>

由此 PreferenceActivity 调用。

import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
import android.os.Bundle;
import android.preference.ListPreference;
import android.preference.Preference;
import android.preference.PreferenceActivity;
import android.preference.PreferenceGroup;
import android.preference.PreferenceScreen;
import android.text.TextUtils;

import com.actionbarsherlock.view.Menu;
import com.csipsimple.R;
import com.csipsimple.utils.Log;

public abstract class GenericPrefs extends PreferenceActivity implements
        OnSharedPreferenceChangeListener, IPreferenceHelper {

    private static final String THIS_FILE = "GenericPrefs";
    private static String TAG = "ricky";

    public abstract boolean onCreateOptionsMenu(Menu menu);

    /**
     * Get the xml preference resource for this screen
     * 
     * @return the resource reference
     */
    protected abstract int getXmlPreferences();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        beforeBuildPrefs();
        addPreferencesFromResource(getXmlPreferences());
        afterBuildPrefs();
        Log.d(TAG, "GenericPrefs");
    }

    @Override
    public void onResume() {
        super.onResume();
        getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
        updateDescriptions();
    }

    @Override
    public void onPause() {
        super.onPause();
        getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
    }

    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        updateDescriptions();
    }

    /**
     * Process update of description of each preference field
     */
    protected abstract void updateDescriptions();

    /**
     * Optional hook for doing stuff before preference xml is loaded
     */
    protected void beforeBuildPrefs() {
        // By default, nothing to do
    }

    /**
     * Optional hook for doing stuff just after preference xml is loaded
     */
    protected void afterBuildPrefs() {
        // By default, nothing to do
    }

    // Utilities for update Descriptions
    /**
     * Get field summary if nothing set. By default it will try to add _summary
     * to name of the current field
     * 
     * @param field_name Name of the current field
     * @return Translated summary for this field
     */
    protected String getDefaultFieldSummary(String field_name) {
        try {
            String keyid = R.string.class.getField(field_name + "_summary").get(null).toString();
            return getString(Integer.parseInt(keyid));
        } catch (SecurityException e) {
            // Nothing to do : desc is null
        } catch (NoSuchFieldException e) {
            // Nothing to do : desc is null
        } catch (IllegalArgumentException e) {
            // Nothing to do : desc is null
        } catch (IllegalAccessException e) {
            // Nothing to do : desc is null
        }

        return "";
    }

    /**
     * Set summary of a standard string field If empty will display the default
     * summary Else it displays the preference value
     * 
     * @param fieldName the preference key name
     */
    public void setStringFieldSummary(String fieldName) {
        PreferenceScreen pfs = getPreferenceScreen();
        SharedPreferences sp = pfs.getSharedPreferences();
        Preference pref = pfs.findPreference(fieldName);

        String val = sp.getString(fieldName, null);
        if (TextUtils.isEmpty(val)) {
            val = getDefaultFieldSummary(fieldName);
            Log.d(TAG, "genericPrefs field summary: "+val);
        }
        setPreferenceSummary(pref, val);
    }

    /**
     * Set summary of a password field If empty will display default summary If
     * password will display a * char for each letter of password
     * 
     * @param fieldName the preference key name
     */
    public void setPasswordFieldSummary(String fieldName) {
        PreferenceScreen pfs = getPreferenceScreen();
        SharedPreferences sp = pfs.getSharedPreferences();
        Preference pref = pfs.findPreference(fieldName);

        String val = sp.getString(fieldName, null);

        if (TextUtils.isEmpty(val)) {
            val = getDefaultFieldSummary(fieldName);
        } else {
            val = val.replaceAll(".", "*");
        }
        setPreferenceSummary(pref, val);
    }

    /**
     * Set summary of a list field If empty will display default summary If one
     * item selected will display item name
     * 
     * @param fieldName the preference key name
     */
    public void setListFieldSummary(String fieldName) {
        PreferenceScreen pfs = getPreferenceScreen();
        ListPreference pref = (ListPreference) pfs.findPreference(fieldName);
        if (pref == null) {
            Log.w(THIS_FILE, "Unable to find preference " + fieldName);
            return;
        }

        CharSequence val = pref.getEntry();
        if (TextUtils.isEmpty(val)) {
            val = getDefaultFieldSummary(fieldName);
        }
        setPreferenceSummary(pref, val);
    }

    /**
     * Safe setSummary on a Preference object that make sure that the preference
     * exists before doing anything
     * 
     * @param pref the preference to change summary of
     * @param val the string to set as preference summary
     */
    protected void setPreferenceSummary(Preference pref, CharSequence val) {
        if (pref != null) {
            pref.setSummary(val);
        }
    }

    /**
     * Hide a preference from the screen so that user can't see and modify it
     * 
     * @param parent the parent group preference if any, leave null if
     *            preference is a root pref
     * @param fieldName the preference key name to hide
     */
    public void hidePreference(String parent, String fieldName) {
        PreferenceScreen pfs = getPreferenceScreen();
        PreferenceGroup parentPref = pfs;
        if (parent != null) {
            parentPref = (PreferenceGroup) pfs.findPreference(parent);
        }

        Preference toRemovePref = pfs.findPreference(fieldName);

        if (toRemovePref != null && parentPref != null) {
            parentPref.removePreference(toRemovePref);
        } else {
            Log.w("Generic prefs", "Not able to find" + parent + " " + fieldName);
        }
    }


    @Override
    public void setPreferenceScreenType(String key, int type) {
        setPreferenceScreenType(getClass(), key, type);
    }

    @Override
    public void setPreferenceScreenSub(String key, Class<?> activityClass, Class<?> fragmentClass, int type) {
        setPreferenceScreenType(activityClass, key, type);
    }

    private void setPreferenceScreenType(Class<?> classObj, String key, int type) {
        Preference pf = findPreference(key);
        Intent it = new Intent(this, classObj);
        it.putExtra(PrefsLogic.EXTRA_PREFERENCE_TYPE, type);
        pf.setIntent(it);
    }

    /* (non-Javadoc)
     * @see android.preference.PreferenceActivity#isValidFragment(java.lang.String)
     */
    public boolean isValidFragment(String fragmentName) {
        // This pref activity does not include any fragment
        return false;
    }
}

我看了很多关于 PreferenceScreen 的教程，xml 看起来不错。这是之前使用 SherlockFragment 的项目的一部分，我目前正在升级它的部分代码。当我编译应用程序时，summary 由于某种原因没有显示。 dialogMessage 显示得很好。

我已经在我的 AndroidManifest 中添加了它。

implementation 'com.android.support:preference-v7:28.0.0'

我今天发现代码使用的 ListView 即使在布局编辑器中也没有显示任何内容。我尝试用 RecyclerView 替换它，但它抛出错误 Caused by: java.lang.ClassCastException: android.support.v7.widget.RecyclerView cannot be cast to android.widget.ListView。我寻找任何类似 findViewById 的东西，但找不到任何东西。我宁愿处理不显示任何错误，因为我觉得它比前者更复杂。

这是用于显示 PreferenceScreen 的 xml。

<?xml version="1.0" encoding="utf-8"?>
<!--
    Copyright (C) 2010 Regis Montoya (aka r3gis - www.r3gis.fr) 

    This file is part of CSipSimple.
    CSipSimple is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
    If you own a pjsip commercial license you can also redistribute it
    and/or modify it under the terms of the GNU Lesser General Public License
    as an android library.

    CSipSimple is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with CSipSimple.  If not, see <http://www.gnu.org/licenses/>.
-->
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:id="@+id/settings_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/validation_bar"
        android:orientation="vertical">

        <LinearLayout
            android:id="@+id/custom_wizard_row"
            android:layout_width="match_parent"
            android:layout_height="?android:attr/listPreferredItemHeight"
            android:orientation="vertical"
            android:visibility="gone">

            <TextView
                android:id="@+id/custom_wizard_text"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:gravity="center"
                android:paddingLeft="12dp"
                android:paddingRight="12dp"
                android:textAppearance="?android:attr/textAppearanceLarge"
                android:textColor="@android:color/white" />

            <ImageView
                android:layout_width="match_parent"
                android:layout_height="1dp"
                android:background="@android:drawable/divider_horizontal_dark"
                android:contentDescription="@string/empty_description" />
        </LinearLayout>

        <ListView
            android:id="@android:id/list"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:drawSelectorOnTop="false"
            tools:listitem="@layout/adptr_simple"
            android:layoutAnimation="@anim/layout_slide_right"
            android:persistentDrawingCache="animation|scrolling" />
    </LinearLayout>

    <LinearLayout
        android:id="@+id/validation_bar"
        style="@style/ButtonBar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:orientation="horizontal">

        <Button
            android:id="@+id/cancel_bt"
            style="@style/ButtonBarButton"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="0.5"
            android:text="@string/cancel" />

        <Button
            android:id="@+id/save_bt"
            style="@style/ButtonBarButton"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="0.5"
            android:text="@string/save" />
    </LinearLayout>

</RelativeLayout>

我尝试更改 Theme 但它仍然不显示文本。我尝试删除 android:layoutAnimation 和 android:persistentDrawingCache 但它仍然没有显示 summary。

这是 adptr_simple.xml 因为有人要求它。

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="TextView"
        android:textColor="#FFFFFF"
        android:textSize="18sp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:layout_marginBottom="16dp"
        android:text="TextView"
        android:textColor="#FFFFFF"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="@+id/textView"
        app:layout_constraintHorizontal_bias="0.507"
        app:layout_constraintStart_toStartOf="@+id/textView"
        app:layout_constraintTop_toBottomOf="@+id/textView" />
</android.support.constraint.ConstraintLayout>

最佳答案

猜测这些线路有问题:

String keyid = R.string.class.getField(field_name + "_summary").get(null).toString();
return getString(Integer.parseInt(keyid));

关于android - 更新应用程序后 PreferenceScreen 不显示摘要，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/57230978/