这个问题肯定经常出现。

当用户在Android应用程序中编辑首选项时,我希望他们能够在首选项摘要中看到当前设置的首选项值。

例如:如果我有“丢弃旧消息”的首选项设置,该设置指定了需要清理消息的天数。在PreferenceActivity中,我想让用户看到:

"丢弃旧消息" <- title

“x天后清理消息”<- summary,其中x是当前首选项值

额外的学分:使此可重用,所以我可以很容易地将它应用到我的所有首选项,而不管它们的类型(使它与EditTextPreference, ListPreference等工作,只需最少的编码)。


当前回答

我发现这种方法使EditTextPreference从支持库句柄“%s”在总结(因为ListPreference已经处理):

public class EditTextPreference extends android.support.v7.preference.EditTextPreference {
    public EditTextPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public void setText(String text) {
        super.setText(text);
        notifyChanged();
    }

    @Override
    public CharSequence getSummary() {
        String text = super.getText();
        String summary = super.getSummary().toString();
        return String.format(summary, text == null ? "" : text);
    }
}

在xml中它看起来是这样的:

<com.example.yourapp.EditTextPreference
    android:defaultValue="1"
    android:key="cleanup_period"
    android:summary="Clean up messages after %s days"
    android:title="Clean up period" />

其他回答

我的解决方案是创建一个自定义的EditTextPreference,像这样在XML中使用:EditTextPreference android:title="示例title " />

EditTextPreference.java: -

package com.example;

import android.content.Context;
import android.util.AttributeSet;

public class EditTextPreference extends android.preference.EditTextPreference
{
    public EditTextPreference(Context context, AttributeSet attrs, int defStyle)
    {
        super(context, attrs, defStyle);
    }

    public EditTextPreference(Context context, AttributeSet attrs)
    {
        super(context, attrs);
    }

    public EditTextPreference(Context context)
    {
        super(context, null);
    }

    @Override
    protected void onDialogClosed(boolean positiveResult)
    {
        super.onDialogClosed(positiveResult);

        setSummary(getSummary());
    }

    @Override
    public CharSequence getSummary()
    {
        return getText();
    }
}

如果您只想显示每个字段的纯文本值作为摘要,那么下面的代码应该是最容易维护的。它只需要两处更改(第13行和第21行,标记为“此处更改”):

package com.my.package;

import android.content.SharedPreferences;
import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
import android.os.Bundle;
import android.preference.EditTextPreference;
import android.preference.ListPreference;
import android.preference.Preference;
import android.preference.PreferenceActivity;

public class PreferencesActivity extends PreferenceActivity implements OnSharedPreferenceChangeListener {

    private final String[] mAutoSummaryFields = { "pref_key1", "pref_key2", "pref_key3" }; // change here
    private final int mEntryCount = mAutoSummaryFields.length;
    private Preference[] mPreferenceEntries;

    @SuppressWarnings("deprecation")
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences_file); // change here
        mPreferenceEntries = new Preference[mEntryCount];
        for (int i = 0; i < mEntryCount; i++) {
            mPreferenceEntries[i] = getPreferenceScreen().findPreference(mAutoSummaryFields[i]);
        }
    }

    @SuppressWarnings("deprecation")
    @Override
    protected void onResume() {
        super.onResume();
        for (int i = 0; i < mEntryCount; i++) {
            updateSummary(mAutoSummaryFields[i]); // initialization
        }
        getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this); // register change listener
    }

    @SuppressWarnings("deprecation")
    @Override
    protected void onPause() {
        super.onPause();
        getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this); // unregister change listener
    }

    private void updateSummary(String key) {
        for (int i = 0; i < mEntryCount; i++) {
            if (key.equals(mAutoSummaryFields[i])) {
                if (mPreferenceEntries[i] instanceof EditTextPreference) {
                    final EditTextPreference currentPreference = (EditTextPreference) mPreferenceEntries[i];
                    mPreferenceEntries[i].setSummary(currentPreference.getText());
                }
                else if (mPreferenceEntries[i] instanceof ListPreference) {
                    final ListPreference currentPreference = (ListPreference) mPreferenceEntries[i];
                    mPreferenceEntries[i].setSummary(currentPreference.getEntry());
                }
                break;
            }
        }
    }

    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        updateSummary(key);
    }

}
public class ProfileManagement extends PreferenceActivity implements
OnPreferenceChangeListener {
    EditTextPreference screenName;
    ListPreference sex;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            addPreferencesFromResource(R.layout.profile_management);

            screenName = (EditTextPreference) findPreference("editTextPref");
            sex = (ListPreference) findPreference("sexSelector");

            screenName.setOnPreferenceChangeListener(this);
            sex.setOnPreferenceChangeListener(this);

    }   

    @Override
    public boolean onPreferenceChange(Preference preference, Object newValue) {
        preference.setSummary(newValue.toString());
        return true;
    }
}

FYI:

findPreference(CharSequence key)
This method was deprecated in API level 11. This function is not relevant
for a modern fragment-based PreferenceActivity.

更有理由看看上面@ASD的非常圆滑的答案(来源在这里找到),它说在android:summary中对preferences.xml中的每个字段使用%s。(首选项的当前值替换为%s。)

<ListPreference
 ...        
 android:summary="Length of longest word to return as match is %s"
 ...
 />

在Android Studio中,打开“root_preferences.xml”,选择设计模式。选择所需的EditTextPreference首选项,在“所有属性”下,寻找“useSimpleSummaryProvider”属性,并将其设置为true。然后它将显示当前值。