android - SharedPreferences setChecked 崩溃

Question

我正在尝试在关闭另一个切换按钮后将首选项屏幕中的切换按钮切换为 false。所以在这里，当时间翻转时，我想关闭名称。然而它爆炸了。有人看到我做错了什么吗？

import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
import android.os.Bundle;
import android.preference.PreferenceActivity;
import android.widget.Toast;
import android.widget.ToggleButton;


public class UserSettingActivity extends PreferenceActivity implements OnSharedPreferenceChangeListener{
    SharedPreferences mPreferences;
    Boolean frequency;


    @SuppressWarnings("deprecation")
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.settings);
    }


    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        boolean mBool = false;

        if (key.equals("cervical_mucus")) {
             // do something
            Context context = getApplicationContext();
            Toast.makeText(context, "Hello toast 1!", Toast.LENGTH_LONG).show();

            ToggleButton mToggle = (ToggleButton)findViewById(R.id.mucus_stamps);
            mToggle.setChecked(mBool);
         }
    }

    protected void onPause()
    {
        super.onPause();
        getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
    }

    protected void onResume()
    {
        super.onResume();
        getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
    }

}

错误:

    05-09 14:40:18.914: E/AndroidRuntime(25005): FATAL EXCEPTION: main
    05-09 14:40:18.914: E/AndroidRuntime(25005): java.lang.NullPointerException
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at com.projectcaruso.naturalfamilyplaning.UserSettingActivity.onSharedPreferenceChanged(UserSettingActivity.java:37)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.app.SharedPreferencesImpl$EditorImpl.notifyListeners(SharedPreferencesImpl.java:475)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.app.SharedPreferencesImpl$EditorImpl.apply(SharedPreferencesImpl.java:385)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.preference.Preference.tryCommit(Preference.java:1349)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.preference.Preference.persistBoolean(Preference.java:1615)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.preference.TwoStatePreference.setChecked(TwoStatePreference.java:83)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.preference.SwitchPreference$Listener.onCheckedChanged(SwitchPreference.java:54)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.widget.CompoundButton.setChecked(CompoundButton.java:126)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.widget.Switch.setChecked(Switch.java:666)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.widget.CompoundButton.toggle(CompoundButton.java:87)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.widget.CompoundButton.performClick(CompoundButton.java:99)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.view.View$PerformClick.run(View.java:17355)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.os.Handler.handleCallback(Handler.java:725)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.os.Handler.dispatchMessage(Handler.java:92)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.os.Looper.loop(Looper.java:137)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at android.app.ActivityThread.main(ActivityThread.java:5041)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at java.lang.reflect.Method.invokeNative(Native Method)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at java.lang.reflect.Method.invoke(Method.java:511)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
    05-09 14:40:18.914: E/AndroidRuntime(25005):    at dalvik.system.NativeStart.main(Native Method)

编辑:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >

    <PreferenceCategory 
        android:title="@string/pref_user_profile" 
        android:textSize="20px">

        <SwitchPreference 
                android:title="@+string/pref_frequency"
                android:summary="@+string/pref_frequency_summary"
                android:key="frequency" 
                android:defaultValue="true"
                android:layout="@layout/pref_layout"/>

        <SwitchPreference 
                android:title="@+string/pref_time"
                android:summary="@+string/pref_time_summary"
                android:key="time"
                android:defaultValue="true"
                android:layout="@layout/pref_layout"
                android:dependency="frequency"/>

        <SwitchPreference  
                android:title="@+string/pref_symptothermal"
                android:summary="@+string/pref_symptothermal_summary"
                android:key="symptothermal"
                android:defaultValue="true"
                android:layout="@layout/pref_layout"/>

        <SwitchPreference 
                android:title="@+string/pref_cervical_mucus"
                android:summary="@+string/pref_cervical_mucus_summary"
                android:key="cervical_mucus"
                android:defaultValue="true"
                android:layout="@layout/pref_layout"
                android:disableDependentsState="false"/>    

        <SwitchPreference 
                android:id="@+id/mucus_stamps"
                android:title="@+string/pref_mucus_stamps"
                android:summary="@+string/pref_mucus_stamps_summary"
                android:key="mucus_stamps"
                android:defaultValue="true"
                android:layout="@layout/pref_layout"
                android:dependency="cervical_mucus"/>

        <SwitchPreference 
                android:title="@+string/pref_fertile_infertile"
                android:summary="@+string/pref_fertile_infertile_summary"
                android:key="fertile_infertil" 
                android:defaultValue="true"
                android:layout="@layout/pref_layout"
                android:dependency="cervical_mucus"/>
    </PreferenceCategory>

</PreferenceScreen>

Answer 1

您可以使用 findPreference 并传递其 android:key 获取对您的 SwitchPreference 的引用:

@Override
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
    boolean mBool = false;

    if (key.equals("cervical_mucus")) {
        // do something
        Context context = getApplicationContext();
        Toast.makeText(context, "Hello toast 1!", Toast.LENGTH_LONG).show();

        SwitchPreference switchPreference = (SwitchPreference) findPreference("mucus_stamps");
        switchPreference.setChecked(mBool);
    }
}

编辑

您似乎也没有在 onPause 中注销您的监听器:

protected void onPause()
{
    super.onPause();
    getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
}