如何在 PreferenceScreen 中检索 ListPreference？
我尝试过以下方法，它们都抛出空异常。
findPreference(key) getPreferenceScreen().findPreference(key)
private void loadLayout(int appWidgetId) {
SharedPreferences.Editor shared_config = prefs.edit();
Layout layout = db_adapter.fetchLayout(appWidgetId);
...
ListPreference widget_text_color = (ListPreference) findPreference("widget_text_color");
widget_text_color.setValue(String.valueOf(layout.getTextColor()));
...
shared_config.commit();
}
<PreferenceScreen
xmlns:android="http://schemas.android.com/apk/res/android">
...
<PreferenceCategory android:title="Layout/Output">
...
<ListPreference
android:key="widget_text_color"
android:title="Text color"
android:summary="Choose text color"
android:entries="@array/colors"
android:entryValues="@array/colors_rgb"
android:dialogTitle="Choose a color" />
...
</PreferenceCategory>
03-15 17:50:42.250: ERROR/AndroidRuntime(441): FATAL EXCEPTION: main 03-15 17:50:42.250: ERROR/AndroidRuntime(441): java.lang.RuntimeException: Unable to start activity ComponentInfo{com. feral.widget/com.feral.widget.Prefs}：java.lang.NullPointerException 03-15 17:50:42.250：错误/AndroidRuntime（441）：在 android.app.ActivityThread.performLaunchActivity（ActivityThread.java:1622）03 -15 17:50:42.250: 错误/AndroidRuntime(441): 在 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1638) 03-15 17:50:42.250: 错误/AndroidRuntime(441): 在 android.app .ActivityThread.access$1500(ActivityThread.java:117) 03-15 17:50:42.250: 错误/AndroidRuntime(441): 在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:928) 03-15 17: 50：42.250：错误/AndroidRuntime（441）：在 android.os.Handler。dispatchMessage(Handler.java:99) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at android.os.Looper.loop(Looper.java:123) 03-15 17:50:42.250: ERROR/ AndroidRuntime(441): 在 android.app.ActivityThread.main(ActivityThread.java:3647) 03-15 17:50:42.250: 错误/AndroidRuntime(441): 在 java.lang.reflect.Method.invokeNative(Native Method) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at java.lang.reflect.Method.invoke(Method.java:507) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at com.android.internal.os.ZygoteInit.main(ZygoteInit .java:597) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at dalvik.system.NativeStart.main(Native Method) 03-15 17:50:42.250: ERROR/AndroidRuntime(441):引起：java.lang.NullPointerException 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at com.feral.widget.Prefs.loadLayout(Prefs.java:234) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at com.feral.widget.Prefs.loadPreference(Prefs.java:267) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at com.feral.widget.Prefs.onCreate (Prefs.java:77) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 03-15 17:50:42.250: ERROR/AndroidRuntime (441): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1586)loadPreference(Prefs.java:267) 03-15 17:50:42.250: 错误/AndroidRuntime(441): at com.feral.widget.Prefs.onCreate(Prefs.java:77) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java :1586)loadPreference(Prefs.java:267) 03-15 17:50:42.250: 错误/AndroidRuntime(441): at com.feral.widget.Prefs.onCreate(Prefs.java:77) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 03-15 17:50:42.250: ERROR/AndroidRuntime(441): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java :1586)