[英]PreferenceActivity Crashes on Orientation Change
I'm writing a PreferenceActivity
with a PreferenceFragment
, and an InstantiationException
is being thrown when the device's orientation changes (ie landscape to portrait and vice versa). 我正在使用
PreferenceActivity
编写PreferenceFragment
,并且当设备的方向改变时(即横向到纵向,反之亦然),将抛出InstantiationException
。 Also, if I tap 'Ok' on the dialog that pops up ("Unfortunately, YourApp has stopped."), the main activity relaunches, and the PreferenceActivity
works perfectly in the new orientation until it is changed again. 此外,如果我在弹出的对话框上点击“确定”(“不幸的是,YourApp已停止。”),主活动将重新启动,并且
PreferenceActivity
在新方向中完美运行,直到再次更改为止。 I can't seem to find anything about this online. 我似乎无法在网上找到任何相关信息。 Stack trace:
堆栈跟踪:
05-26 09:28:10.860: E/AndroidRuntime(3439): FATAL EXCEPTION: main
05-26 09:28:10.860: E/AndroidRuntime(3439): Process: com.example.myapp, PID: 3439
05-26 09:28:10.860: E/AndroidRuntime(3439): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapp/com.example.myapp.SettingsActivity}: android.app.Fragment$InstantiationException: Unable to instantiate fragment com.devgregw.strikedistance_androidphoneandtablet.SettingsActivity$2: make sure class name exists, is public, and has an empty constructor that is public
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3738)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.ActivityThread.access$900(ActivityThread.java:135)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1202)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.os.Handler.dispatchMessage(Handler.java:102)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.os.Looper.loop(Looper.java:136)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.ActivityThread.main(ActivityThread.java:5027)
05-26 09:28:10.860: E/AndroidRuntime(3439): at java.lang.reflect.Method.invokeNative(Native Method)
05-26 09:28:10.860: E/AndroidRuntime(3439): at java.lang.reflect.Method.invoke(Method.java:515)
05-26 09:28:10.860: E/AndroidRuntime(3439): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-26 09:28:10.860: E/AndroidRuntime(3439): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-26 09:28:10.860: E/AndroidRuntime(3439): at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
05-26 09:28:10.860: E/AndroidRuntime(3439): at dalvik.system.NativeStart.main(Native Method)
05-26 09:28:10.860: E/AndroidRuntime(3439): Caused by: android.app.Fragment$InstantiationException: Unable to instantiate fragment com.example.myapp.SettingsActivity$2: make sure class name exists, is public, and has an empty constructor that is public
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.Fragment.instantiate(Fragment.java:601)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.FragmentState.instantiate(Fragment.java:98)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.FragmentManagerImpl.restoreAllState(FragmentManager.java:1759)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.Activity.onCreate(Activity.java:899)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.preference.PreferenceActivity.onCreate(PreferenceActivity.java:514)
05-26 09:28:10.860: E/AndroidRuntime(3439): at com.example.myapp.SettingsActivity.onCreate(SettingsActivity.java:23)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.Activity.performCreate(Activity.java:5231)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
05-26 09:28:10.860: E/AndroidRuntime(3439): ... 13 more
05-26 09:28:10.860: E/AndroidRuntime(3439): Caused by: java.lang.InstantiationException: can't instantiate class com.example.myapp.SettingsActivity$2; no empty constructor
05-26 09:28:10.860: E/AndroidRuntime(3439): at java.lang.Class.newInstanceImpl(Native Method)
05-26 09:28:10.860: E/AndroidRuntime(3439): at java.lang.Class.newInstance(Class.java:1208)
05-26 09:28:10.860: E/AndroidRuntime(3439): at android.app.Fragment.instantiate(Fragment.java:590)
05-26 09:28:10.860: E/AndroidRuntime(3439): ... 21 more
SettingsActivity.java
: SettingsActivity.java
:
package com.example.myapp;
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.PreferenceFragment;
import android.preference.PreferenceGroup;
public class SettingsActivity extends PreferenceActivity {
public OnSharedPreferenceChangeListener changeListener;
public SharedPreferences preferences;
public PreferenceFragment fragment;
public SettingsActivity() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
changeListener = new OnSharedPreferenceChangeListener() {
@Override
public void onSharedPreferenceChanged(
SharedPreferences sharedPreferences, String key) {
Preference preference = fragment.findPreference(key);
if (preference instanceof ListPreference) {
ListPreference listPreference = (ListPreference) preference;
listPreference.setSummary(listPreference.getEntry());
}
}
};
fragment = new PreferenceFragment() {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.preferences);
preferences = getPreferenceScreen().getSharedPreferences();
}
@Override
public void onResume() {
super.onResume();
for (int i = 0; i < getPreferenceScreen().getPreferenceCount(); ++i) {
Preference preference = getPreferenceScreen()
.getPreference(i);
if (preference instanceof PreferenceGroup) {
PreferenceGroup preferenceGroup = (PreferenceGroup) preference;
for (int j = 0; j < preferenceGroup
.getPreferenceCount(); ++j) {
updatePreference(preferenceGroup.getPreference(j));
}
} else {
updatePreference(preference);
}
}
}
public void updatePreference(Preference preference) {
if (preference instanceof ListPreference) {
ListPreference listPreference = (ListPreference) preference;
listPreference.setSummary(listPreference.getEntry());
}
}
};
getFragmentManager().beginTransaction()
.replace(android.R.id.content, fragment).commit();
}
@Override
protected void onResume() {
super.onResume();
preferences.registerOnSharedPreferenceChangeListener(changeListener);
}
@Override
protected void onPause() {
super.onPause();
preferences.unregisterOnSharedPreferenceChangeListener(changeListener);
}
}
Your Fragment
should have a constructor 你的
Fragment
应该有一个构造函数
Caused by: android.app.Fragment$InstantiationException: Unable to instantiate fragment com.example.myapp.SettingsActivity$2: make sure class name exists, is public, and has an empty constructor that is public
引起:android.app.Fragment $ InstantiationException:无法实例化片段com.example.myapp.SettingsActivity $ 2:确保类名存在,是公共的,并且有一个公共的空构造函数
Also put the Fragment
declaration out of that function as a static inner class or in another .java file. Fragment
声明作为静态内部类或另一个.java文件放在该函数之外。
For more information, you can read the docs here . 有关更多信息,请阅读此处的文档。 Or you can take a look at the Android training guide about Fragments here .
或者您可以在这里查看有关Fragments的Android培训指南。
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