在这篇文章中，我们将带领您了解java-尝试获取Activity的DefaultSharedPreferences时出现NullPointerException的全貌，包括获取当前activity的相
在这篇文章中，我们将带领您了解java-尝试获取Activity的DefaultSharedPreferences时出现NullPointerException的全貌，包括获取当前activity的相关情况。同时，我们还将为您介绍有关Android Q 中不推荐使用 PreferenceManager getDefaultSharedPreferences、android – java.util.ConcurrentModificationException和SharedPreference、android – PreferenceManager.getDefaultSharedPreferences()vs getPreferences()、android – SharedPreferences ListPreference NullPointerException的知识，以帮助您更好地理解这个主题。
本文目录一览：- java-尝试获取Activity的DefaultSharedPreferences时出现NullPointerException（获取当前activity）
- Android Q 中不推荐使用 PreferenceManager getDefaultSharedPreferences
- android – java.util.ConcurrentModificationException和SharedPreference
- android – PreferenceManager.getDefaultSharedPreferences()vs getPreferences()
- android – SharedPreferences ListPreference NullPointerException
java-尝试获取Activity的DefaultSharedPreferences时出现NullPointerException（获取当前activity）
我必须为实习开发一个应用程序,并且正在使用AndroidStudio.
现在,我只是在尝试事情,并且正在开发Spank计数器应用程序(是的,我知道).
我知道那里已经有一个回应：
What is a NullPointerException, and how do I fix it?
和许多其他类似我的问题.
事实是我误解了错误,但是在我的代码中找不到它.
(我没有放入xml文件,因为我认为这不是有用的,如果您想看到它,请打个招呼.)
对不起,如果很难阅读这篇文章.这是我第一次在论坛上提问.
在此先感谢那些勇于阅读并帮助我的人.
所以这里是错误：
--------- beginning of crash
06-02 18:05:31.515 2680-2680/com.example.florian.fessee E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.florian.fessee, PID: 2680
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.florian.fessee/com.example.florian.fessee.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2236)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.content.Contextwrapper.getPackageName(Contextwrapper.java:132)
at android.preference.PreferenceManager.getDefaultSharedPreferencesName(PreferenceManager.java:374)
at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:369)
at com.example.florian.fessee.MainActivity.<init>(MainActivity.java:23)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.class.newInstance(Class.java:1606)
at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2226)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)Â
at android.app.ActivityThread.access$800(ActivityThread.java:151)Â
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)Â
at android.os.Handler.dispatchMessage(Handler.java:102)Â
at android.os.Looper.loop(Looper.java:135)Â
at android.app.ActivityThread.main(ActivityThread.java:5254)Â
at java.lang.reflect.Method.invoke(Native Method)Â
at java.lang.reflect.Method.invoke(Method.java:372)Â
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)Â
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)Â
06-02 18:11:28.569 3101-3101/com.example.florian.fessee D/AndroidRuntime: Shutting down VM
06-02 18:11:28.570 3101-3101/com.example.florian.fessee E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.florian.fessee, PID: 3101
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.florian.fessee/com.example.florian.fessee.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2236)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.content.Contextwrapper.getPackageName(Contextwrapper.java:132)
at android.preference.PreferenceManager.getDefaultSharedPreferencesName(PreferenceManager.java:374)
at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:369)
at com.example.florian.fessee.MainActivity.<init>(MainActivity.java:23)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.class.newInstance(Class.java:1606)
at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2226)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)Â
at android.app.ActivityThread.access$800(ActivityThread.java:151)Â
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)Â
at android.os.Handler.dispatchMessage(Handler.java:102)Â
at android.os.Looper.loop(Looper.java:135)Â
at android.app.ActivityThread.main(ActivityThread.java:5254)Â
at java.lang.reflect.Method.invoke(Native Method)Â
at java.lang.reflect.Method.invoke(Method.java:372)Â
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)Â
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)Â
06-02 18:16:53.409 3339-3339/com.example.florian.fessee D/AndroidRuntime: Shutting down VM
06-02 18:16:53.435 3339-3339/com.example.florian.fessee E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.florian.fessee, PID: 3339
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.florian.fessee/com.example.florian.fessee.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2236)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.content.Contextwrapper.getPackageName(Contextwrapper.java:132)
at android.preference.PreferenceManager.getDefaultSharedPreferencesName(PreferenceManager.java:374)
at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:369)
at com.example.florian.fessee.MainActivity.<init>(MainActivity.java:23)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.class.newInstance(Class.java:1606)
at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2226)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)Â
at android.app.ActivityThread.access$800(ActivityThread.java:151)Â
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)Â
at android.os.Handler.dispatchMessage(Handler.java:102)Â
at android.os.Looper.loop(Looper.java:135)Â
at android.app.ActivityThread.main(ActivityThread.java:5254)Â
at java.lang.reflect.Method.invoke(Native Method)Â
at java.lang.reflect.Method.invoke(Method.java:372)Â
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)Â
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)Â
06-02 18:19:42.932 3515-3515/com.example.florian.fessee D/AndroidRuntime: Shutting down VM
06-02 18:19:42.935 3515-3515/com.example.florian.fessee E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.florian.fessee, PID: 3515
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.florian.fessee/com.example.florian.fessee.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2236)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.content.Contextwrapper.getPackageName(Contextwrapper.java:132)
at android.preference.PreferenceManager.getDefaultSharedPreferencesName(PreferenceManager.java:374)
at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:369)
at com.example.florian.fessee.MainActivity.<init>(MainActivity.java:23)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.class.newInstance(Class.java:1606)
at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
at android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2226)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)Â
at android.app.ActivityThread.access$800(ActivityThread.java:151)Â
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)Â
at android.os.Handler.dispatchMessage(Handler.java:102)Â
at android.os.Looper.loop(Looper.java:135)Â
at android.app.ActivityThread.main(ActivityThread.java:5254)Â
at java.lang.reflect.Method.invoke(Native Method)Â
at java.lang.reflect.Method.invoke(Method.java:372)Â
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)Â
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)Â
这是我的代码：
package com.example.florian.fessee;
import android.content.SharedPreferences;
import android.preference.PreferenceManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private int compt = 0;
private Button b1 = null;
private Button b5 = null;
private Button b01 = null;
private Button b05 = null;
private Button braz = null;
private TextView t = null;
private String COMPT = "comptfess";
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = preferences.edit();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1 = (Button) findViewById(R.id.button1);
b5 = (Button) findViewById(R.id.button5);
b01 = (Button) findViewById(R.id.button01);
b05 = (Button) findViewById(R.id.button05);
braz = (Button) findViewById(R.id.buttonraz);
t = (TextView) findViewById(R.id.textView);
compt = preferences.getInt(COMPT, 0);
b1.setonClickListener(b1Listener);
b5.setonClickListener(b5Listener);
b01.setonClickListener(b01Listener);
b05.setonClickListener(b05Listener);
braz.setonClickListener(brazListener);
if (compt == 1) {
t.setText("Je dois 1 fessée à Sophie.");
}
else if (compt!=0){
t.setText("Je dois " + compt + "fessées à Sophie.");
}
}
private View.OnClickListener b1Listener = new View.OnClickListener() {
@Override
public void onClick(View v) {
compt +=1;
editor.putInt(COMPT,compt);
editor.commit();
if (compt == 1) {
t.setText("Je dois 1 fessée à Sophie.");
}
else if (compt!=0){
t.setText("Je dois " + compt + "fessées à Sophie.");
}
}
};
private View.OnClickListener b5Listener = new View.OnClickListener() {
@Override
public void onClick(View v) {
compt +=5;
editor.putInt(COMPT,compt);
editor.commit();
if (compt == 1) {
t.setText("Je dois 1 fessée à Sophie.");
}
else if (compt!=0){
t.setText("Je dois " + compt + "fessées à Sophie.");
}
}
};
private View.OnClickListener b01Listener = new View.OnClickListener() {
@Override
public void onClick(View v) {
if(compt!=0){
compt -=1;
editor.putInt(COMPT,compt);
editor.commit();
if (compt==0){
t.setText("Je ne dois plus de fessées å Sophie");
}
else if (compt == 1) {
t.setText("Je dois 1 fessée à Sophie.");
}
else{
t.setText("Je dois " + compt + "fessées à Sophie.");
}
}
else {
Toast.makeText(MainActivity.this, "Un nombre de fessées doit être positif.", Toast.LENGTH_SHORT).show();
}
}
};
private View.OnClickListener b05Listener = new View.OnClickListener() {
@Override
public void onClick(View v) {
if(compt>4){
compt -=5;
editor.putInt(COMPT,compt);
editor.commit();
if (compt==0){
t.setText("Je ne dois plus de fessées å Sophie.");
}
else if (compt == 1) {
t.setText("Je dois 1 fessée à Sophie.");
}
else{
t.setText("Je dois " + compt + "fessées à Sophie.");
}
}
else {
Toast.makeText(MainActivity.this, "Un nombre de fessées doit être positif.", Toast.LENGTH_SHORT).show();
}
}
};
private View.OnClickListener brazListener = new View.OnClickListener() {
@Override
public void onClick(View v) {
compt = 0;
editor.putInt(COMPT,compt);
editor.commit();
t.setText("Je ne dois plus de fessées à Sophie.");
}
};
}
解决方法:
这是你的问题：
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = preferences.edit();
在创建活动之前,您无法初始化SharedPreferences.像这样分开声明和实例化：
...
SharedPreferences preferences;
SharedPreferences.Editor editor;
...
@Override
public void onCreate(Bundle savedInstanceState){
...
preferences = PreferenceManager.getDefaultSharedPreferences(this);
editor = preferences.edit();
...
}
Android Q 中不推荐使用 PreferenceManager getDefaultSharedPreferences
PreferenceManager getDefaultSharedPreferences在Android
10中已弃用。我该如何更换它？
android – java.util.ConcurrentModificationException和SharedPreference
我在崩溃日志中发现了这个崩溃.我不知道它什么时候发生.有人能给我建议是什么原因吗？也许有人有同样的崩溃.
java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:787)
at java.util.HashMap$KeyIterator.next(HashMap.java:814)
at com.android.internal.util.XmlUtils.writeSetXml(XmlUtils.java:350)
at com.android.internal.util.XmlUtils.writeValueXml(XmlUtils.java:688)
at com.android.internal.util.XmlUtils.writeMapXml(XmlUtils.java:295)
at com.android.internal.util.XmlUtils.writeMapXml(XmlUtils.java:264)
at com.android.internal.util.XmlUtils.writeMapXml(XmlUtils.java:230)
at com.android.internal.util.XmlUtils.writeMapXml(XmlUtils.java:187)
at android.app.SharedPreferencesImpl.writetoFile(SharedPreferencesImpl.java:597)
at android.app.SharedPreferencesImpl.access$800(SharedPreferencesImpl.java:51)
at android.app.SharedPreferencesImpl$2.run(SharedPreferencesImpl.java:512)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:818)
解决方法
我们在使用SharedPreferences getStringSet方法时看到了这个异常.此方法返回不应修改的集合.在将SharedPreferences对象序列化为flash时修改此集将产生ConcurrentModificationException.
如果您使用getAll并修改返回的地图,也会发生这种情况.
见documentation
android – PreferenceManager.getDefaultSharedPreferences()vs getPreferences()
PreferenceManager.getDefaultSharedPreferences(context)
和
getPreferences()
似乎检索不同的首选项.
PreferenceManager.getDefaultSharedPreferences(context).getBoolean(
"userWasAskedToEnableGps", false);
对我来说,返回false,
getPreferences(MODE_PRIVATE).getBoolean("userWasAskedToEnableGps", false);
返回true.
Preference是用编辑器编写的
Editor e = getPreferences(MODE_PRIVATE).edit();
e.putBoolean (...);
e.commit();
如何在Context中的Activity之外获得相同的Preferences？
解决方法:
从android github repo(1),我们可以看到getPreferences除了使用当前类名调用getSharedPreferences方法之外什么都不做.
public SharedPreferences getPreferences( int mode ) {
return getSharedPreferences( getLocalClassName(), mode );
}
没有什么限制其他活动/代码使用适当的类名访问共享首选项.更重要的是,我不想使用getPreferences,因为这意味着=>永远不会更改活动名称.如果更改,则使用明确提及的早期类名称(升级前)来处理访问共享首选项.
android – SharedPreferences ListPreference NullPointerException
我正在尝试在我的首选项xml中设置频率列表,但我一直收到此错误.我也附上了所有相关文件.我相信我正确设置了值,但我找不到我的错误当前的位置.另外,当我使用SharedPreferences.getString(key,defaultValue)时返回什么值？ ENTRY或ENTRYVALUE？
我的错误：
08-20 00:14:25.195: E/AndroidRuntime(1260): FATAL EXCEPTION: main
08-20 00:14:25.195: E/AndroidRuntime(1260): java.lang.NullPointerException
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.preference.ListPreference.findindexOfValue(ListPreference.java:215)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.preference.ListPreference.getValueIndex(ListPreference.java:224)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.preference.ListPreference.getEntry(ListPreference.java:202)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.preference.ListPreference.getSummary(ListPreference.java:148)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.preference.Preference.onBindView(Preference.java:515)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.preference.Preference.getView(Preference.java:453)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.preference.PreferenceGroupAdapter.getView(PreferenceGroupAdapter.java:222)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.AbsListView.obtainView(AbsListView.java:2461)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.ListView.makeAndAddView(ListView.java:1775)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.ListView.fillDown(ListView.java:678)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.ListView.fillFromTop(ListView.java:739)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.ListView.layoutChildren(ListView.java:1628)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.AbsListView.onLayout(AbsListView.java:2296)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.View.layout(View.java:14063)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.ViewGroup.layout(ViewGroup.java:4603)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1655)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1513)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.LinearLayout.onLayout(LinearLayout.java:1426)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.View.layout(View.java:14063)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.ViewGroup.layout(ViewGroup.java:4603)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.View.layout(View.java:14063)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.ViewGroup.layout(ViewGroup.java:4603)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1655)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1513)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.LinearLayout.onLayout(LinearLayout.java:1426)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.View.layout(View.java:14063)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.ViewGroup.layout(ViewGroup.java:4603)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.View.layout(View.java:14063)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.ViewGroup.layout(ViewGroup.java:4603)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.ViewRootImpl.performlayout(ViewRootImpl.java:1994)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1815)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1112)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4518)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.Choreographer.doCallbacks(Choreographer.java:555)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.Choreographer.doFrame(Choreographer.java:525)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.view.Choreographer$FramedisplayEventReceiver.run(Choreographer.java:711)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.os.Handler.handleCallback(Handler.java:615)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.os.Handler.dispatchMessage(Handler.java:92)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.os.Looper.loop(Looper.java:137)
08-20 00:14:25.195: E/AndroidRuntime(1260): at android.app.ActivityThread.main(ActivityThread.java:4898)
08-20 00:14:25.195: E/AndroidRuntime(1260): at java.lang.reflect.Method.invokeNative(Native Method)
08-20 00:14:25.195: E/AndroidRuntime(1260): at java.lang.reflect.Method.invoke(Method.java:511)
08-20 00:14:25.195: E/AndroidRuntime(1260): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
08-20 00:14:25.195: E/AndroidRuntime(1260): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
08-20 00:14:25.195: E/AndroidRuntime(1260): at dalvik.system.NativeStart.main(Native Method)
xml布局：
<ListPreference
android:key="frequency_key"
android:title="Sample Rate"
android:defaultValue="8000"
android:entries="@array/freq_titles"
android:entryValues="@array/freq_values"
/>
xml数组：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string-array name="freq_titles">
<item name="8000">8k Hz</item>
<item name="16000">16k Hz</item>
<item name="22050">22.05k Hz</item>
<item name="44100">44.1k Hz</item>
<item name="48000">48k Hz</item>
</string-array>
<array name="freq_values">
<item name="8000">8000</item>
<item name="16000">16000</item>
<item name="22050">22050</item>
<item name="44100">44100</item>
<item name="48000">48000</item>
</array>
</resources>
更新：即使我从默认的共享首选项中执行getAll(),它也很奇怪,它向我显示“frequency_key = 8k Hz”.所以它已经初始化了.
来自我的偏好类的更多代码：
public class Settings_ActivityAH extends PreferenceFragment implements OnSharedPreferencechangelistener{
private SharedPreferences prefs;
private Preference myAccountName;
private Preference myGoogleUsername;
private Preference myGooglePassword;
private static Context context;
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
addPreferencesFromresource(R.xml.preferences);
context = getActivity();
if (context == null){
Log.e("error","context is null");
}
prefs = PreferenceManager.getDefaultSharedPreferences(context);
myAccountName = (Preference) findPreference("account_name_title_key");
myGoogleUsername = (Preference) findPreference("googleusername_key");
myGooglePassword = (Preference) findPreference("googlepassword_key");
myAccountName.setSummary(prefs.getString("account_name_title_key", "none"));
myGoogleUsername.setTitle("username: "+prefs.getString("googleusername_key", "none"));
myGooglePassword.setTitle("password: "+prefs.getString("googlepassword_key", "none"));
Log.e("Check prefs",prefs.getAll().toString());
prefs.registerOnSharedPreferencechangelistener(this);
}
@Override
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences,
String key) {
Log.e("in onSharedPref","yea");
Preference preference = findPreference(key);
if (preference.getClass() == EditTextPreference.class){
Log.e("in editText Pref", "yeah");
if( key.equals("account_name_title_key")){
myAccountName.setSummary(sharedPreferences.getString("account_name_key","none"));
Log.e("accountname prefs",sharedPreferences.getString("account_name_key","none"));
}
if( key.equals("account_name_key")){
myAccountName.setSummary(sharedPreferences.getString("account_name_key","none"));
Log.e("accountname prefs",sharedPreferences.getString("account_name_key","none"));
}
else if (preference.getClass() == PreferenceCategory.class){
Log.e("in category Pref", "yeah");
if (key.equals("googleusername_key")){
myGoogleUsername.setTitle("Username: "+sharedPreferences.getString(key, "none"));
Log.e("googleusername prefs",sharedPreferences.getString(key, "none"));
}
else if( key.equals("googlepassword_key")){
myGooglePassword.setTitle("Password: "+sharedPreferences.getString(key, "none"));
Log.e("googlepassword prefs",sharedPreferences.getString(key, "none"));
}
}
}
else{
Log.e("insufficient key called","onSharedPreferenceChanged AH");
}
}
}
解决方法:
似乎Android只接受字符串数组作为ListPreference XML属性android：entryValues的参数.这与所有XML属性仅采用具有一种特定的预定类型(即int,bool,string等)的参数一致.请参阅以下问题：ListPreference: use string-array as Entry and integer-array as Entry Values doesn’t work
关于你的问题,getString()将返回与被点击的条目对应的android：entryValues数组的元素. android：entries数组仅用作用户的一系列显示字符串,并且在代码中没有其他影响,而android：entryValues中的值用于应用程序中的持久存储.
今天的关于java-尝试获取Activity的DefaultSharedPreferences时出现NullPointerException和获取当前activity的分享已经结束，谢谢您的关注，如果想了解更多关于Android Q 中不推荐使用 PreferenceManager getDefaultSharedPreferences、android – java.util.ConcurrentModificationException和SharedPreference、android – PreferenceManager.getDefaultSharedPreferences()vs getPreferences()、android – SharedPreferences ListPreference NullPointerException的相关知识，请在本站进行查询。
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