我现在有这个问题已经有一段时间了，每当我试图解决它时，我已经放弃了几个小时。
这是我用来与共享偏好进行交互的课程。
public class AppStatus {
final static String TAG = "AppStatus";
private static AppStatus instance = new AppStatus();
static Context context;
boolean connected = false;
public boolean IF_PAST = false;
ConnectivityManager connectivityManager;
public static final String FILE_NAME = "appdata";
public final String AUTH_KEY = "auth_key";
public final String TEAM_NAME = "team_name";
public final String TEAM_LOGO = "team_logo";
public final String LOGIN_STATUS = "login_status";
public final String CURRENT_TEAM = "current_team";
public final String TOTAL_TEAMS = "total_teams";
public final String USER_NAME = "user_name";
public final String PASSWORD = "password";
public final String USERID = "user_id";
public final String GCM_KEY = "gcm_key";
public final String NOTIFIER_TEAM_ID = "id";
public final String NOTIFIER_SCHEDULE_ID = "schedule_id";
public final boolean IS_FROM_PUSH_NOTIFICATION = false;
public final String FAMILY_MEMBERS_ID = "family_memebers_id";
public final String IS_PARENT = "is_parent";
public final String IS_PUSH_NOTIFICATION_ENABLED = "is_notification_enabled";
public final String BASE_URL = "https://www.fasfasdf.com";
public final String IS_USER_API_CALLED = "is_user_api_called";
public static AppStatus getInstance(Context ctx) {
context = ctx;
return instance;
}
public Boolean isOnline() {
try {
connectivityManager = (ConnectivityManager) context
.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connectivityManager
.getActiveNetworkInfo();
connected = networkInfo != null && networkInfo.isAvailable()
&& networkInfo.isConnected();
return connected;
} catch (Exception e) {
LogUtils.LOGE(TAG, e.toString());
}
return connected;
}
public Boolean isRegistered() {
try {
if (!getSharedBoolValue(LOGIN_STATUS))
return false;
else
return true;
} catch (Exception e) {
LogUtils.LOGE(TAG, e.toString());
}
return false;
}
public Boolean validateEditText(EditText field) {
String strField = field.getText().toString();
if (strField.trim().equals("")) {
return false;
}
return true;
}
public String getSharedStringValue(String key) {
SharedPreferences sp = context.getSharedPreferences("FILE_NAME", 0);
String value = sp.getString(key, null);
return value;
}
public boolean saveSharedStringValue(String key, String value) {
SharedPreferences sp = context.getSharedPreferences("FILE_NAME", 0);
Editor edit = sp.edit();
edit.putString(key, value);
return edit.commit();
}
public boolean clearSharedData() {
SharedPreferences sp = context.getSharedPreferences("FILE_NAME", 0);
Editor edit = sp.edit();
edit.clear();
return edit.commit();
}
public boolean clearSharedDataWithKey(String key) {
SharedPreferences sp = context.getSharedPreferences("FILE_NAME", 0);
Editor edit = sp.edit();
edit.remove(key);
return edit.commit();
}
public Boolean getSharedBoolValue(String key) {
SharedPreferences sp = context.getSharedPreferences("FILE_NAME", 0);
Boolean value = sp.getBoolean(key, false);
return value;
}
public boolean saveSharedBoolValue(String key, Boolean value) {
SharedPreferences sp = context.getSharedPreferences("FILE_NAME", 0);
Editor edit = sp.edit();
edit.putBoolean(key, value);
return edit.commit();
}
public int getSharedIntValue(String key) {
SharedPreferences sp = context.getSharedPreferences("FILE_NAME", 0);
int value = sp.getInt(key, 0);
return value;
}
public boolean saveSharedIntValue(String key, int value) {
SharedPreferences sp = context.getSharedPreferences("FILE_NAME", 0);
Editor edit = sp.edit();
edit.putInt(key, value);
return edit.commit();
}
}
我遇到的问题是，看似随机共享的首选项会获得零点异常。
我实例化appStatus = AppStatus.getInstance(context);。并以这种方式使用appStatus.getSharedStringValue(appStatus.CURRENT_TEAM);
我可以在不同的片段/活动之间切换几次，没有任何问题，然后无处不在我收到我的错误。
--------- beginning of crash
08-10 10:28:42.761 25908-25908/com.bonziteamandroid E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.bonziteamandroid, PID: 25908
java.lang.IllegalStateException: Could not execute method of the activity
at android.view.View$1.onClick(View.java:4007)
at android.view.View.performClick(View.java:4756)
at android.view.View$PerformClick.run(View.java:19749)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
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:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.view.View$1.onClick(View.java:4002)
at android.view.View.performClick(View.java:4756)
at android.view.View$PerformClick.run(View.java:19749)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
at com.bonziteamandroid.helpers.AppStatus.getSharedStringValue(AppStatus.java:94)
at com.bonziteamandroid.annoucement.AnnouncementsFragment.getAnnouncments(AnnouncementsFragment.java:121)
at com.bonziteamandroid.annoucement.AnnouncementsFragment.onCreateView(AnnouncementsFragment.java:50)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:953)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1136)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1499)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:488)
at com.bonziteamandroid.BonziNativeActivity$ActionManager.setActionOnChange(BonziNativeActivity.java:1352)
at com.bonziteamandroid.BonziNativeActivity.onAnnouncementsItemClick(BonziNativeActivity.java:337)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.view.View$1.onClick(View.java:4002)
at android.view.View.performClick(View.java:4756)
at android.view.View$PerformClick.run(View.java:19749)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
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:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
我想知道是否有人有类似的问题？或者或许有一个比这个更有建议的方法，我已经google了，以前的答案似乎并不真正适用。此外，一旦我第一次设置共享首选项，我就不会在大多数视图之间清除/擦除它们，但它们偶尔也会获得空指针异常。
答案 0 :(得分：5)
在某些情况下，您的上下文似乎为空。更简洁的方法是使用静态方法声明一个类来更新和检索SharedPreferences。这些静态方法中的每一个都将采用上下文参数和要更新的值。像这样：
public class PreferenceUtil {
public static void setEnabled(final Context context, final boolean enabled) {
SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(context);
sharedPref.edit().putBoolean("your_key", enabled).commit();
}
public static boolean isEnabled(final Context context) {
SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(context);
return sharedPref.getBoolean("your_key", true);
}
}