Question

我有一个带有线程（闹钟）的主屏幕，并且可以启动带有PreferentsFragments的设置屏幕活动。当应用程序使用时间较长而用户更改回应用程序时，我会崩溃。一些变量为空。这些是在另一个类中声明的静态变量，供所有活动使用。

主屏幕：

public class FullscreenActivity extends BaseAppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    Tools.mAppSettings = new AppSettings(this);
    ...
}

Tools.java

public class Tools {
    static public BrightnessManager brightnessManager;
    static public SoundManager soundManager;
    static public AppSettings mAppSettings;
    static public AlarmMan alarmMan;
    static public Vibrator vibrator;
    ...
}

应用设置：

public class AppSettingsActivity extends BaseSettingsActivity {

SettingsFragment prefFragment; 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        prefFragment = new SettingsFragment();
        prefFragment.context = this;
        addFragment(prefFragment);
    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        Tools.grantIntentIfUsesAnyDeviceBrightnessNotAllowed(this, new GrantIntentListener() {
            @Override
            public void intentIfNeeded(boolean intentNeeded, Intent grantIntent) {
                if (intentNeeded) {
                    startActivityForResult(grantIntent, ASK_WRITE_PERMISSION);
                }
            }
        });
    }

    public static class SettingsFragment extends PreferenceFragment {
        public static Context context;
        Preference unlock;
        PreferenceCategory about;

        @Override
        public void onCreate(final Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            addPreferencesFromResource(R.xml.pref_settings);

            MultiSelectListPreference clockInfo = ((MultiSelectListPreference) findPreference("clockInfo"));
            Set<String> clockInfoSet = new HashSet<String>();

                if (Tools.mAppSettings.showDate)
                    clockInfoSet.add("showDate");
>>>>>>>>>>>  Tools.mAppSettings is null sometimes !!!
.....
}

我的猜测是操作系统正在销毁我的活动，然后只恢复设置活动，但Tools.java由主活动初始化，然后一切都为空。

我的概念是在Tools.java中使用静态变量来在不同的Android系统之间共享数据吗？我是否需要使用intent.putExtra传递“所有内容”？
我是否需要实现Bundle savedInstanceState？

这是我从另一个PreferenceActivity崩溃的日志。

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.changemystyle.gentlewakeup/com.changemystyle.gentlewakeup.settings.LightSettingsActivity}: java.lang.NullPointerException
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2404)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2464)
    at android.app.ActivityThread.access$900(ActivityThread.java:172)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:146)
    at android.app.ActivityThread.main(ActivityThread.java:5653)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:515)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
    at com.changemystyle.gentlewakeup.settings.LightSettingsActivity$LightFragment.updateUI(LightSettingsActivity.java:192)
    at com.changemystyle.gentlewakeup.settings.LightSettingsActivity$LightFragment.onCreate(LightSettingsActivity.java:177)
    at android.app.Fragment.performCreate(Fragment.java:1678)
    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:859)
    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
    at android.app.BackStackRecord.run(BackStackRecord.java:684)
    at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1453)
    at android.app.Activity.performStart(Activity.java:5550)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2377)
    ... 11 more

Answer 1

您应该在当前活动回调 onSaveInstanceState 中保存变量的状态，并在 onRestoreInstanceState 中检索其值，如此处所述（ how-to-use-onsaveinstancestate-and-onrestoreinstancestate) < /强>

有时候更改回我的Android应用程序时变量全为null

1 个答案: