如何解决Xamarin中的OnRestoreInstanceState出现问题
我正在使用一个警报应用程序,而我的布局恰好包含一个TimePicker View,用于设置用户希望被提醒的时间。当将“活动”发送到后台时,保存值所应用的方法似乎出现问题。编译器中的代码是干净的,没有错误,但是当我在智能手机上调试它时,我将应用程序发送到后台,然后在恢复它时,TimePicker当前时间未被这两种方法修改...您的时间和贡献是非常感谢
class SecondActivity : AppCompatActivity
{
TimePicker timePicker2;
int x=2;
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
//Timepicker deFinition
timepicker1=this.FindViewById<TimePicker>(Resource.Id.timepicker1);
//Setting the default selected time of the Timepicker via OnCreate
timepicker1.CurrentHour=java.lang.Integer.ValueOf(x);
}
//This method supposedly overrides another method called OnSavedInstanceState and allows programmer to save values to it
protected override void OnSaveInstanceState(Bundle savedInstanceState)
{
int y;
y = 2;
//Saving my value to Bundle savedInstanceState
savedInstanceState.PutInt("value",y);
//This super is being called but i dont kNow what it does
base.OnSaveInstanceState(savedInstanceState);
}
//This method is supposed to remember all the values user saved before the Activity went into OnPause()
//Changed this from public to protected because i figured onsavedInstanceState has its parameters protected so unless its an inheritance,access to its members is forbidden
protected override void OnRestoreInstanceState(Bundle savedInstanceState)
{
base.OnRestoreInstanceState(savedInstanceState);
//Restore the time value from the SavedInstance state
int c = savedInstanceState.GetInt("value");
//Assign the value to The Timepicker
timePicker2.CurrentHour=(java.lang.Integer.ValueOf(c));
}
}````
What am i doing wrong? An additional alert dialog code to detect when activity goes into Onpause and OnRestore will greatly be appreciated
解决方法
当“活动”发送到后台时,我似乎对保存值所采用的方法存在疑问。
您可以通过此 Activity.OnRestoreInstanceState Method 查看以下信息:
从先前保存的状态(在
OnStart()
中给出的状态开始重新初始化活动时,在savedInstanceState
之后调用此方法。
从后台返回时将不会调用此方法,只有在重新初始化后才能调用此方法。例如Recreate()
方法将调用它。
因此,此处进入后台时,OnSaveInstanceState
方法有效。但是,OnRestoreInstanceState
将不会被调用。
现在,如果您想存储一些数据并恢复背景和前景之间的视图,则可以在活动的SharedPreferences
和OnResume()
中使用OnPause()
。 / p>
例如,代码如下:
protected override void OnResume()
{
base.OnResume();
ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences(this);
int value = prefs.GetInt("value",0);
timePicker1.CurrentHour = (Java.Lang.Integer.ValueOf(value));
}
protected override void OnPause()
{
base.OnPause();
ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences(this);
ISharedPreferencesEditor editor = prefs.Edit();
int y;
y = 2;
editor.PutInt("value",y);
editor.Apply();
}
然后效果将显示:
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