资源
功能和要求
- （Mainpage.xaml.cs）在MainPage中点击checkbox出现横线，输入数据（选择图片），挂起并关闭程序，重新启动时，程序显示在Mainpage界面，并且点击的checkbox与对应横线，数据与图片都存在。
- （Newpage.xaml.cs）在NewPage中输入数据（或选择图片），挂起并关闭程序，重新启动时，程序显示在Newpage界面，数据与图片都存在。
功能实现
对week3项目的修改
因为week3的部分实现，不满足week4的设计，所以要对week3修改，主要原因是OnNavigationTo这个函数，第二个参数，在week3传递自定义参数到NewPage，但是week4要求保存现场，没法序列化自定义的复杂变量，所以将所有变量写到App.xaml.cs中，采用全局变量的方法，所以无需在页面中传值。
public bool issuspend = true;
public string currentId;
public ListItemViewModels ViewModel;
public BitmapImage srcImage;
public App()
{
this.InitializeComponent();
this.Suspending += OnSuspending;
ViewModel = new ListItemViewModels();
}这样的改变会造成其他页面的相应的改变，public ListItemViewModels ViewModel = ((App) App.Current).ViewModel; 这样可以不改变MainPage.xaml的绑定书写，这样的赋值，经测试不是引用，所以应该还要将改动的内容改回App中的ViewModel，我是直接用((App) App.Current).ViewModel，所以代码看起来不太美观，改动也比较大。
具体实现
MainPage的实现
protected override void OnNavigatedFrom(NavigationEventArgs e)
{
bool suspending = ((App)App.Current).issuspend;
if (suspending)
{
var composite = new ApplicationDataCompositeValue();
composite["Title"] = TitleBlock.Text;
composite["Details"] = DetailBlock.Text;
composite["Date"] = Date.Date;
composite["Visible"] = ((App)App.Current).ViewModel.AllItems[0].Completed;
ApplicationData.Current.LocalSettings.Values["MainPage"] = composite;
}
}
protected override async void OnNavigatedTo(NavigationEventArgs e)
{
bool suspending = ((App)App.Current).issuspend;
if (ApplicationData.Current.LocalSettings.Values["TempImage"] != null)
{
StorageFile tempimg;
tempimg = await StorageApplicationPermissions.FutureAccessList.GetFileAsync((string)ApplicationData.Current.LocalSettings.Values["TempImage"]);
IRandomAccessStream ir = await tempimg.OpenAsync(FileAccessMode.Read);
BitmapImage bi = new BitmapImage();
await bi.SetSourceAsync(ir);
NewImage.Source = bi;
ApplicationData.Current.LocalSettings.Values["TempImage"] = null;
}
if (e.NavigationMode == NavigationMode.New)
{
ApplicationData.Current.LocalSettings.Values.Remove("MainPage");
}
else
{
if (ApplicationData.Current.LocalSettings.Values.ContainsKey("MainPage"))
{
var composite = ApplicationData.Current.LocalSettings.Values["MainPage"] as ApplicationDataCompositeValue;
TitleBlock.Text = (string)composite["Title"];
DetailBlock.Text = (string)composite["Details"];
Date.Date = (DateTimeOffset)composite["Date"];
((App)App.Current).ViewModel.AllItems[0].Completed = (bool)composite["Visible"];
ApplicationData.Current.LocalSettings.Values.Remove("MainPage");
}
}
}
private async void Select_Click(object sender, RoutedEventArgs e)
{
//文件选择器
FileOpenPicker openPicker = new FileOpenPicker();
//选择视图模式
openPicker.ViewMode = PickerViewMode.Thumbnail;
//openPicker.ViewMode = PickerViewMode.List;
//初始位置
openPicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
//添加文件类型
openPicker.FileTypeFilter.Add(".jpg");
openPicker.FileTypeFilter.Add(".jpeg");
openPicker.FileTypeFilter.Add(".png");
StorageFile file = await openPicker.PickSingleFileAsync();
if (file != null)
{
ApplicationData.Current.LocalSettings.Values["TempImage"] = StorageApplicationPermissions.FutureAccessList.Add(file);
using (IRandomAccessStream stream = await file.OpenAsync(FileAccessMode.Read))
{
var srcImage = new BitmapImage();
await srcImage.SetSourceAsync(stream);
NewImage.Source = srcImage;
}
}
}加入OnNavigatedFrom和OnNavigatedTo两个函数
- OnNavigatedFrom作用，是跳转到其他页面对MainPage的值做保存，
var composite = new ApplicationDataCompositeValue();这个相当于声明一个空间，采用键值对存储，但是只能存储基本类型，而且容量比较小，所以没法储存图片形式的值，在Select_Click函数中有改动，ApplicationData.Current.LocalSettings.Values["TempImage"] = StorageApplicationPermissions.FutureAccessList.Add(file);这句话将file存了起来，在OnNavigateTo中要还原。 OnNavigatedTo作用，跳转到MainPage，还原MainPage，这个用了异步方法，因为要处理图片，方法和Select_Click中的方法一样。
NewPage的改动
protected override void OnNavigatedTo(NavigationEventArgs e)
{
if (e.NavigationMode == NavigationMode.New)
{
ApplicationData.Current.LocalSettings.Values.Remove("NewPage");
}
else
{
if (ApplicationData.Current.LocalSettings.Values.ContainsKey("NewPage"))
{
var composite = ApplicationData.Current.LocalSettings.Values["NewPage"] as ApplicationDataCompositeValue;
TitleBlock.Text = (string)composite["Title2"];
DetailBlock.Text = (string)composite["Details2"];
Date.Date = (DateTimeOffset)composite["Date2"];
ApplicationData.Current.LocalSettings.Values.Remove("NewPage");
}
}
if (((App)App.Current).currentId != "NULL")
{
Create_To_Update();
var temp = false;
ListItem result = new ListItem();
for (int i = 0; i < ((App)App.Current).ViewModel.AllItems.Count(); i++)
{
if (((App)App.Current).currentId == ((App)App.Current).ViewModel.AllItems[i].id)
{
result = ((App)App.Current).ViewModel.AllItems[i];
temp = true;
break;
}
}
if (temp == true)
{
TitleBlock.Text = result.title;
DetailBlock.Text = result.description;
Date.Date = result.date;
NewImage.Source = result.src;
}
}
else
{
Update_To_Create();
}
}
protected override void OnNavigatedFrom(NavigationEventArgs e) // 从该页面离开时
{
bool suspending = ((App)App.Current).issuspend;
if (suspending)
{
var composite = new ApplicationDataCompositeValue();
composite["Title2"] = TitleBlock.Text;
composite["Details2"] = DetailBlock.Text;
composite["Date2"] = Date.Date;
ApplicationData.Current.LocalSettings.Values["NewPage"] = composite;
}
}和MainPage的改动一致，没有做图片的处理。