我遇到了日益增长的内存问题。有时几分钟后，应用程序因内存不足异常而崩溃。我从SQL服务器数据库中检索图像，并从单独的类中的字节转换。
我的XAML视图：
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="TestProject.Views.DetailViews.JsonDesertPage"
xmlns:local ="clr-namespace:TestProject.Data">
<ContentPage.Resources>
<ResourceDictionary>
<local:ByteArrayToImageConverter x:Key="severityTypeImageConvertertwo"/>
</ResourceDictionary>
</ContentPage.Resources>
<ListView x:Name="listviewConactstwo" RowHeight="100" HorizontalOptions="FillAndExpand" HasUnevenRows="True" ItemSelected="listviewContacts_ItemSelected">
<ActivityIndicator x:Name="ProgressLoadertwo" IsRunning="True"/>
<ListView.ItemTemplate >
<DataTemplate>
<ViewCell>
<StackLayout Orientation="Vertical" Padding="5">
<StackLayout Orientation="Horizontal" BackgroundColor="Ivory" Opacity="0.9">
<Image Source="{Binding Image,Converter={StaticResource severityTypeImageConvertertwo}}" HeightRequest="120" WidthRequest="120"/>
<StackLayout Orientation="Vertical">
<Label Text="{Binding Name}" FontSize="Medium" TextColor="Gray" FontAttributes="Bold"/>
<BoxView HeightRequest="2" Margin="0,10,10,0" BackgroundColor="Gray" HorizontalOptions="FillAndExpand" />
<Label Text="{Binding Description}" FontSize="Micro" TextColor="Gray" FontAttributes="Bold"/>
<StackLayout Orientation="Horizontal" VerticalOptions="Start" HorizontalOptions="Start">
<Label Text="$" FontSize="Micro" VerticalOptions="Start" HorizontalOptions="Start" TextColor="Gray" FontAttributes="Bold"/>
<Label Text="{Binding Price}" FontSize="Micro" TextColor="Gray" FontAttributes="Bold"/>
</StackLayout>
</StackLayout>
<Image Source="arrowtwo.png" BackgroundColor="Transparent" WidthRequest="25" Margin="0,10,10,0"/>
</StackLayout>
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentPage>
我的代码背后：
using Newtonsoft.Json;
using Plugin.Connectivity;
using System;
using System.IO;
using System.Net.Http;
using TestProject.Data;
using TestProject.Models;
using Xamarin.Forms;
namespace TestProject.Views.DetailViews
{
public partial class JsonDesertPage : ContentPage
{
public JsonDesertPage ()
{
InitializeComponent ();
this.BackgroundImage = "background.png";
this.Title = "Soup Menu";
GetJSON();
// CrossConnectivity.Current.ConnectivityChanged += Current_ConnectivityChanged;
}
protected async override void OnAppearing()
{
base.OnAppearing();
if (!CrossConnectivity.Current.IsConnected)
{
await DisplayAlert("fail", "No Internet Connection.Offline Menu Activated", "Ok");
await Navigation.PushAsync(new MainTabbed());
}
else
{
// await DisplayAlert("sucess", " Network Is Available.", "Ok");
GetJSON();
}
}
public async void GetJSON()
{
var client = new HttpClient();
// var response = await client.GetAsync("http://192.168.43.226/GetContactsDesert.php");
var response = await client.GetAsync(Constants.BaseUrlpos + "GetContactsDesert.php");
string contactsJson = response.Content.ReadAsStringAsync().Result;
ContectList ObjContactList = new ContectList();
if (response.IsSuccessStatusCode)
{
ObjContactList = JsonConvert.DeserializeObject<ContectList>(contactsJson);
listviewConactstwo.ItemsSource = ObjContactList.contacts;
}
else
{
var textReader = new JsonTextReader(new StringReader(contactsJson));
dynamic responseJson = new JsonSerializer().Deserialize(textReader);
contactsJson = "Deserialized JSON error message: " + responseJson.Message;
await DisplayAlert("fail", "no Network Is Available.", "Ok");
}
ProgressLoadertwo.IsVisible = false;
}
private void listviewContacts_ItemSelected(object sender, SelectedItemChangedEventArgs e)
{
var itemSelectedData = e.SelectedItem as Contactone;
Navigation.PushAsync(new JsonDetailsPage(itemSelectedData.ID, itemSelectedData.Image, itemSelectedData.Name, itemSelectedData.Code, itemSelectedData.Description, itemSelectedData.Price,itemSelectedData.isservicecharge, itemSelectedData.CostPrice));
}
}
}
这是我正在使用的页面之一：
using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
namespace TestProject.Data
{
public class ByteArrayToImageConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
ImageSource retSource = null;
if (value != null)
{
byte[] imageAsBytes = (byte[])value;
// byte[] decodedByteArray = System.Convert.FromBase64String(Encoding.UTF8.GetString(imageAsBytes, 0, imageAsBytes.Length));
// var stream = new MemoryStream(decodedByteArray);
retSource = ImageSource.FromStream(() => new MemoryStream(imageAsBytes));
}
return retSource;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
//return null;
throw new NotImplementedException();
}
}
}
当我运行配置文件时，我可以看到，当我在页面之间移动时，再见[]正在成长。我尝试了FFimageloading选项，它似乎不支持字节数组图像转换器。
如何摆脱内存增长问题？
答案 0 :(得分：0)
发现了一些事情。如果没有完整的运行，我无法确定哪些是你的头痛，但是......
使用HttpClient作为单身人士。我已经通过Xam arch证实，单例使用对于Xam以及其他所有内容都是最佳选择。
注意IDiposable对象。
以下代码返回HttpResponse方法。 HttpResponseMessage是IDisposeable。使用＆＃34;
将其包裹在＆＃34;中StringReader继承自TextReader，它是IDisposable。使用＆＃34;包装＆＃34;
动态类型是不确定的。最好将它包装在一个使用中。有关详细信息，请参阅Do you need to dispose of objects and set them to null?。
HttpClient的PNP指南 - https://github.com/mspnp/performance-optimization/blob/465514674354c8f833c73882f7405ac22c4fd437/ImproperInstantiation/docs/ImproperInstantiation.md
PNP好/坏HttpClient示例 - https://github.com/mspnp/performance-optimization/tree/465514674354c8f833c73882f7405ac22c4fd437/ImproperInstantiation
您正在使用HttpClient错误，这会破坏您的软件稳定性 - http://aspnetmonsters.com/2016/08/2016-08-27-httpclientwrong/
看看这是否有帮助。
private HttpClient m_httpClient = new HttpClient();
private HttpClient MyHttpClient
{
get
{
if ( m_httpClient==null )
{
m_httpClient = new HttpClient();
}
return m_httpClient;
}
}
public async void GetJSON()
{
// var client = new HttpClient();
var client = MyHttpClient;
// var response = await client.GetAsync("http://192.168.43.226/GetContactsDesert.php");
// var response = await client.GetAsync(Constants.BaseUrlpos + "GetContactsDesert.php");
string contactsJson = string.Empty;
using (HttpResponseMessage response = await client.GetAsync(Constants.BaseUrlpos + "GetContactsDesert.php"))
{
contactsJson = response.Content.ReadAsStringAsync().Result;
}
ContectList ObjContactList = new ContectList();
if (response.IsSuccessStatusCode)
{
ObjContactList = JsonConvert.DeserializeObject<ContectList>(contactsJson);
listviewConactstwo.ItemsSource = ObjContactList.contacts;
}
else
{
using (var textReader = new JsonTextReader(new StringReader(contactsJson)) )
{
using (dynamic responseJson = new JsonSerializer().Deserialize(textReader))
{
contactsJson = "Deserialized JSON error message: " + responseJson.Message;
}
await DisplayAlert("fail", "no Network Is Available.", "Ok");
}
}
ProgressLoadertwo.IsVisible = false;
}