Question

我已经在Xamarin中实现了一个项目。在模拟器和设备上运行它，它表明不幸的是，App已停止。

我是xamarin的新手，我对这个问题毫无头绪。我已经解决了所有的错误和警告，但它只显示了这一点。

我的设备catlog如下：

自定义spinner.cs

namespace App1.Assets.Ccode.Cspinner
{


    class CustomSpinner : BaseAdapter
    {
        private Context c;
        private JavaList<CountryName> countries;
        private LayoutInflater inflater;

        public CustomSpinner(Context c, JavaList<CountryName> countries)
        {
            this.c = c;
            this.countries = countries;
        }

        public override Java.Lang.Object GetItem(int position)
        {
            return countries.Get(position);
        }

        public override long GetItemId(int position)
        {
            return position;
        }

        public override View GetView(int position, View convertView, ViewGroup parent)
        {
            if (inflater == null)
            {
                inflater = (LayoutInflater)c.GetSystemService(Context.LayoutInflaterService);
            }

            if (convertView == null)
            {
                convertView = inflater.Inflate(Resource.Layout.country_list, parent, false);
            }

            TextView nameTxt = convertView.FindViewById<TextView>(Resource.Id.nameTxt);
            ImageView img = convertView.FindViewById<ImageView>(Resource.Id.India);

            //BIND
            nameTxt.Text = countries[position].Name;
            img.SetImageResource(countries[position].Image);


            return convertView;
        }

        public override int Count
        {
            get
            {
                return countries.Size();
            }
        }

    }
  }
  }

主要活动

[Activity(Label = "App1", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
    private Spinner sp;
    private CustomSpinner adapter;
    private JavaList<CountryName> countries;

    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.Main);

        sp = FindViewById<Spinner>(Resource.Id.country);
        countries = CountriesList.GetCountrys();
        adapter = new CustomSpinner(this, countries);

        sp.Adapter = (ISpinnerAdapter)adapter;
        sp.ItemSelected += sp_ItemSelected;
    }

    void sp_ItemSelected(object sender, AdapterView.ItemSelectedEventArgs e)
    {
        Toast.MakeText(this, countries[e.Position].Name, ToastLength.Short).Show();
    }
}
}

清单文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="App1.App1" android:versionCode="1" android:versionName="1.0"
android:installLocation="auto">
<uses-sdk android:minSdkVersion="16" />
<uses-permission android:name="android.permission.INTERNET" />
<application android:label="App1"></application>
</manifest>

请保存我的日子并帮我在设备上运行它。

谢谢

Answer 1

您收到 NullPointerException

#Python 3.4    
list=[]
list_of_list=[]

list.append("Test")
list.append("This")
list_of_list.append(list)
list=[]

print(list_of_list)
print(type(list_of_list))
print(len(list_of_list))

for element in list_of_list:
 if(element[0]=="Test"):
     print("[OK]")
 if(element[0]=="NO"):
     print("[OK]Condition is not verified")
 else:
     print("[OK]Why the condition is verified??")#<--------------------------

[['Test', 'This']] <class 'list'> 1 [OK] [OK]Why the condition is verified??说[['Test', 'This']] <class 'list'> 1 [OK]客观 null

这是确切的错误： -

Answer 2

在你的问题中没有背景细节或没有你的实际代码我可以建议你：

修改您的.csproj。如果<AndroidUseLatestPlatformSdk>True</AndroidUseLatestPlatformSdk>在文件中，请尝试将其设置为False，如<AndroidUseLatestPlatformSdk>False</AndroidUseLatestPlatformSdk>。清理所有内容并重建，重新安装应用程序。
转到AndroidManifest.xml并将“安装位置”设置为internalOnly。
尝试降级Target Framework。

P.S：以上是3个不同的建议，而不是同一建议的3个不同步骤。上述建议通常有效，但您没有在问题中提及太多细节。

Xamarin应用已停止

2 个答案: