我遇到了一个问题,无法从资产目录中读取简单的txt文件。我真的想不出为什么它不起作用以及哪里出了问题。
这是我编写的方法代码:
private string ReadFile(){
var stream = Assets.Open ("sampleText.txt");
StreamReader sr = new StreamReader (stream);
string text = sr.ReadToEnd ();
sr.Close ();
return text;
}
以下是错误信息:
Java.Lang.NullPointerException: Exception of type 'Java.Lang.NullPointerException' was thrown.
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/data/lanes/2970/46c3f7e0/source/mono/external/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143
at Android.Runtime.JNIEnv.CallNonvirtualObjectMethod (IntPtr jobject, IntPtr jclass, IntPtr jmethod) [0x00084] in /Users/builder/data/lanes/2970/46c3f7e0/source/monodroid/src/Mono.Android/src/Runtime/JNIEnv.g.cs:596
at Android.Content.ContextWrapper.get_Assets () [0x0005f] in /Users/builder/data/lanes/2970/46c3f7e0/source/monodroid/src/Mono.Android/platforms/android-19/src/generated/Android.Content.ContextWrapper.cs:154
我在Windows上运行整个应用程序没有问题,但在Android上运行时遇到了问题。我尝试过各种方法,例如使用AssetManager实例,但都没有成功。
该文本文件标记为AndroidAsset。
这是我的代码:
public class TextChangeBench : Activity
{
public TextChangeBench (){}
private void SaveFile(string[] tab){
string saveLocation = "sampleTextReworked.txt";
StreamWriter sw = new StreamWriter (saveLocation);
foreach (string s in tab) {
sw.Write (s);
}
sw.Close ();
}
private string ReadFile(){
var stream = Assets.Open ("sampleText.txt");
StreamReader sr = new StreamReader (stream);
string text = sr.ReadToEnd ();
sr.Close ();
return text;
}
public void ChangeText(){
try{
File.Delete("sampleTextReworked.txt");
}catch(FileNotFoundException e){Console.WriteLine (e);}
try{
string text = ReadFile ();
char c;
string[] newTab = new string[text.Length];
for (int i = 0; i < text.Length; i++)
{
c = (char)text [i];
if (Char.IsUpper(c))
{
newTab[i] = text[i].ToString().ToLower();
}
else if (Char.IsLower(c))
{
newTab[i] = text[i].ToString().ToUpper();
}
else
{
newTab[i] = text[i].ToString();
}
}
SaveFile(newTab);
}
catch(Exception e){Console.WriteLine ("{0} ", e);}
}
}
这是我的
MainActivity
:[Activity (Label = "csBench", MainLauncher = true, Icon = "@mipmap/icon")]
public class MainActivity : Activity
{
protected override void OnCreate (Bundle savedInstanceState)
{
base.OnCreate (savedInstanceState);
SetContentView (Resource.Layout.Main);
Button startButton = FindViewById<Button> (Resource.Id.start);
startButton.Click += delegate {
MathBench mb = new MathBench ();
TextChangeBench tcb = new TextChangeBench ();
PassedTime pt = new PassedTime ();
EditText et = (EditText)FindViewById (Resource.Id.textInfo);
for (int i = 0; i < 5; i++) {
pt.StartMeasuring ();
//mb.Silnia (25);
//mb.Fibonacci (32);
//mb.BubbleSort ();
tcb.ChangeText ();
if (i == 4) {
pt.StopMeasuring ();
et.SetText(pt.ReturnResult(), TextView.BufferType.Normal);
//et.SetText(pt.ReturnResult().ToString());
//Console.WriteLine(pt.ReturnResult ());
pt.ResetTimers ();
}
}
};
}
}
欢迎提供任何帮助,非常感谢。
sampleText.txt
的构建操作是否设置为AndroidAsset
? - Sven-Michael StübeReadFile()
周围的代码?通常Java.Lang.NullPointerException
表示该活动已被丢弃并处于无效状态。 - matthewrdev