Java 在Android中创建xml文件时出错

我有以下代码创建一个xml文件并将其保存在设备中

package com.ex.createXml;

import android.app.Activity;
import android.os.Bundle;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import org.xmlpull.v1.XmlSerializer;
import android.os.Environment;
import android.util.Log;
import android.util.Xml;
import android.widget.TextView;


public class createXml extends Activity {
 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_create_xml);

  File newxmlfile = new File("/sdcard/Downloads/new.xml");
  try {
   newxmlfile.createNewFile();
  } catch (IOException e) {
   Log.e("IOException", "Exception in create new File(");
  }
  FileOutputStream fileos = null;
  try {
   fileos = new FileOutputStream(newxmlfile);
  } catch (FileNotFoundException e) {
   Log.e("FileNotFoundException", e.toString());
  }
  XmlSerializer serializer = Xml.newSerializer();
  try {
   serializer.setOutput(fileos, "UTF-8");
   serializer.startDocument(null, Boolean.valueOf(true));
   serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent- output", true);
   serializer.startTag(null, "root");
   serializer.startTag(null, "Child1");
   serializer.endTag(null, "Child1");
   serializer.startTag(null, "Child2");
   serializer.attribute(null, "attribute", "value");
   serializer.endTag(null, "Child2");
   serializer.startTag(null, "Child3");
   serializer.text("Some text inside child 3");
   serializer.endTag(null, "Child3");
   serializer.endTag(null, "root");
   serializer.endDocument();
   serializer.flush();
   fileos.close();
   //TextView tv = (TextView)findViewById(R.);

  } catch (Exception e) {
   Log.e("Exception", "Exception occured in wroting");
  }
 }
}

当我运行应用程序时，会出现以下错误

06-02 15:20:03.753 2530-2530/com.ex.createXml E/IOException:        Exception in create new File(
06-02 15:20:03.753 2530-2530/com.ex.createXml   E/FileNotFoundException: java.io.FileNotFoundException:    /sdcard/Downloads/new.xml (No such file or directory)
06-02 15:20:03.753 2530-2530/com.ex.createXml E/Exception: Exception    occured in wroting

我已将这些权限添加到清单中

<uses-permission      android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

---

其中一个错误是/sdcard/Downloads/new.xml（没有这样的文件或目录）。你能给我一个正确的路径来保存我的文件吗？或者你能告诉我是否有其他问题吗？谢谢

您必须确保根SD卡存在。尝试使用Environment.getExternalStorageDirectory（）获取外部目录，而不是静态路径/sdcard。如果要使用静态路径，请打印Environment.getExternalStorageDirectory（）以查看外部存储的根目录是什么

您能给我一个如何在我的代码中使用Environment.getExternalStorageDirectory（）的示例吗？我对Android和java非常业余，谢谢。替换这行文件newxmlfile=newfile（“/sdcard/Downloads/new.xml”）；按文件newxmlfile=new文件（Environment.getExternalStorageDirectory（）+“/Downloads/new.xml”）；