朋友们，我有这个代码，我正在写一个xml文件到我的SD卡：
public class SingleItemView extends Activity {
File newxmlfile = new File(Environment.getExternalStorageDirectory() + "/testfinal.xml");
TextView txtmdname,txtutcost,txtdesc,txtmodno;
// Declare Variables
String mdname;
String utcost;
String desc;
String modno;
String flag;
String toolscat;
String tan;
int number;
String numberOfItems;
ProgressDialog mProgressDialog;
Bitmap bmImg = null;
ImageView addToCartButton;
final Context context = this;
FileOutputStream fileos = null;
//String newxmlfile;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
overridePendingTransition(android.R.anim.slide_in_left, android.R.anim.slide_out_right);
// Get the view from singleitemview.xml
setContentView(R.layout.singleitemview);
// Execute loadSingleView AsyncTask
toolscat=getIntent().getExtras().getString("toolscat");
tan=getIntent().getExtras().getString("tan");
new loadSingleView().execute();
if (newxmlfile.exists()){
try{
fileos = new FileOutputStream(newxmlfile, true);
}catch(FileNotFoundException e){
Log.e("FileNotFoundException", "can't create FileOutputStream");
}
} else {
try{
newxmlfile.createNewFile();
}catch(IOException e){
Log.e("IOException", "exception in createNewFile() method");
}
try{
fileos = new FileOutputStream(newxmlfile);
}catch(FileNotFoundException e){
Log.e("FileNotFoundException", "can't create FileOutputStream");
}
}
//xml
addToCartButton=(ImageView)findViewById(R.id.imageView1);
addToCartButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// get prompts.xml view
LayoutInflater li = LayoutInflater.from(context);
View promptsView = li.inflate(R.layout.promptdialog, null);
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
context);
// set prompts.xml to alertdialog builder
alertDialogBuilder.setView(promptsView);
final EditText userInput = (EditText) promptsView
.findViewById(R.id.editTextDialogUserInput);
// set dialog message
alertDialogBuilder
.setCancelable(false)
.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
@SuppressWarnings("null")
public void onClick(DialogInterface dialog,int id) {
numberOfItems=userInput.getText().toString();
number=Integer.parseInt(numberOfItems);
String utCostString=txtutcost.getText().toString();
float cost=Float.parseFloat(utCostString);
float totalCost=Float.parseFloat(utCostString)*number;
String tc = Float.toString(totalCost);
String codeText=txtmodno.getText().toString();
//Loop for writing xml
XmlSerializer serializer = Xml.newSerializer();
try {
serializer.setOutput(fileos, "UTF-8");
if(newxmlfile.length()==0) {
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, "code");
serializer.text(codeText);
serializer.endTag(null, "code");
serializer.startTag(null, "price");
serializer.text(utCostString);
serializer.endTag(null, "price");
serializer.startTag(null, "quantity");
serializer.text(numberOfItems);
serializer.endTag(null, "quantity");
serializer.startTag(null, "totalcost");
serializer.text(tc);
serializer.endTag(null, "totalcost");
serializer.endTag(null, "root");
} else {
serializer.startTag(null, "root");
serializer.startTag(null, "code");
serializer.text(codeText);
serializer.endTag(null, "code");
serializer.startTag(null, "price");
serializer.text(utCostString);
serializer.endTag(null, "price");
serializer.startTag(null, "quantity");
serializer.text(numberOfItems);
serializer.endTag(null, "quantity");
serializer.startTag(null, "totalcost");
serializer.text(tc);
serializer.endTag(null, "totalcost");
serializer.endTag(null, "root");
}
serializer.endDocument();
serializer.flush();
fileos.close();
Context context = getApplicationContext();
CharSequence text = "Save!";
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, text, duration);
toast.show();
} catch (Exception e) {
Log.e("Exception","error occurred while creating xml file");
}
//end of xml lopp
}
})
.setNegativeButton("Cancel",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
dialog.cancel();
}
});
// create alert dialog
AlertDialog alertDialog = alertDialogBuilder.create();
// show it
alertDialog.show();
}
});
}
public class loadSingleView extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(SingleItemView.this);
// Set progressdialog title
mProgressDialog.setTitle("Progress");
// Set progressdialog message
mProgressDialog.setMessage("Loading...");
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected String doInBackground(String... args) {
try {
// Retrieve data from ListViewAdapter on click event
Intent i = getIntent();
// Get the result of rank
mdname = i.getStringExtra("mdname");
// Get the result of country
utcost = i.getStringExtra("utcost");
// Get the result of population
desc = i.getStringExtra("desc");
modno = i.getStringExtra("modno");
// Get the result of flag
flag = i.getStringExtra("flag");
// Download the Image from the result URL given by flag
URL url = new URL(flag);
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
conn.setDoInput(true);
conn.connect();
InputStream is = conn.getInputStream();
bmImg = BitmapFactory.decodeStream(is);
} catch (IOException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String args) {
// Locate the TextViews in singleitemview.xml
txtmdname = (TextView) findViewById(R.id.mdname);
txtutcost = (TextView) findViewById(R.id.utcost);
txtdesc = (TextView) findViewById(R.id.desc);
txtmodno = (TextView) findViewById(R.id.modno);
// Locate the ImageView in singleitemview.xml
ImageView imgflag = (ImageView) findViewById(R.id.flag);
// Set results to the TextViews
txtmdname.setText(mdname);
txtutcost.setText(utcost);
txtdesc.setText(desc);
txtmodno.setText(modno);
// txtpopulation.setText(population);
// Set results to the ImageView
imgflag.setImageBitmap(bmImg);
// Close the progressdialog
mProgressDialog.dismiss();
}
}
}
这段代码在我的xml文件中给出了这样的输出：
<?xml version='1.0' encoding='UTF-8' standalone='yes' ?>
<root>
<code>ACT445</code>
<price>110.00</price>
<quantity>4</quantity>
<totalcost>440.0</totalcost>
</root><root><code>ACT430</code><price>110.00</price><quantity>5</quantity><totalcost>550.0</totalcost></root>
我希望输出xml文件是这样的：
<?xml version='1.0' encoding='UTF-8' standalone='yes' ?>
<root>
<code>ACT445</code>
<price>110.00</price>
<quantity>4</quantity>
<totalcost>440.0</totalcost>
<code>ACT430</code>
<price>110.00</price>
<quantity>5</quantity>
<totalcost>550.0</totalcost>
</root>
请提出我需要做的更改，以便按上述方式获取输出。任何帮助将不胜感激。提前致谢。
的 的 ** * ** * ** * 的** * ** * ** 更新的 * ** * ** * ** * ** * ****
按照桑德斯特提到的方式进行更改。现在它可以轻松地向xml输入两个条目而不会出现问题。但是当我尝试编写第三个条目时，它会被写成一些额外的字符：
<?xml version='1.0' standalone='yes' ?>
<root>
<item>
<code>ACT358</code>
<price>110.00</price>
<quantity>3</quantity>
<totalcost>330.0</totalcost>
</item>
<item>
<code>ACT443</code>
<price>110.00</price>
<quantity>5</quantity>
<totalcost>550.0</totalcost>
</item>
<
<item>
<code>ACT388</code>
<price>110.00</price>
<quantity>4</quantity>
<totalcost>440.0</totalcost>
</item>
</root>
正如您在第二次看到之后会有额外的<写入。我似乎无法找出原因。
我的新代码如下：
public class SingleItemView extends Activity {
File newxmlfile = new File(Environment.getExternalStorageDirectory() + "/testfinal.xml");
TextView txtmdname,txtutcost,txtdesc,txtmodno;
// Declare Variables
String mdname;
String utcost;
String desc;
String modno;
String flag;
String toolscat;
String tan;
int number;
String numberOfItems;
ProgressDialog mProgressDialog;
Bitmap bmImg = null;
ImageView addToCartButton;
final Context context = this;
FileOutputStream fileos = null;
//String newxmlfile;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
overridePendingTransition(android.R.anim.slide_in_left, android.R.anim.slide_out_right);
// Get the view from singleitemview.xml
setContentView(R.layout.singleitemview);
// Execute loadSingleView AsyncTask
toolscat=getIntent().getExtras().getString("toolscat");
tan=getIntent().getExtras().getString("tan");
new loadSingleView().execute();
if (!newxmlfile.exists()){
try{
newxmlfile.createNewFile();
}catch(IOException e){
Log.e("IOException", "exception in createNewFile() method");
}
}
//xml
addToCartButton=(ImageView)findViewById(R.id.imageView1);
addToCartButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// get prompts.xml view
LayoutInflater li = LayoutInflater.from(context);
View promptsView = li.inflate(R.layout.promptdialog, null);
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
context);
// set prompts.xml to alertdialog builder
alertDialogBuilder.setView(promptsView);
final EditText userInput = (EditText) promptsView
.findViewById(R.id.editTextDialogUserInput);
// set dialog message
alertDialogBuilder
.setCancelable(false)
.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
@SuppressWarnings("null")
public void onClick(DialogInterface dialog,int id) {
numberOfItems=userInput.getText().toString();
number=Integer.parseInt(numberOfItems);
String utCostString=txtutcost.getText().toString();
float cost=Float.parseFloat(utCostString);
float totalCost=Float.parseFloat(utCostString)*number;
String tc = Float.toString(totalCost);
String codeText=txtmodno.getText().toString();
//Loop for writing xml
try {
updateFile(codeText, utCostString, tc);
Context context = getApplicationContext();
CharSequence text = "Save!";
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, text, duration);
toast.show();
} catch (Exception e) {
Log.e("Exception", "error occurred while creating xml file");
}
//end of xml lopp
}
})
.setNegativeButton("Cancel",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
dialog.cancel();
}
});
// create alert dialog
AlertDialog alertDialog = alertDialogBuilder.create();
// show it
alertDialog.show();
}
});
}
//start of update function
public class loadSingleView extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(SingleItemView.this);
// Set progressdialog title
mProgressDialog.setTitle("Progress");
// Set progressdialog message
mProgressDialog.setMessage("Loading...");
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected String doInBackground(String... args) {
try {
// Retrieve data from ListViewAdapter on click event
Intent i = getIntent();
// Get the result of rank
mdname = i.getStringExtra("mdname");
// Get the result of country
utcost = i.getStringExtra("utcost");
// Get the result of population
desc = i.getStringExtra("desc");
modno = i.getStringExtra("modno");
// Get the result of flag
flag = i.getStringExtra("flag");
// Download the Image from the result URL given by flag
URL url = new URL(flag);
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
conn.setDoInput(true);
conn.connect();
InputStream is = conn.getInputStream();
bmImg = BitmapFactory.decodeStream(is);
} catch (IOException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String args) {
// Locate the TextViews in singleitemview.xml
txtmdname = (TextView) findViewById(R.id.mdname);
txtutcost = (TextView) findViewById(R.id.utcost);
txtdesc = (TextView) findViewById(R.id.desc);
txtmodno = (TextView) findViewById(R.id.modno);
// Locate the ImageView in singleitemview.xml
ImageView imgflag = (ImageView) findViewById(R.id.flag);
// Set results to the TextViews
txtmdname.setText(mdname);
txtutcost.setText(utcost);
txtdesc.setText(desc);
txtmodno.setText(modno);
// txtpopulation.setText(population);
// Set results to the ImageView
imgflag.setImageBitmap(bmImg);
// Close the progressdialog
mProgressDialog.dismiss();
}
}
private void updateFile(final String codeText, final String utCostString, final String tc)
{
RandomAccessFile randomAccessFile = null;
String lastLine = null;
boolean fileExists = true;
if (newxmlfile.length() == 0) {
fileExists = false;
try {
randomAccessFile = new RandomAccessFile(newxmlfile, "rw");
} catch(FileNotFoundException e) {
Log.e("FileNotFoundException", "can't create FileOutputStream");
}
} else {
try {
randomAccessFile = new RandomAccessFile(newxmlfile, "rw");
randomAccessFile.seek(0);
final Scanner scanner = new Scanner(newxmlfile);
int lastLineOffset = 0;
int lastLineLength = 0;
while (scanner.hasNextLine()) {
// +1 is for end line symbol
lastLine = scanner.nextLine();
lastLineLength = lastLine.length() + 2;
lastLineOffset += lastLineLength;
}
// don't need last </root> line offset
lastLineOffset -= lastLineLength;
// got to string before last
randomAccessFile.seek(lastLineOffset);
} catch(FileNotFoundException e) {
Log.e("FileNotFoundException", "can't create FileOutputStream");
} catch (IOException e) {
Log.e("IOException", "Failed to find last line");
}
}
// Now random access file is positioned properly, we can append new xml data
//we create a XmlSerializer in order to write xml data
XmlSerializer serializer = Xml.newSerializer();
if (randomAccessFile == null) {
return;
}
try {
final StringWriter writer = new StringWriter();
serializer.setOutput(writer);
if (!fileExists) {
serializer.startDocument(null, true);
serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent-output", true);
serializer.startTag(null, "root");
} else {
serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent-output", true);
}
serializer.startTag(null, "item");
serializer.startTag(null, "code");
serializer.text(codeText);
serializer.endTag(null, "code");
serializer.startTag(null, "price");
serializer.text(utCostString);
serializer.endTag(null, "price");
serializer.startTag(null, "quantity");
serializer.text(numberOfItems);
serializer.endTag(null, "quantity");
serializer.startTag(null, "totalcost");
serializer.text(tc);
serializer.endTag(null, "totalcost");
serializer.endTag(null, "item");
if (!fileExists) {
serializer.endTag(null, "root");
}
serializer.flush();
if (lastLine != null) {
serializer.endDocument();
writer.append("\n");
writer.append(lastLine);
}
// Add \n just for better output in console
randomAccessFile.writeBytes(writer.toString() + "\n");
randomAccessFile.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
提前致谢。
答案 0 :(得分：0)
您的代码存在的问题是您没有正确添加新数据。
如this answer中所述，如果文件存在你需要找到它的最后一行（在这种情况下它是</root>）并在它之前提供新数据，因此它将出现在同一个xml中文件，但不是新文件。
代码如下（我已将文件修改部分移至单独的功能并删除了与您的问题无关的所有内容）：
public class MyActivity extends Activity {
private static final String TAG = "MyActivity";
File newxmlfile = new File(Environment.getExternalStorageDirectory() + "/testfinal.xml");
int number;
String numberOfItems;
ImageView addToCartButton;
final Context context = this;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Log.e(TAG, "File is " + Environment.getExternalStorageDirectory() + "/testfinal.xml");
if (!newxmlfile.exists()){
try{
newxmlfile.createNewFile();
}catch(IOException e){
Log.e("IOException", "exception in createNewFile() method");
}
}
//xml
addToCartButton = (ImageView)findViewById(R.id.imageView1);
addToCartButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// get prompts.xml view
LayoutInflater li = LayoutInflater.from(context);
View promptsView = li.inflate(R.layout.promptdialog, null);
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
context);
if (promptsView == null) {
return;
}
// set prompts.xml to alertdialog builder
alertDialogBuilder.setView(promptsView);
final EditText userInput = (EditText) promptsView.findViewById(R.id.editTextDialogUserInput);
// set dialog message
alertDialogBuilder
.setCancelable(false)
.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int id) {
if (userInput == null || userInput.getText() == null) {
return;
}
numberOfItems = userInput.getText().toString();
number = Integer.parseInt(numberOfItems);
String utCostString = "200";//txtutcost.getText().toString();
float cost = Float.parseFloat(utCostString);
float totalCost = Float.parseFloat(utCostString) * number;
String tc = Float.toString(totalCost);
String codeText = "codeText";//txtmodno.getText().toString();
//Loop for writing xml
try {
updateFile(codeText, utCostString, tc);
Context context = getApplicationContext();
CharSequence text = "Save!";
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, text, duration);
toast.show();
} catch (Exception e) {
Log.e("Exception", "error occurred while creating xml file");
}
//end of xml lopp
}
})
.setNegativeButton("Cancel",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
}
});
// create alert dialog
AlertDialog alertDialog = alertDialogBuilder.create();
// show it
alertDialog.show();
}
});
}
/**
* Appends new data to the file
*
* @param codeText
* @param utCostString
* @param tc
*/
private void updateFile(final String codeText, final String utCostString, final String tc) throws IOException {
RandomAccessFile randomAccessFile = null;
String closingLine = null;
boolean fileExists = true;
if (newxmlfile.length() == 0) {
fileExists = false;
try {
randomAccessFile = new RandomAccessFile(newxmlfile, "rw");
} catch(FileNotFoundException e) {
Log.e("FileNotFoundException", "can't create FileOutputStream");
}
} else {
try {
randomAccessFile = new RandomAccessFile(newxmlfile, "rw");
randomAccessFile.seek(0);
String lastLine;
long lastLineOffset = 0;
int lastLineLength = 0;
lastLine = randomAccessFile.readLine();
while (lastLine != null) {
// +1 is for end line symbol
lastLineLength = lastLine.length();
lastLineOffset = randomAccessFile.getFilePointer();
closingLine = lastLine;
lastLine = randomAccessFile.readLine();
}
lastLineOffset -= lastLineLength;
// got to string before last
randomAccessFile.seek(lastLineOffset);
} catch(FileNotFoundException e) {
Log.e("FileNotFoundException", "can't create FileOutputStream");
} catch (IOException e) {
Log.e("IOException", "Failed to find last line");
}
}
// Now random access file is positioned properly, we can append new xml data
//we create a XmlSerializer in order to write xml data
XmlSerializer serializer = Xml.newSerializer();
if (randomAccessFile == null) {
return;
}
try {
final StringWriter writer = new StringWriter();
serializer.setOutput(writer);
if (!fileExists) {
serializer.startDocument(null, true);
serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent-output", true);
serializer.startTag(null, "root");
} else {
serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent-output", true);
}
serializer.startTag(null, "code");
serializer.text(codeText);
serializer.endTag(null, "code");
serializer.startTag(null, "price");
serializer.text(utCostString);
serializer.endTag(null, "price");
serializer.startTag(null, "quantity");
serializer.text(numberOfItems);
serializer.endTag(null, "quantity");
serializer.startTag(null, "totalcost");
serializer.text(tc);
serializer.endTag(null, "totalcost");
if (!fileExists) {
serializer.endTag(null, "root");
}
serializer.flush();
if (closingLine != null) {
serializer.endDocument();
writer.append("\n");
writer.append(closingLine);
}
// Add \n just for better output in console
randomAccessFile.writeBytes(writer.toString());
randomAccessFile.close();
} catch (IOException e) {
e.printStackTrace();
} finally {
randomAccessFile.close();
}
}
}