我是Android开发的新手，我构建了一个简单的应用程序，通过蓝牙从我的计算机接收xml文件。现在我想解析xml个文件，我希望在AsyncTask doInBackground方法中执行此操作。首先，我将字节写入xml文件
private void writeBytesToOutputStream(byte[] bytes, String path) {
File file = new File(path);
OutputStream out;
try {
if(file.exists()){
file.delete();
}
file.createNewFile();
out = new FileOutputStream(file);
out.write(bytes);
out.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
// method that sets file and later calls execute().
xml.setFile(file);
}
这是我内心的AsyncTask类。
public class XmlParser extends AsyncTask<Void, Void, String> {
private XmlPullParserFactory xmlFactoryObject;
private XmlPullParser myParser;
private File file;
String value;
public XmlParser() {
try {
xmlFactoryObject = XmlPullParserFactory.newInstance();
myParser = xmlFactoryObject.newPullParser();
} catch (XmlPullParserException e) {
e.printStackTrace();
}
}
public void setFile(File file1) {
file = file1;
execute();
}
@Override
protected void onPreExecute() {
super.onPreExecute();
FileInputStream fis = null;
try {
if(file == null){
Toast.makeText(getActivity(), "NULL", Toast.LENGTH_LONG).show();
}else{
Toast.makeText(getActivity(), "NOT NULL " + file.getName(), Toast.LENGTH_LONG).show();
fis = new FileInputStream(file);
myParser.setInput(fis, null);
fis.close();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (XmlPullParserException e) {
e.printStackTrace();
}
}
@Override
protected String doInBackground(Void... params) {
int event;
try {
event = myParser.getEventType();
while (event != XmlPullParser.END_DOCUMENT) {
String name = myParser.getName();
switch (event) {
case XmlPullParser.START_TAG:
break;
case XmlPullParser.END_TAG:
if (name.equals("from")) {
value = myParser.getAttributeValue(null, "value");
System.out.println("JUST FOR TEST " + value);
event = XmlPullParser.END_DOCUMENT;
}
break;
default:
break;
}
try {
event = myParser.next();
} catch (IOException e) {
e.printStackTrace();
}
}
}catch (XmlPullParserException e) {
e.printStackTrace();
}
return value;
}
@Override
protected void onPostExecute(String aVoid) {
super.onPostExecute(aVoid);
System.out.println("myEND " + aVoid);
Toast.makeText(getActivity(), "THE END!!! " + aVoid, Toast.LENGTH_LONG).show();
}
}
某种方法doInBackground()永远不会完成。我花了差不多四个小时试图解决它，但我找不到什么是错的。我还添加了我的完整代码
public class UiFragment extends Fragment {
private static final int REQUEST_CONNECT_DEVICE_SECURE = 1;
private static final int REQUEST_ENABLE_BT = 3;
private String deviceName = null;
private BluetoothAdapter adapter = null;
//private ListView listViewConversation;
//private ArrayAdapter<String> conversationAdapter;
private Button onButton, offButton;
private BluetoothConnection connection = null;
ImageView im;
private XmlParser xml;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_ui, container, false);
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
//listViewConversation = (ListView) view.findViewById(R.id.in);
onButton = (Button) view.findViewById(R.id.onButton);
offButton = (Button) view.findViewById(R.id.offButton);
im = (ImageView) view.findViewById(R.id.imageView);
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
adapter = BluetoothAdapter.getDefaultAdapter();
xml = new XmlParser();
// If the adapter is null, then Bluetooth is not supported
if (adapter == null) {
FragmentActivity activity = getActivity();
Toast.makeText(activity, "Bluetooth is not available", Toast.LENGTH_LONG).show();
activity.finish();
}
}
@Override
public void onStart() {
super.onStart();
// If BT is not on, request that it be enabled.
// setupChat() will then be called during onActivityResult
if (!adapter.isEnabled()) {
Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
// Otherwise, setup the chat session
} else if (connection == null) {
setupChat();
}
}
private void setupChat() {
//conversationAdapter = new ArrayAdapter<String>(getActivity(), R.layout.message);
//listViewConversation.setAdapter(conversationAdapter);
onButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
sendCommand(1);
}
});
offButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
sendCommand(0);
}
});
// Initialize the BluetoothChatService to perform bluetooth connections
connection = new BluetoothConnection(handler);
}
public void onActivityResult(int requestCode, int resultCode, Intent data) {
switch (requestCode) {
case REQUEST_CONNECT_DEVICE_SECURE:
// When DeviceListActivity returns with a device to connect
if (resultCode == Activity.RESULT_OK) {
connectDevice(data);
}
break;
case REQUEST_ENABLE_BT:
// When the request to enable Bluetooth returns
if (resultCode == Activity.RESULT_OK) {
// Bluetooth is now enabled, so set up a chat session
setupChat();
} else {
// User did not enable Bluetooth or an error occurred
Toast.makeText(getActivity(), "Bluetooth not enable", Toast.LENGTH_SHORT).show();
getActivity().finish();
}
}
}
private void connectDevice(Intent data) {
// Get the device MAC address
String address = data.getExtras().getString(DeviceListActivity.EXTRA_DEVICE_ADDRESS);
// Get the BluetoothDevice object
BluetoothDevice device = adapter.getRemoteDevice(address);
// Attempt to connect to the device
connection.connect(device);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.secure_connect_scan: {
// Launch the DeviceListActivity to see devices and do scan
Intent serverIntent = new Intent(getActivity(), DeviceListActivity.class);
startActivityForResult(serverIntent, REQUEST_CONNECT_DEVICE_SECURE);
return true;
}
}
return false;
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.menu_device_list, menu);
}
private void setStatus(CharSequence subTitle) {
FragmentActivity activity = getActivity();
if (null == activity) {
return;
}
final ActionBar actionBar = activity.getActionBar();
if (null == actionBar) {
return;
}
actionBar.setSubtitle(subTitle);
}
private final Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
FragmentActivity activity = getActivity();
switch (msg.what) {
case Constants.MESSAGE_STATE_CHANGE:
switch (msg.arg1) {
case BluetoothConnection.STATE_CONNECTED:
String name = getString(R.string.title_connected_to, deviceName);
setStatus(name);
break;
case BluetoothConnection.STATE_CONNECTING:
setStatus("Connecting...");
break;
case BluetoothConnection.STATE_NONE:
setStatus("Not connected");
break;
case BluetoothConnection.STATE_LISTEN:
}
break;
case Constants.MESSAGE_DEVICE_NAME:
deviceName = msg.getData().getString(Constants.DEVICE_NAME);
if (activity != null) {
Toast.makeText(activity, "Connected to " + deviceName, Toast.LENGTH_SHORT).show();
}
break;
case Constants.MESSAGE_TOAST:
if (null != activity) {
Toast.makeText(activity, msg.getData().getString(Constants.TOAST), Toast.LENGTH_SHORT).show();
}
break;
case Constants.MESSAGE_READ:
byte[] readBuffer = (byte[]) msg.obj;
//Bitmap bmp = BitmapFactory.decodeByteArray(readBuffer, 0, msg.arg1);
//im.setImageBitmap(bmp);
String path = activity.getFilesDir() + "/mano.xml";
writeBytesToOutputStream(readBuffer, path);
break;
}
}
};
private void sendCommand(int command) {
if (connection.getState() != BluetoothConnection.STATE_CONNECTED) {
Toast.makeText(getActivity(), "You are not connected!", Toast.LENGTH_LONG).show();
return;
}
byte[] bytes = ByteBuffer.allocate(4).putInt(command).array();
connection.write(bytes);
}
private void writeBytesToOutputStream(byte[] bytes, String path) {
File file = new File(path);
OutputStream out;
try {
if(file.exists()){
file.delete();
}
file.createNewFile();
out = new FileOutputStream(file);
out.write(bytes);
out.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
xml.setFile(file);
}
public class XmlParser extends AsyncTask<Void, Void, String> {
private XmlPullParserFactory xmlFactoryObject;
private XmlPullParser myParser;
private File file;
String value;
public XmlParser() {
try {
xmlFactoryObject = XmlPullParserFactory.newInstance();
myParser = xmlFactoryObject.newPullParser();
} catch (XmlPullParserException e) {
e.printStackTrace();
}
}
public void setFile(File file1) {
file = file1;
execute();
}
@Override
protected void onPreExecute() {
super.onPreExecute();
FileInputStream fis = null;
try {
if(file == null){ // failas == null
Toast.makeText(getActivity(), "NULL", Toast.LENGTH_LONG).show();
}else{
Toast.makeText(getActivity(), "NOT NULL " + file.getName(), Toast.LENGTH_LONG).show();
fis = new FileInputStream(file);
myParser.setInput(fis, null);
fis.close();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (XmlPullParserException e) {
e.printStackTrace();
}
}
@Override
protected String doInBackground(Void... params) {
int event;
try {
event = myParser.getEventType();
while (event != XmlPullParser.END_DOCUMENT) {
String name = myParser.getName();
switch (event) {
case XmlPullParser.START_TAG:
break;
case XmlPullParser.END_TAG:
if (name.equals("from")) {
value = myParser.getAttributeValue(null, "value");
System.out.println("JUST FOR TEST " + value);
event = XmlPullParser.END_DOCUMENT;
}
break;
default:
break;
}
try {
event = myParser.next();
} catch (IOException e) {
e.printStackTrace();
}
}
}catch (XmlPullParserException e) {
e.printStackTrace();
}
return value;
}
@Override
protected void onPostExecute(String aVoid) {
super.onPostExecute(aVoid);
System.out.println("myEND " + aVoid);
Toast.makeText(getActivity(), "THE END!!! " + aVoid, Toast.LENGTH_LONG).show();
}
}
}
修改
我的文件
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
答案 0 :(得分：1)
只是一个猜测，但这可能是你的问题
try {
event = myParser.next();
} catch (IOException e) {
e.printStackTrace();
}
这是因为如果由于某种原因你的解析器无法移动到下一个元素 - 也许你的xml没有正确格式化？ - 然后这个错误永远不会升级，从而让你陷入无限循环。
你可以做的是打电话＆＃34;打破＆＃34;。如果抛出异常。另外，使用Log类进行日志记录，如下所示：
try {
event = myParser.next();
} catch (IOException e) {
Log.d(TAG, e.getLocalizedMessage();
break;
}
答案 1 :(得分：0)
试试这个：
while (myParser.getEventType() != XmlPullParser.END_DOCUMENT) {
//code
}
答案 2 :(得分：0)
我想我解决了这个问题。我需要关闭FileInputStream上的onPostExecute而不是onPreExecute方法。