Question

我正在浏览来自外部usb存储的xml文件（使用otg cable，连接在tablet / android手机中）进行解析。

步骤：

从外部USB存储中浏览文件
解析xml文件
将文件保存在文本文件中

目前，我现在能够浏览并解析xml文件，然后显示已解析的文件，其中它在列表视图中显示所需的信息。现在，我想将显示的信息保存为文本文件，并将其保存到平板电脑的外部SD卡中。这是代码：

Model.java：

public class Model {
String _model;
String _part;
String _sw;
String _desc;

// constructor
public Model() { 
}

// constructor with parameters
public Model(String model, String part, String sw, String desc) {
    this._model = model;
    this._part  = part;
    this._sw    = sw;
    this._desc  = desc;
}

// Set all methods
public void setModel(String model) {
    this._model = model;
}

public void setPart(String part) {
    this._part = part;
}

public void setSw(String sw) {
    this._sw = sw;
}

public void setDesc(String desc) {
    this._desc = desc;
}

// Get all methods
public String getModel() {
    return this._model;
}

public String getPart() {
    return this._part;
}

public String getSw() {
    return this._sw;
}

public String getDesc() {
    return this._desc;
}

//
@Override
public String toString() {
    return  "\n" + "Device" + "\n" + "\n"
            + "Model ID : " + _model + "\n" 
            + "Part Number : " + _part + "\n" 
            + "Software Version: " + _sw + "\n" 
            + "Description : " + _desc ;
}
}

ModelParser.java：

public class ModelParser extends DefaultHandler{
static final String ERROR = "Errors";
static final String ID = "ID";
static final String PART = "PartNumber";
static final String SW = "SoftwareVersion";
static final String DESC = "Description";

private boolean done = false;
private String currentTag = null;
private Model current = null;    
private ArrayList<Model> model = new ArrayList<Model>();

public ArrayList<Model> getItemsList() {
    return model;
}

public ArrayList<Model> parse(Context context) {        
    try {
        String file = ReadSystemActivity.getFilename();
        file.toString();

        XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
        factory.setNamespaceAware(true);
        XmlPullParser parser = factory.newPullParser();
        FileInputStream fis = new FileInputStream(file);
        parser.setInput(new InputStreamReader(fis));

        int eventType = parser.getEventType();


        while (eventType != XmlPullParser.END_DOCUMENT && !done) {
            switch (eventType) {
            case XmlPullParser.START_DOCUMENT:
                model = new ArrayList<Model>();
                break;
            case XmlPullParser.START_TAG:
                currentTag = parser.getName();
                    if (currentTag.equalsIgnoreCase(ERROR)) {
                        current = new Model(); 
                        }

                    else if (current != null) { 
                    if (currentTag.equalsIgnoreCase(ID)) {
                        current.setModel(parser.nextText());
                    } else if (currentTag.equalsIgnoreCase(PART)) {
                        current.setPart(parser.nextText());
                    } else if (currentTag.equalsIgnoreCase(SW)) {
                        current.setSw(parser.nextText());
                    }else if (currentTag.equalsIgnoreCase(DESC)) {
                        current.setDesc(parser.nextText());
                    }


                }

             break;
             case XmlPullParser.END_TAG:
            currentTag = parser.getName();
            if (currentTag.equalsIgnoreCase(ERROR) && current != null) {
                model.add(current);
            } else if (currentTag.equalsIgnoreCase(ERROR)) {
                done = true;
            }
            break;
        }
        eventType = parser.next();
    }

} catch (XmlPullParserException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}
return model;
}
}

和ReadActivity.java：

public class ReadActivity extends ListActivity implements OnClickListener {

public List<Model> model = null;
private String filename = "SystemInfo.txt";

String modd = modId.getModel();


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_read);

    new LoadSystemTask().execute();

    Button save = (Button) findViewById(R.id.btnSave);
    save.setOnClickListener(new OnClickListener() {

    public void onClick(View v) {
        // write on SD card file data in the text box
        if (isSDCardWritable()) {

              StringBuilder locationStrBuilder = new StringBuilder();
              locationStrBuilder.append("Model ID: "+ modd);
              String locationStr = locationStrBuilder.toString();
        try {
            File sdCard = Environment.getExternalStorageDirectory();
            File directory = new File(sdCard.getAbsolutePath()+"/FileReader");
            directory.mkdirs();
            File myFile = new File(directory, filename);

       myFile.createNewFile();
       FileOutputStream fOut = new FileOutputStream(myFile, true);
       OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
       myOutWriter.append(locationStr);
       myOutWriter.close();
       fOut.close();
       Toast.makeText(getBaseContext(),"Done writing to SD Card",Toast.LENGTH_SHORT).show();
      } 
      catch (Exception e) {
       Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_SHORT).show();
      } }
      else 
        {
            // SD Card Not Available
            Toast.makeText(getBaseContext(),"SD Card Not Available",Toast.LENGTH_SHORT).show();
        } //else

    }// onClick
    }); // btnSave
    }

    private class LoadSystemTask extends AsyncTask<String, Void, List<Model>> { 

    @Override
    protected List<Model> doInBackground(String... args) {

        // CALL XMLPULLPARSER & RETURN A LIST           
        ModelParser parser = new ModelParser();
        model = parser.parse(getBaseContext());
        return model;
    }

    @Override
    protected void onPostExecute(List<Model> models) {

        ArrayAdapter<Model> adapter = new ArrayAdapter<Model>(getBaseContext(), android.R.layout.simple_list_item_1, models);

        setListAdapter(adapter);

    }
}



public boolean isSDCardWritable() {
String status = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(status)) 
{
  return true;
}
      return false;
} //isSDCardWritable

@Override
public void onClick(View v) {
// TODO Auto-generated method stub  
}
}

问题是，我想保存Id，但是当我点击保存按钮时，我在SystemInfo.txt中得到一个空值。

Answer 1

您将模型存储在另一个对象中并尝试从新对象中检索它。

这是您在ModelParser

中存储模型对象的位置

current = new GarminModel()

而您正试图从ReadActivity

中的新对象中检索它

GarminModel modId = new GarminModel();
String modd = modId.getModel();

通过调用ModelParser's内的getItemsList() ReadActivity来获取对模型arraylist的引用，并从中尝试获取模型对象

检查以下代码中以下两行的位置

 ModelParser parser = new ModelParser();

 ArrayList<Model> modelList = parser.getItemsList();
              Model modd = modelList.get(0);

请注意，您需要删除ModelParser解析器= new ModelParser（）;来自LoadSystemTask

public class ReadActivity extends ListActivity implements OnClickListener {

public List<Model> model = null;
private String filename = "SystemInfo.txt";
ModelParser parser = new ModelParser();
//-----------------

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_read);

    new LoadSystemTask().execute();

    Button save = (Button) findViewById(R.id.btnSave);
    save.setOnClickListener(new OnClickListener() {

    public void onClick(View v) {
        // write on SD card file data in the text box
        if (isSDCardWritable()) {
              ArrayList<Model> modelList = parser.getItemsList();
              //-----
              Model modd = modelList.get(0);
              StringBuilder locationStrBuilder = new StringBuilder();
              locationStrBuilder.append("Model ID: "+ modd);
              String locationStr = locationStrBuilder.toString();
        try {
            File sdCard = Environment.getExternalStorageDirectory();
            File directory = new File(sdCard.getAbsolutePath()+"/FileReader");
            directory.mkdirs();
            File myFile = new File(directory, filename);

       myFile.createNewFile();
       FileOutputStream fOut = new FileOutputStream(myFile, true);
       OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
       myOutWriter.append(locationStr);
       myOutWriter.close();
       fOut.close();
       Toast.makeText(getBaseContext(),"Done writing to SD Card",Toast.LENGTH_SHORT).show();
      } 
      catch (Exception e) {
       Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_SHORT).show();
      } }
      else 
        {
            // SD Card Not Available
            Toast.makeText(getBaseContext(),"SD Card Not Available",Toast.LENGTH_SHORT).show();
        } //else

    }// onClick
    }); // btnSave
    }

    private class LoadSystemTask extends AsyncTask<String, Void, List<Model>> { 

    @Override
    protected List<Model> doInBackground(String... args) {

        // CALL XMLPULLPARSER & RETURN A LIST           

        model = parser.parse(getBaseContext());
        return model;
    }

将列表视图中的项目保存到android中的文本文件中

1 个答案: