Làm cách nào để tạo một tập tin trong Android?

Làm cách nào để tạo một tệp, ghi dữ liệu vào đó và đọc dữ liệu từ nó trên Android? Nếu có thể hãy cung cấp một đoạn mã.

Từ đây: http://www.anddev.org/usiness_with_files-t115.html

//Writing a file...  



try { 
       // catches IOException below
       final String TESTSTRING = new String("Hello Android");

       /* We have to use the openFileOutput()-method
       * the ActivityContext provides, to
       * protect your file from others and
       * This is done for security-reasons.
       * We chose MODE_WORLD_READABLE, because
       *  we have nothing to hide in our file */             
       FileOutputStream fOut = openFileOutput("samplefile.txt",
                                                            MODE_PRIVATE);
       OutputStreamWriter osw = new OutputStreamWriter(fOut); 

       // Write the string to the file
       osw.write(TESTSTRING);

       /* ensure that everything is
        * really written out and close */
       osw.flush();
       osw.close();

//Reading the file back...

       /* We have to use the openFileInput()-method
        * the ActivityContext provides.
        * Again for security reasons with
        * openFileInput(...) */

        FileInputStream fIn = openFileInput("samplefile.txt");
        InputStreamReader isr = new InputStreamReader(fIn);

        /* Prepare a char-Array that will
         * hold the chars we read back in. */
        char[] inputBuffer = new char[TESTSTRING.length()];

        // Fill the Buffer with data from the file
        isr.read(inputBuffer);

        // Transform the chars to a String
        String readString = new String(inputBuffer);

        // Check if we read back the same chars that we had written out
        boolean isTheSame = TESTSTRING.equals(readString);

        Log.i("File Reading stuff", "success = " + isTheSame);

    } catch (IOException ioe) 
      {ioe.printStackTrace();}

Tôi đã sử dụng đoạn mã sau để tạo một tệp tạm thời để ghi byte. Và nó hoạt động tốt.

File file = new File(Environment.getExternalStorageDirectory() + "/" + File.separator + "test.txt");
file.createNewFile();
byte[] data1={1,1,0,0};
//write the bytes in file
if(file.exists())
{
     OutputStream fo = new FileOutputStream(file);              
     fo.write(data1);
     fo.close();
     System.out.println("file created: "+file);
}               

//deleting the file             
file.delete();
System.out.println("file deleted");

Tôi quyết định viết một lớp từ chủ đề này có thể hữu ích cho những người khác. Lưu ý rằng điều này hiện chỉ nhằm mục đích ghi trong thư mục "tệp" (ví dụ: không ghi vào đường dẫn "sdcard").

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

import android.content.Context;

public class AndroidFileFunctions {

    public static String getFileValue(String fileName, Context context) {
        try {
            StringBuffer outStringBuf = new StringBuffer();
            String inputLine = "";
            /*
             * We have to use the openFileInput()-method the ActivityContext
             * provides. Again for security reasons with openFileInput(...)
             */
            FileInputStream fIn = context.openFileInput(fileName);
            InputStreamReader isr = new InputStreamReader(fIn);
            BufferedReader inBuff = new BufferedReader(isr);
            while ((inputLine = inBuff.readLine()) != null) {
                outStringBuf.append(inputLine);
                outStringBuf.append("\n");
            }
            inBuff.close();
            return outStringBuf.toString();
        } catch (IOException e) {
            return null;
        }
    }

    public static boolean appendFileValue(String fileName, String value,
            Context context) {
        return writeToFile(fileName, value, context, Context.MODE_APPEND);
    }

    public static boolean setFileValue(String fileName, String value,
            Context context) {
        return writeToFile(fileName, value, context,
                Context.MODE_WORLD_READABLE);
    }

    public static boolean writeToFile(String fileName, String value,
            Context context, int writeOrAppendMode) {
        // just make sure it's one of the modes we support
        if (writeOrAppendMode != Context.MODE_WORLD_READABLE
                && writeOrAppendMode != Context.MODE_WORLD_WRITEABLE
                && writeOrAppendMode != Context.MODE_APPEND) {
            return false;
        }
        try {
            /*
             * We have to use the openFileOutput()-method the ActivityContext
             * provides, to protect your file from others and This is done for
             * security-reasons. We chose MODE_WORLD_READABLE, because we have
             * nothing to hide in our file
             */
            FileOutputStream fOut = context.openFileOutput(fileName,
                    writeOrAppendMode);
            OutputStreamWriter osw = new OutputStreamWriter(fOut);
            // Write the string to the file
            osw.write(value);
            // save and close
            osw.flush();
            osw.close();
        } catch (IOException e) {
            return false;
        }
        return true;
    }

    public static void deleteFile(String fileName, Context context) {
        context.deleteFile(fileName);
    }
}

Ghi vào tệp test.txt:

String filepath ="/mnt/sdcard/test.txt";
FileOutputStream fos = null;
try {
        fos = new FileOutputStream(filepath);
        byte[] buffer = "This will be writtent in test.txt".getBytes();
        fos.write(buffer, 0, buffer.length);
        fos.close();
    } catch (FileNotFoundException e) {
         e.printStackTrace();
    } catch (IOException e) {
         e.printStackTrace();
    }finally{
        if(fos != null)
            fos.close();
    }

Đọc từ tệp test.txt:

String filepath ="/mnt/sdcard/test.txt";        
FileInputStream fis = null;
try {
       fis = new FileInputStream(filepath);
       int length = (int) new File(filepath).length();
       byte[] buffer = new byte[length];
       fis.read(buffer, 0, length);
       fis.close();
    } catch (FileNotFoundException e) {
         e.printStackTrace();
    } catch (IOException e) {
         e.printStackTrace();
    }finally{
        if(fis != null)
            fis.close();
   }

Lưu ý: đừng quên thêm hai quyền này trong AndroidManifest.xml

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