Cách tạo tệp trong Android?

Question

Cách tạo tệp, ghi dữ liệu vào tệp và đọc dữ liệu từ tệp đó trên Android? Nếu có thể, hãy cung cấp đoạn mã.

Answer 1

From here: http://www.anddev.org/working_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();} 

Answer 2

tôi đã sử dụng đoạn mã sau để tạo ra một tập tin tạm thời để viết 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); 
    url = upload.upload(file); 
}    

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

Answer 3

Tôi quyết định viết một lớp học từ chuỗi này có thể hữu ích cho người khác. Lưu ý rằng điều này hiện được dự định chỉ viết 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); 
    } 
} 

Answer 4

Viết vào một tập tin 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 tập tin 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 phép này trong AndroidManifest. xml

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