如何读取和写入文件

我想编写一个程序，它获得3个文本框值和1个全局变量保存在文本文档中，但是我想追加到文本文档中，而不是每次重写！这是我迄今为止;如何读取和写入文件

public class Proceed extends Activity { 

    // Defining edittext variables and where they will be used 
    EditText edittext; 
    EditText edittext1; 
    EditText edittext2; 

    // Getting global variable to get price data from past activity 
    String PriceResult = Main2Activity.GSTFinal; 

    // Defining textview to show data 
    TextView tvResult2; 

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

     // assigning variables from their respective EditText and textview box 
     edittext = (EditText) findViewById(R.id.Name); 
     edittext1 = (EditText) findViewById(R.id.Phone); 
     edittext2 = (EditText) findViewById(R.id.Address); 
     tvResult2 = (TextView) findViewById(R.id.tvResult2); 
     // Assigning tvresult what string to show 
     tvResult2.setText(PriceResult + ""); 
     // 
    } 

    public void save(View view) { 
     String n1 = edittext.getText().toString(); 
     String n2 = edittext1.getText().toString(); 
     String n3 = edittext2.getText().toString(); 
     String n4 = tvResult2.getText().toString(); 
     String Writetotxtfile = n1 + "," + n2 + "," + n3 + "," + n4; 
     String filename = "myfile"; 
     FileOutputStream outputStream; 

     try { 
      outputStream = openFileOutput(filename, Context.MODE_PRIVATE); 
      outputStream.write(Writetotxtfile.getBytes()); 
      outputStream.close(); 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 

    } 
}

来源

2016-03-04 Kripzy

对于读取文件

public String readFromFile() { 
      File sdcard = Environment.getExternalStorageDirectory(); 
      File file = new File(sdcard,".YOURAPP/myFile.txt"); 
      StringBuilder text = new StringBuilder(); 
      try { 
       BufferedReader br = new BufferedReader(new FileReader(file)); 
       String line; 

       while ((line = br.readLine()) != null) { 
        text.append(line); 
        text.append('\n'); 
       } 
       br.close(); 
      } 
      catch (IOException e) { 
       //You'll need to add proper error handling here 
      } 
      return text.toString(); 
     }

用于写文件

public void writeFile(String data){ 
     try { 
      File logFile = new File(Environment.getExternalStorageDirectory().toString(), ".YOURAPP/myFile.txt"); 
      File dirFile = new File(Environment.getExternalStorageDirectory().toString(), ".YOURAPP"); 
      if(!logFile.exists()) { 
       dirFile.mkdir(); 
       logFile.createNewFile(); 
      } 
      BufferedWriter output = new BufferedWriter(new FileWriter(logFile)); 
      output.write(data); 
      output.close(); 
     }catch (Exception e){ 
      System.out.print("Exception e"+e); 
     } 
    }

对于删除文件

public void deleteFile(){ 

     File logFile = new File(Environment.getExternalStorageDirectory().toString(), ".YOURAPP/myFile.txt"); 
     File dirFile = new File(Environment.getExternalStorageDirectory().toString(), ".YOURAPP"); 
     if(logFile.exists()) { 
      logFile.delete(); 
      dirFile.delete(); 

     } 
    }

向menifest添加权限

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

来源

2016-03-04 05:48:04

如何附加到已经写好的文件？ – Kripzy

阅读文件后，我们必须追加字符串，删除旧文件，并用附加字符串编写新文件 –

所有的好东西我想了一下，如何在1分钟的研究后自己做到这一点：P哈哈 – Kripzy

而不是

outputStream = openFileOutput(filename, Context.MODE_PRIVATE);

使用

outputStream = new FileOutputStream(filename, true);

这将确保你附加到文件，而不是截断它。

来源

2016-03-04 05:38:51

谢谢！我使用了上面的代码！但它不会追加！ - – Kripzy

你所试图做的是叫做

追加

FileOutputStream有追加Constructor。

创建一个文件输出流以写入由指定的File对象表示的文件。

FileOutputStream(File file, boolean append)

实例的FileOutputStream中时，那么使用该构造。

来源

2016-03-04 05:43:22 giannisf

如何读取和写入文件

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