Android, file io e encoding

  Vamos fazer umas alterações no projeto anterior para testarmos gravação e leitura de arquivos de textos e encoding.
  Usaremos:
  Para output:
   openFileOutput - médodo que abre um arquivo e retorna um objeto tipo FileOutputStream.
   OutputStreamWriter - classe que faz a tradução de character em byte(s) usando o encoding. Se não for informado um específico assume o default.
   BufferedWriter - grava characters. no buffer.

  Para input:
    openFileInput - médodo que abre um arquivo e retorna um objeto tipo FileInputStream
    InputStreamReader - classe que faz a tradução de bytes para character usando o encoding. Se não for informado um específico assume o default
    BufferedReader - classe que faz a leitura de characters via buffer.

   Vamos aos códigos:

 main.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <EditText android:id="@+id/et1" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_weight="1" android:gravity="top" /> <Button android:id="@+id/clear" android:text="@string/clear" android:layout_width="fill_parent" android:layout_height="wrap_content" /> <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content"> <EditText android:id="@+id/encodingOut" android:layout_width="0dip" android:layout_height="wrap_content" android:hint="@string/encodingOut" android:layout_weight="2" /> <EditText android:id="@+id/fileNameOut" android:layout_width="0dip" android:layout_height="wrap_content" android:hint="@string/fileNameOut" android:layout_weight="2" /> <Button android:id="@+id/write" android:text="@string/write" android:layout_width="15dp" android:layout_weight="1" android:layout_height="wrap_content" /> </LinearLayout> <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content"> <EditText android:id="@+id/encodingIn" android:layout_width="0dip" android:layout_height="wrap_content" android:hint="@string/encodingIn" android:layout_weight="2" /> <EditText android:id="@+id/fileNameIn" android:layout_width="0dip" android:layout_height="wrap_content" android:hint="@string/fileNameIn" android:layout_weight="2" /> <Button android:id="@+id/read" android:text="@string/read" android:layout_width="15dp" android:layout_weight="1" android:layout_height="wrap_content" /> </LinearLayout> </LinearLayout>

strings.xml
<?xml version="1.0" encoding="utf-8"?> <resources> <string name="hello">Hello World, TesteFileEcondingActivity!</string> <string name="app_name">TesteFileEconding</string> <string name="clear">Clear Text</string> <string name="encodingOut">Encoding</string> <string name="fileNameOut">File Name</string> <string name="write">Gravar</string> <string name="encodingIn">Encoding</string> <string name="fileNameIn">File Name</string> <string name="read">Ler</string> <string name="digite_fileName">Informe o nome do arquivo</string> <string name="fileWrited">Arquivo gravado com sucesso</string> <string name="writeError">Erro na gravação do arquivo</string> <string name="fileNotFound">Arquivo não existe</string> <string name="readError">Erro na leitura do arquivo</string> </resources>

TesteFileEcondingActivity.java package br.com.agorandroid.encoding; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import android.app.Activity; import android.content.Context; import android.os.Bundle; import android.view.View; import android.view.inputmethod.InputMethodManager; import android.widget.Button; import android.widget.EditText; import android.widget.Toast; public class TesteFileEcondingActivity extends Activity { EditText et, encodingOut, fileNameOut, encodingIn, fileNameIn; Button clear, write, read; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); et = (EditText) findViewById(R.id.et1); clear = (Button) findViewById(R.id.clear); clear.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE); imm.hideSoftInputFromWindow(clear.getApplicationWindowToken(), 0); et.setText(""); } }); encodingOut = (EditText) findViewById(R.id.encodingOut); fileNameOut = (EditText) findViewById(R.id.fileNameOut); write = (Button) findViewById(R.id.write); write.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE); imm.hideSoftInputFromWindow(write.getApplicationWindowToken(), 0); writeFile(); } }); encodingIn = (EditText) findViewById(R.id.encodingIn); fileNameIn = (EditText) findViewById(R.id.fileNameIn); read = (Button) findViewById(R.id.read); read.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE); imm.hideSoftInputFromWindow(read.getApplicationWindowToken(), 0); readFile(); } }); } private void writeFile() { FileOutputStream fos = null; String fileName = fileNameOut.getText().toString(); String encoding = encodingOut.getText().toString(); if (fileName.equals("")) { Toast.makeText(getBaseContext(), this.getString(R.string.digite_fileName), Toast.LENGTH_LONG).show(); return; } try { fos = openFileOutput(fileName, Context.MODE_WORLD_READABLE); OutputStreamWriter osw = null; if (encoding.equals("")) { osw = new OutputStreamWriter(fos); } else { osw = new OutputStreamWriter(fos, encoding); } BufferedWriter bw = new BufferedWriter(osw); bw.write(et.getText().toString()); bw.flush(); osw.close(); Toast.makeText(getBaseContext(), this.getString(R.string.fileWrited), Toast.LENGTH_LONG).show(); } catch (IOException e) { Toast.makeText(getBaseContext(), this.getString(R.string.writeError), Toast.LENGTH_LONG).show(); e.printStackTrace(); } } private void readFile() { StringBuilder sBuilder = new StringBuilder(); FileInputStream fis = null; String fileName = fileNameIn.getText().toString(); String encoding = encodingIn.getText().toString(); if (fileName.equals("")) { Toast.makeText(getBaseContext(), this.getString(R.string.digite_fileName), Toast.LENGTH_LONG).show(); return; } try { fis = openFileInput(fileName); InputStreamReader isr = null; if (encoding.equals("")) { isr = new InputStreamReader(fis); } else { isr = new InputStreamReader(fis, encoding); } BufferedReader br = new BufferedReader(isr); char[] buffer = new char[1024 * 8]; int length; while ((length = br.read(buffer)) != -1) { sBuilder.append(buffer, 0, length); } br.close(); et.setText(sBuilder.toString()); } catch (FileNotFoundException e) { Toast.makeText(getBaseContext(), this.getString(R.string.fileNotFound), Toast.LENGTH_LONG).show(); } catch (IOException e) { Toast.makeText(getBaseContext(), this.getString(R.string.readError), Toast.LENGTH_LONG).show(); e.printStackTrace(); } } }

Vamos digitar alguns caracteres acentuados para testar:

Acima gravamos texto.txt com o encoding default

Acima, leitura do arquivo texto.txt, usando o encoding Cp1252. Vejam os caracteres acentuados.

Acima, lendo o arquivo informando o encoding UTF8. Como foi com ele que gravamos, leitura ok.

É isso.
Abraços.