package com.xh.tx.fileio;import java.io.File;
import java.util.Map;import com.xh.tx.utils.FileIOUtils;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;public class MainActivity extends Activity  implements OnClickListener{EditText number = null;EditText pwd = null;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);number = (EditText) findViewById(R.id.number);pwd = (EditText) findViewById(R.id.pwd);Button btn = (Button) findViewById(R.id.btn);Map<String,String> infos = FileIOUtils.readFile(new File(this.getFilesDir(),"rember.txt"));if(null != infos){number.setText(infos.get("number"));pwd.setText(infos.get("pwd"));}btn.setOnClickListener(this);}@Overridepublic void onClick(View v) {String num = number.getText().toString();String pwds = pwd.getText().toString();String content = num + "#" + pwds;File file = new File(this.getFilesDir(),"rember.txt");//File file = new File(this.getCacheDir(),"rember.txt");boolean status = FileIOUtils.writeFile(file, content);if(status)//如果保存成功那么提示保存成功，否则提示失败{Toast.makeText(this, "保存成功", Toast.LENGTH_SHORT).show();}else{Toast.makeText(this, "保存失败", Toast.LENGTH_SHORT).show();}}}

读取写入到文件的代码如下：

package com.xh.tx.utils;import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;public class FileIOUtils
{public static boolean writeFile(File file, String content){//data/data/com.xh.tx.fileioFileOutputStream out  = null;try {out = new FileOutputStream(file);out.write(content.getBytes());//byte[205]return true;} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{try {if(null != out){out.flush();out.close();}} catch (IOException e) {e.printStackTrace();}}return false;}public static Map<String,String> readFile(File file){try {BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(file)));String content = reader.readLine();String[] info = content.split("#");Map<String,String> infos = new HashMap<String,String>();infos.put("number", info[0]);infos.put("pwd", info[1]);return infos;} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}return null;}
}

布局文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:paddingBottom="@dimen/activity_vertical_margin"android:paddingLeft="@dimen/activity_horizontal_margin"android:paddingRight="@dimen/activity_horizontal_margin"android:paddingTop="@dimen/activity_vertical_margin"tools:context="com.xh.tx.fileio.MainActivity" ><EditText android:id="@+id/number"android:layout_width="match_parent"android:layout_height="wrap_content"/><EditText android:id="@+id/pwd"android:layout_below="@id/number"android:layout_width="match_parent"android:layout_height="wrap_content"/><CheckBox android:id="@+id/checkbox"android:layout_below="@id/pwd"android:layout_width="wrap_content"android:layout_height="wrap_content"android:checked="true"android:text="记住密码"/><Button android:id="@+id/btn"android:layout_below="@id/checkbox"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="登录"/></RelativeLayout>