效果图：

MainActivity.java

package jk.quickpay.login;import jk.quickpay.login.FileService;
import java.util.Map;
import android.app.Activity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;public class MainActivity extends Activity {public EditText edit_name, edit_pass;public Button btn_login;public CheckBox box_remeber;public FileService fileService;protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);fileService = new FileService(this);edit_name = (EditText) findViewById(R.id.edit_name);edit_pass = (EditText) findViewById(R.id.edit_pass);btn_login = (Button) findViewById(R.id.btn_login);box_remeber = (CheckBox) findViewById(R.id.cbx_remember);btn_login.setOnClickListener(new MyOnClickListener());Map<String, String> map = fileService.readFile("private.txt");if (map != null) {edit_name.setText(map.get("name"));edit_pass.setText(map.get("pass"));}}public boolean onCreateOptionsMenu(Menu menu) {getMenuInflater().inflate(R.menu.main, menu);return true;}class MyOnClickListener implements View.OnClickListener {public void onClick(View v) {int id = v.getId();switch (id) {case R.id.btn_login:String name = edit_name.getText().toString();String pass = edit_pass.getText().toString();if (TextUtils.isEmpty(name)) {Toast.makeText(MainActivity.this, "用户名不能为空",Toast.LENGTH_SHORT).show();return;} else if (TextUtils.isEmpty(pass)) {Toast.makeText(MainActivity.this, "密码不能为空",Toast.LENGTH_SHORT).show();return;} else {if (box_remeber.isChecked()) {MainActivity.this.fileService.saveToRom(name, pass,"private.txt");Toast.makeText(MainActivity.this, "用户名和密码已保存",Toast.LENGTH_SHORT).show();} else {Toast.makeText(MainActivity.this, "用户名和密码不需要保存",Toast.LENGTH_SHORT).show();}}break;default:break;}}}
}

FileService.java

package jk.quickpay.login;import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.HashMap;
import java.util.Map;import jk.quickpay.login.StreamTools;import android.content.Context;public class FileService {public Context context;public FileService(Context context) {this.context = context;}public boolean saveToRom(String name,String pass,String fileName){try{FileOutputStream fos=context.openFileOutput(fileName, Context.MODE_PRIVATE);String result=name+":"+pass;fos.write(result.getBytes());fos.flush();fos.close();}catch(Exception e){e.printStackTrace();return false;}return true;}public Map<String,String> readFile(String fileName){Map<String,String> map=null;try{FileInputStream fis=context.openFileInput(fileName);String value=StreamTools.getValue(fis);String values[]=value.split(":");if(values.length>0){map=new HashMap<String, String>();map.put("name", values[0]);map.put("pass", values[1]);}}catch(Exception e){e.printStackTrace();}return map;}}

StreamTools.java

package jk.quickpay.login;import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;public class StreamTools {public static String getValue(FileInputStream fis) throws Exception{ByteArrayOutputStream stream=new ByteArrayOutputStream();byte[] buffer=new byte[1024];int length=-1;while((length=fis.read(buffer))!=-1){stream.write(buffer,0,length);}stream.flush();stream.close();String value=stream.toString();return value;}
}

activity_main.xml

<LinearLayout 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=".LoginActivity" ><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:layout_alignParentLeft="true"android:layout_alignParentTop="true"android:orientation="vertical" ><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content" ><TextViewandroid:id="@+id/view_account"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/account" /><EditTextandroid:id="@+id/edit_name"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:ems="10"android:inputType="textPersonName" ><requestFocus /></EditText></LinearLayout><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content" ><TextViewandroid:id="@+id/view_pass"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/password" /><EditTextandroid:id="@+id/edit_pass"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:ems="10"android:inputType="textPassword" /></LinearLayout><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content" android:orientation="horizontal"><Buttonandroid:id="@+id/btn_login"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_weight="0.1"android:text="@string/login" /><Buttonandroid:id="@+id/btn_reg"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_weight="0.1"android:text="@string/register" /><Buttonandroid:id="@+id/btn_out"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_weight="0.1"android:text="@string/quit" /></LinearLayout><CheckBoxandroid:id="@+id/cbx_remember"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginLeft="80dp"android:text="@string/text_rember" /></LinearLayout></LinearLayout>