对SD卡的操作

<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:orientation="vertical"    tools:context=".MainActivity" >    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="请输入用户名" />    <EditText        android:id="@+id/et_usename"        android:layout_width="fill_parent"        android:layout_height="wrap_content" />    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="请输入密码" />    <EditText        android:inputType="textPassword"        android:id="@+id/password"        android:layout_width="fill_parent"        android:layout_height="wrap_content" />    <RelativeLayout        android:layout_width="fill_parent"        android:layout_height="wrap_content" >        <CheckBox            android:id="@+id/cb_remenber_passward"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:checked="true"            android:text="记住密码" />        <Button            android:layout_alignParentRight="true"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:onClick="login"            android:text="登陆" >        </Button>    </RelativeLayout></LinearLayout>

package com.example.shenchao2;import java.util.Map;import android.app.Activity;import android.os.Bundle;import android.text.TextUtils;import android.util.Log;import android.view.View;import android.widget.CheckBox;import android.widget.EditText;import android.widget.Toast;import com.example.shenchao2.service.LoginService;public class MainActivity extends Activity {private static final String TAG = "MainActivity";private EditText ed_usename;private EditText ed_password;private CheckBox cb;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);ed_usename = (EditText) this.findViewById(R.id.et_usename);ed_password = (EditText) this.findViewById(R.id.password);cb = (CheckBox) this.findViewById(R.id.cb_remenber_passward);//控制回显的代码Map<String,String> map = LoginService.getSaveUserInfo(this);if (map!=null) {ed_usename.setText(map.get("usename"));//设置密码和用户名ed_password.setText(map.get("password"));}}/** * 登陆成功 * @param vew */public void login(View vew) {String usename = ed_usename.getText().toString().trim();String password = ed_password.getText().toString().trim();// 将其内容拿出来// 判断是否为空if (TextUtils.isEmpty(usename) || TextUtils.isEmpty(password)) {Toast.makeText(this, "不能为空", Toast.LENGTH_LONG).show();} else {// 登陆,是否保存密码if (cb.isChecked()) {// 保存用户密码Log.i(TAG, "需要保存用户密码!");//日志文件信息boolean result = LoginService.saveUseInfo(this, usename,password);if (result) {Toast.makeText(this, "好高兴,保存成功!", Toast.LENGTH_LONG).show();}}// 登陆发送消到服务器,服务器验证是否正确if ("zhangsan".equals(usename) && "123".equals(password)) {Toast.makeText(this, "登陆成功!", Toast.LENGTH_LONG).show();} else {Toast.makeText(this, "登陆失败!", Toast.LENGTH_LONG).show();}}}}

package com.example.shenchao2.service;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.InputStreamReader;import java.util.HashMap;import java.util.Map;import android.content.Context;import android.os.Environment;import android.widget.Toast;public class LoginService {public static boolean saveUseInfo(Context context, String usename,String password) {try {//判断SD卡是否存在if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {File file = new File(Environment.getExternalStorageDirectory(),"/info.txt"); // 指定保存到SDCARD卡FileOutputStream fos = new FileOutputStream(file);fos.write((usename + "##" + password).getBytes());// getBytes()是将一个字符串转化为一个字节数组。fos.close();return true;}else {Toast.makeText(context, "不可用", 0).show();return false;}} catch (Exception e) {e.printStackTrace();return false;}}/** * 获取保存的数据 *  * @param context */public static Map<String, String> getSaveUserInfo(Context context) {File file = new File(Environment.getExternalStorageDirectory(),"/info.txt");try {FileInputStream fis = new FileInputStream(file);// 缓冲当前的数据BufferedReader br = new BufferedReader(new InputStreamReader(fis));String str = br.readLine(); // 读取第一行的数据String[] infos = str.split("##");// 分割开Map<String, String> map = new HashMap<String, String>(); // 初始化mapmap.put("usename", infos[0]);map.put("password", infos[1]);return map;} catch (Exception e) {e.printStackTrace();return null;}}}

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