android的基础学习

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今天看视频主要学习了android下文件访问的权限和android的存储。

首先，android下文件访问权限Permission：

文件权限

读(R)

写(W)

执行(X)

对应数字

第0位

第1~3位（当前用户）

第4~6（当前用户所在的分组）

第7~9（其他的用户）

对应权限数字相加

-代表文件（0）

r w x

d代表目录（1）

4 2 0

4 0 0

0 0 0

640

4 2 1

4 0 1

755

修改文件权限的方法暂时学到了两种：一种是通过代码：out = context.openFileOutput(filename, Context.MODE_PRIVATE);

一种是通过cmd命令：将private.txt文件修改为全可读可写可执行

adb shell 找到对应文件 chmod 666 private.txt

其次，android的存储分为两个方面，一部分是手机内部存储空间（可以理解成一块微硬盘/data/data），另一部分就是外部存储空间SD卡（sdcard）。将eclipse调成DDMS下FileExplorer中就可找到。

可以通过代码来获取SD卡的空间：

在用户登录注册环节，可以利用sharedPreference保存用户信息来完成记住密码信息的功能。

代码如下：

package com.example.application;

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.Map;

import com.example.application.LoginService.LoginService;
import com.example.applicationsharepreference.R;

import android.os.Bundle;
import android.app.Activity;
import android.content.SharedPreferences;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

   private static final String TAG="MainActivity";
   private EditText et_userid;
   private EditText et_password;
   private CheckBox cb;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
       et_userid=(EditText) this.findViewById(R.id.userid);
       et_password=(EditText) this.findViewById(R.id.password);
       cb=(CheckBox) this.findViewById(R.id.cb);

       SharedPreferences sPreferences=getSharedPreferences("config", MODE_PRIVATE);
       String userid=sPreferences.getString("username", "");
       et_userid.setText(userid);
       String password=sPreferences.getString("password", "");
       et_password.setText(password);
    }

    public void userLogin(View view)
    {
       String userid=et_userid.getText().toString().trim();
       String password=et_password.getText().toString().trim();
       Map<String, String> map=LoginService.getSaveUserInfo(this);
       try {
           if(TextUtils.isEmpty(userid)||TextUtils.isEmpty(password)){
               Toast.makeText(this, "用户名或者密码不能为空",Toast.LENGTH_LONG).show();
           }else {
               if(cb.isChecked()){
                   Log.i(TAG, "需要保存用户名密码");
                   LoginService.saveUserInfo(this, userid, password)
                           ;

                       Toast.makeText(this, "保存用户信息成功", Toast.LENGTH_LONG).show();

               }
               if("ljr".equals(userid)&&"123".equals(password))
               {
                   Toast.makeText(this, "登录成功", Toast.LENGTH_LONG).show();


               }else {
                   Toast.makeText(this, "密码用户错误",Toast.LENGTH_LONG).show();
               }
           }


       } catch (Exception e) {
           // TODO Auto-generated catch block

           e.printStackTrace();
           Toast.makeText(this, "失败", Toast.LENGTH_LONG).show();
       }
    }
}

package com.example.application.LoginService;

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;
import java.util.jar.Attributes.Name;

import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.graphics.AvoidXfermode.Mode;
import android.os.Environment;
import android.widget.Toast;

public class LoginService {
   /*
   * 保存用户名和密码的业务流程
   *
   * @param context 上下文
   *
   * @param userid用户名
   *
   * @param password密码
   *
   * @return true 保存成功 false保存失败
   */
   public static void saveUserInfo(Context context, String userid,
           String password) {

       SharedPreferences sPreferences=context.getSharedPreferences("config", context.MODE_PRIVATE);
       Editor editor=sPreferences.edit();
       editor.putString("username", userid);
       editor.putString("password", password);
       editor.putBoolean("open", true);
       editor.putInt("count", 23);
       editor.putFloat("pi", (float) 3.21);
       editor.commit();


   }

   public static Map<String, String> getSaveUserInfo(Context context) {

       File file = new File("/sdcard/info.txt");
       try {
           FileInputStream fis=new FileInputStream(file);
           BufferedReader br=new BufferedReader(new InputStreamReader(fis));
           String str=br.readLine();
           //zhangsan##123
           String[] infos=str.split("##");
           Map<String, String> map=new HashMap<String, String>();
           map.put("userid", infos[0]);
           map.put("password", infos[1]);
           return map;


       } catch (Exception e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
           return null;
       }

   }

}

用代码生成xml文件，这里演示的是备份手机中的短信内容到xml文件，采用了两种方式

代码入下：

package com.example.genXML;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import org.xmlpull.v1.XmlSerializer;

import com.example.genXML.domain.smsInfo;

import android.os.Bundle;
import android.os.Environment;
import android.app.Activity;
import android.util.Xml;
import android.view.Menu;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends Activity {
private List<smsInfo> smsInfos;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       smsInfos=new ArrayList<smsInfo>();
       Random random=new Random();
       long number= 1350000000;
       for(int i=0;i<10;i++)
       smsInfos.add(new smsInfo(System.currentTimeMillis(),1,"duanxinneirong"+i,Long.toString(number+i),i));

   }
/*
* 备份手机的短信
*/
   public void backupSMS1(View view){
       StringBuilder sbBuilder=new StringBuilder();

       sbBuilder.append("<smss>");
       for(smsInfo info:smsInfos){
           sbBuilder.append("<sms>");
           sbBuilder.append("<address>");
           sbBuilder.append(info.getAddress());
           sbBuilder.append("</address>");

           sbBuilder.append("<type>");
           sbBuilder.append(info.getType());
           sbBuilder.append("</type>");

           sbBuilder.append("<body>");
           sbBuilder.append(info.getAddress());
           sbBuilder.append("</body>");

           sbBuilder.append("<date>");
           sbBuilder.append(info.getTime());
           sbBuilder.append("</date>");
       }
           sbBuilder.append("</smss>");
           try {
               File file=new File(Environment.getExternalStorageDirectory(),"backup.xml");
               FileOutputStream foStream=new FileOutputStream(file);
               foStream.write(sbBuilder.toString().getBytes());
               foStream.close();
               Toast.makeText(this, "备份成功", Toast.LENGTH_LONG).show();
           } catch (Exception e) {
               // TODO Auto-generated catch block
               e.printStackTrace();
               Toast.makeText(this, "备份失败", Toast.LENGTH_LONG).show();
           }

   }
   public void backupSMS2(View view){
       try {
           XmlSerializer serializer=Xml.newSerializer();//序列化器
           File file=new File(Environment.getExternalStorageDirectory(),"backup2.xml");
           FileOutputStream os=new FileOutputStream(file);
           serializer.setOutput(os, "utf-8");
           serializer.startDocument("utf-8", true);
           serializer.startTag(null, "smss");

           for(smsInfo info:smsInfos){
               serializer.startTag(null, "sms");
               serializer.attribute(null, "id", info.getId()+"");

               serializer.startTag(null, "body");
               serializer.text(info.getBody());
               serializer.endTag(null, "body");

               serializer.startTag(null, "address");
               serializer.text(info.getAddress());
               serializer.endTag(null, "address");

               serializer.startTag(null, "date");
               serializer.text(info.getTime()+"");
               serializer.endTag(null, "date");

               serializer.startTag(null, "type");
               serializer.text(info.getType()+"");
               serializer.endTag(null, "type");
               serializer.endTag(null, "sms");
           }

           serializer.endTag(null, "smss");
           serializer.endDocument();

           os.close();
           Toast.makeText(this, "备份成功", Toast.LENGTH_LONG).show();

       } catch (Exception e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
           Toast.makeText(this, "备份失败", Toast.LENGTH_LONG).show();

       }
   }


}

package com.example.genXML.domain;

public class smsInfo {

   private long time;
   private int type;
   private String body;
   private String address;
   private int id;


   public smsInfo() {

   }

   public smsInfo(long time, int type, String body, String address,int id) {
       super();
       this.time = time;
       this.type = type;
       this.body = body;
       this.address = address;
       this.id=id;

   }

   public long getTime() {
       return time;
   }

   public void setTime(long time) {
       this.time = time;
   }

   public int getType() {
       return type;
   }

   public void setType(int type) {
       this.type = type;
   }

   public String getBody() {
       return body;
   }

   public void setBody(String body) {
       this.body = body;
   }

   public String getAddress() {
       return address;
   }

   public void setAddress(String address) {
       this.address = address;
   }
   public int getId() {
       return id;
   }

   public void setId(int id) {
       this.id = id;
   }
}

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