（1）android中的数据存储主要有五种方式：

第一种、sharedPreferences存储数据，

适用范围：保存少量的数据，且这些数据的格式非常简单：字符串型、基本类型的值。比如应用程序的各种配置信息（如是否打开音效、是否使用震动效果、小游戏的玩家积分等），解锁口 令密码等

核心原理：保存基于XML文件存储的key-value键值对数据，通常用来存储一些简单的配置信息。通过DDMS的File Explorer面板，展开文件浏览树,很明显SharedPreferences数据总是存储在/data/data//shared_prefs目录下。SharedPreferences对象本身只能获取数据而不支持存储和修改,存储修改是通过SharedPreferences.edit()获取的内部接口Editor对象实现。 SharedPreferences本身是一 个接口，程序无法直接创建SharedPreferences实例，只能通过Context提供的getSharedPreferences(String name, int mode)方法来获取SharedPreferences实例，该方法中name表示要操作的xml文件名，第二个参数具体如下：

Context.MODE_PRIVATE: 指定该SharedPreferences数据只能被本应用程序读、写。

Context.MODE_WORLD_READABLE:  指定该SharedPreferences数据能被其他应用程序读，但不能写。

Context.MODE_WORLD_WRITEABLE:  指定该SharedPreferences数据能被其他应用程序读，写

Editor有如下主要重要方法：

SharedPreferences.Editor clear():清空SharedPreferences里所有数据

SharedPreferences.Editor putXxx(String key , xxx value): 向SharedPreferences存入指定key对应的数据，其中xxx 可以是boolean,float,int等各种基本类型据

SharedPreferences.Editor remove(): 删除SharedPreferences中指定key对应的数据项

boolean commit(): 当Editor编辑完成后，使用该方法提交修改

下面是具体的demo，登录注册通过sharedPreferences保存注册数据到user.xml文件中，通过sharedPerferences的contains方法验证用户是否存在，截图如下

具体实现代码如下：

package com.example.shareperferencesdemo1;

import android.app.Activity;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {
EditText edtName, edtPwd;
Button btnLogin, btnRegister;
SharedPreferences sp;
Editor editor;

@Override  
protected void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);  
    setContentView(R.layout.activity\_main);  
    edtName = (EditText) findViewById(R.id.editText1);  
    edtPwd = (EditText) findViewById(R.id.editText2);  
    btnLogin = (Button) findViewById(R.id.button1);  
    btnRegister = (Button) findViewById(R.id.button2);  
    //实例化sharedperferences对象  
    sp = getSharedPreferences("user", Activity.MODE\_PRIVATE);

    btnLogin.setOnClickListener(new View.OnClickListener() {

        @Override  
        public void onClick(View v) {  
            String uName=edtName.getText().toString();  
            String uPwd=edtPwd.getText().toString();  
            if(uName.equals("")||uPwd.equals("")){  
                Toast.makeText(MainActivity.this, "用户名或密码不能为空", 2000).show();  
            }else{  
                //如果sharedpreferences中用户名已经存在  
                if(sp.contains(uName)){  
                    //调用sharedpferences对象的getString（键值对）方法判断是否存在用户  
                    if(uPwd.equals(sp.getString(uName,uPwd))){  
                        Toast.makeText(MainActivity.this, "登录成功",2000 ).show();  
                    }else{  
                        Toast.makeText(MainActivity.this, "登录失败",2000).show();  
                    }  
                }  
            }  
        }  
    });  
    btnRegister.setOnClickListener(new View.OnClickListener() {

        @Override  
        public void onClick(View v) {  
            if (edtName.getText().toString().equals("") || edtPwd.getText().toString().equals("")) {  
                Toast.makeText(MainActivity.this, "用户名或者密码不能为空！", 2000).show();  
            } else {  
                String name = edtName.getText().toString();  
                String pwd = edtPwd.getText().toString();  
                if (sp.contains(name)) {  
                    Toast.makeText(MainActivity.this, "用户已存在", 2000).show();  
                } else {  
                    //获取edit对象  
                    editor = sp.edit();  
                    //向user文件中添加用户信息键值对  
                    editor.putString(name, pwd);  
                    //添加数据  
                    editor.commit();  
                    Toast.makeText(MainActivity.this, "注册成功", 2000).show();  
                }  
            }  
        }  
    });  
}

}

（2）文件存储

文件如果不放在sdcrad中则存在data/data目录下，如果文件要放在SDCard中，则首先要判断SDCard是否存在，如果存在，要获取SDCard文件对象，代码为

if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
//存在的情况
//Environment.getExternalStorageState(),获取SDCard的状态
//获取sdcard的文件对象
File sdCard=Environment.getExternalStorageDirectory();

    }

还需要在注册文件中声明对Sdcard的读写权限

效果图

代码如下：

package com.example.filestoragedemo;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.RandomAccessFile;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
private TextView tvContext;
private EditText edtContext;
private Button btnWrite;
private Button btnRead;

@Override  
protected void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);  
    setContentView(R.layout.activity\_main);  
    // 关联控件  
    tvContext = (TextView) findViewById(R.id.txtContext);  
    edtContext = (EditText) findViewById(R.id.edtContext);  
    btnWrite = (Button) findViewById(R.id.btnWrite);  
    btnRead = (Button) findViewById(R.id.btnRead);

    btnWrite.setOnClickListener(new View.OnClickListener() {

        @Override  
        public void onClick(View v) {  
            String str = edtContext.getText().toString();  
            try {  
                writeFile(str);  
                edtContext.setText("");  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
    });

    btnRead.setOnClickListener(new View.OnClickListener() {

        @Override  
        public void onClick(View v) {  
            try {  
                String str=readFile();  
                tvContext.setText(str);  
            } catch (IOException e) {  
                e.printStackTrace();  
            }  
        }  
    });

}

// 写入文件的方法  
public void writeFile(String str) throws IOException {  
    // 将文件写到sdcard中  
    // 首先判断sdcard是否存在  
    if (Environment.getExternalStorageState().equals(Environment.MEDIA\_MOUNTED)) {  
        // 存在的情况  
        // 获取sdcard的文件对象  
        File sdCard = Environment.getExternalStorageDirectory();  
        // 创建文件  
        File file = new File(sdCard.getAbsolutePath() + "/abc.txt");  
        // 随机流  
        RandomAccessFile rf = new RandomAccessFile(file, "rw");  
        // 将文件指针放到末尾  
        rf.seek(file.length());  
        // 写入文件  
        rf.write(str.getBytes());  
        // 关闭随机流  
        rf.close();  
    } else {  
        Toast.makeText(MainActivity.this, "请插入内存卡", 2000).show();  
    }  
}

public String readFile() throws IOException {  
    // 将文件写到sdcard中  
    // 首先判断sdcard是否存在  
    if (Environment.getExternalStorageState().equals(Environment.MEDIA\_MOUNTED)) {  
        // 存在的情况  
        // 获取sdcard的文件对象  
        File sdCard = Environment.getExternalStorageDirectory();  
        // 创建文件  
        File file = new File(sdCard.getAbsolutePath() + "/abc.txt");  
        //将文件转化为字节流  
        FileInputStream fs = new FileInputStream(file);  
        // 将字节流转化为字符流  
        BufferedReader bf = new BufferedReader(new InputStreamReader(fs));  
        StringBuffer sb = new StringBuffer();  
        String line = null;  
        // 读取  
        while ((line = bf.readLine()) != null) {  
            sb.append(line);  
        }  
        bf.close();  
        fs.close();  
        return sb.toString();  
    } else {  
        Toast.makeText(MainActivity.this, "请插入内存卡", 2000).show();  
        return null;  
    }  
}  

}

（3）sqlite 数据存储

SQLite是轻量级嵌入式数据库引擎，它支持 SQL 语言，并且只利用很少的内存就有很好的性能。现在的主流移动设备像Android、iPhone等都使用SQLite作为复杂数据的存储引擎，在我们为移动设备开发应用程序时，也许就要使用到SQLite来存储我们大量的数据，所以我们就需要掌握移动设备上的SQLite开发技巧，SQLiteDatabase类为我们提供了很多种方法。

要使用sqlite数据存储需要创建一个继承于SQLiteOpenHelper的类，该类封装了sqlite和android之间的驱动，所以我们不用向在java中一样要加载数据库驱动。

下面用一个学生信息demo，来实现学生的增删改查，demo的界面如下

首先建一个student实体类，代码如下

package com.example.androidsqlitedemo;

import java.io.Serializable;

public class Student implements Serializable{
private int id;
private String name;
private String sex;
private int age;
public Student(){

}  
public Student(int id){  
    super();  
    this.id = id;  
}  
public Student(String name, String sex, int age) {  
    super();  
    this.name = name;  
    this.sex = sex;  
    this.age = age;  
}  
public Student(int id, String name, String sex, int age) {  
    super();  
    this.id = id;  
    this.name = name;  
    this.sex = sex;  
    this.age = age;  
}  
public int getId() {  
    return id;  
}  
public void setId(int id) {  
    this.id = id;  
}  
public String getName() {  
    return name;  
}  
public void setName(String name) {  
    this.name = name;  
}  
public String getSex() {  
    return sex;  
}  
public void setSex(String sex) {  
    this.sex = sex;  
}  
public int getAge() {  
    return age;  
}  
public void setAge(int age) {  
    this.age = age;  
}

}

　　数据库操作类

package com.example.androidsqlitedemo;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class MyDB extends SQLiteOpenHelper {

public MyDB(Context context){  
    super(context, "myDB.db", null, 1);  
}  
public MyDB(Context context, String name, CursorFactory factory, int version) {  
    super(context, "myDB.db", null, 1);  
}

@Override  
public void onCreate(SQLiteDatabase db) {  
    //建表  
    String sql="create table student(id Integer primary key not null,name varchar(20),sex varchar,age Integer)";  
    db.execSQL(sql);  
}

@Override  
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}  
//根据学号验证学生是否存在  
public Boolean isStudentExit(Student student){  
    SQLiteDatabase db = this.getWritableDatabase();  
    String sql="select \* from student where id='"+student.getId()+"'";  
    Cursor cursor = db.rawQuery(sql, null);  
    if(cursor.getCount()==0){  
        return false;  
    }else{  
        return true;  
    }  
}  
//添加数据  
public void insertStudent(Student student){  
    SQLiteDatabase db = this.getWritableDatabase();  
    String sql="insert into student(name,sex,age) values (?,?,?)";  
    db.execSQL(sql,new Object\[\]{student.getName(),student.getSex(),student.getAge()});  
    db.close();//关闭数据库  
}  
//删除数据  
public void deleteStudent(Student student){  
    SQLiteDatabase db = this.getWritableDatabase();  
    String sql="delete from student where id=?";  
    db.execSQL(sql, new Object\[\]{student.getId()});  
    db.close();  
}  
//修改学生信息  
public void updateStudent(Student student){  
    SQLiteDatabase db = this.getWritableDatabase();  
    String sql="update student set name=?,sex=?,age=? where id=?";  
    db.execSQL(sql, new Object\[\]{student.getName(),student.getSex(),student.getAge(),student.getId()});  
    db.close();  
}  
//查一个学生的信息  
public Student getStudent(int id){  
    Student student=new Student();  
    SQLiteDatabase db = this.getWritableDatabase();  
    String sql="select \* from student where id='"+id+"'";  
    Cursor cursor = db.rawQuery(sql, null);  
    while(cursor.moveToNext()){  
        String name=cursor.getString(1);  
        String sex=cursor.getString(2);  
        int age=cursor.getInt(3);  
        student.setId(id);  
        student.setName(name);  
        student.setSex(sex);  
        student.setAge(age);  
    }  
    return student;  
}  
//查询所有学生的信息  
public ArrayList<Student> getAllStudent(){  
    ArrayList<Student> list=new ArrayList<Student>();  
    SQLiteDatabase db = this.getWritableDatabase();  
    String sql="select \* from student";  
    Cursor cursor = db.rawQuery(sql, null);  
    while (cursor.moveToNext()) {  
        int id=cursor.getInt(0);  
        String name = cursor.getString(1);  
        String sex = cursor.getString(2);  
        int age = cursor.getInt(3);  
        list.add(new Student(id,name, sex, age));  
    }  
    return list;

}

}

　　主界面的后台代码

package com.example.androidsqlitedemo;

import java.io.Serializable;
import java.util.ArrayList;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

private EditText edtId,edtName,edtSex,edtAge;  
private Button btnAdd,btnDelete,btnUpdate,btnFind,btnFindAll;  
private MyDB mydata;  
@Override  
protected void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);  
    setContentView(R.layout.activity\_main);  
    edtId=(EditText) findViewById(R.id.edtId);  
    edtName=(EditText) findViewById(R.id.edtName);  
    edtSex=(EditText) findViewById(R.id.edtSex);  
    edtAge=(EditText) findViewById(R.id.edtAge);  
    btnAdd=(Button)findViewById(R.id.btnAdd);  
    btnDelete=(Button)findViewById(R.id.btnDelete);  
    btnUpdate=(Button)findViewById(R.id.btnUpdate);  
    btnFind=(Button)findViewById(R.id.btnFind);  
    btnFindAll=(Button)findViewById(R.id.btnFindAll);  
    mydata=new MyDB(MainActivity.this);

    btnAdd.setOnClickListener(new View.OnClickListener() {

        @Override  
        public void onClick(View v) {  
            //edtId.setEnabled(false);  
            if(edtName.getText().toString().equals("")||edtAge.getText().toString().equals("")||edtSex.getText().equals("")){  
                Toast.makeText(MainActivity.this, "学生信息不能为空", 2000).show();  
            }else{  
                String name=edtName.getText().toString();  
                String sex=edtSex.getText().toString();  
                int age=Integer.parseInt(edtAge.getText().toString());  
                //Log.i("key", age+"");  
                Student student=new Student(name, sex, age);  
                mydata.insertStudent(student);  
                Toast.makeText(MainActivity.this, "添加成功", 2000).show();  
                edtAge.setText("");  
                edtName.setText("");  
                edtSex.setText("");  
            }  
        }  
    });  
    btnDelete.setOnClickListener(new View.OnClickListener() {

        @Override  
        public void onClick(View v) {  
            if(edtId.getText().toString().equals("")){  
                Toast.makeText(MainActivity.this, "请输入要删除学生的学号", 2000).show();  
            }else{  
                int id=Integer.parseInt(edtId.getText().toString());  
                Student student=new Student(id);  
                if(mydata.isStudentExit(student)){  
                    mydata.deleteStudent(student);  
                    edtId.setText("");  
                    Toast.makeText(MainActivity.this, "删除成功", 2000).show();  
                }else{  
                    Toast.makeText(MainActivity.this, "要删除的学生不存在", 2000).show();  
                }  
            }  
        }  
    });  
    btnUpdate.setOnClickListener(new View.OnClickListener() {

        @Override  
        public void onClick(View v) {  
            if(edtId.getText().toString().equals("")){  
                Toast.makeText(MainActivity.this, "请输入要修改学生信息的学号", 2000).show();  
            }else{  
                int id=Integer.parseInt(edtId.getText().toString());  
                Student student=new Student(id);  
                if(mydata.isStudentExit(student)){  
                    if(edtAge.getText().toString().equals("")||edtName.getText().toString().equals("")||edtSex.getText().toString().equals("")){  
                        Toast.makeText(MainActivity.this, "要修改的学生信息不能为空", 2000).show();  
                    }  
                    else{  
                        String name=edtName.getText().toString();  
                        String sex=edtSex.getText().toString();  
                        int age=Integer.parseInt(edtAge.getText().toString());  
                        Student stu=new Student(id, name, sex, age);  
                        mydata.updateStudent(stu);  
                        Toast.makeText(MainActivity.this, "修改成功", 2000).show();  
                    }  
                }else{  
                    Toast.makeText(MainActivity.this, "该学生不存在，请重新输入学号", 2000).show();  
                }  
            }  
        }  
    });  
    btnFind.setOnClickListener(new View.OnClickListener() {

        @Override  
        public void onClick(View v) {  
            if(edtId.getText().toString().equals("")){  
                Toast.makeText(MainActivity.this, "请输入要查找学生的学号", 2000).show();  
            }else{  
                int id=Integer.parseInt(edtId.getText().toString());  
                //Log.i("key", id+"");  
                Student stu=new Student(id);  
                if(mydata.isStudentExit(stu)){  
                    Student student=mydata.getStudent(id);  
                    edtName.setText(student.getName().toString());  
                    edtAge.setText(student.getAge()+"");  
                    edtSex.setText(student.getSex().toString());  
                }else{  
                    Toast.makeText(MainActivity.this, "改学生不存在，请重新输入学号", 2000).show();  
                }  
            }  
        }  
    });  
    btnFindAll.setOnClickListener(new View.OnClickListener() {

        @Override  
        public void onClick(View v) {  
            ArrayList<Student> list=mydata.getAllStudent();  
            Bundle bundle=new Bundle();  
            //这里list里面存储的student要实现Serializable接口菜可以被传递  
            bundle.putSerializable("list", (Serializable)list);  
            Intent intent=new Intent(MainActivity.this,StudentInfo.class);  
            intent.putExtras(bundle);  
            startActivity(intent);  
            Log.i("list", "success");  
        }  
    });  
}

}

　　传递参数后的第二个界面代码

package com.example.androidsqlitedemo;

import java.util.ArrayList;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.ListView;

public class StudentInfo extends Activity {
private ListView lvStudent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.student);
lvStudent=(ListView) findViewById(R.id.lvStudent);
Intent intent=getIntent();
ArrayList list =(ArrayList) intent.getSerializableExtra("list");
lvStudent.setAdapter(new MyAdapter(this, list));
}
}

　　listView适配器代码

package com.example.androidsqlitedemo;

import java.util.ArrayList;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

public class MyAdapter extends BaseAdapter {
private Context context;
private ArrayList list;

public MyAdapter(Context context, ArrayList<Student> list) {  
    super();  
    this.context = context;  
    this.list = list;  
}

@Override  
public int getCount() {  
    return list.size();  
}

@Override  
public Object getItem(int position) {  
    return position;  
}

@Override  
public long getItemId(int position) {  
    return position;  
}

@Override  
public View getView(int position, View view, ViewGroup parent) {  
    ViewHolder holder;  
    if(view==null){  
        holder=new ViewHolder();  
        view=LayoutInflater.from(context).inflate(R.layout.item, null);  
        holder.txtID=(TextView) view.findViewById(R.id.tvID);  
        holder.txtName=(TextView) view.findViewById(R.id.tvName);  
        holder.txtSex=(TextView) view.findViewById(R.id.tvSex);  
        holder.txtAge=(TextView) view.findViewById(R.id.tvAge);  
        view.setTag(holder);  
    }  
    else{  
        holder=(ViewHolder) view.getTag();  
    }  
    holder.txtID.setText(list.get(position).getId()+"");  
    holder.txtName.setText(list.get(position).getName().toString());  
    holder.txtSex.setText(list.get(position).getSex().toString());  
    holder.txtAge.setText(list.get(position).getAge()+"");  
    return view;  
}  
private final class ViewHolder{  
    TextView txtID;  
    TextView txtName;  
    TextView txtSex;  
    TextView txtAge;  
}

}

　　android与sqlite中游标cursor对象类似于dataset对象，其主要的方法有

1 c.move(int offset); //以当前位置为参考,移动到指定行
2 c.moveToFirst(); //移动到第一行
3 c.moveToLast(); //移动到最后一行
4 c.moveToPosition(int position); //移动到指定行
5 c.moveToPrevious(); //移动到前一行
6 c.moveToNext(); //移动到下一行
7 c.isFirst(); //是否指向第一条
8 c.isLast(); //是否指向最后一条
9 c.isBeforeFirst(); //是否指向第一条之前
10 c.isAfterLast(); //是否指向最后一条之后
11 c.isNull(int columnIndex); //指定列是否为空(列基数为0)
12 c.isClosed(); //游标是否已关闭
13 c.getCount(); //总数据项数
14 c.getPosition(); //返回当前游标所指向的行数
15 c.getColumnIndex(String columnName);//返回某列名对应的列索引值
16 c.getString(int columnIndex); //返回当前行指定列的值

（4）contentprovider存储数据

（5）网络存储数据