Android的五大存储方式：SharedPreferences、内部存储、外部存储、SQLite和网络存储

概述

1、SharedPreferences：
用getPreferences(“文件名”,MODE_XXX),有四种MODE,最常用的是MODE_PRIVATE,用sharedPreferences.edit的到editor，用putXXX(“key”,”data”)来写入数据，读取数据用preferences.getXXX(“key”,”默认文本”),XXX可以是String、Integer等引用数据类型;创建后的文件在shared_prefs里面（文件后缀为.xml）。
2、内部存储：
分为cache缓存和cache Dir两种存储方式。
cahe的存储需要用到文件输入输出流，通过openOutputStream(“文件名”，MODE_XXX)得到文件输出流，openInputStream(“文件名”)得到文件输入流。创建完后的文件在files文件夹下。
cache Dir和的输入输出方式和cache类似，创建方式有所不同，需要用 new File(getCacheDir(),”文件名”)类创建，创建后的文件在cache目录下。
3、外部存储sdcard：
外部存储需要用到Environment.XXX得到sdcard下的指定目录来存储，也是用到new File(父路径，文件名)。创建完的文件在mnt的sdcard路径下，位置不确定。
4、SQLite数据库：
SQLite没有数据类型。
首先要建一个继承于SQLiteOpenHelper的类，实现其中的至少一个构造方法和两个方法onCreate()、onUpdate()。在onCreate()中用execSQL()方法创建数据库，创建完的数据库在data/data/项目名称/databases路径下，往SQLite的增删改查分别需要用到insert()、delete()、update()、query()方法。
网络存储：
略。

知识

SharedPreferences、外部存储与内部存储

public class MainActivity extends Activity implements View.OnClickListener {    private TextView mTextRead;    private EditText mEditWrite;    private Button mButtonWrite;    private Button mButtonRead;    private Button mButtonReadCache;    private Button mButtonWriteCache;    private Button mButtonWriteCacheDir;    private Button mButtonReadCacheDir;    private Button mButtonWriteSdcard;    private Button mButtonReadSdcard;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mTextRead = (TextView) findViewById(R.id.text_read);        mEditWrite = (EditText) findViewById(R.id.edit_write);        mButtonWrite = (Button) findViewById(R.id.button_write);        mButtonRead = (Button) findViewById(R.id.button_read);        mButtonReadCache = (Button) findViewById(R.id.button_read_cache);        mButtonWriteCache = (Button) findViewById(R.id.button_write_cache);        mButtonWriteCacheDir = (Button) findViewById(R.id.button_write_cache_dir);        mButtonReadCacheDir = (Button) findViewById(R.id.button_read_cache_dir);        mButtonWriteSdcard = (Button) findViewById(R.id.button_write_sdcard);        mButtonReadSdcard = (Button) findViewById(R.id.button_read_sdcard);        mButtonRead.setOnClickListener(this);        mButtonWrite.setOnClickListener(this);        mButtonReadCache.setOnClickListener(this);        mButtonWriteCache.setOnClickListener(this);        mButtonWriteCacheDir.setOnClickListener(this);        mButtonReadCacheDir.setOnClickListener(this);        mButtonWriteSdcard.setOnClickListener(this);        mButtonReadSdcard.setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.button_write:                writeToPreferences();                break;            case R.id.button_read:                readFromPreferences();                break;            case R.id.button_write_cache:                writeToCache();                break;            case R.id.button_read_cache:                readFromCache();                break;            case R.id.button_write_cache_dir:                writeToCacheDir();                break;            case R.id.button_read_cache_dir:                readToCacheDir();                break;            case R.id.button_write_sdcard:                writeToSdcard();                break;            case R.id.button_read_sdcard:                readFromSdcard();                break;            default:                break;        }    }    private void readFromSdcard() {        try {            File file = new File(Environment.getExternalStorageDirectory(),"hello.txt");            BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));            String line = br.readLine();            while(line!=null){                mTextRead.setText(line);                line = br.readLine();            }            br.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    /**     * 外部存储     * 将数据输出到sdcard里     */    private void writeToSdcard() {        File file = new File(Environment.getExternalStorageDirectory(),"hello.txt");        if(!file.exists()){            try {                file.createNewFile();            } catch (IOException e) {                e.printStackTrace();            }        }        try {            FileOutputStream fos = new FileOutputStream(file);            PrintWriter pw = new PrintWriter(fos);            pw.write(mEditWrite.getText().toString());            pw.flush();            pw.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    /**     *内部存储dir     * 读缓存     */    private void readToCacheDir() {        File file = new File(getCacheDir(),"cache_dir");        if(!file.exists()){            try {                file.createNewFile();            } catch (IOException e) {                e.printStackTrace();            }        }        try {            BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));            String line = br.readLine();            while(line!=null){                mTextRead.setText(line);                line = br.readLine();            }            br.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    /**     *内部存储dir     * 写缓存     */    private void writeToCacheDir() {        File file = new File(getCacheDir(),"cache_dir");        if(!file.exists()){            try {                file.createNewFile();            } catch (IOException e) {                e.printStackTrace();            }        }        try {            PrintWriter pw = new PrintWriter(new FileOutputStream(file));            pw.write(mEditWrite.getText()+"");            pw.flush();            pw.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        }    }    /**     * 内部存储     *写缓存     */    private void readFromCache() {        try {            FileInputStream is = openFileInput("cache_test");            BufferedReader br = new BufferedReader(new InputStreamReader(is));            String line = br.readLine();            while(line!=null){                mTextRead.setText(mTextRead.getText()+line);                line = br.readLine();            }            br.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    /**     * 内部存储     * 读缓存     */    private void writeToCache() {        try {            FileOutputStream os = openFileOutput("cache_test", MODE_PRIVATE);            PrintWriter pw = new PrintWriter(os);            pw.write("你好缓存");            pw.flush();            pw.close();        } catch (FileNotFoundException e) {            e.printStackTrace();        }    }    /**     * SharedPreferences存储方式的输入，会自动找到shared_prefs文件夹，里面存放     * SharedPreferences的存储数据的文件，通过Key Word得到数据     * 去除数据不需要用到editor     */    private void readFromPreferences() {        SharedPreferences preferences = getSharedPreferences("preferences_test", MODE_PRIVATE);        String content = preferences.getString("edit_input","默认值");        mTextRead.setText(content);    }    /**     * SharedPreferences存储方式的输出，会自动生成shared_prefs文件夹，里面存放     * SharedPreferences的存储数据的文件，这里是preferences_test.xml文件，edit_input是Key Word     * 利用editor存储数据     */    private void writeToPreferences() {        SharedPreferences preferences = getSharedPreferences("preferences_test",MODE_PRIVATE);        SharedPreferences.Editor editor = preferences.edit();        editor.putString("edit_input",mEditWrite.getText().toString());        editor.commit();    }}

布局:

<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">    <TextView        android:id="@+id/text_read"        android:layout_width="wrap_content"        android:layout_height="wrap_content"/>    <EditText        android:id="@+id/edit_write"        android:layout_width="match_parent"        android:layout_height="wrap_content"/>    <Button        android:id="@+id/button_write"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Write To Preferences"/>    <Button        android:id="@+id/button_read"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Read From Preferences"/>    <Button        android:id="@+id/button_write_cache"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Write To Cache"/>    <Button        android:id="@+id/button_read_cache"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Read From Cache"/>    <Button        android:id="@+id/button_write_cache_dir"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Write To Cache Dir"/>    <Button        android:id="@+id/button_read_cache_dir"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Read From Cache Dir"/>    <Button        android:id="@+id/button_write_sdcard"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Write To Sdcard"/>    <Button        android:id="@+id/button_read_sdcard"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Read From Sdcard"/></LinearLayout>

结果演示：

SQLide数据库

建立一个集成于SQLiteOpenHelper类的类，实现至少一个构造方法和两个方法onCreate()和onUpdate():

public class MySQliteOpenHelper extends SQLiteOpenHelper {    public MySQliteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {        super(context, name, factory, version);    }    public MySQliteOpenHelper(Context context,String name){        this(context,name,null,1);    }    @Override    public void onCreate(SQLiteDatabase db) {        //创建一个SQLite数据库，路径在活动路径的databases里。        db.execSQL("create table if not exists user(id integer primary key autoincrement,userName varchar(18),password varchar(18))");    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {    }}

主活动:

public class TestSQLiteActivity extends Activity implements View.OnClickListener {    private Button mButtonCreateSQLite;    private Button mButtonInsertData;    private Button mButtonDeleteData;    private Button mButtonUpdateData;    private Button mButtonQueryData;    private SQLiteDatabase mDb;    private EditText mUserNameEdit;    private EditText mPasswordEdit;    private TextView mUserText;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.layout_sqlite);        mButtonCreateSQLite = (Button) findViewById(R.id.button_create_sqlite);        mButtonInsertData = (Button) findViewById(R.id.button_insert_data);        mButtonDeleteData = (Button) findViewById(R.id.button_delete_data);        mButtonUpdateData = (Button) findViewById(R.id.button_update_data);        mButtonQueryData = (Button) findViewById(R.id.button_query_data);        mUserNameEdit = (EditText) findViewById(R.id.edit_user_name);        mPasswordEdit = (EditText) findViewById(R.id.edit_password);        mUserText = (TextView) findViewById(R.id.text_user);        MySQliteOpenHelper mySQliteOpenHelper = new MySQliteOpenHelper(getApplicationContext(),"SQLite_DB.db");        //必须要得到一个database        mDb = mySQliteOpenHelper.getWritableDatabase();//必须这样才能创建数据库        mButtonCreateSQLite.setOnClickListener(this);        mButtonInsertData.setOnClickListener(this);        mButtonDeleteData.setOnClickListener(this);        mButtonUpdateData.setOnClickListener(this);        mButtonQueryData.setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.button_create_sqlite:                Toast.makeText(getApplicationContext(),"创建SQLite数据库成功",Toast.LENGTH_SHORT).show();                break;            case R.id.button_insert_data:                insertData();                break;            case R.id.button_delete_data:                deleteData();                break;            case R.id.button_update_data:                updateData();                break;            case R.id.button_query_data:                Cursor cursor = mDb.query("user",null,null,null,null,null,"id DESC","2,3");//limit语句：偏移量，查询的数据                        //mDb.rawQuery("select * from user",null);                cursor.moveToFirst();                mUserText.setText("数据：\n");                int n=1;                while (!cursor.isAfterLast()){                    int id = cursor.getInt(cursor.getColumnIndex("id"));                    String userName = cursor.getString(cursor.getColumnIndex("userName"));                    String password = cursor.getString(cursor.getColumnIndex("password"));                    mUserText.setText(mUserText.getText().toString()+n+":id:"+id+"\t userName:"+userName+"\t password:"+password+"\n");                    cursor.moveToNext();                    n++;                }                break;            default:                break;        }    }    private void updateData() {        ContentValues values = new ContentValues();        values.put("password", "789456");        mDb.update("user", values, "userName=?", new String[]{"zhangsan"});        Toast.makeText(getApplicationContext(), "修改用户名为张三的用户成功！", Toast.LENGTH_SHORT).show();    }    private void deleteData() {        mDb.delete("user","userName=?",new String[]{"zhangsan"});        Toast.makeText(getApplicationContext(), "删除用户名为zhangsan的用户成功", Toast.LENGTH_SHORT).show();    }    private void insertData() {        //contentValue用于加载要存储的数据        ContentValues value = new ContentValues();        String userName = mUserNameEdit.getText().toString();        String password = mPasswordEdit.getText().toString();        //put("属性名","value")        value.put("userName",userName);        value.put("password",password);        mDb.insert("user", null, value);        Toast.makeText(getApplicationContext(), "插入用户名为"+userName+"的用户成功", Toast.LENGTH_SHORT).show();        return;    }}

布局：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"              android:orientation="vertical"              android:layout_width="match_parent"              android:layout_height="match_parent">    <EditText        android:id="@+id/edit_user_name"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="userName"/>    <EditText        android:id="@+id/edit_password"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="password"/>    <TextView        android:id="@+id/text_user"        android:layout_width="match_parent"        android:layout_height="wrap_content"/>    <Button        android:id="@+id/button_create_sqlite"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Create SQlite"/>    <Button        android:id="@+id/button_insert_data"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Insert Data"/>    <Button        android:id="@+id/button_delete_data"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Delete Data"/>    <Button        android:id="@+id/button_update_data"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Update Data"/>    <Button        android:id="@+id/button_query_data"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Query Data"/></LinearLayout>

结果演示：