Android数据存储3种方式

1、key-value 方式保存

①如果你想存储的数据是一个相对小的集合的键值，你可以使用SharedPreferences。

②使用：

定义布局：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context="com.james.datasave.MainActivity">    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="onKeyValueSave"        android:text="key-value save"/>    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="onKeyValueRead"        android:text="key-value read"/>    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="onKeyValueClear"        android:text="key-value clear"/></LinearLayout>

package com.james.datasave;import android.content.Context;import android.content.SharedPreferences;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.Toast;public class MainActivity extends AppCompatActivity {    public static final String SP_NAME = "sp_name";    public static final String SP_KEY = "sp_key";    private String defValue = "this is defValue";    private SharedPreferences sharedPreferences;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        sharedPreferences = getPreferences(Context.MODE_PRIVATE);    }    public void onKeyValueSave(View view) {        SharedPreferences.Editor editor = sharedPreferences.edit();        editor.putString(SP_KEY, "this is save content");        editor.commit();    }    public void onKeyValueRead(View view) {        String readValue = sharedPreferences.getString(SP_KEY, defValue);        Toast.makeText(this, readValue, Toast.LENGTH_SHORT).show();    }    public void onKeyValueClear(View view){        SharedPreferences.Editor editor = sharedPreferences.edit();        editor.clear();        editor.commit();        Toast.makeText(this, "清除数据成功", Toast.LENGTH_SHORT).show();    }}

记得添加读写权限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

2、文件保存

①适合于读或写大量的数据

②怎么使用？

定义布局：

activity_main.xml：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context="com.james.datasave.MainActivity">    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="onFileSave"        android:text="文件保存"/>    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="onFileRead"        android:text="文件读取"/></LinearLayout>

package com.james.datasave;import android.content.Context;import android.os.Bundle;import android.os.Handler;import android.os.Looper;import android.os.Message;import android.support.v7.app.AppCompatActivity;import android.view.View;import android.widget.Toast;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;public class MainActivity extends AppCompatActivity {    private String filename = "myfile";    private String handlerKey = "handlerKey";    private Handler handler = new Handler(Looper.getMainLooper()){        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            switch (msg.what){                case 0:                    Toast.makeText(MainActivity.this,"无数据",Toast.LENGTH_SHORT).show();                    break;                case 1:                    String fileContent = msg.getData().getString(handlerKey);                    Toast.makeText(MainActivity.this,fileContent,Toast.LENGTH_SHORT).show();                    break;            }        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);    }       public void onFileSave(View view){        new Thread(){            @Override            public void run() {                saveFile();            }        }.start();    }    public void onFileRead(View view){        new Thread(){            @Override            public void run() {                readFile();            }        }.start();    }    private void saveFile(){        String string = "Hello world!";        FileOutputStream outputStream;        try {            outputStream = openFileOutput(filename, Context.MODE_PRIVATE);            outputStream.write(string.getBytes());            outputStream.close();        } catch (Exception e) {            e.printStackTrace();        }    }    private void readFile(){        File file = new File(getFilesDir(), filename);        //如果有这个文件并且有内容就读取文件的内容，没有不做任何操作        if(file != null && file.length() > 0){            try {                //把要读取的数据new 成一个FileInputStream,建一个字节，把读到的数据放到byte数组中，再从byte数组中取出数据放到StringBuilder                FileInputStream inputStream = openFileInput(filename);                byte[] buffer = new byte[1024];                int hasRead = 0;                StringBuffer sb = new StringBuffer();                while ((hasRead = inputStream.read(buffer))!=-1){                    sb.append(new String(buffer,0,hasRead));                }                //把消息放到Bundle,再把Bundle放到Message,在用handler发送Message.                Message message = new Message();                Bundle bundle = new Bundle();                bundle.putString(handlerKey,sb.toString());                message.setData(bundle);                message.what = 1;                handler.sendMessage(message);            } catch (Exception e) {                e.printStackTrace();                handler.sendEmptyMessage(0);            }        }    }}

3、SQL保存

①数据复杂，或者涉及到查询比较复杂，可以使用SQLite来保存数据。

②怎么使用？

定义布局：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context="com.james.datasave.MainActivity">    <EditText        android:id="@+id/id_et_title"        android:layout_width="match_parent"        android:layout_height="wrap_content"       />    <EditText        android:id="@+id/id_et_content"        android:layout_width="match_parent"        android:layout_height="wrap_content"       />    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="onSQLiteAdd"        android:text="SQLite add"/>    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="onSQLiteQuery"        android:text="SQLite Query"/>    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="onSQLiteDelete"        android:text="SQLite delete"/>    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:onClick="onSQLiteUpdate"        android:text="SQLite update"/></LinearLayout>

FeedReaderContract.java

package com.james.datasave;import android.provider.BaseColumns;/** * Created by 1 on 2017/3/21. */public class FeedReaderContract {    public FeedReaderContract() {}    /* Inner class that defines the table contents */    public static abstract class FeedEntry implements BaseColumns {        public static final String TABLE_NAME = "entry";//表名        public static final String COLUMN_NAME_ENTRY_ID = "entryid";//列id        public static final String COLUMN_NAME_TITLE = "title";//列名        public static final String COLUMN_NAME_CONTENT = "subtitle";//主题    }}

上面是定义表结构

FeedReaderDbHelper.java

package com.james.datasave;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;/** * Created by 1 on 2017/3/21. */public class FeedReaderDbHelper extends SQLiteOpenHelper {    private static final String TEXT_TYPE = " TEXT";//列中数据类型    private static final String COMMA_SEP = ",";//    private static final String SQL_CREATE_ENTRIES =            "CREATE TABLE " + FeedReaderContract.FeedEntry.TABLE_NAME + " (" +                    FeedReaderContract.FeedEntry._ID + " INTEGER PRIMARY KEY  autoincrement," +                    FeedReaderContract.FeedEntry.COLUMN_NAME_ENTRY_ID + TEXT_TYPE + COMMA_SEP +                    FeedReaderContract.FeedEntry.COLUMN_NAME_TITLE + TEXT_TYPE + COMMA_SEP + FeedReaderContract.FeedEntry.COLUMN_NAME_CONTENT + TEXT_TYPE+            " )";//创建表语句    private static final String SQL_DELETE_ENTRIES =            "DROP TABLE IF EXISTS " + FeedReaderContract.FeedEntry.TABLE_NAME;//删除表，根据表名删除表    public static final int DATABASE_VERSION = 2;//数据库的版本    public static final String DATABASE_NAME = "FeedReader.db";//数据库名字    public FeedReaderDbHelper(Context context) {        super(context, DATABASE_NAME, null, DATABASE_VERSION);    }    public void onCreate(SQLiteDatabase db) {        db.execSQL(SQL_CREATE_ENTRIES);    }    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        // This database is only a cache for online data, so its upgrade policy is        // to simply to discard the data and start over        db.execSQL(SQL_DELETE_ENTRIES);        onCreate(db);    }    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {        onUpgrade(db, oldVersion, newVersion);    }}

引用：

package com.james.datasave;import android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.text.TextUtils;import android.util.Log;import android.view.View;import android.widget.EditText;import static android.R.attr.id;import static com.james.datasave.FeedReaderContract.FeedEntry.TABLE_NAME;public class MainActivity extends AppCompatActivity {    private FeedReaderDbHelper mDbHelper;    private  SQLiteDatabase db;    private EditText etTitle;    private EditText etContent;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        etTitle = (EditText) findViewById(R.id.id_et_title);        etContent = (EditText) findViewById(R.id.id_et_content);        //创建表（定义表的结构，执行创建表的语句）        mDbHelper = new FeedReaderDbHelper(this);        db = mDbHelper.getWritableDatabase();        //增删改查    }    //增加数据    public void onSQLiteAdd(View view) {        new Thread(){            @Override            public void run() {                super.run();                saveData();            }        }.start();    }    //查找数据,把查找到的数据打印出来    public void onSQLiteQuery(View view){        String[] projection = {                FeedReaderContract.FeedEntry._ID,                FeedReaderContract.FeedEntry.COLUMN_NAME_TITLE,                FeedReaderContract.FeedEntry.COLUMN_NAME_CONTENT,    };        String sortOrder =                FeedReaderContract.FeedEntry.COLUMN_NAME_CONTENT + " DESC";        Cursor cursor = db.query(TABLE_NAME,projection,null,null,null,null,sortOrder);        while (cursor.moveToNext()){            String id = cursor.getColumnName(0);            String title = cursor.getString(1);            String content = cursor.getString(2);            Log.d("debug","id:"+id+";title:"+title+";content:"+content);        }        cursor.close();    }    public void onSQLiteDelete(View view){        deleteData();    }    /**     * 更新     */    public void onSQLiteUpdate(View view){        new Thread(){            @Override            public void run() {                super.run();                updateData();            }        }.start();    }    private void updateData(){        ContentValues values = new ContentValues();        values.put(FeedReaderContract.FeedEntry.COLUMN_NAME_TITLE, "eerrrr");//更新的内容        String selection = FeedReaderContract.FeedEntry.COLUMN_NAME_CONTENT + " LIKE ?";        String[] selectionArgs = { String.valueOf("hh") };//内容是hh这一列        int count = db.update(TABLE_NAME,                values,                selection,                selectionArgs);//更新内容是hh这一列的title为eerrrr。得保证你有hh这个内容。    }    private void deleteData(){        //获取        String selection = FeedReaderContract.FeedEntry.COLUMN_NAME_TITLE + " LIKE ?";        String[] selectionArgs = { String.valueOf("ww") };//根据COLUMN_NAME_TITLE 为ww的删除        db.delete(TABLE_NAME, selection, selectionArgs);    }    private void saveData(){        if(etTitle == null || etContent == null || TextUtils.isEmpty(etTitle.getText()) || TextUtils.isEmpty(etContent.getText())){            return;        }        String title = etTitle.getText().toString();        String content = etContent.getText().toString();        if(!TextUtils.isEmpty(title) && !TextUtils.isEmpty(content)) {            SQLiteDatabase db = mDbHelper.getWritableDatabase();            ContentValues values = new ContentValues();            values.put(FeedReaderContract.FeedEntry.COLUMN_NAME_ENTRY_ID, id);            values.put(FeedReaderContract.FeedEntry.COLUMN_NAME_TITLE, title);            values.put(FeedReaderContract.FeedEntry.COLUMN_NAME_CONTENT, content);            db.insert(TABLE_NAME, FeedReaderContract.FeedEntry.COLUMN_NAME_ENTRY_ID, values);            Log.d("debug","title:"+title+";content:"+content);//                    Toast.makeText(this, "添加成功", Toast.LENGTH_SHORT).show();        }    }}