SQLite数据库与Contentprovider（1）

SQlite：类似mysql的数据库。把数据保存到.db文件夹中。

Contentprovider：一般用于不同进程之间的数据共享（两个APP）。

手动建库：http://www.runoob.com/sqlite/sqlite-drop-table.html（命令集手册）

创建/打开DB文件：

1. 打开CMD命令行窗口。
2. Sqlite3 D:/mydb.db

确保有sqlite3.exe文件（D:sdk oolssqlite3.exe）

创建Table:

sqlite> create table peopleinfo (_id integer primary key autoincrement,name text not null,age integer,height float);

查看Table：

sqlite>.tables

插入数据到Table中：

    sqlite> insert into peopleinfo values(null,'Tom',21,1.81); 
    sqlite> insert into peopleinfo values(null,'Jim',22,1.78); 
    sqlite> insert into peopleinfo values(null,'Lily',19,1.68); 

查看Table中的数据：

    select * from peopleinfo; 

然后也可以用一些where语句后like之类的去过滤数据。

也可以事先通过.mode column之类的设置一下输出格式。

相关命令可以通过.help去看看。

更新Table中的数据：

    sqlite> update peopleinfo set height=1.88 where name="Lily"; 
    sqlite> select * from peopleinfo; 

删除Table中的单个数据：

    sqlite> delete from peopleinfo where _id=3; 
    sqlite> select * from peopleinfo; 

删除Table中的所有数据：

sqlite> delete from peopleinfo

删除Table:

sqlite> drop table peopleinfo

修改Table名：

sqlite> ALTER TABLE peopleinfo RENAME TO newtable；

sqlite3工具还支持大量的命令：

代码建库：

只要记住以下两个类就可以：

SQLiteDatabase：类封装了非常多的方法，用以建立、删除数据库，执行SQL命令，对数据进行管理等实质性操作工作。

SQLiteOpenHelper：这个帮助类可以辅助建立、更新和打开数据库。

　　*SQLiteOpenHelper的onUpgrade()是当在数据库需要升级时被调用，一般用来删除旧的数据库表，并将数据转移到新版本的数据库表中。第一次建立（onCreate()）数据库时调用。

　　*调用SQLiteOpenHelper类的getWritableDatabase()函数和getReadableDatabase()函数。这个两个函数会根据数据库是否存在、版本号和是否可写等情况，决定在返回数据库对象前，是否需要建立数据库。

　　*SQLiteDatabase中也封装了打开数据库的函数openDatabases()和创建数据库函数openOrCreateDatabases()，

　　　因为代码中使用了帮助类SQLiteOpenHelper，从而避免直接调用SQLiteDatabase中的打开和创建数据库的方法，简化了数据库打开过程中繁琐的逻辑判断过程。

SQLiteOpenHelper的getWritableDatabase()：用来建立或打开可读写的数据库对象，一旦函数调用成功，数据库对象将被缓存，任何需要使用数据库对象时，都可以调用这个方法获取到数据库对象，

　　　　　　　　　　　　　　　　　　　　　　  但一定要在不使用时调用close()函数关闭数据库。
SQLiteOpenHelper的getReadableDatabase()：如果保存数据库文件的磁盘空间已满，调用getWritableDatabase()函数则无法获得可读写的数据库对象，这时可以调用getReadableDatabase()函数，获得一个只读的数据库对象。

数据库操作：

也就是增删改查。

ContentValues：把数据已Map的形式打包起来用于数据库的insert，update等操作时以参数形式传递。

Cursor：在Android系统中，数据库查询结果的返回值并不是数据集合的完整拷贝，而是返回数据集的指针，这个指针就是Cursor类。

Cursor类的方法和说明：

其他操作相关方法可以直接看实例来了解，就说明一个参数较多的query()：

Cursor android.database.sqlite.SQLiteDatabase.query(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy)

下面是实例代码：

package com.example.demo_sql;

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

public class DBAdapter {
    private static final String DB_NAME = "people.db";
    private static final String DB_TABLE = "peopleinfo";
    private static final int DB_VERSION = 2;

    public static final String KEY_ID = "_id";
    public static final String KEY_NAME = "name";
    public static final String KEY_AGE = "age";
    public static final String KEY_HEIGHT = "height";

    private static SQLiteDatabase db;
    private final Context context;
    private static DBOpenHelper dbOpenHelper;

    private static class DBOpenHelper extends SQLiteOpenHelper {

        public DBOpenHelper(Context context, String name,
                CursorFactory factory, int version) {
            super(context, name, factory, version);
        }

        private static final String DB_CREATE = "create table " + DB_TABLE
                + " (" + KEY_ID + " integer primary key autoincrement, "
                + KEY_NAME + " text not null, " + KEY_AGE + " integer,"
                + KEY_HEIGHT + " float);";

        @Override
        public void onCreate(SQLiteDatabase _db) {
            _db.execSQL(DB_CREATE);
        }

        @Override
        public void onUpgrade(SQLiteDatabase _db, int _oldVersion,
                int _newVersion) {
            _db.execSQL("DROP TABLE IF EXISTS " + DB_TABLE);
            onCreate(_db);
        }
    }

    public DBAdapter(Context _context) {
        context = _context;
    }

    public void open() throws SQLiteException {
        dbOpenHelper = new DBOpenHelper(context, DB_NAME, null, DB_VERSION);
        try {
            db = dbOpenHelper.getWritableDatabase();
        } catch (SQLiteException ex) {
            db = dbOpenHelper.getReadableDatabase();
        }

    }

    /*
     * public void read() { db = dbOpenHelper.getReadableDatabase(); Cursor
     * cursor = db.query(DB_TABLE, new String[] { KEY_ID, KEY_NAME, KEY_AGE,
     * KEY_HEIGHT }, null, null, null, null, null, null);
     * 
     * while (cursor.moveToNext()) { int id = cursor.getInt(0); //
     * 获取第一列的值,第一列的索引从0开始 String name = cursor.getString(1);// 获取第二列的值 int age =
     * cursor.getInt(2);// 获取第三列的值 float height = cursor.getFloat(3);
     * System.out.println("id:" + id + "  " + "name: " + name + "  " + "age: " +
     * age + "  " + "height: " + height); } cursor.close(); db.close(); }
     * 
     * public static void write() { db = dbOpenHelper.getWritableDatabase();
     * db.execSQL("insert into " + DB_TABLE + "(" + KEY_NAME + "," + KEY_AGE +
     * "," + KEY_HEIGHT + ") values('bb',20,17.6)"); // 使用insert方法向表中插入数据
     * ContentValues values = new ContentValues(); values.put(KEY_NAME, "xh");
     * values.put(KEY_AGE, 5); values.put(KEY_HEIGHT, 5.2); // 调用方法插入数据
     * db.insert(DB_TABLE, null, values); // 关闭SQLiteDatabase对象 db.close(); }
     */

    public long insert(People people) {
        ContentValues newValues = new ContentValues();

        newValues.put(KEY_NAME, people.Name);
        newValues.put(KEY_AGE, people.Age);
        newValues.put(KEY_HEIGHT, people.Height);

        return db.insert(DB_TABLE, null, newValues);

    }

    public long deleteAllData() {
        return db.delete(DB_TABLE, null, null);
    }

    public long deleteOneData(long id) {
        return db.delete(DB_TABLE, KEY_ID + "=" + id, null);
    }

    public People[] queryAllData() {
        Cursor results = db.query(DB_TABLE, new String[] { KEY_ID, KEY_NAME,
                KEY_AGE, KEY_HEIGHT }, null, null, null, null, null);
        return ConvertToPeople(results);

    }

    public People[] queryOneData(long id) {
        Cursor results = db.query(DB_TABLE, new String[] { KEY_ID, KEY_NAME,
                KEY_AGE, KEY_HEIGHT }, KEY_ID + "=" + id, null, null, null,
                null);
        return ConvertToPeople(results);

    }

    public long updateOneData(long id, People people) {
        ContentValues updateValues = new ContentValues();
        updateValues.put(KEY_NAME, people.Name);
        updateValues.put(KEY_AGE, people.Age);
        updateValues.put(KEY_HEIGHT, people.Height);

        return db.update(DB_TABLE, updateValues, KEY_ID + "=" + id, null);

    }

    private People[] ConvertToPeople(Cursor cursor) {
        int resultCounts = cursor.getCount();
        if (resultCounts == 0 || !cursor.moveToFirst()) {
            return null;
        }
        People[] peoples = new People[resultCounts];
        for (int i = 0; i < resultCounts; i++) {
            peoples[i] = new People();
            peoples[i].ID = cursor.getInt(0);
            peoples[i].Name = cursor.getString(cursor.getColumnIndex(KEY_NAME));
            peoples[i].Age = cursor.getInt(cursor.getColumnIndex(KEY_AGE));
            peoples[i].Height = cursor.getFloat(cursor
                    .getColumnIndex(KEY_HEIGHT));
            cursor.moveToNext();
        }
        return peoples;

    }

    public void close() {
        if (db != null) {
            db.close();
            db = null;
        }
    }

}

package com.example.demo_sql;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {
    private DBAdapter dbadapter;
    private EditText et_id;
    private EditText et_name;
    private EditText et_age;
    private EditText et_height;
    private Button bt_insert;
    private Button bt_query;
    private Button bt_clear;
    private Button bt_delete;
    private Button bt_deleteById;
    private Button bt_queryById;
    private Button bt_updateById;
    private EditText displayView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        dbadapter = new DBAdapter(this);

        et_id = (EditText) findViewById(R.id.et_id);
        et_name = (EditText) findViewById(R.id.et_name);
        et_age = (EditText) findViewById(R.id.et_age);
        et_height = (EditText) findViewById(R.id.et_height);

        bt_insert = (Button) findViewById(R.id.insert_data);
        bt_query = (Button) findViewById(R.id.query_all);
        bt_clear = (Button) findViewById(R.id.clear_all);
        bt_delete = (Button) findViewById(R.id.delete_all);
        bt_insert.setOnClickListener(this);
        bt_query.setOnClickListener(this);
        bt_clear.setOnClickListener(this);
        bt_delete.setOnClickListener(this);

        bt_deleteById = (Button) findViewById(R.id.deleteById);
        bt_queryById = (Button) findViewById(R.id.queryById);
        bt_updateById = (Button) findViewById(R.id.updateById);
        bt_deleteById.setOnClickListener(this);
        bt_queryById.setOnClickListener(this);
        bt_updateById.setOnClickListener(this);

        displayView = (EditText) findViewById(R.id.displayview);

    }

    @Override
    protected void onStart() {
        // TODO Auto-generated method stub
        super.onStart();
        dbadapter.open();
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        if (v.getId() == R.id.insert_data) {
            People people = getInsertData();
            if (people != null) {
                dbadapter.insert(people);
                printall();
            } else
                Toast.makeText(this, "Error:Empty data!Please insert data", 0)
                        .show();
        } else if (v.getId() == R.id.query_all) {
            printall();
        } else if (v.getId() == R.id.clear_all) {
            displayView.setText(" ");
        } else if (v.getId() == R.id.delete_all) {
            dbadapter.deleteAllData();
            displayView.setText(" ");
        } else if (v.getId() == R.id.deleteById) {
            long id = Long.valueOf(et_id.getText().toString().trim());
            if (id > 0) {
                dbadapter.deleteOneData(id);
                printall();
            }
        } else if (v.getId() == R.id.queryById) {
            long id = Long.valueOf(et_id.getText().toString().trim());
            if (id > 0) {
                People[] peoples = dbadapter.queryOneData(id);
                if (peoples != null)
                    printOneData(peoples);
                else
                    Toast.makeText(this, "Error:not found Exception!", 0)
                            .show();
            }
        } else if (v.getId() == R.id.updateById) {
            long id = Long.valueOf(et_id.getText().toString().trim());
            if (id > 0) {
                People people = getInsertData();
                if (people != null)
                    dbadapter.updateOneData(Long.valueOf(id), people);
                else
                    Toast.makeText(this, "Error:Empty data!Please insert data",
                            0).show();
                printall();
            }
        }
    }

    private void printOneData(People[] peoples) {
        // TODO Auto-generated method stub

        displayView.setText(" ");
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < peoples.length; i++) {
            sb.append(peoples[i].toString() + "
");
        }
        displayView.setText(sb);

    }

    private People getInsertData() {
        // TODO Auto-generated method stub
        People people = new People();
        people.setName(et_name.getText().toString());
        people.setAge(Integer.valueOf(et_age.getText().toString()));
        people.setHeight(Float.valueOf(et_height.getText().toString()));
        return people;
    }

    private void printall() {
        // TODO Auto-generated method stub
        displayView.setText(" ");
        People[] peoples = dbadapter.queryAllData();
        if (peoples != null) {
            StringBuffer sb = new StringBuffer();
            for (int i = 0; i < peoples.length; i++) {
                sb.append(peoples[i].toString() + "
");
            }
            displayView.setText(sb);
        } else
            Toast.makeText(this, "Error:Empty data!", 0).show();

    }

    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        dbadapter.close();
    }
}

package com.example.demo_sql;

public class People {
    public int ID = -1;
    public String Name;
    public int Age;

    public int getID() {
        return ID;
    }

    public void setID(int iD) {
        ID = iD;
    }

    public String getName() {
        return Name;
    }

    public void setName(String name) {
        Name = name;
    }

    public int getAge() {
        return Age;
    }

    public void setAge(int age) {
        Age = age;
    }

    public float getHeight() {
        return Height;
    }

    public void setHeight(float height) {
        Height = height;
    }

    public float Height;

    @Override
    public String toString() {
        String result = "";
        result += "ID：" + this.ID + "，";
        result += "姓名：" + this.Name + "，";
        result += "年龄：" + this.Age + "， ";
        result += "身高：" + this.Height + ";";
        return result;
    }

}

布局文件代码也贴上：

<RelativeLayout 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:textAlignment="viewStart"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/et_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_toRightOf="@+id/tv_name"
        android:ems="10"
        android:text=" " >

        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/et_age"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/et_name"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/et_name"
        android:ems="10"
        android:text="0" />

    <TextView
        android:id="@+id/tv_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/et_name"
        android:layout_alignBottom="@+id/et_name"
        android:layout_alignParentLeft="true"
        android:text="姓名：" />

    <TextView
        android:id="@+id/tv_age"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/et_age"
        android:layout_alignBottom="@+id/et_age"
        android:layout_alignParentLeft="true"
        android:text="年龄：" />

    <EditText
        android:id="@+id/et_height"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/et_age"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/et_age"
        android:ems="10"
        android:text="0" />

    <TextView
        android:id="@+id/tv_height"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/et_height"
        android:layout_alignBottom="@+id/et_height"
        android:layout_alignParentLeft="true"
        android:text="身高：" />

    <Button
        android:id="@+id/insert_data"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/tv_height"
        android:minWidth="50dp"
        android:text="添加数据"
        android:textSize="14sp" />

    <Button
        android:id="@+id/query_all"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/insert_data"
        android:layout_alignBottom="@+id/insert_data"
        android:layout_toRightOf="@+id/insert_data"
        android:text="全部显示"
        android:textSize="14sp" />

    <Button
        android:id="@+id/clear_all"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/query_all"
        android:layout_alignBottom="@+id/query_all"
        android:layout_toRightOf="@+id/query_all"
        android:text="清除显示"
        android:textSize="14sp" />

    <Button
        android:id="@+id/delete_all"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@+id/clear_all"
        android:layout_toRightOf="@+id/clear_all"
        android:text="全部删除"
        android:textSize="14sp" />

    <EditText
        android:id="@+id/et_id"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/insert_data"
        android:layout_toLeftOf="@+id/deleteById"
        android:layout_toRightOf="@+id/tv_id"
        android:ems="10"
        android:hint="insert id"
        android:text="0" />

    <TextView
        android:id="@+id/tv_id"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/et_id"
        android:layout_alignBottom="@+id/et_id"
        android:layout_alignParentLeft="true"
        android:text="ID：" />

    <Button
        android:id="@+id/deleteById"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/et_id"
        android:layout_alignBottom="@+id/et_id"
        android:layout_toLeftOf="@+id/queryById"
        android:text="ID删除" />

    <Button
        android:id="@+id/queryById"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/deleteById"
        android:layout_alignBottom="@+id/deleteById"
        android:layout_toLeftOf="@+id/updateById"
        android:text="ID查询" />

    <Button
        android:id="@+id/updateById"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/queryById"
        android:layout_alignBottom="@+id/queryById"
        android:layout_alignParentRight="true"
        android:text="ID更新" />

    <EditText
        android:id="@+id/displayview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/deleteById"
        android:ems="10"
        android:gravity="top|left"
        android:inputType="textMultiLine"
        android:textSize="10sp" />

</RelativeLayout>

运行结果：

下一节再讲ContentProvider。。。