Android 操作Sqlite

首先要用一个类来继承SQLiteOpenHelper，并必须实现

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

具体类如下（关键地方我都加了注释）：

package com.example.sqllitedemo;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper;public class DatabaseHelper extends SQLiteOpenHelper {    private static final int VERSION = 2;    // SQLiteOpenHelper子类必须有该构造函数    // 第一次参数Activity对象，第二个表名，第三个暂时空值，第四个数据库的版本号    public DatabaseHelper(Context context, String name, CursorFactory factory,            int version) {        super(context, name, factory, version);        // TODO Auto-generated constructor stub    }    public DatabaseHelper(Context context, String name, int version) {        this(context, name, null, version);    }    public DatabaseHelper(Context context, String name) {        this(context, name, VERSION);    }    // 该函数第一次创建数据库的时候执行，实际上是在第一次得到SqliteDatabase对象的时候执行    @Override    public void onCreate(SQLiteDatabase db) {        // TODO Auto-generated method stub        System.out.println("create a database");        db.execSQL("create table user(id int,name verchar(20))");    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        // TODO Auto-generated method stub        System.out.println("update a database");    }}

调用代码如下：

package com.example.sqllitedemo;import android.app.Activity;import android.app.ActionBar;import android.app.Fragment;import android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.View.OnClickListener;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.AutoCompleteTextView;public class MainActivity extends Activity implements OnClickListener {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Button btnCreate = (Button) findViewById(R.id.btnCreateDatabase);        btnCreate.setOnClickListener(this);        Button btnUpdatDatabase = (Button) findViewById(R.id.btnUpdateDatabase);        btnUpdatDatabase.setOnClickListener(this);        Button btnInsert = (Button) findViewById(R.id.btnInsert);        btnInsert.setOnClickListener(this);        Button btnUpdate = (Button) findViewById(R.id.btnUpdate);        btnUpdate.setOnClickListener(this);        Button btnQuery = (Button) findViewById(R.id.btnQuery);        btnQuery.setOnClickListener(this);    }    @Override    public void onClick(View v) {        // TODO Auto-generated method stub        switch (v.getId()) {        case R.id.btnCreateDatabase:            DatabaseHelper helper = new DatabaseHelper(this, "School_db");            SQLiteDatabase db = helper.getReadableDatabase();            break;        case R.id.btnUpdateDatabase:            DatabaseHelper helper1 = new DatabaseHelper(this, "School_db", 2);            SQLiteDatabase db1 = helper1.getReadableDatabase();            break;        case R.id.btnInsert:            // 用于存储数据的键值对，键为列名            ContentValues values = new ContentValues();            values.put("name", "张山");            values.put("id", 1);            DatabaseHelper helper2=new DatabaseHelper(this,"School_db");            SQLiteDatabase db2=helper2.getWritableDatabase();            db2.insert("user", null, values);            //方法二、直接使用ExecSQL            db2.execSQL("insert into user(id,name) values(?,?)", new Object[]{2,"李四"});            break;        case R.id.btnUpdate:            DatabaseHelper helper3=new DatabaseHelper(this,"School_db");            SQLiteDatabase db3=helper3.getWritableDatabase();            ContentValues values1=new ContentValues();            values1.put("name", "zhangshan");                        db3.update("user", values1, "id=?"    , new String[]{"1"});            break;        case R.id.btnQuery:            DatabaseHelper helper4=new DatabaseHelper(this,"School_db");            SQLiteDatabase db4=helper4.getReadableDatabase();            Cursor cursor=db4.query("user",new String[]{"id","name"},"id=?",new String[]{"1"},                    "","","");            while(cursor.moveToNext())            {                String name=cursor.getString(cursor.getColumnIndex("name"));                System.out.println(name);            }            break;        default:            break;        }    }}

除了上述的crud的方法，还可以使用下面的方式

DatabaseHelper myDBHelper=new DatabaseHelper(this,"School_db");//增加    public void addPerson(String name) {        SQLiteDatabase database = myDBHelper.getWritableDatabase();        //先判断数据库是否可用        if (database.isOpen()) {            database.execSQL("insert into user(name) values(?,?)", new Object[]{name});            database.close();        }    }    //查找    public boolean findPerson(String name) {        boolean result = false;        SQLiteDatabase database = myDBHelper.getReadableDatabase();        if (database.isOpen()) {            Cursor cursor = database.rawQuery("select * from user where name=?", new String[]{name});            if (cursor.moveToFirst()) {//游标是否移动到下一行,如果是,那说明有数据返回                Log.d(tag, "count:" + cursor.getColumnCount());                int nameIndex = cursor.getColumnIndex("name");                Log.d(tag, "name:" + cursor.getString(nameIndex));                cursor.close();                result = true;            } else {                result = false;            }            database.close();        }        return result;    }    //删除一条数据    public void deletePerson(String name) {        SQLiteDatabase database = myDBHelper.getWritableDatabase();        if (database.isOpen()) {            database.execSQL("delete from user where name=?", new Object[]{name});        }        database.close();    }    //更新一条数据    public void updatePerson( String newName,String name) {        SQLiteDatabase database = myDBHelper.getWritableDatabase();        if (database.isOpen()) {            database.execSQL("update user set name=? where name=?", new Object[]{newName, name});        }        database.close();    }    //查找所有person    public List<user> findAllPerson(){        List<user> userList = new ArrayList<user>();        SQLiteDatabase database = myDBHelper.getReadableDatabase();        if(database.isOpen()){            Cursor cursor = database.rawQuery("select * from user", null);            while(cursor.moveToNext()){                int nameIndex = cursor.getColumnIndex("name");                  Person  person = new Person(name);                personList.add(user);            }        }        database.close();        return uerList;    }

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