SQLite基本用法
1.MainActivity.java
import android.app.Activity; import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; public class MainActivity extends Activity { private Button create_database = null; private Button update_database = null; private Button insert = null; private Button update = null; private Button query = null; private Button delete = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); create_database = (Button)findViewById(R.id.create_database); create_database.setOnClickListener(new CreateDatabaseOnClickListener()); update_database = (Button)findViewById(R.id.update_database); update_database.setOnClickListener(new UpdateDatabaseOnClickListener()); insert = (Button)findViewById(R.id.insert); insert.setOnClickListener(new InsertOnClickListener()); update = (Button)findViewById(R.id.update); update.setOnClickListener(new UpdateOnClickListener()); query = (Button)findViewById(R.id.query); query.setOnClickListener(new QueryOnClickListener()); delete = (Button)findViewById(R.id.delete); delete.setOnClickListener(new DeleteOnClickListener()); } public class CreateDatabaseOnClickListener implements OnClickListener{ public void onClick(View v) { // TODO Auto-generated method stub //创建一个DatabaseHelper类的对象,该类是单独一个java文件,这里采用2个参数的构造函数,建立的数据 //库的名字为tornadomeet.db DatabaseHelper database_helper = new DatabaseHelper(MainActivity.this, "tornadomeet.db"); //只有调用getReadableDatabase()或者getWriteableDatabase()函数后才能返回一个SQLiteDatabase对象 SQLiteDatabase db = database_helper.getReadableDatabase(); } } public class UpdateDatabaseOnClickListener implements OnClickListener{ public void onClick(View v) { // TODO Auto-generated method stub DatabaseHelper database_helper = new DatabaseHelper(MainActivity.this, "tornadomeet.db", 2); SQLiteDatabase db = database_helper.getReadableDatabase(); } } public class InsertOnClickListener implements OnClickListener{ public void onClick(View v) { // 生成contentvallues对象,该对象用来存数据的 ContentValues values = new ContentValues(); values.put("id", 1);//注意值的类型要匹配 values.put("name", "tornado"); DatabaseHelper database_helper = new DatabaseHelper(MainActivity.this, "tornadomeet.db"); SQLiteDatabase db = database_helper.getWritableDatabase();//这里是获得可写的数据库 db.insert("user1", null, values); } } public class UpdateOnClickListener implements OnClickListener{ public void onClick(View v) { // TODO Auto-generated method stub DatabaseHelper database_helper = new DatabaseHelper(MainActivity.this, "tornadomeet.db"); SQLiteDatabase db = database_helper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("name", "tornadomeet"); //参数1为表名,参数2为更新后的值,参数3表示满足条件的列名称,参数4为该列名下的值 db.update("user1", values, "id=?", new String[]{"1"}); } } public class QueryOnClickListener implements OnClickListener{ public void onClick(View v) { // TODO Auto-generated method stub DatabaseHelper database_helper = new DatabaseHelper(MainActivity.this, "tornadomeet.db"); SQLiteDatabase db = database_helper.getWritableDatabase(); //查询的语法,参数1为表名;参数2为表中的列名;参数3为要查询的列名;参数时为对应列的值;该函数返回的是一个游标 Cursor cursor = db.query("user1", new String[]{"id", "name"}, "id=?", new String[]{"1"}, null, null, null); //遍历每一个记录 while(cursor.moveToNext()) { String name = cursor.getString(cursor.getColumnIndex("name"));//返回列名为name的值 System.out.println("query---->" + name); } } } public class DeleteOnClickListener implements OnClickListener{ public void onClick(View v) { // TODO Auto-generated method stub DatabaseHelper database_helper = new DatabaseHelper(MainActivity.this, "tornadomeet.db"); SQLiteDatabase db = database_helper.getWritableDatabase(); //直接删除名为tornadomeet对应的那条记录 db.delete("user1", "name=?" ,new String[]{"tornadomeet"}); } } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.activity_main, menu); return true; } }
2.DatabaseHelper.java
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 VERSON = 1;//默认的数据库版本 //继承SQLiteOpenHelper类的类必须有自己的构造函数 //该构造函数4个参数,直接调用父类的构造函数。其中第一个参数为该类本身;第二个参数为数据库的名字; //第3个参数是用来设置游标对象的,这里一般设置为null;参数四是数据库的版本号。 public DatabaseHelper(Context context, String name, CursorFactory factory, int verson){ super(context, name, factory, verson); } //该构造函数有3个参数,因为它把上面函数的第3个参数固定为null了 public DatabaseHelper(Context context, String name, int verson){ this(context, name, null, verson); } //该构造函数只有2个参数,在上面函数 的基础山将版本号固定了 public DatabaseHelper(Context context, String name){ this(context, name, VERSON); } //该函数在数据库第一次被建立时调用 @Override public void onCreate(SQLiteDatabase arg0) { // TODO Auto-generated method stub System.out.println("create a sqlite database"); //execSQL()为执行参数里面的SQL语句,因此参数中的语句需要符合SQL语法,这里是创建一个表 arg0.execSQL("create table user1(id int, name varchar(20))"); } @Override public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) { // TODO Auto-generated method stub System.out.println("update a sqlite database"); } }
3.activity_main.xml
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 2 xmlns:tools="http://schemas.android.com/tools" 3 android:layout_width="match_parent" 4 android:layout_height="match_parent" > 5 6 <Button 7 android:id="@+id/create_database" 8 android:layout_width="fill_parent" 9 android:layout_height="wrap_content" 10 android:layout_alignParentBottom="true" 11 android:text="@string/create_database" 12 /> 13 14 <Button 15 android:id="@+id/update_database" 16 android:layout_width="fill_parent" 17 android:layout_height="wrap_content" 18 android:layout_above="@id/create_database" 19 android:layout_alignParentLeft="true" 20 android:text="@string/update_database" /> 21 22 <Button 23 android:id="@+id/insert" 24 android:layout_width="fill_parent" 25 android:layout_height="wrap_content" 26 android:layout_above="@id/update_database" 27 android:layout_alignParentLeft="true" 28 android:text="@string/insert" /> 29 30 <Button 31 android:id="@+id/update" 32 android:layout_width="fill_parent" 33 android:layout_height="wrap_content" 34 android:layout_above="@id/insert" 35 android:layout_alignParentLeft="true" 36 android:text="@string/update" /> 37 38 <Button 39 android:id="@+id/query" 40 android:layout_width="fill_parent" 41 android:layout_height="wrap_content" 42 android:layout_alignParentLeft="true" 43 android:layout_above="@id/update" 44 android:text="@string/query" 45 /> 46 <Button 47 android:id="@+id/delete" 48 android:layout_width="fill_parent" 49 android:layout_height="wrap_content" 50 android:layout_alignParentLeft="true" 51 android:layout_above="@id/query" 52 android:text="@string/delete" 53 /> 54 55 </RelativeLayout>
作者:何海洋
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