Android演示操作数据库之二

Android演示操作数据库SQLite之二，演示如何使用SQLiteOpenHelper。

Android开发中还可以使用SQLiteOpenHelper的子类操作数据库，具体步骤如下：

1. 继承SQLiteOpenHelper得到SuperDBHelper子类，实现构造函数、onCreate、onUpgrade等方法；
2. 实现数据库查询、插入、删除等方法；
3. Activity中构造SuperDBHelper对象，然后使用；

具体代码如下(演示例子参见点击打开链接)：

SuperDBHelper.java

package com.freesoft.utility;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.SQLException;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper;import android.util.Log;public class SuperDBHelper extends SQLiteOpenHelper {private static String TAG="SQLiteOpenHelper";private static int VERSION = 1;private static String TABLE_NAME = "myTestTable";public SuperDBHelper(Context context, String name, CursorFactory factory,int version) {super(context, name, factory, version);}public SuperDBHelper(Context context, String name, int version) {this(context, name, null, 1);}public SuperDBHelper(Context context, String name) {this(context, name, VERSION);}public SuperDBHelper(Context context) {this(context, TABLE_NAME);}@Overridepublic void onCreate(SQLiteDatabase db) {String sql = "";try {sql = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + " ("+ "ID INTEGER PRIMARY KEY autoincrement,  "+ "NAME TEXT,  " + "NICKNAME TEXT, " + "AGE INTEGER, "+ "EMAIL TEXT)";db.execSQL(sql);} catch (SQLException e) {Log.v(TAG, "Create Table failed.");}}@Overridepublic void onUpgrade(SQLiteDatabase db, int iOldVer, int iNewVer) {String sql = "";try {sql = "DROP TABLE IF EXISTS " + TABLE_NAME;db.execSQL(sql);onCreate(db);} catch (SQLException e) {Log.v(TAG, "Upgrade Table failed.");}}public void addRecord(String username, String nickname, int age, String email){ContentValues values = new ContentValues();values.clear();values.put("NAME", username);values.put("NICKNAME", nickname);values.put("AGE", age);values.put("EMAIL", email);this.getWritableDatabase().insert(TABLE_NAME, null, values);}public Cursor queryAll(){return this.getReadableDatabase().query(TABLE_NAME, null, "ID>?", new String[]{"0"},null, null, null);}public void delRecord(int id){this.getWritableDatabase().delete(TABLE_NAME, "ID=?", new String[]{String.format("%d", id)});}}

使用SuperDBHelper的Activity:

package com.freesoft.anttest;import com.freesoft.utility.IntWrapper;import com.freesoft.utility.SuperDBHelper;import android.app.Activity;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;public class SuperDatabaseActivity extends Activity {private static String TABLE_NAME = "testtable";private EditText et_id = null;private EditText et_username = null;private EditText et_nickname = null;private EditText et_age = null;private EditText et_email = null;private Button btn_next = null;private Button btn_prev = null;private Button btn_del = null;private Button btn_insert = null;private SuperDBHelper dbhelper = null;private Cursor cur = null;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.database);findControls();initControls();}private void initControls() {dbhelper = new SuperDBHelper(SuperDatabaseActivity.this, TABLE_NAME);cur = dbhelper.queryAll();if (cur != null) {cur.moveToFirst();refreshUI();}}private void findControls() {et_id = (EditText) findViewById(R.id.et_db_id);et_username = (EditText) findViewById(R.id.et_db_username);et_nickname = (EditText) findViewById(R.id.et_db_nickname);et_age = (EditText) findViewById(R.id.ed_db_age);et_email = (EditText) findViewById(R.id.ed_db_email);btn_next = (Button) findViewById(R.id.btn_db_next);btn_prev = (Button) findViewById(R.id.btn_db_prev);btn_del = (Button) findViewById(R.id.btn_db_del);btn_insert = (Button) findViewById(R.id.btn_db_insert);btn_next.setOnClickListener(new btnnext_onclick());btn_prev.setOnClickListener(new btnprev_onclick());btn_del.setOnClickListener(new btndel_onclick());btn_insert.setOnClickListener(new btninsert_onclick());}private void refreshUI() {// 确保cur内存有有效数据if ((cur != null) && (cur.getCount() > 0)) {btn_del.setEnabled(true);et_id.setText(cur.getInt(0) + "");et_username.setText(cur.getString(1));et_nickname.setText(cur.getString(2));et_age.setText(cur.getInt(3) + "");et_email.setText(cur.getString(4));if (cur.isLast())btn_next.setEnabled(false);elsebtn_next.setEnabled(true);if (cur.isFirst())btn_prev.setEnabled(false);elsebtn_prev.setEnabled(true);} else {btn_next.setEnabled(false);btn_prev.setEnabled(false);btn_del.setEnabled(false);et_id.setText("");et_username.setText("");et_nickname.setText("");et_age.setText("");et_email.setText("");}}class btnnext_onclick implements OnClickListener {@Overridepublic void onClick(View arg0) {if (cur != null) {cur.moveToNext();refreshUI();}}}class btnprev_onclick implements OnClickListener {@Overridepublic void onClick(View arg0) {if (cur != null) {cur.moveToPrevious();refreshUI();}}}class btndel_onclick implements OnClickListener {@Overridepublic void onClick(View arg0) {dbhelper.delRecord(IntWrapper.wrap(et_id.getText().toString(), 1));cur = dbhelper.queryAll();if (cur != null) {cur.moveToFirst();refreshUI();}}}class btninsert_onclick implements OnClickListener {@Overridepublic void onClick(View arg0) {dbhelper.addRecord(et_username.getText().toString(), et_nickname.getText().toString(), IntWrapper.wrap(et_age.getText().toString(), 1), et_email.getText().toString());cur = dbhelper.queryAll();cur.moveToLast();refreshUI();}}}