Android SQLiteOpenHelper(手机数据库)

通过使用SQLiteOpenHelper来操作android内置的一个很小的关系型数据库（SQLite）。

1）效果图

Android SQLiteOpenHelper(手机数据库)_第1张图片

2）关键代码如下

1. 创建classMyDataBase.java代码如下

package com.example.androidsqlitedemo;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.util.Log;public class MyDataBase extends SQLiteOpenHelper {private static final String DATABASE_NAME = "demo_db";//数据库的名字private static final int DATABASEVERSION = 1;//版本号private static final String TABLE_NAME = "demo_table";//表名public static final String FIELD_id = "_id";//必须为_idpublic static final String FIELD_TEXT = "demo_text";private SQLiteDatabase db;//数据库private static final String TAG = "MyDataBase";public MyDataBase(Context context) {super(context, DATABASE_NAME, null, DATABASEVERSION);// TODO Auto-generated constructor stubdb = this.getWritableDatabase();// 打开或新建数据库(第一次时创建)获得SQLiteDatabase对象，为了读取和写入数据}@Overridepublic void onCreate(SQLiteDatabase db) {// TODO Auto-generated method stub/* 建立表table */Log.i(TAG, " onCreate() ");String sql = "CREATE TABLE " + TABLE_NAME + " (" + FIELD_id+ " INTEGER PRIMARY KEY AUTOINCREMENT," + " " + FIELD_TEXT+ " TEXT)";db.execSQL(sql);}//更新数据库@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {// TODO Auto-generated method stubLog.i(TAG, " onUpgrade() ");//删除表的SQLString sql = "DROP TABLE IF EXISTS " + TABLE_NAME;db.execSQL(sql);onCreate(db);}//关闭数据库@Overridepublic synchronized void close() {// TODO Auto-generated method stubLog.i(TAG, " close() ");db.close();super.close();}@Overridepublic void onOpen(SQLiteDatabase db1) {// TODO Auto-generated method stubLog.i(TAG, " onOpen() ");super.onOpen(db1);}// 增加数据public long addMethod(String str) {/* 将新增的值放入ContentValues */ContentValues cv = new ContentValues();cv.put(FIELD_TEXT, str);//键值对long row = db.insert(TABLE_NAME, null, cv);Log.i(TAG, "addMethod row=" + row);return row;}// 删除public void deleteMethod(int id) {String[] whereArgs = { Integer.toString(id) };int rowsaffected = db.delete(TABLE_NAME, FIELD_id + "=?", whereArgs);Log.i(TAG, "deleteMethod() rowsaffected=" + rowsaffected);}// 修改public void modMethod(int id, String str) {ContentValues values = new ContentValues();values.put(FIELD_TEXT, str);String[] whereArgs = { Integer.toString(id) };int rowsaffected = db.update(TABLE_NAME, values, FIELD_id + " = ?",whereArgs);Log.i(TAG, "modMethod() rowsaffected=" + rowsaffected);}// 查询所有的数据 ，返回Cursor对象public Cursor query() {//asc是升序desc为降序（默认为asc）return db.query(TABLE_NAME, null, null, null, null, null,  FIELD_id + " ASC");}}

2.在res\layout下创建list.xml代码如下

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent" >    <TextView        android:id="@+id/textView1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="TextView"         android:textSize="30sp"/>    <TextView        android:id="@+id/textView2"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="TextView"         android:textSize="30sp"/></LinearLayout>

3.修改activity_main.xml代码如下

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="vertical" >    <EditText        android:id="@+id/editText1"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:ems="10"        android:inputType="text" >        <requestFocus />    </EditText>    <ListView        android:id="@+id/listView1"        android:layout_width="match_parent"        android:layout_height="wrap_content" >    </ListView></LinearLayout>

4.修改MainActivity.java代码如下

package com.example.androidsqlitedemo;import android.os.Bundle;import android.app.Activity;import android.database.Cursor;import android.database.sqlite.SQLiteCursor;import android.support.v4.widget.SimpleCursorAdapter;import android.view.KeyEvent;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.AdapterView;import android.widget.AdapterView.OnItemClickListener;import android.widget.AdapterView.OnItemSelectedListener;import android.widget.EditText;import android.widget.ListView;public class MainActivity extends Activity {private final static int MENU_ADD=0;private final static int MENU_EDIT=1;private final static int MENU_DEL=2;private EditText editText1=null;private ListView listView1=null;private MyDataBase mDataBase=null;private SimpleCursorAdapter adapter=null; private Cursor mCursor=null;private int _id;@SuppressWarnings("deprecation")@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);editText1=(EditText)findViewById(R.id.editText1);listView1=(ListView)findViewById(R.id.listView1);listView1.setOnItemClickListener(clickListener);listView1.setOnItemSelectedListener(selectedListener);/*创建SQLiteOpenHelper对象引用*/mDataBase=new MyDataBase(this);/*获得DataBase里的数据*/mCursor=mDataBase.query();/*new SimpleCursorAdapter并将mCursor传入,  显示数据字段为_id,todo_text*/adapter=new SimpleCursorAdapter(this, R.layout.list,mCursor, new String[]{MyDataBase.FIELD_id,MyDataBase.FIELD_TEXT},new int[]{R.id.textView1,R.id.textView2});listView1.setAdapter(adapter);}@Override/*添加Menu*/public boolean onCreateOptionsMenu(Menu menu) {menu.add(0, MENU_ADD, 0, "添加");menu.add(0, MENU_EDIT, 1, "修改");menu.add(0, MENU_DEL, 2, "删除");return super.onCreateOptionsMenu(menu);}/*ListView的单击事件处理*/OnItemClickListener clickListener=new OnItemClickListener() {public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3){mCursor.moveToPosition(arg2);_id=mCursor.getInt(mCursor.getColumnIndex(MyDataBase.FIELD_id));editText1.setText(mCursor.getString(mCursor.getColumnIndex(MyDataBase.FIELD_TEXT)));}};/*监听处理鼠标滚轮的事件处理*/OnItemSelectedListener selectedListener=new OnItemSelectedListener() {public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3){_id=mCursor.getInt(mCursor.getColumnIndex(MyDataBase.FIELD_id));SQLiteCursor c=(SQLiteCursor)arg0.getSelectedItem();editText1.setText(c.getString(c.getColumnIndex(MyDataBase.FIELD_TEXT)));}@Overridepublic void onNothingSelected(AdapterView<?> arg0) {// TODO Auto-generated method stub}};@Override/*给Menu添加事件*/public boolean onOptionsItemSelected(MenuItem item){super.onOptionsItemSelected(item);switch (item.getItemId()) {case MENU_ADD://添加addToDo();break;case MENU_DEL://删除deleteToDo();break;case MENU_EDIT://修改editToDo();break;default:break;}return true;}/*添加*/private void addToDo(){String str=editText1.getText().toString();if(str.equalsIgnoreCase("")){return;}mDataBase.addMethod(str);myUpDataShow();}/*删除*/private void deleteToDo(){if(_id==0){return;}mDataBase.deleteMethod(_id);myUpDataShow();}/*修改*/private void editToDo(){String str=editText1.getText().toString();if(str.equalsIgnoreCase("")||_id==0){return;}mDataBase.modMethod(_id, str);myUpDataShow();}/*更新ListView*/private void myUpDataShow(){/*重新查询*/mCursor.requery();/*告知适配器已经变化*/adapter.notifyDataSetChanged();editText1.setText("");_id=0;}@Override/*退出程序*/public boolean onKeyDown(int keyCode, KeyEvent event){if(keyCode==KeyEvent.KEYCODE_BACK){mDataBase.close();this.finish();}return super.onKeyDown(keyCode, event);}}

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