一个SQLite对数据库的增加、修改、删除功能的例子
来自：http://www.eoeandroid.com/case/2012/0327/1070.html
一个SQLite对数据库的增加、修改、删除功能，对刚学习android程序是很有帮助的，代码简单但是对数据库的操作基本都包括了。
AndroidManifest.xml如下：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.test"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".DBActivity"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-sdk android:minSdkVersion="7" />
</manifest>
color.xml如下：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<drawable name="black">#000000</drawable>
<drawable name="white">#FFFFFFFF</drawable>
<drawable name="red">#FF0000</drawable>
</resources>
strings.xml变量定义如下：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="hello">按MENU可新增、修改、刪除</string>
<string name="app_name">数据库操作</string>
<string name="strEditButton">修改</string>
<string name="strMenu1">Delete</string>
<string name="strAddButton">新增</string>
<string name="strDeleteButton">刪除</string>
</resources>
main.xml布局文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/white"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello"
android:textColor="@drawable/black"
>
</TextView>
<EditText
android:id="@+id/myEditText"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="@drawable/black"
>
</EditText>
<ListView
android:id="@+id/myListView"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="@drawable/red"
>
</ListView>
</LinearLayout>
list.xml布局文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<CheckedTextView android:id="@+id/listTextView1"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="@drawable/black"
>
</CheckedTextView>
</LinearLayout>
数据库操作SQLiteOpenHelper基类 ToDoDB.java代码如下：
package com.test;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class ToDoDB extends SQLiteOpenHelper {
private final static String DATABASE_NAME = "todo_db";
private final static int DATABASE_VERSION = 1;
private final static String TABLE_NAME = "todo_table";
public final static String FIELD_id = "_id";
public final static String FIELD_TEXT = "todo_text";
public ToDoDB(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public void onCreate(SQLiteDatabase db) {
String sql = "CREATE TABLE " + TABLE_NAME + " (" + FIELD_id
+ " INTEGER primary key autoincrement, " + " " + FIELD_TEXT
+ " text)";
db.execSQL(sql);
}
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
String sql = "DROP TABLE IF EXISTS " + TABLE_NAME;
db.execSQL(sql);
onCreate(db);
}
public Cursor select() {
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db
.query(TABLE_NAME, null, null, null, null, null, null);
return cursor;
}
public long insert(String text) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(FIELD_TEXT, text);
long row = db.insert(TABLE_NAME, null, cv);
return row;
}
public void delete(int id) {
SQLiteDatabase db = this.getWritableDatabase();
String where = FIELD_id + " = ?";
String[] whereValue = { Integer.toString(id) };
db.delete(TABLE_NAME, where, whereValue);
}
public void update(int id, String text) {
SQLiteDatabase db = this.getWritableDatabase();
String where = FIELD_id + " = ?";
String[] whereValue = { Integer.toString(id) };
ContentValues cv = new ContentValues();
cv.put(FIELD_TEXT, text);
db.update(TABLE_NAME, cv, where, whereValue);
}
}
执行文件首页面如下所示：
package com.test;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteCursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class DBActivity extends Activity {
private ToDoDB myToDoDB;
private Cursor myCursor;
private ListView myListView;
private EditText myEditText;
private int _id;
protected final static int MENU_ADD = Menu.FIRST;
protected final static int MENU_EDIT = Menu.FIRST + 1;
protected final static int MENU_DELETE = Menu.FIRST + 2;
public boolean onOptionsItemSelected(MenuItem item)
{
super.onOptionsItemSelected(item);
switch (item.getItemId())
{
case MENU_ADD:
this.addTodo();
break;
case MENU_EDIT:
this.editTodo();
break;
case MENU_DELETE:
this.deleteTodo();
break;
}
return true;
}
public boolean onCreateOptionsMenu(Menu menu)
{
super.onCreateOptionsMenu(menu);
menu.add(Menu.NONE, MENU_ADD, 0, R.string.strAddButton);
menu.add(Menu.NONE, MENU_EDIT, 0, R.string.strEditButton);
menu.add(Menu.NONE, MENU_DELETE, 0, R.string.strDeleteButton);
return true;
}
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
myListView = (ListView) this.findViewById(R.id.myListView);
myEditText = (EditText) this.findViewById(R.id.myEditText);
myToDoDB = new ToDoDB(this);
/* 取得DataBase里的数据 */
myCursor = myToDoDB.select();
/* new SimpleCursorAdapter并将myCursor传入，
显示数据的字段为todo_text */
//public SimpleCursorAdapter (Context context, int layout, Cursor c, String[] from, int[] to)
//
SimpleCursorAdapter adapter =
new SimpleCursorAdapter
(this,
R.layout.list,
myCursor,
new String[] { ToDoDB.FIELD_TEXT },
new int[] { R.id.listTextView1 }
);
myListView.setAdapter(adapter);
/* 将myListView添加OnItemClickListener */
myListView.setOnItemClickListener
(new AdapterView.OnItemClickListener()
{
public void onItemClick
(AdapterView<?> arg0, View arg1, int arg2, long arg3)
{
/* 将myCursor移到所点击的值 */
myCursor.moveToPosition(arg2);
/* 取得字段_id的值 */
_id = myCursor.getInt(0);
/* 取得字段todo_text的值 */
myEditText.setText(myCursor.getString(1));
}
});
}
private void addTodo()
{
if (myEditText.getText().toString().equals(""))
return;
/* 添加数据到数据库 */
myToDoDB.insert(myEditText.getText().toString());
/* 重新查询 */
myCursor.requery();
/* 重新整理myListView */
myListView.invalidateViews();
myEditText.setText("");
_id = 0;
}
private void editTodo()
{
if (myEditText.getText().toString().equals(""))
return;
/* 修改数据 */
myToDoDB.update(_id, myEditText.getText().toString());
myCursor.requery();
myListView.invalidateViews();
myEditText.setText("");
_id = 0;
}
private void deleteTodo()
{
if (_id == 0)
return;
/* 删除数据 */
myToDoDB.delete(_id);
myCursor.requery();
myListView.invalidateViews();
myEditText.setText("");
_id = 0;
}
}
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