這一章我們來學習Android數據庫SQLite,還是接上一章的,對于唐僧師徙去西天,三個徙弟得要殺妖怪啊,那得有個匯總啊,有個記數啊,這里我們就用SQLite來存儲各徙弟殺死妖怪的數量,OK,上main.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <TextView android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" android:layout_width="wrap_content" android:text="西游記各主人公殺死妖怪數" android:id="@+id/textView1"></TextView> <Button android:text="增加一個主角" android:id="@+id/add_btn" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button> <Button android:text="更新主角殺死妖怪數" android:id="@+id/update_btn" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button> <Button android:text="刪除一個主角" android:id="@+id/del_btn" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button> <ListView android:layout_height="wrap_content" android:id="@+id/listView1" android:layout_width="match_parent"></ListView> </LinearLayout>

這里定義了三個按鈕,一個ListView,接下來又定義了三個Layout,分別顯示"增加一個主角","更新主角殺死妖怪數","刪除一個主角"的頁面,分別如下:

add_item.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent" android:padding="10dp"> <TextView android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" android:layout_width="wrap_content" android:text="主角名稱"></TextView> <EditText android:layout_height="wrap_content" android:layout_width="match_parent" android:id="@+id/add_name"> <requestFocus></requestFocus> </EditText> <TextView android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" android:layout_width="wrap_content" android:text="殺死妖怪數量"></TextView> <EditText android:layout_height="wrap_content" android:layout_width="match_parent" android:id="@+id/add_number" android:inputType="number"></EditText> </LinearLayout>

update_item.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent" android:padding="10dp"> <TextView android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" android:layout_width="wrap_content" android:text="ID"></TextView> <EditText android:layout_height="wrap_content" android:layout_width="match_parent" android:id="@+id/update_id" android:inputType="number"> <requestFocus></requestFocus> </EditText> <TextView android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" android:layout_width="wrap_content" android:text="殺死妖怪數量"></TextView> <EditText android:layout_height="wrap_content" android:layout_width="match_parent" android:id="@+id/update_number" android:inputType="number"></EditText> </LinearLayout>

delete_item.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent" android:padding="10dp"> <TextView android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" android:layout_width="wrap_content" android:text="ID"></TextView> <EditText android:layout_height="wrap_content" android:layout_width="match_parent" android:id="@+id/delete_id" android:inputType="number"> <requestFocus></requestFocus> </EditText> </LinearLayout>

最后再定義一個List_item.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <LinearLayout android:layout_height="wrap_content" android:id="@+id/linearLayout1" android:layout_width="match_parent"> <TextView android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" android:layout_width="wrap_content" android:text="ID: " android:paddingLeft="10dp"></TextView> <TextView android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" android:layout_width="wrap_content" android:text="TextView" android:id="@+id/id"></TextView> <TextView android:layout_height="wrap_content" android:textAppearance="?android:attr/textAppearanceMedium" android:layout_width="wrap_content" android:text="TextView" android:id="@+id/name" android:paddingLeft="30dp"></TextView> </LinearLayout> <LinearLayout android:layout_height="wrap_content" android:id="@+id/linearLayout2" android:layout_width="match_parent"> <TextView android:layout_height="wrap_content" android:layout_width="wrap_content" android:text="殺死了" android:paddingLeft="10dp"></TextView> <TextView android:text="TextView" android:id="@+id/number" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textColor="#FF0000"></TextView> <TextView android:text="只妖怪" android:layout_width="wrap_content" android:layout_height="wrap_content"></TextView> </LinearLayout> </LinearLayout>

OK,定義完了,,我們就來創建數據庫了,創建一個DatabaseHelper.java

import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class DatabaseHelper extends SQLiteOpenHelper { //數據庫名稱 private static final String DB_NAME = "SQLiteDemo.db"; //數據庫版本 private static final int DB_VERSION = 1; //表名 public static final String TABLE_NAME = "demo"; private static final String DB_CREATE = "create table " + TABLE_NAME + " (_id integer primary key autoincrement, name varchar(20), number varchar(10))"; public DatabaseHelper(Context context) { super(context, DB_NAME, null, DB_VERSION); } /** * 創建表 */ @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DB_CREATE); } /** * 更新表 */ @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // db.execSQL("drop table if exists " + TABLE_NAME); // onCreate(db); } }

另外再創建一個數據庫操作輔助類DatabaseServer.java

import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; public class DatabaseServer { private DatabaseHelper dbHelper; public DatabaseServer(Context context) { this.dbHelper = new DatabaseHelper(context); } /** * 插入數據 * * @param name * 名字 * @param number * 數據 * @return 如果成功則返回true,否則返回false */ public boolean insert(String name, String number) { //創建或打開數據庫 SQLiteDatabase db = dbHelper.getWritableDatabase(); ContentValues cv = new ContentValues(); cv.put("name", name); cv.put("number", number); //插入數據,返回插入數據ID long id = db.insert(dbHelper.TABLE_NAME, null, cv); if (id != 0) { return true; } return false; } /** * 更新數據 * * @param id * 數據列_id * @param number * 數量 * @return 如果成功則返回true,否則返回false */ public boolean update(int id, String number) { SQLiteDatabase db = dbHelper.getWritableDatabase(); //Android自帶的ContetValues,類似于Map,提供了put(String key, XXX value)的方法存入數據 ContentValues cv = new ContentValues(); cv.put("number", number); //通過ContentValues更新數據表,返回更新的ID值 int result = db.update(dbHelper.TABLE_NAME, cv, "_id=?", new String[] { String.valueOf(id) }); if (result != 0) { return true; } return false; } /** * 刪除數據 * * @param id * 數據列_id * @return */ public boolean delete(int id) { SQLiteDatabase db = dbHelper.getWritableDatabase(); //刪除指定ID值 int result = db.delete(dbHelper.TABLE_NAME, "_id=?", new String[] { String.valueOf(id) }); if (result != 0) { return true; } return false; } /** * 查詢數據 * * @return 返回數據列表 */ public Cursor fetchAll() { SQLiteDatabase db = dbHelper.getReadableDatabase(); //查詢數據表中所有字段 Cursor cursor = db.query(dbHelper.TABLE_NAME, null, null, null, null, null, "_id desc"); if (cursor != null) { return cursor; } return null; } }

這里將插入,更新,刪除,查詢分別做了簡單的封裝,OK,最后就是Activity類了

import android.app.Activity; import android.app.AlertDialog; import android.content.DialogInterface; import android.database.Cursor; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.ListView; import android.widget.SimpleCursorAdapter; import android.widget.Toast; public class SQLiteDemo extends Activity implements OnClickListener { private Button add_btn; private Button update_btn; private Button del_btn; private ListView listView; private DatabaseServer dbServer; @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); setContentView(R.layout.sqlite); add_btn = (Button) findViewById(R.id.add_btn); add_btn.setOnClickListener(this); update_btn = (Button) findViewById(R.id.update_btn); update_btn.setOnClickListener(this); del_btn = (Button) findViewById(R.id.del_btn); del_btn.setOnClickListener(this); listView = (ListView) findViewById(R.id.listView1); dbServer = new DatabaseServer(this); //自定義方法 SetInAdapter(); } /** * 將數據庫里查詢到的數據匹配進ListView中 */ private void SetInAdapter() { Cursor cursor = dbServer.fetchAll(); SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.list_item, cursor, new String[] { "_id", "name", "number" }, new int[] { R.id.id, R.id.name, R.id.number }); listView.setAdapter(adapter); } @Override public void onClick(View v) { switch (v.getId()) { case R.id.add_btn: //數據插入 data_add(); break; case R.id.update_btn: //數據更新 data_update(); break; case R.id.del_btn: //數據刪除 data_delete(); break; } } /** * 刪除主角 */ private void data_delete() { //通過擴展,將delete_item.xml放入視圖中 final View delete_view = LayoutInflater.from(this).inflate(R.layout.delete_item, null); AlertDialog.Builder dialog = new AlertDialog.Builder(this); dialog.setTitle("刪除主角"); //設置顯示視圖為delete_item.xml dialog.setView(delete_view); dialog.setPositiveButton("確定", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { //取得delete_item.xml中的EditText控件 EditText delete_id = (EditText)delete_view.findViewById(R.id.delete_id); //取得輸入的ID值 int id = Integer.parseInt(delete_id.getText().toString()); //調用數據庫輔助類中的刪除數據方法 boolean flag = dbServer.delete(id); if(flag){ showToast("主角刪除成功"); }else{ showToast("主角刪除失敗"); } dialog.dismiss(); //調用自定義方法更新ListView SetInAdapter(); } }); dialog.setNegativeButton("取消", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { //對話框取消 dialog.dismiss(); } }); dialog.show(); } /** * 更新主角殺死妖怪數 */ private void data_update() { //同上 final View update_view = LayoutInflater.from(this).inflate(R.layout.update_item, null); AlertDialog.Builder dialog = new AlertDialog.Builder(this); dialog.setTitle("更新主角殺死ID數"); dialog.setView(update_view); dialog.setPositiveButton("確定", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { EditText update_id = (EditText)update_view.findViewById(R.id.update_id); int id =Integer.parseInt(update_id.getText().toString()); EditText update_number = (EditText)update_view.findViewById(R.id.update_number); String number_str = update_number.getText().toString(); boolean flag = dbServer.update(id, number_str); if(flag){ showToast("主角數據更新成功"); }else{ showToast("主角數據更新失敗"); } dialog.dismiss(); SetInAdapter(); } }); dialog.setNegativeButton("取消", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { dialog.dismiss(); } }); dialog.show(); } /** * 增加一個主角方法 */ private void data_add() { //同上 final View add_view = LayoutInflater.from(this).inflate(R.layout.add_item, null); AlertDialog.Builder dialog = new AlertDialog.Builder(this); dialog.setTitle("增加一個主角"); dialog.setView(add_view); dialog.setPositiveButton("確定", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { EditText add_name = (EditText)add_view.findViewById(R.id.add_name); String name_str = add_name.getText().toString(); EditText add_number = (EditText)add_view.findViewById(R.id.add_number); String number_str = add_number.getText().toString(); boolean flag = dbServer.insert(name_str, number_str); if(flag){ showToast("主角增加成功"); }else{ showToast("主角增加失敗"); } dialog.dismiss(); SetInAdapter(); } }); dialog.setNegativeButton("取消", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { dialog.dismiss(); } }); dialog.show(); } /* * 按指定內容顯示Toast */ protected void showToast(String string) { Toast.makeText(this, string, 1).show(); } }

這里有點長,希望大家能夠看完,其實不是太難,這里上圖:

下一章我們將介紹Android中的單元測試TestCase,謝謝,如果哪位同學想要源碼的,請留郵箱,我會及時給你發過去.

Android[中級教程]第三章 數據存儲之SQLite