Android[中级教程]第三章 数据存储之SQLite

这一章我们来学习Android数据库SQLite,还是接上一章的,对于唐僧师徙去西天,三个徙弟得要杀妖怪啊,那得有个汇总啊,有个记数啊,这里我们就用SQLite来存储各徙弟杀死妖怪的数量,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="西游记各主人公杀死妖怪数" android:id="@+id/textView1"></TextView> <Button android:text="增加一个主角" android:id="@+id/add_btn" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button> <Button android:text="更新主角杀死妖怪数" android:id="@+id/update_btn" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button> <Button android:text="删除一个主角" 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>

这里定义了三个按钮,一个ListView,接下来又定义了三个Layout,分别显示"增加一个主角","更新主角杀死妖怪数","删除一个主角"的页面,分别如下:

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="主角名称"></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="杀死妖怪数量"></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="杀死妖怪数量"></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>

最后再定义一个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="杀死了" 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,定义完了,,我们就来创建数据库了,创建一个DatabaseHelper.java

import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class DatabaseHelper extends SQLiteOpenHelper { //数据库名称 private static final String DB_NAME = "SQLiteDemo.db"; //数据库版本 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); } /** * 创建表 */ @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); } }

另外再创建一个数据库操作辅助类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); } /** * 插入数据 * * @param name * 名字 * @param number * 数据 * @return 如果成功则返回true,否则返回false */ public boolean insert(String name, String number) { //创建或打开数据库 SQLiteDatabase db = dbHelper.getWritableDatabase(); ContentValues cv = new ContentValues(); cv.put("name", name); cv.put("number", number); //插入数据,返回插入数据ID long id = db.insert(dbHelper.TABLE_NAME, null, cv); if (id != 0) { return true; } return false; } /** * 更新数据 * * @param id * 数据列_id * @param number * 数量 * @return 如果成功则返回true,否则返回false */ public boolean update(int id, String number) { SQLiteDatabase db = dbHelper.getWritableDatabase(); //Android自带的ContetValues,类似于Map,提供了put(String key, XXX value)的方法存入数据 ContentValues cv = new ContentValues(); cv.put("number", number); //通过ContentValues更新数据表,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; } /** * 删除数据 * * @param id * 数据列_id * @return */ public boolean delete(int id) { SQLiteDatabase db = dbHelper.getWritableDatabase(); //删除指定ID值 int result = db.delete(dbHelper.TABLE_NAME, "_id=?", new String[] { String.valueOf(id) }); if (result != 0) { return true; } return false; } /** * 查询数据 * * @return 返回数据列表 */ public Cursor fetchAll() { SQLiteDatabase db = dbHelper.getReadableDatabase(); //查询数据表中所有字段 Cursor cursor = db.query(dbHelper.TABLE_NAME, null, null, null, null, null, "_id desc"); if (cursor != null) { return cursor; } return null; } }

这里将插入,更新,删除,查询分别做了简单的封装,OK,最后就是Activity类了

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); //自定义方法 SetInAdapter(); } /** * 将数据库里查询到的数据匹配进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: //数据插入 data_add(); break; case R.id.update_btn: //数据更新 data_update(); break; case R.id.del_btn: //数据删除 data_delete(); break; } } /** * 删除主角 */ private void data_delete() { //通过扩展,将delete_item.xml放入视图中 final View delete_view = LayoutInflater.from(this).inflate(R.layout.delete_item, null); AlertDialog.Builder dialog = new AlertDialog.Builder(this); dialog.setTitle("删除主角"); //设置显示视图为delete_item.xml dialog.setView(delete_view); dialog.setPositiveButton("确定", 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); //取得输入的ID值 int id = Integer.parseInt(delete_id.getText().toString()); //调用数据库辅助类中的删除数据方法 boolean flag = dbServer.delete(id); if(flag){ showToast("主角删除成功"); }else{ showToast("主角删除失败"); } dialog.dismiss(); //调用自定义方法更新ListView SetInAdapter(); } }); dialog.setNegativeButton("取消", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { //对话框取消 dialog.dismiss(); } }); dialog.show(); } /** * 更新主角杀死妖怪数 */ 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("更新主角杀死ID数"); dialog.setView(update_view); dialog.setPositiveButton("确定", 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("主角数据更新成功"); }else{ showToast("主角数据更新失败"); } dialog.dismiss(); SetInAdapter(); } }); dialog.setNegativeButton("取消", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { dialog.dismiss(); } }); dialog.show(); } /** * 增加一个主角方法 */ 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("增加一个主角"); dialog.setView(add_view); dialog.setPositiveButton("确定", 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("主角增加失败"); } dialog.dismiss(); SetInAdapter(); } }); dialog.setNegativeButton("取消", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { dialog.dismiss(); } }); dialog.show(); } /* * 按指定内容显示Toast */ protected void showToast(String string) { Toast.makeText(this, string, 1).show(); } }

这里有点长,希望大家能够看完,其实不是太难,这里上图:

下一章我们将介绍Android中的单元测试TestCase,谢谢,如果哪位同学想要源码的,请留邮箱,我会及时给你发过去.

Android[中级教程]第三章 数据存储之SQLite