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*/@Overridepublic void onCreate(SQLiteDatabase db){db.execSQL(DB_CREATE);}/*** 更新表*/@Overridepublic 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IDlong 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;@Overrideprotected void onCreate(Bundle savedInstanceState){// TODO Auto-generated method stubsuper.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);}@Overridepublic 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.xmldialog.setView(delete_view);dialog.setPositiveButton("确定", new DialogInterface.OnClickListener(){@Overridepublic 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ListViewSetInAdapter();}});dialog.setNegativeButton("取消", new DialogInterface.OnClickListener(){@Overridepublic 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(){@Overridepublic 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(){@Overridepublic 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(){@Overridepublic 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(){@Overridepublic 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.
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