android学习笔记50——SQLiteOpenHelper、android实现系统自带样式

SQLiteOpenHelper

SQLiteOpenHelper是android提供的一个管理数据库的工具类，可用于管理数据库的创建和版本更新。

一般的用法是创建SQLiteOpenHelper的子类，并扩展它的onCreate(SQLiteDatabase db)和onUpgrade(SQLiteDatabase db,int oldVersion,newVersion)方法。

SQLiteOpenHelper包含如下常用方法：

sychronized SQLiteDatabase getReadableDatabase()	以读写的方式打开数据库对应的SQLiteDataBase对象
sychronized SQLiteDatabase getWriteableDataBase()	以写的方式打开数据库对应的SQLiteDataBase对象
abstract void onCreate(SQLiteDatabase db)	当第一次创建数据库时回调该方法
abstract void onUpgrade(SQLiteDatabase db,int oldVersion,newVersion)	当数据库版本更新时回调该方法
sychronized void close()	关闭所有打开的SQLiteDatabase

实例如下：

布局文件==》main
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/edit1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <EditText
        android:id="@+id/edit2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/btnInsert"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="添加生词" />

    <EditText
        android:id="@+id/edit3"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/btnQuery"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="查询" />

</LinearLayout>
result.xml==>
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <EditText
        android:id="@+id/word"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <EditText
        android:id="@+id/detial"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

代码实现==》
package com.example.mysqlite2;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class MyDatabaseHelper extends SQLiteOpenHelper
{
	final String CREATE_TABLE_SQL = "create table dict(_id integer primary key autoincrement,word,detial)";

	public MyDatabaseHelper(Context context, String name, int version)
	{
		super(context, name, null, version);
		Log.i("swg", "-----------MyDatabaseHelper------------");
	}

	@Override
	public void onCreate(SQLiteDatabase db)
	{
		// 第一个使用数据库时自动见表
		db.execSQL(CREATE_TABLE_SQL);
		Log.i("swg", "-----------创建表成功------------");
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
	{
		System.out
				.println("-----------onUpgrade----------" + oldVersion + "-------->" + newVersion);
	}

}

package com.example.mysqlite2;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity
{
	MyDatabaseHelper dbHelper;
	EditText edit1;
	EditText edit2;
	EditText edit3;
	String dbName = "test.db3";

	@Override
	protected void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		// 创建MyDatabaseHelper对象，指定数据库版本为1，此处使用相对路径
		// 数据库文件会自动保存在程序的数据文件夹下的databases目录下
		dbHelper = new MyDatabaseHelper(this, dbName, 1);

		edit1 = (EditText) this.findViewById(R.id.edit1);
		edit2 = (EditText) this.findViewById(R.id.edit2);
		edit3 = (EditText) this.findViewById(R.id.edit3);
		Button btnInsert = (Button) this.findViewById(R.id.btnInsert);
		Button btnQuery = (Button) this.findViewById(R.id.btnQuery);
		btnInsert.setOnClickListener(new MyButtonOnClick());
		btnQuery.setOnClickListener(new MyButtonOnClick());
	}

	private class MyButtonOnClick implements OnClickListener
	{
		@Override
		public void onClick(View v)
		{
			switch (v.getId())
			{
			case R.id.btnInsert:
				String word = edit1.getText().toString();
				String detial = edit2.getText().toString();

				Log.i("swg", "insert content==" + word + "=========" + detial);
				// 插入生词记录
				insertData(dbHelper.getReadableDatabase(), word, detial);
				Toast.makeText(MainActivity.this, "添加生词成功", Toast.LENGTH_LONG).show();
				break;
			case R.id.btnQuery:
				String key = edit3.getText().toString();
				Log.i("swg", "key==" + key);
				// 执行查询
				String sql = "select * from dict where word like ? or detial like ? ";
				Cursor cursor = dbHelper.getReadableDatabase().rawQuery(sql,
						new String[] { "%" + key + "%", "%" + key + "%" });

				Bundle data = new Bundle();
				data.putSerializable("data", convertCursorToList(cursor));

				Intent intent = new Intent(MainActivity.this, ResultActivity.class);
				intent.putExtras(data);
				startActivity(intent);
				break;
			}
		}

		private ArrayList<Map<String, String>> convertCursorToList(Cursor cursor)
		{
			ArrayList<Map<String, String>> result = new ArrayList<Map<String, String>>();
			while (cursor.moveToNext())
			{
				Map<String, String> map = new HashMap<String, String>();
				map.put("word", cursor.getString(1));
				map.put("detial", cursor.getString(2));
				result.add(map);
			}
			return result;
		}

		private void insertData(SQLiteDatabase db, String word, String detial)
		{
			String sql = "insert into dict values (null,?,?)";
			db.execSQL(sql, new String[] { word, detial });
		}

	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu)
	{
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	@Override
	protected void onDestroy()
	{
		super.onDestroy();
		// 退出程序时关闭MyDatabaseHelper里的SQLitedatabase
		if (dbHelper != null)
			dbHelper.close();
	}

}

package com.example.mysqlite2;

import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.widget.ListView;
import android.widget.SimpleAdapter;

public class ResultActivity extends Activity
{
	@Override
	protected void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.result);

		ListView lv = (ListView) this.findViewById(R.id.lv);
		Intent intent = getIntent();
		Bundle data = intent.getExtras();
		@SuppressWarnings("unchecked")
		List<Map<String, String>> list = (List<Map<String, String>>) data.getSerializable("data");
		// 将list封装成SimpleAdapter
		SimpleAdapter adapter = new SimpleAdapter(ResultActivity.this, list, R.layout.result,
				new String[] { "word", "detial" }, new int[] { R.id.word, R.id.detial });
		int count = adapter.getCount();
		Log.i("swg", "查到" + count + "条");
		lv.setAdapter(adapter);
	}

}

注意：AndroidMainfest.xml需要添加==》<activity android:name="com.example.mysqlite2.ResultActivity" android:theme="@android:style/Theme.Dialog"/>

运行效果：

注意：android实现系统自带样式如下方式：

android:theme="@android:style/Theme.Dialog" : Activity显示为对话框模式

android:theme="@android:style/Theme.NoTitleBar" : 不显示应用程序标题栏

android:theme="@android:style/Theme.NoTitleBar.Fullscreen" : 不显示应用程序标题栏，并全屏

android:theme="Theme.Light ": 背景为白色

android:theme="Theme.Light.NoTitleBar" : 白色背景并无标题栏

android:theme="Theme.Light.NoTitleBar.Fullscreen" : 白色背景，无标题栏，全屏

android:theme="Theme.Black" : 背景黑色

android:theme="Theme.Black.NoTitleBar" : 黑色背景并无标题栏

android:theme="Theme.Black.NoTitleBar.Fullscreen" : 黑色背景，无标题栏，全屏

android:theme="Theme.Wallpaper" : 用系统桌面为应用程序背景

android:theme="Theme.Wallpaper.NoTitleBar" : 用系统桌面为应用程序背景，且无标题栏

android:theme="Theme.Wallpaper.NoTitleBar.Fullscreen" : 用系统桌面为应用程序背景，无标题栏，全屏

android:theme="Theme.Translucent : 透明背景

android:theme="Theme.Translucent.NoTitleBar" : 透明背景并无标题

android:theme="Theme.Translucent.NoTitleBar.Fullscreen" : 透明背景并无标题，全屏

android:theme="Theme.Panel ": 面板风格显示

android:theme="Theme.Light.Panel" : 平板风格显示