Android复习(十五)

SQLite

 

SQLiteActivity

package org.wp.activity;

import org.wp.db.DatabaseHelper;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

/**
 * adb访问SQLite
 * cmd --> adb
 * adb shell
 * 
 * ls -l --> cd data --> ls -l --> cd data --> ls -l --> cd org.wp.activity --> ls
 * cd --> databases
 * SQLite sqlite_db
 * .schema
 * select * from user;
 * 
 * @author wp
 * 
 */
public class SQLiteActivity extends Activity {
	private static final String TAG = "SQLiteActivity";

	private Button createDBButton;
	private Button updateDBButton;
	private Button insertButton;
	private Button updateButton;
	private Button deleteButton;
	private Button queryButton;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		createDBButton = (Button) findViewById(R.id.createDatabase);
		updateDBButton = (Button) findViewById(R.id.updateDatabase);
		insertButton = (Button) findViewById(R.id.insert);
		updateButton = (Button) findViewById(R.id.update);
		deleteButton = (Button) findViewById(R.id.delete);
		queryButton = (Button) findViewById(R.id.query);

		createDBButton.setOnClickListener(listener);
		updateDBButton.setOnClickListener(listener);
		insertButton.setOnClickListener(listener);
		updateButton.setOnClickListener(listener);
		deleteButton.setOnClickListener(listener);
		queryButton.setOnClickListener(listener);

	}

	private View.OnClickListener listener = new View.OnClickListener() {
		@Override
		public void onClick(View arg0) {
			Button button = (Button) arg0;
			switch (button.getId()) {
			case (R.id.createDatabase):
				// 创建一个DatabaseHelper对象
				DatabaseHelper dbHelper1 = new DatabaseHelper(
						SQLiteActivity.this, "sqlite_db");
				// 只有调用了DatabaseHelper对象的getReadableDatabase()方法，或者是getWritableDatabase()方法之后，才会创建，或打开一个数据库
				SQLiteDatabase db1 = dbHelper1.getReadableDatabase();
				break;
			case (R.id.updateDatabase):
				DatabaseHelper dbHelper2 = new DatabaseHelper(
						SQLiteActivity.this, "sqlite_db", 2);
				SQLiteDatabase db2 = dbHelper2.getReadableDatabase();
				break;
			case (R.id.insert):
				DatabaseHelper dbHelper3 = new DatabaseHelper(
						SQLiteActivity.this, "sqlite_db");
				SQLiteDatabase db3 = dbHelper3.getWritableDatabase();
				// 生成ContentValues对象
				ContentValues values1 = new ContentValues();
				// 向该对象当中插入键值对，其中键是列名，值是希望插入到这一列的值，值必须和数据库当中的数据类型一致
				values1.put("id", 1);
				values1.put("name", "某某某1");
				values1.put("age", 25);
				// 调用insert方法，就可以将数据插入到数据库当中
				db3.insert("user", null, values1);
				values1.put("id", 2);
				values1.put("name", "某某某2");
				values1.put("age", 10);
				// 调用insert方法，就可以将数据插入到数据库当中
				db3.insert("user", null, values1);
				break;
			case (R.id.delete):
				DatabaseHelper dbHelper4 = new DatabaseHelper(
						SQLiteActivity.this, "sqlite_db");
				SQLiteDatabase db4 = dbHelper4.getWritableDatabase();
				db4.delete("user", "id = ?", new String[] { "1" });
				break;
			case (R.id.update):
				DatabaseHelper dbHelper5 = new DatabaseHelper(
						SQLiteActivity.this, "sqlite_db");
				SQLiteDatabase db5 = dbHelper5.getWritableDatabase();
				ContentValues values2 = new ContentValues();
				values2.put("name", "张三1");
				values2.put("age", 33);
				db5.update("user", values2, "id = ?", new String[] { "1" });
				values2.put("name", "张三2");
				values2.put("age", 15);
				db5.update("user", values2, "id = ?", new String[] { "2" });
				break;
			case (R.id.query):
				DatabaseHelper dbHelper6 = new DatabaseHelper(
						SQLiteActivity.this, "sqlite_db");
				SQLiteDatabase db6 = dbHelper6.getReadableDatabase();
				Cursor cursor = db6.query("user", new String[] { "id", "name",
						"age" }, "id = ?", new String[] { "1" }, null, null,
						null);
				while (cursor.moveToNext()) {
					int id = cursor.getInt(cursor.getColumnIndex("id"));
					String name = cursor.getString(cursor
							.getColumnIndex("name"));
					int age = cursor.getInt(cursor.getColumnIndex("age"));
					Log.i(TAG, "count:" + cursor.getCount());
					Log.i(TAG, "columnCount:" + cursor.getColumnCount());
					Log.i(TAG, "id:" + id + ",name:" + name + ",age:" + age);
				}
				break;
			}
		}
	};
}

 

DatabaseHelper

package org.wp.db;

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

/**
 * DatabaseHelper作为一个访问SQLite的助手类，提供两个方面的功能 
 * 第一: getReadableDatabase(),getWritableDatabase()
 *       可以获得SQLiteDatabse对象，通过该对象可以对数据库进行操作
 * 第二: 提供了onCreate()和onUpgrade()两个回调函数
 *       允许我们在创建和升级数据库时，进行自己的操作
 * 
 * @author wp
 * 
 */
public class DatabaseHelper extends SQLiteOpenHelper {
	private static final String TAG = "DatabaseHelper";
	private static final int VERSION = 1;

	public DatabaseHelper(Context context, String name) {
		this(context, name, VERSION);
	}

	public DatabaseHelper(Context context, String name, int version) {
		this(context, name, null, version);
	}

	// 在SQLiteOpenHelper的子类当中，必须有该构造函数
	public DatabaseHelper(Context context, String name, CursorFactory factory,
			int version) {
		// 必须通过super调用父类当中的构造函数
		super(context, name, factory, version);
	}

	// 该函数是在第一次创建数据库的时候执行,实际上是在第一次得到SQLiteDatabse对象的时候，才会调用这个方法
	@Override
	public void onCreate(SQLiteDatabase db) {
		Log.i(TAG, "Create Database");
		db.execSQL("create table user(id int,name varchar(20),age int)");
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		Log.i(TAG, "Update Database");
	}
}

 

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="fill_parent"
    android:layout_height="fill_parent"
    >
	<Button
		android:id="@+id/createDatabase"
		android:layout_width="fill_parent"
		android:layout_height="wrap_content"
		android:text="createDatabase"
		/>
	<Button
		android:id="@+id/updateDatabase"
		android:layout_width="fill_parent"
		android:layout_height="wrap_content"
		android:text="updateDatabase"
		/>
	<Button
		android:id="@+id/insert"
		android:layout_width="fill_parent"
		android:layout_height="wrap_content"
		android:text="insert"
		/>
	<Button
		android:id="@+id/update"
		android:layout_width="fill_parent"
		android:layout_height="wrap_content"
		android:text="update"
		/>
	<Button
		android:id="@+id/delete"
		android:layout_width="fill_parent"
		android:layout_height="wrap_content"
		android:text="delete"
		/>
	<Button
		android:id="@+id/query"
		android:layout_width="fill_parent"
		android:layout_height="wrap_content"
		android:text="query"
		/>		
</LinearLayout>