Android 数据库操作-优快云博客

本文详细介绍了如何在Android应用中使用SQLite数据库进行数据存储和检索，并通过ContentProvider实现数据库数据的外部访问。包括数据库创建、数据插入、查询、更新和删除等基本操作，以及ContentProvider的实现和注册。

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在数据库中保存了三个字段：id,name,url
首先实现数据库的操作类：代码如下

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.net.Uri;
public class DatabaseHelper extends SQLiteOpenHelper {
	public static final int COLUMN_ID = 1;
	public static final int COLUMN_INDEX = 0;
	public static final int COLUMN_NAME = 2;
	public static final int COLUMN_URL = 3;
	public static final String ID_STRING = "id";
	private static DatabaseHelper mDatabaseHelper = null;
	public static final String NAME = "mydatabase.db";
	public static final String TABLE_NAME = "web_broadcast";
	private static final int VERSION = 1;

	public static DatabaseHelper getDatabaseHelper(Context context) {
		if (mDatabaseHelper == null) {
			mDatabaseHelper = new DatabaseHelper(context);
		}
		return mDatabaseHelper;
	}

	private String TABLE_BROADCAST = "name";
	private String TABLE_ID = ID_STRING;
	private String TABLE_INDEX = "index_num";
	private String TABLE_URL = "url";

	// private String TABLE_NUM="_num";
	// private String TABLE_DATA="_data";
	private DatabaseHelper(Context context) {
		super(context, NAME, null, VERSION);
		// TODO Auto-generated constructor stub
	}

	/**
	 * /** 删除记录
	 * 
	 * 
	 */
	public void delete(String index) {
		SQLiteDatabase db = getWritableDatabase();
		db.delete(TABLE_NAME, "index_num=?", new String[] { index });
	}

	/**
	 * 添加数据
	 */
	public long insert(String id, String name, String url) {
		SQLiteDatabase db = getWritableDatabase();// 获取可写SQLiteDatabase对象
		// ContentValues类似map，存入的是键值对
		ContentValues contentValues = new ContentValues();
		contentValues.put(TABLE_ID, id);
		contentValues.put(TABLE_BROADCAST, name);
		contentValues.put(TABLE_URL, url);
		return db.insert(TABLE_NAME, null, contentValues);
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		// TODO Auto-generated method stub
		String sql = "CREATE TABLE " + TABLE_NAME + "(" + TABLE_INDEX
				+ " INTEGER PRIMARY KEY AUTOINCREMENT," + TABLE_ID + " text,"
				+ TABLE_BROADCAST + " text," + TABLE_URL + " text)";
		// String sql = "CREATE TABLE "
		// + TABLE_NAME
		// + "(_idnum INTEGER PRIMARY KEY AUTOINCREMENT,_num text,_data text)";
		db.execSQL(sql);// 需要异常捕获
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// TODO Auto-generated method stub
		String sql = "drop table " + TABLE_NAME;
		db.execSQL(sql);
		onCreate(db);

	}

	public Cursor query(String selection) {
		SQLiteDatabase db = getReadableDatabase();
		Cursor cursor = db.query(TABLE_NAME, null, selection, null, null, null,
				"index_num desc");
		return cursor;
	}

	/**
	 * 查询所有数据
	 * 
	 * @return Cursor
	 */
	public Cursor select() {
		SQLiteDatabase db = getReadableDatabase();
		Cursor cursor = db.query(TABLE_NAME, new String[] { "index_num",
				TABLE_ID, TABLE_BROADCAST, TABLE_URL }, null, null, null, null,
				"index_num desc"); // desc 降序排列,asc 升序排列
		return cursor;
	}

	/**
	 * 更新记录的，跟插入的很像
	 */
	public void update(String index, String id, String name, String url) {
		SQLiteDatabase db = getWritableDatabase();
		ContentValues contentValues = new ContentValues();
		contentValues.put(TABLE_ID, id);
		contentValues.put(TABLE_BROADCAST, name);
		contentValues.put(TABLE_URL, url);
		db.update(TABLE_NAME, contentValues, "index_num=?",
				new String[] { index });
	}

}

然后实现一个ContentProvider


package com.tcl.kang;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.text.TextUtils;
import android.util.Log;

public class MyContentProvider extends ContentProvider

{
	public static final String PROVIDER_NAME = "com.tcl.myprovider";
	public static final Uri CONTENT_URI = Uri.parse("content://"
			+ PROVIDER_NAME + "/urls");
	public static final String _ID = DatabaseHelper.ID_STRING;
	private static final int URLS = 1;
	private static final int URL_ID = 2;
	private static final UriMatcher uriMatcher;
	private static final String DATABASE_TABLE = DatabaseHelper.TABLE_NAME;
	private SQLiteDatabase mDb;
	private DatabaseHelper mDbHelper;
	static {
		uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
		// 返回所有的
		uriMatcher.addURI(PROVIDER_NAME, "urls", URLS);
		// 返回指定的
		uriMatcher.addURI(PROVIDER_NAME, "urls/#", URL_ID);
	}
	@Override
	public boolean onCreate() {
		Context context = getContext();
		mDbHelper = DatabaseHelper.getDatabaseHelper(context);
		Log.v("", "kang:mdb="+mDb);
		return (mDb == null) ? false : true;
	}

	@Override
	public String getType(Uri uri) {
		switch (uriMatcher.match(uri)) {
		// ---get all books---
		case URLS:
			return "vnd.android.cursor.dir/vnd.learn2develop.urls ";
			// ---get a particular book---
		case URL_ID:
			return "vnd.android.cursor.item/vnd.learn2develop.urls ";
		default:
			throw new IllegalArgumentException("Unsupported URI: " + uri);
		}
	}

	@Override
	public Cursor query(Uri uri, String[] projection, String selection,
			String[] selectionArgs, String sortOrder) {
		SQLiteQueryBuilder sqlBuilder = new SQLiteQueryBuilder();
		sqlBuilder.setTables(DATABASE_TABLE);
		mDb = mDbHelper.getWritableDatabase();
		if (uriMatcher.match(uri) == URL_ID)
			// ---if getting a particular book---
			sqlBuilder.appendWhere(_ID + " = " + uri.getPathSegments().get(1));
		Cursor c = sqlBuilder.query(mDb, projection, selection, selectionArgs,
				null, null, sortOrder);
		// ---register to watch a content URI for changes---
		c.setNotificationUri(getContext().getContentResolver(), uri);
		return c;
	}

	@Override
	public Uri insert(Uri uri, ContentValues values) {
		mDb = mDbHelper.getReadableDatabase();
		long rowID = mDb.insert(DATABASE_TABLE, "", values);
		// ---if added successfully---
		if (rowID > 0) {
			Uri _uri = ContentUris.withAppendedId(CONTENT_URI, rowID);
			getContext().getContentResolver().notifyChange(_uri, null);
			return _uri;
		}
		throw new SQLException("Failed to insert row into " + uri);
	}

	@Override
	public int delete(Uri arg0, String arg1, String[] arg2) {
		mDb = mDbHelper.getWritableDatabase();
		int count = 0;
		switch (uriMatcher.match(arg0)) {
		case URLS:
			count = mDb.delete(DATABASE_TABLE, arg1, arg2);
			break;

		case URL_ID:
			String id = arg0.getPathSegments().get(1);
			count = mDb.delete(DATABASE_TABLE, _ID + " = " + id
					+ (!TextUtils.isEmpty(arg1) ? " AND (" + arg1 + ')' : ""),
					arg2);
			break;

		default:
			throw new IllegalArgumentException("Unknown URI " + arg0);

		}

		getContext().getContentResolver().notifyChange(arg0, null);

		return count;

	}

	@Override
	public int update(Uri uri, ContentValues values,

	String selection, String[] selectionArgs)

	{
		mDb = mDbHelper.getWritableDatabase();
		int count = 0;

		switch (uriMatcher.match(uri)) {

		case URLS:

			count = mDb.update(

			DATABASE_TABLE,

			values,

			selection,

			selectionArgs);

			break;

		case URL_ID:

			count = mDb.update(

			DATABASE_TABLE,

			values,

			_ID + " = " + uri.getPathSegments().get(1) +

			(!TextUtils.isEmpty(selection) ? " AND (" +

			selection + ')' : ""),

			selectionArgs);

			break;

		default:
			throw new IllegalArgumentException(

			"Unknown URI " + uri);

		}

		getContext().getContentResolver().notifyChange(uri, null);

		return count;

	}
}

贴上Manifest.xml,在其中添加provider字段


<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.tcl.kang"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".ActivityMain"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
	    <provider android:name="com.tcl.kang.MyContentProvider" 
        android:authorities="com.tcl.myprovider" 
        android:multiprocess="true"
        />
    </application>
    <uses-sdk android:minSdkVersion="8" />

</manifest>

测试直接操作数据库：


package com.tcl.kang;

import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;

public class ActivityMain extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        DatabaseHelper databaseHelper = DatabaseHelper.getDatabaseHelper(this);
        databaseHelper.insert("1", "name1", "http://name1");
        databaseHelper.insert("2", "name2", "http://name2");
        databaseHelper.close();
    }
}
测试用ContentProvider操作数据库
[code="java"]

package com.tcl.testsql2;

import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.widget.ImageView;

public class TestSql2Activity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Uri uri = Uri.parse("content://"+ "com.tcl.myprovider" + "/urls");
ContentResolver resolver = getContentResolver();
ContentValues values = new ContentValues();
// values.put("id", "5");
// values.put("name", "name5");
// values.put("url", "http://name5");
// resolver.insert(uri, values);
Cursor cursor = resolver.query(uri, null, null, null, null);
}
}
[/code]