android sqlite

系出名门Android(9) - 数据库支持(SQLite), 内容提供器(ContentProvider) 


作者：webabcd 


介绍 
在 Android 中使用 SQLite, ContentProvider  
数据库支持(SQLite) - Android 开发平台提供了操作 SQLite 数据库的相关 API 
内容提供器(ContentProvider) - 当数据需要在应用程序之间共享时，可以在某程序中使用 ContentProvider 定义 URI， 以使其它应用程序可以通过此 URI 访问指定的数据 


1、SQLite 的 Demo 
DatabaseHelper.java 

Java代码 
代码    
package com.webabcd.SQLite;   
  
import android.content.Context;   
import android.database.sqlite.SQLiteDatabase;   
import android.database.sqlite.SQLiteOpenHelper;   
import android.database.sqlite.SQLiteDatabase.CursorFactory;   
  
// 数据库操作的 Helper 类   
public class DatabaseHelper extends SQLiteOpenHelper {   
  
    DatabaseHelper(Context context, String name, CursorFactory cursorFactory, int version) {   
        super(context, name, cursorFactory, version);   
    }   
  
    @Override  
    public void onCreate(SQLiteDatabase db) {   
        // TODO 创建数据库后，对数据库的操作   
    }   
  
    @Override  
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {   
        // TODO 更改数据库版本的操作   
    }   
  
    @Override  
    public void onOpen(SQLiteDatabase db) {   
        super.onOpen(db);   
           
        // TODO 每次成功打开数据库后首先被执行   
    }   
}   
  
  
Main.java   
  
代码    
package com.webabcd.SQLite;   
  
import java.util.Random;   
  
import android.app.Activity;   
import android.content.ContentValues;   
import android.database.Cursor;   
import android.database.SQLException;   
import android.database.sqlite.SQLiteDatabase;   
import android.os.Bundle;   
import android.view.View;   
import android.widget.Button;   
import android.widget.TextView;   
  
public class Main extends Activity {   
  
    private DatabaseHelper dbHelper;   
  
    private static final String DATABASE_NAME = "db.db";   
    private static final int DATABASE_VERSION = 1;   
    private static final String TABLE_NAME = "employee";   
  
    TextView txtMsg;   
  
    /** Called when the activity is first created. */  
    @Override  
    public void onCreate(Bundle savedInstanceState) {   
        super.onCreate(savedInstanceState);   
        setContentView(R.layout.main);   
  
        dbHelper = new DatabaseHelper(this, DATABASE_NAME, null,   
                DATABASE_VERSION);   
  
        txtMsg = (TextView) this.findViewById(R.id.txtMsg);   
  
        Button btn1 = (Button) this.findViewById(R.id.btn1);   
        btn1.setText("创建表");   
        btn1.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                CreateTable();   
            }   
        });   
  
        Button btn2 = (Button) this.findViewById(R.id.btn2);   
        btn2.setText("插入 3 条记录");   
        btn2.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                insertItem();   
            }   
        });   
  
        Button btn3 = (Button) this.findViewById(R.id.btn3);   
        btn3.setText("删除全部记录");   
        btn3.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                deleteItem();   
            }   
        });   
  
        Button btn4 = (Button) this.findViewById(R.id.btn4);   
        btn4.setText("更新指定数据");   
        btn4.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                updateItem();   
            }   
        });   
  
        Button btn5 = (Button) this.findViewById(R.id.btn5);   
        btn5.setText("显示全部数据");   
        btn5.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                showItems();   
            }   
        });   
  
        Button btn6 = (Button) this.findViewById(R.id.btn6);   
        btn6.setText("删除表");   
        btn6.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                dropTable();   
            }   
        });   
    }   
  
    // 创建数据表   
    private void CreateTable() {   
        SQLiteDatabase db = dbHelper.getWritableDatabase();   
        String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME   
                + " (ID INTEGER PRIMARY KEY, Name VARCHAR, Age INTEGER);";   
        try {   
            db.execSQL(sql);   
            txtMsg.append("数据表成功创建\n");   
        } catch (SQLException ex) {   
            txtMsg.append("数据表创建错误\n" + ex.toString() + "\n");   
        }   
    }   
  
    // 插入数据   
    private void insertItem() {   
        SQLiteDatabase db = dbHelper.getWritableDatabase();   
           
        try {   
            Random random = new Random();   
            for (int i = 0; i < 3; i++) {   
                String sql = "insert into " + TABLE_NAME   
                        + " (name, age) values ('name" + String.valueOf(i)   
                        + "', " + random.nextInt() + ")";   
                // execSQL() - 执行指定的 sql   
                db.execSQL(sql);   
            }   
            txtMsg.append("成功插入 3 条数据\n");   
        } catch (SQLException ex) {   
            txtMsg.append("插入数据失败\n" + ex.toString() + "\n");   
        }   
    }   
  
    // 删除数据   
    private void deleteItem() {   
        try {   
            SQLiteDatabase db = dbHelper.getWritableDatabase();   
            db.delete(TABLE_NAME, " id < 999999", null);   
            txtMsg.append("成功删除数据\n");   
        } catch (SQLException e) {   
            txtMsg.append("删除数据失败\n");   
        }   
    }   
  
    // 更新数据   
    private void updateItem() {   
        SQLiteDatabase db = dbHelper.getWritableDatabase();   
  
        try {   
            ContentValues values = new ContentValues();   
            values.put("name", "批量更新后的名字");   
  
            db.update(TABLE_NAME, values, "id<?", new String[] { "3" });   
            txtMsg.append("成功更新数据\n");   
        } catch (SQLException e) {   
            txtMsg.append("更新数据失败\n");   
        }   
    }   
  
    // 查询数据   
    private void showItems() {   
        SQLiteDatabase db = dbHelper.getReadableDatabase();   
  
        try {   
            String[] column = { "id", "name", "age" };   
            Cursor cursor = db.query(TABLE_NAME, column, null, null, null,   
                    null, null);   
            Integer num = cursor.getCount();   
            txtMsg.append("共 " + Integer.toString(num) + " 条记录\n");   
            cursor.moveToFirst();   
  
            while (cursor.getPosition() != cursor.getCount()) {   
                txtMsg.append(Integer.toString(cursor.getPosition()) + ","  
                        + String.valueOf(cursor.getString(0)) + ","  
                        + cursor.getString(1) + ","  
                        + String.valueOf(cursor.getString(2)) + "\n");   
                cursor.moveToNext();   
            }   
        } catch (SQLException ex) {   
            txtMsg.append("读取数据失败\n" + ex.toString() + "\n");   
        }   
    }   
  
    // 删除数据表   
    private void dropTable() {   
        SQLiteDatabase db = dbHelper.getWritableDatabase();   
        String sql = "DROP TABLE IF EXISTS " + TABLE_NAME;   
        try {   
            db.execSQL(sql);   
            txtMsg.append("数据表删除成功\n");   
        } catch (SQLException ex) {   
            txtMsg.append("数据表删除错误\n" + ex.toString() + "\n");   
        }   
    }   
}   
  
  
2、ContentProvider 的 Demo   
MyUser.java   
  
代码    
package com.webabcd.contentprovider;   
  
import android.net.Uri;   
import android.provider.BaseColumns;   
  
// 自定义 ContentProvider 所需的实体类   
public class MyUser {   
  
    // 必须要有 _id 字段。本例中 BaseColumn 类中已经包含了 _id 字段   
    public static final class User implements BaseColumns {   
           
        // 定义 CONTENT_URI   
        public static final Uri CONTENT_URI = Uri.parse("content://com.webabcd.MyContentProvider");   
  
        // 表数据列   
        public static final String USER_NAME = "USER_NAME";   
    }   
}   
  
  
MyContentProvider.java   
  
代码    
package com.webabcd.contentprovider;   
  
import java.io.File;   
import java.io.FileInputStream;   
import java.io.FileOutputStream;   
  
import org.apache.http.util.EncodingUtils;   
  
import android.content.ContentProvider;   
import android.content.ContentUris;   
import android.content.ContentValues;   
import android.database.Cursor;   
import android.database.MatrixCursor;   
import android.net.Uri;   
  
// 继承 ContentProvider 以实现自定义的 ContentProvider（基于文件的信息存储）   
public class MyContentProvider extends ContentProvider {   
  
    private File file;   
    private FileOutputStream out;   
    private FileInputStream in;   
  
    // ContentProvider 的删除数据接口   
    @Override  
    public int delete(Uri uri, String selection, String[] selectionArgs) {   
        // TODO Auto-generated method stub   
        return 0;   
    }   
  
    @Override  
    public String getType(Uri uri) {   
        // TODO Auto-generated method stub   
        return null;   
    }   
  
    // ContentProvider 的插入数据接口    
    @Override  
    public Uri insert(Uri uri, ContentValues values) {   
  
        try {   
            out = new FileOutputStream(file);   
            out.write(values.getAsString(MyUser.User.USER_NAME).getBytes());   
            out.close();   
  
            int rowId = 0;   
            Uri rowUri = ContentUris.appendId(   
                    MyUser.User.CONTENT_URI.buildUpon(), rowId).build();   
            getContext().getContentResolver().notifyChange(rowUri, null);   
  
            return rowUri;   
        } catch (Exception e) {   
            return null;   
        }   
    }   
  
    // 创建用于保存信息的文件   
    @Override  
    public boolean onCreate() {   
        try {   
            // 每个包中应用程序的私有目录为：/data/data/包名/   
            // SD 卡目录为：/sdcard   
            file = new File("/data/data/com.webabcd.contentprovider/",   
                    "demo.txt");   
            if (!file.exists())   
                file.createNewFile();   
  
            return true;   
        } catch (Exception ex) {   
            return false;   
        }   
    }   
  
    // ContentProvider 的查询数据接口   
    @Override  
    public Cursor query(Uri uri, String[] projection, String selection,   
            String[] selectionArgs, String sortOrder) {   
           
        String content;   
  
        try {   
            in = new FileInputStream(file);   
            int length = (int) file.length();   
            byte[] buffer = new byte[length];   
            in.read(buffer, 0, length);   
            content = EncodingUtils.getString(buffer, "UTF-8");   
            in.close();   
  
            String[] columns = new String[] { MyUser.User._ID, MyUser.User.USER_NAME };   
            MatrixCursor cur = new MatrixCursor(columns);   
            String[] values = new String[] { "0", content };   
            cur.moveToFirst();   
            cur.addRow(values);   
  
            return cur;   
        } catch (Exception e) {   
            return null;   
        }   
    }   
  
    // ContentProvider 的更新数据接口   
    @Override  
    public int update(Uri uri, ContentValues values, String selection,   
            String[] selectionArgs) {   
        // TODO Auto-generated method stub   
        return 0;   
    }   
}   
  
  
Main.java   
  
代码    
package com.webabcd.contentprovider;   
  
import java.util.Random;   
  
import android.app.Activity;   
import android.content.ContentUris;   
import android.content.ContentValues;   
import android.database.Cursor;   
import android.net.Uri;   
import android.os.Bundle;   
import android.provider.Contacts;   
import android.provider.Contacts.People;   
import android.util.Log;   
import android.view.View;   
import android.widget.Button;   
import android.widget.Toast;   
  
/*  
 * 几个常用的系统内置的 ContentProvider 如下：   
 * content://media/internal/images  这个URI将返回设备上存储的所有图片  
 * content://contacts/people/ 这个URI将返回设备上的所有联系人信息  
 * content://contacts/people/45 这个URI返回单个结果（联系人信息中ID为45的联系人记录）  
 */  
public class Main extends Activity {   
    /** Called when the activity is first created. */  
    @Override  
    public void onCreate(Bundle savedInstanceState) {   
        super.onCreate(savedInstanceState);   
        setContentView(R.layout.main);   
  
        Button btn1 = (Button) this.findViewById(R.id.btn1);   
        btn1.setText("新增联系人记录");   
        btn1.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                Random random = new Random();   
                insertRecords("name" + String.valueOf(random.nextInt()), String   
                        .valueOf(random.nextInt()));   
            }   
        });   
  
        Button btn2 = (Button) this.findViewById(R.id.btn2);   
        btn2.setText("查看联系人记录");   
        btn2.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                displayRecords();   
            }   
        });   
  
        Button btn3 = (Button) this.findViewById(R.id.btn3);   
        btn3.setText("清除联系人记录");   
        btn3.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                deleteRecords();   
            }   
        });   
  
        Button btn4 = (Button) this.findViewById(R.id.btn4);   
        btn4.setText("更新联系人记录");   
        btn4.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                // 此处只是演示，id 来自 People._ID ，可参见 displayRecords() 是如何获取 id 的   
                int id = 0;   
                updateRecord(id, "修改后的name");   
            }   
        });   
  
        Button btn5 = (Button) this.findViewById(R.id.btn5);   
        btn5.setText("新增记录到 MyContentProvider");   
        btn5.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                insertRecord2MyContentProvider("webabcd");   
            }   
        });   
  
        Button btn6 = (Button) this.findViewById(R.id.btn6);   
        btn6.setText("获取记录从 MyContentProvider");   
        btn6.setOnClickListener(new Button.OnClickListener() {   
            public void onClick(View v) {   
                displayRecord2MyContentProvider();   
            }   
        });   
    }   
  
    // 调用 ContentProvider 的插入接口   
    private void insertRecords(String name, String phoneNum) {   
        ContentValues values = new ContentValues();   
        values.put(People.NAME, name);   
        Uri uri = getContentResolver().insert(People.CONTENT_URI, values);   
        Log.d("MyDebug", uri.toString());   
        Uri numberUri = Uri.withAppendedPath(uri,   
                People.Phones.CONTENT_DIRECTORY);   
        Log.d("MyDebug", numberUri.toString());   
  
        values.clear();   
        values.put(Contacts.Phones.TYPE, People.Phones.TYPE_MOBILE);   
        values.put(People.NUMBER, phoneNum);   
        getContentResolver().insert(numberUri, values);   
    }   
  
    // 调用 ContentProvider 的查询接口   
    private void displayRecords() {   
        String[] columns = new String[] { People._ID, People.NAME,   
                People.NUMBER };   
        Uri contacts = People.CONTENT_URI;   
        Log.d("MyDebug", contacts.toString());   
        Cursor cur = managedQuery(contacts, columns, // 要返回的数据字段   
                null, // WHERE子句   
                null, // WHERE 子句的参数   
                null // Order-by子句   
        );   
  
        if (cur.moveToFirst()) {   
            String id = null;   
            String name = null;   
            String phoneNo = null;   
            while (cur.getPosition() != cur.getCount()) {   
                id = cur.getString(cur.getColumnIndex(People._ID));   
                name = cur.getString(cur.getColumnIndex(People.NAME));   
                phoneNo = cur.getString(cur.getColumnIndex(People.NUMBER));   
  
                Toast.makeText(this, id + " / " + name + " / " + phoneNo,   
                        Toast.LENGTH_SHORT).show();   
                cur.moveToNext();   
            }   
        }   
    }   
  
    // 调用 ContentProvider 的删除接口   
    private void deleteRecords() {   
        Uri uri = People.CONTENT_URI;   
        Log.d("MyDebug", uri.toString());   
        getContentResolver().delete(uri, null, null);   
        // getContentResolver().delete(uri, "NAME=" + "'name'", null);   
    }   
  
    // 调用 ContentProvider 的更新接口   
    private void updateRecord(int recordNo, String name) {   
        Uri uri = ContentUris.withAppendedId(People.CONTENT_URI, recordNo);   
        Log.d("MyDebug", uri.toString());   
        ContentValues values = new ContentValues();   
        values.put(People.NAME, name);   
        getContentResolver().update(uri, values, null, null);   
    }   
  
       
    // 调用自定义 ContentProvider 的插入接口   
    private void insertRecord2MyContentProvider(String name) {   
        ContentValues values = new ContentValues();   
        values.put(MyUser.User.USER_NAME, name);   
        getContentResolver().insert(MyUser.User.CONTENT_URI, values);   
  
    }   
  
    // 调用自定义 ContentProvider 的查询接口   
    private void displayRecord2MyContentProvider() {   
        String[] columns = new String[] { MyUser.User.USER_NAME };   
        Uri uri = MyUser.User.CONTENT_URI;   
        Cursor cur = managedQuery(uri, columns, null, null, null);   
  
        while (cur.getPosition() != cur.getCount()) {   
            String id = cur.getString(cur.getColumnIndex(People._ID));   
            String name = cur.getString(cur.getColumnIndex(MyUser.User.USER_NAME));   
            Toast.makeText(this,   
                    id + " / " + name,   
                    Toast.LENGTH_SHORT).show();   
            cur.moveToNext();   
        }   
    }   
}   
  
AndroidManifest.xml   
  
代码    
<?xml version="1.0" encoding="utf-8"?>   
<manifest xmlns:android="http://schemas.android.com/apk/res/android"  
      package="com.webabcd.contentprovider"  
      android:versionCode="1"  
      android:versionName="1.0">   
    <application android:icon="@drawable/icon" android:label="@string/app_name">   
        <activity android:name=".Main"  
                  android:label="@string/app_name">   
            <intent-filter>   
                <action android:name="android.intent.action.MAIN" />   
                <category android:name="android.intent.category.LAUNCHER" />   
            </intent-filter>   
        </activity>   
           
        <!--   
            配置一个自定义的 ContentProvider"   
        -->   
        <provider android:name="MyContentProvider" android:authorities="com.webabcd.MyContentProvider" />   
    </application>   
    <uses-permission android:name="android.permission.WRITE_CONTACTS"></uses-permission>   
    <uses-permission android:name="android.permission.READ_CONTACTS"></uses-permission>   
    <uses-sdk android:minSdkVersion="3" />   
</manifest>