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

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

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>