系出名门Android(9) - 数据库支持(SQLite), - android

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

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 DemoMyUser.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>
系出名门Android(9) - 数据库支持(SQLite),

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