每天进步一点----- 内容提供者ContentProvider

一个简单的读取系统联系人

package com.example.contactstest;

import java.util.ArrayList;
import java.util.List;

import android.os.Bundle;
import android.provider.ContactsContract;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.app.Activity;
import android.database.Cursor;

public class MainActivity extends Activity {

    ListView contactsView;

    ArrayAdapter<String> adapter;

    List<String> contactsList = new ArrayList<String>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        contactsView = (ListView) findViewById(R.id.contacts_view);
        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, contactsList);
        contactsView.setAdapter(adapter);
        readContacts();
    }

    private void readContacts() {
        Cursor cursor = null;
        try {
            cursor = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
                    null, null, null, null);
            while (cursor.moveToNext()) {
                String displayName = cursor.getString(cursor
                        .getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
                String number = cursor.getString(cursor
                        .getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
                contactsList.add(displayName + "\n" + number);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (cursor != null) {
                cursor.close();
            }
        }
    }

}

 

创建自己的内容提供器

在这六个方法中，相信大多数你都已经非常熟悉了，我再来简单介绍一下吧。

1. onCreate() 初始化内容提供器的时候调用。通常会在这里完成对数据库的创建和升级等操作， 返回 true 表示内容提供器初始化成功，返回 false 则表示失败。注意，只有当存在 ContentResolver尝试访问我们程序中的数据时，内容提供器才会被初始化。

2. query() 从内容提供器中查询数据。使用 uri参数来确定查询哪张表，projection参数用于确 定查询哪些列，selection和 selectionArgs参数用于约束查询哪些行，sortOrder参数用于 对结果进行排序，查询的结果存放在 Cursor对象中返回。

3. insert() 向内容提供器中添加一条数据。使用 uri参数来确定要添加到的表，待添加的数据 保存在 values参数中。添加完成后，返回一个用于表示这条新记录的 URI。

4. update() 更新内容提供器中已有的数据。使用 uri参数来确定更新哪一张表中的数据，新数 据保存在 values参数中，selection和 selectionArgs参数用于约束更新哪些行，受影响的 行数将作为返回值返回。

5. delete() 从内容提供器中删除数据。使用 uri参数来确定删除哪一张表中的数据，selection 和 selectionArgs参数用于约束删除哪些行，被删除的行数将作为返回值返回。

6. getType() 根据传入的内容 URI来返回相应的 MIME类型。 可以看到，几乎每一个方法都会带有Uri这个参数，这个参数也正是调用ContentResolver 的增删改查方法时传递过来的。而现在，我们需要对传入的 Uri参数进行解析，从中分析出 调用方期望访问的表和数据

package com.example.databasetest;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;

public class DatabaseProvider extends ContentProvider {

    public static final int BOOK_DIR = 0;

    public static final int BOOK_ITEM = 1;

    public static final int CATEGORY_DIR = 2;

    public static final int CATEGORY_ITEM = 3;

    public static final String AUTHORITY = "com.example.databasetest.provider";

    private static UriMatcher uriMatcher;

    private MyDatabaseHelper dbHelper;

    static {
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        uriMatcher.addURI(AUTHORITY, "book", BOOK_DIR);
        uriMatcher.addURI(AUTHORITY, "book/#", BOOK_ITEM);
        uriMatcher.addURI(AUTHORITY, "category", CATEGORY_DIR);
        uriMatcher.addURI(AUTHORITY, "category/#", CATEGORY_ITEM);
    }

    @Override
    public boolean onCreate() {
        dbHelper = new MyDatabaseHelper(getContext(), "BookStore.db", null, 2);
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
            String sortOrder) {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor cursor = null;
        switch (uriMatcher.match(uri)) {
        case BOOK_DIR:
            cursor = db.query("Book", projection, selection, selectionArgs, null, null, sortOrder);
            break;
        case BOOK_ITEM:
            String bookId = uri.getPathSegments().get(1);
            cursor = db.query("Book", projection, "id = ?", new String[] { bookId }, null, null,
                    sortOrder);
            break;
        case CATEGORY_DIR:
            cursor = db.query("Category", projection, selection, selectionArgs, null, null,
                    sortOrder);
            break;
        case CATEGORY_ITEM:
            String categoryId = uri.getPathSegments().get(1);
            cursor = db.query("Category", projection, "id = ?", new String[] { categoryId }, null,
                    null, sortOrder);
            break;
        default:
            break;
        }
        return cursor;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        Uri uriReturn = null;
        switch (uriMatcher.match(uri)) {
        case BOOK_DIR:
        case BOOK_ITEM:
            long newBookId = db.insert("Book", null, values);
            uriReturn = Uri.parse("content://" + AUTHORITY + "/book/" + newBookId);
            break;
        case CATEGORY_DIR:
        case CATEGORY_ITEM:
            long newCategoryId = db.insert("Category", null, values);
            uriReturn = Uri.parse("content://" + AUTHORITY + "/category/" + newCategoryId);
            break;
        default:
            break;
        }
        return uriReturn;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int updatedRows = 0;
        switch (uriMatcher.match(uri)) {
        case BOOK_DIR:
            updatedRows = db.update("Book", values, selection, selectionArgs);
            break;
        case BOOK_ITEM:
            String bookId = uri.getPathSegments().get(1);
            updatedRows = db.update("Book", values, "id = ?", new String[] { bookId });
            break;
        case CATEGORY_DIR:
            updatedRows = db.update("Category", values, selection, selectionArgs);
            break;
        case CATEGORY_ITEM:
            String categoryId = uri.getPathSegments().get(1);
            updatedRows = db.update("Category", values, "id = ?", new String[] { categoryId });
            break;
        default:
            break;
        }
        return updatedRows;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int deletedRows = 0;
        switch (uriMatcher.match(uri)) {
        case BOOK_DIR:
            deletedRows = db.delete("Book", selection, selectionArgs);
            break;
        case BOOK_ITEM:
            String bookId = uri.getPathSegments().get(1);
            deletedRows = db.delete("Book", "id = ?", new String[] { bookId });
            break;
        case CATEGORY_DIR:
            deletedRows = db.delete("Category", selection, selectionArgs);
            break;
        case CATEGORY_ITEM:
            String categoryId = uri.getPathSegments().get(1);
            deletedRows = db.delete("Category", "id = ?", new String[] { categoryId });
            break;
        default:
            break;
        }
        return deletedRows;
    }

    @Override
    public String getType(Uri uri) {
        switch (uriMatcher.match(uri)) {
        case BOOK_DIR:
            return "vnd.android.cursor.dir/vnd.com.example.databasetest.provider.book";
        case BOOK_ITEM:
            return "vnd.android.cursor.item/vnd.com.example.databasetest.provider.book";
        case CATEGORY_DIR:
            return "vnd.android.cursor.dir/vnd.com.example.databasetest.provider.category";
        case CATEGORY_ITEM:
            return "vnd.android.cursor.item/vnd.com.example.databasetest.provider.category";
        }
        return null;
    }

}

 

package com.example.databasetest;

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

public class MyDatabaseHelper extends SQLiteOpenHelper {

    public static final String CREATE_BOOK = "create table Book ("
            + "id integer primary key autoincrement, " 
            + "author text, "
            + "price real, " 
            + "pages integer, " 
            + "name text)";
    
    public static final String CREATE_CATEGORY = "create table Category ("
            + "id integer primary key autoincrement, "
            + "category_name text, "
            + "category_code integer)";

    public MyDatabaseHelper(Context context, String name,
            CursorFactory factory, int version) {
        super(context, name, factory, version);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_BOOK);
        db.execSQL(CREATE_CATEGORY);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("drop table if exists Book");
        db.execSQL("drop table if exists Category");
        onCreate(db);
    }

}

 

package com.example.databasetest;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;

public class DatabaseProvider extends ContentProvider {

    public static final int BOOK_DIR = 0;

    public static final int BOOK_ITEM = 1;

    public static final int CATEGORY_DIR = 2;

    public static final int CATEGORY_ITEM = 3;

    public static final String AUTHORITY = "com.example.databasetest.provider";

    private static UriMatcher uriMatcher;

    private MyDatabaseHelper dbHelper;

    static {
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        uriMatcher.addURI(AUTHORITY, "book", BOOK_DIR);
        uriMatcher.addURI(AUTHORITY, "book/#", BOOK_ITEM);
        uriMatcher.addURI(AUTHORITY, "category", CATEGORY_DIR);
        uriMatcher.addURI(AUTHORITY, "category/#", CATEGORY_ITEM);
    }

    @Override
    public boolean onCreate() {
        dbHelper = new MyDatabaseHelper(getContext(), "BookStore.db", null, 2);
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
            String sortOrder) {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor cursor = null;
        switch (uriMatcher.match(uri)) {
        case BOOK_DIR:
            cursor = db.query("Book", projection, selection, selectionArgs, null, null, sortOrder);
            break;
        case BOOK_ITEM:
            String bookId = uri.getPathSegments().get(1);
            cursor = db.query("Book", projection, "id = ?", new String[] { bookId }, null, null,
                    sortOrder);
            break;
        case CATEGORY_DIR:
            cursor = db.query("Category", projection, selection, selectionArgs, null, null,
                    sortOrder);
            break;
        case CATEGORY_ITEM:
            String categoryId = uri.getPathSegments().get(1);
            cursor = db.query("Category", projection, "id = ?", new String[] { categoryId }, null,
                    null, sortOrder);
            break;
        default:
            break;
        }
        return cursor;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        Uri uriReturn = null;
        switch (uriMatcher.match(uri)) {
        case BOOK_DIR:
        case BOOK_ITEM:
            long newBookId = db.insert("Book", null, values);
            uriReturn = Uri.parse("content://" + AUTHORITY + "/book/" + newBookId);
            break;
        case CATEGORY_DIR:
        case CATEGORY_ITEM:
            long newCategoryId = db.insert("Category", null, values);
            uriReturn = Uri.parse("content://" + AUTHORITY + "/category/" + newCategoryId);
            break;
        default:
            break;
        }
        return uriReturn;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int updatedRows = 0;
        switch (uriMatcher.match(uri)) {
        case BOOK_DIR:
            updatedRows = db.update("Book", values, selection, selectionArgs);
            break;
        case BOOK_ITEM:
            String bookId = uri.getPathSegments().get(1);
            updatedRows = db.update("Book", values, "id = ?", new String[] { bookId });
            break;
        case CATEGORY_DIR:
            updatedRows = db.update("Category", values, selection, selectionArgs);
            break;
        case CATEGORY_ITEM:
            String categoryId = uri.getPathSegments().get(1);
            updatedRows = db.update("Category", values, "id = ?", new String[] { categoryId });
            break;
        default:
            break;
        }
        return updatedRows;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int deletedRows = 0;
        switch (uriMatcher.match(uri)) {
        case BOOK_DIR:
            deletedRows = db.delete("Book", selection, selectionArgs);
            break;
        case BOOK_ITEM:
            String bookId = uri.getPathSegments().get(1);
            deletedRows = db.delete("Book", "id = ?", new String[] { bookId });
            break;
        case CATEGORY_DIR:
            deletedRows = db.delete("Category", selection, selectionArgs);
            break;
        case CATEGORY_ITEM:
            String categoryId = uri.getPathSegments().get(1);
            deletedRows = db.delete("Category", "id = ?", new String[] { categoryId });
            break;
        default:
            break;
        }
        return deletedRows;
    }

    @Override
    public String getType(Uri uri) {
        switch (uriMatcher.match(uri)) {
        case BOOK_DIR:
            return "vnd.android.cursor.dir/vnd.com.example.databasetest.provider.book";
        case BOOK_ITEM:
            return "vnd.android.cursor.item/vnd.com.example.databasetest.provider.book";
        case CATEGORY_DIR:
            return "vnd.android.cursor.dir/vnd.com.example.databasetest.provider.category";
        case CATEGORY_ITEM:
            return "vnd.android.cursor.item/vnd.com.example.databasetest.provider.category";
        }
        return null;
    }

}

 

 读取第三方的内容

package com.example.providertest;

import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {
    
    private String newId;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button addData = (Button) findViewById(R.id.add_data);
        addData.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Uri uri = Uri
                        .parse("content://com.example.databasetest.provider/book");
                ContentValues values = new ContentValues();
                values.put("name", "A Clash of Kings");
                values.put("author", "George Martin");
                values.put("pages", 1040);
                values.put("price", 55.55);
                Uri newUri = getContentResolver().insert(uri, values);
                newId = newUri.getPathSegments().get(1);
            }
        });
        Button queryData = (Button) findViewById(R.id.query_data);
        queryData.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Uri uri = Uri
                        .parse("content://com.example.databasetest.provider/book");
                Cursor cursor = getContentResolver().query(uri, null, null,
                        null, null);
                if (cursor != null) {
                    while (cursor.moveToNext()) {
                        String name = cursor.getString(cursor
                                .getColumnIndex("name"));
                        String author = cursor.getString(cursor
                                .getColumnIndex("author"));
                        int pages = cursor.getInt(cursor
                                .getColumnIndex("pages"));
                        double price = cursor.getDouble(cursor
                                .getColumnIndex("price"));
                        Log.d("MainActivity", "book name is " + name);
                        Log.d("MainActivity", "book author is " + author);
                        Log.d("MainActivity", "book pages is " + pages);
                        Log.d("MainActivity", "book price is " + price);
                    }
                    cursor.close();
                }
            }
        });
        Button updateData = (Button) findViewById(R.id.update_data);
        updateData.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Uri uri = Uri
                        .parse("content://com.example.databasetest.provider/book/" + newId);
                ContentValues values = new ContentValues();
                values.put("name", "A Storm of Swords");
                values.put("pages", 1216);
                values.put("price", 24.05);
                getContentResolver().update(uri, values, null, null);
            }
        });
        Button deleteData = (Button) findViewById(R.id.delete_data);
        deleteData.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Uri uri = Uri
                        .parse("content://com.example.databasetest.provider/book/" + newId);
                getContentResolver().delete(uri, null, null);
            }
        }); 
    }

}