创建自己的内容提供器

package demo.jq.com.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;

/**
 * @author jim
 */
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 = "demo.jq.com.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 int delete(Uri uri, String selection, String[] selectionArgs) {
        // 删除数据
        SQLiteDatabase db = dbHelper.getReadableDatabase();

        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 "book.dir";
            case BOOK_ITEM:
                return "book.item";
            case CATEGORY_DIR:
                return "category.dir";
            case CATEGORY_ITEM:
                return "category.item";
        }
        return null;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        // 添加数据
        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 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) {
        // 查询数据
        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 int update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {
        // 修改数据
        SQLiteDatabase db = dbHelper.getReadableDatabase();

        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;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/add_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Add to Book"
        />

    <Button
        android:id="@+id/update_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Update Book"
        />


    <Button
        android:id="@+id/delete_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Delete From Book"
        />

    <Button
        android:id="@+id/query_data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Query From Book"
        />
</LinearLayout>

package demo.jq.com.providertest;

import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

/**
 * @author jim
 */
public class MainActivity extends AppCompatActivity {
    private String newId;
    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        // 初始化添加数据按钮
        Button addData = (Button) findViewById(R.id.add_data);
        addData.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                // 添加数据
                Uri uri = Uri.parse("content://demo.jq.com.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",22.85);

                Uri newUri = getContentResolver().insert(uri,values);
                newId = newUri.getPathSegments().get(1);
            }
        });

        // 更改数据
        Button updateData = (Button) findViewById(R.id.update_data);
        updateData.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                Uri uri = Uri.parse("content://demo.jq.com.databasetest.provider/book/"+newId);
                ContentValues values = new ContentValues();
                values.put("name","A Storm of Swords");
                values.put("pages",1246);
                values.put("price",24.05);

                getContentResolver().update(uri,values,null,null);
            }
        });

        // 删除数据
        Button deleteData = (Button) findViewById(R.id.delete_data);
        deleteData.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                Uri uri = Uri.parse("content://demo.jq.com.databasetest.provider/book/"+newId);
                getContentResolver().delete(uri,null,null);
            }
        });

        // 查询数据
        Button queryData = (Button) findViewById(R.id.query_data);
        queryData.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                // 查询数据
                Uri uri = Uri.parse("content://demo.jq.com.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(TAG,"book name is "+name);
                        Log.d(TAG,"book author is "+author);
                        Log.d(TAG,"book pages is "+pages);
                        Log.d(TAG,"book price is "+price);
                    }
                }

                cursor.close();

            }
        });
    }
}