Android ContentProvider 使用实例

MyDatabaseHelper.java 的内容如下：

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;

/**
 * Created by toby on 17-12-28.
 */

public class MyDatabaseHelper extends SQLiteOpenHelper {

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

    private static final String CREATE_CATEGORY = "create table Category (" +
            "id integer primary key autoincrement, " +
            "category_name text, " +
            "category_code integer)";

    private Context mContext;

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

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        sqLiteDatabase.execSQL(CREATE_BOOK);
        sqLiteDatabase.execSQL(CREATE_CATEGORY);
        Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
        switch (oldVersion) {
            case 1:
                sqLiteDatabase.execSQL(CREATE_CATEGORY);
                // 不要加 break，以保证每次数据库的修改都会被执行
                // break;
            case 2:
                sqLiteDatabase.execSQL("alter table Book add column category_id integer");
                // 不要加 break，以保证每次数据库的修改都会被执行
                // break;
            default:
        }
    }
}

MyProvider.java 的代码如下：

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;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;

/**
 * Created by toby on 18-1-2.
 */

public class MyProvider 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.syberos.learnandroid.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;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] strings, @Nullable String s,
                        @Nullable String[] strings1, @Nullable String s1) {

        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor cursor = null;

        switch (uriMatcher.match(uri)) {
            case BOOK_DIR:
                cursor = db.query("Book", strings, s, strings1, null, null, s1);
                break;
            case BOOK_ITEM:
                String bookId = uri.getPathSegments().get(1);
                cursor = db.query("Book", strings, "id = ?", new String[] { bookId },
                        null, null, s1);
                break;
            case CATEGORY_DIR:
                cursor = db.query("Category", strings, s, strings1, null, null, s1);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                cursor = db.query("Category", strings, "id = ?", new String[] { categoryId },
                        null, null, s1);
                break;
            default:
                break;
        }
        return cursor;
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        switch (uriMatcher.match(uri)) {
            case BOOK_DIR:
                return "vdn.android.cursor.dir/"+AUTHORITY+".book";
            case BOOK_ITEM:
                return "vdn.android.cursor.item/"+AUTHORITY+".book";
            case CATEGORY_DIR:
                return "vdn.android.cursor.dir/"+AUTHORITY+".category";
            case CATEGORY_ITEM:
                return "vdn.android.cursor.item/"+AUTHORITY+".category";
            default:
                break;
        }
        return null;
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues contentValues) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        Uri uriReturn = null;

        switch (uriMatcher.match(uri)) {
            case BOOK_DIR:
            case BOOK_ITEM:
                long newBookId = db.insert("Book", null, contentValues);
                uriReturn = Uri.parse("content://" + AUTHORITY + "/book/" + newBookId);
                break;
            case CATEGORY_DIR:
            case CATEGORY_ITEM:
                long newCategoryId = db.insert("Category", null, contentValues);
                uriReturn = Uri.parse("content://" + AUTHORITY + "/category/" + newCategoryId);
                break;
            default:
                break;
        }

        return uriReturn;
    }

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

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues contentValues, @Nullable String s,
                      @Nullable String[] strings) {

        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int updateRows = 0;

        switch (uriMatcher.match(uri)) {
            case BOOK_DIR:
                updateRows = db.update("Book", contentValues, s, strings);
                break;
            case BOOK_ITEM:
                String bookId = uri.getPathSegments().get(1);
                updateRows = db.update("Book", contentValues, "id = ?",
                        new String[] { bookId });
                break;
            case CATEGORY_DIR:
                updateRows = db.update("Category", contentValues, s, strings);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                updateRows = db.update("Category", contentValues, "id = ?",
                        new String[] { categoryId });
                break;
            default:
                break;
        }
        return updateRows;
    }
}

使用的实例代码如下：

import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;

public class MainActivity extends Activity {

    private static final String TAG = "MainActivity";
    private MyDatabaseHelper dbHelper;
    private String newId;

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

        dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 2);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
    }

    public void create(View view) {
        dbHelper.getWritableDatabase();
    }

    public void add(View view) {

        Uri uri = Uri.parse("content://" + MyProvider.AUTHORITY + "/book");

        ContentValues values = new ContentValues();
        values.put("name", "The first");
        values.put("author", "None");
        values.put("pages", 123);
        values.put("price", 12.34);
        Uri newUri = getContentResolver().insert(uri, values);
        newId = newUri.getPathSegments().get(1);
    }

    public void update(View view) {
        Uri uri = Uri.parse("content://" + MyProvider.AUTHORITY + "/book/" + newId);
        ContentValues values = new ContentValues();
        values.put("price","10.00");
        // 不指定，第三和第四个参数，将会更新所有行
        getContentResolver().update(uri, values, "name = ?", new String[] {"The first"});
    }

    public void delete(View view) {
        Uri uri = Uri.parse("content://" + MyProvider.AUTHORITY + "/book/" + newId);
        // 第二个和第三个参数如果不指定将会删除所有行
        getContentResolver().delete(uri, "pages > ?", new String[] {"200"});
    }

    public void query(View view) {

        Uri uri = Uri.parse("content://" + MyProvider.AUTHORITY + "/book");

        Cursor cursor = getContentResolver().query(uri, null, null,
                null, null);

        if (cursor != null && cursor.moveToFirst()) {
            do {
                String value = cursor.getString(cursor.getColumnIndex("name"));
                Log.d(TAG, "Book name is " + value);

                value = cursor.getString(cursor.getColumnIndex("author"));
                Log.d(TAG, "Book author is " + value);

                value = cursor.getString(cursor.getColumnIndex("pages"));
                Log.d(TAG, "Book pages is " + value);

                value = cursor.getString(cursor.getColumnIndex("price"));
                Log.d(TAG, "Book price is " + value);
            } while (cursor.moveToNext());
            cursor.close();
        }
    }

    public void replace(View view) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        db.beginTransaction();
        try {
            db.delete("Book", null, null);
//            if (true) { // 抛出一个异常测试事务
//                throw new NullPointerException();
//            }
            ContentValues values = new ContentValues();
            values.put("name", "The Third");
            values.put("author", "Toby");
            values.put("pages", 720);
            values.put("price", 23.45);
            db.insert("Book", null, values);
            db.setTransactionSuccessful();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            db.endTransaction();
        }
    }
}

布局文件的代码如下：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.syberos.learnandroid.MainActivity">

    <Button
        android:id="@+id/create"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginStart="136dp"
        android:layout_marginTop="22dp"
        android:text="@string/create"
        android:onClick="create"
        />

    <Button
        android:id="@+id/add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/create"
        android:layout_below="@+id/create"
        android:layout_marginTop="17dp"
        android:onClick="add"
        android:text="@string/add"
        />

    <Button
        android:id="@+id/update"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/add"
        android:layout_below="@+id/add"
        android:layout_marginTop="11dp"
        android:onClick="update"
        android:text="@string/update" />

    <Button
        android:id="@+id/delete"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/update"
        android:layout_below="@+id/update"
        android:layout_marginTop="15dp"
        android:onClick="delete"
        android:text="@string/delete" />

    <Button
        android:id="@+id/query"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/delete"
        android:layout_below="@+id/delete"
        android:layout_marginTop="14dp"
        android:text="@string/query"
        android:onClick="query"
        />

    <Button
        android:id="@+id/replace"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignStart="@+id/query"
        android:layout_below="@+id/query"
        android:text="@string/replace"
        android:onClick="replace"
        />


</RelativeLayout>

string 文件的内容如下：

<resources>
    <string name="app_name">LearnAndroid</string>
    <string name="create">create</string>
    <string name="add">add</string>
    <string name="update">update</string>
    <string name="delete">delete</string>
    <string name="query">query</string>
    <string name="replace">replace</string>
</resources>

AndroidManifest.xml 的代码如下：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.syberos.learnandroid">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        
        <provider
            android:name="com.syberos.learnandroid.MyProvider"
            android:authorities="com.syberos.learnandroid.provider"
            android:exported="true" />
    </application>

</manifest>

本文参考自 《Android 第一行代码》