java - ContentResolver.notifyChange 不工作

Question

我想玩一个 ContentProvider 示例，但我遇到了一个我似乎无法解决的问题。

这个例子包含一个Activity:

import android.content.ContentUris;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.support.v4.widget.SimpleCursorAdapter;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ListView;


public class MainActivity extends ActionBarActivity
{

    final String LOG_TAG = "myLogs";

    final Uri CONTACT_URI = Uri.parse("content://zulfigarov.com.trainingprj.MyContactsProvider/contacts");

    final String CONTACT_NAME = "name";
    final String CONTACT_EMAIL = "email";

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

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

        startManagingCursor(cursor);

        String[] from = {"name", "email"};
        int[] to = {android.R.id.text1, android.R.id.text2};

        SimpleCursorAdapter adapter
                = new SimpleCursorAdapter(this, android.R.layout.simple_list_item_2, cursor, from, to, 0);

        ListView lvContact = (ListView)findViewById(R.id.lvContacts);
        lvContact.setAdapter(adapter);
    }

    public void onClickInsert(View view)
    {
        ContentValues cv = new ContentValues();
        cv.put(CONTACT_NAME, "name 4");
        cv.put(CONTACT_EMAIL, "email 4");
        Uri newUri = getContentResolver().insert(CONTACT_URI, cv);

        Log.d(LOG_TAG, "insert, result Uri: " + newUri.toString());
    }

    public void onClickUpdate(View view)
    {
        ContentValues cv = new ContentValues();
        cv.put(CONTACT_NAME, "name 5");
        cv.put(CONTACT_EMAIL, "email 5");
        Uri uri = ContentUris.withAppendedId(CONTACT_URI, 2);
        int cnt = getContentResolver().update(uri, cv, null, null);

        Log.d(LOG_TAG, "update, count = " + cnt);
    }

    public void onClickDelete(View view)
    {
        Uri uri = ContentUris.withAppendedId(CONTACT_URI, 3);
        int cnt = getContentResolver().delete(uri, null, null);

        Log.d(LOG_TAG, "delete, count = " + cnt);
    }

    public void onClickError(View view)
    {
        Uri uri = Uri.parse("content://zulfigarov.com.trainingprj.MyContentProvider/phones");

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

        }
        catch (Exception ex)
        {
            Log.d(LOG_TAG, "Error: " + ex.getClass() + ", " + ex.getMessage());
        }

    }
}

和一个ContentProvider:

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.net.Uri;
import android.text.TextUtils;
import android.util.Log;

public class MyContactsProvider extends ContentProvider
{

    final String LOG_TAG = "myLogs";

    static final String DB_NAME = "mydb";
    static final int DB_VERSION = 1;

    static final String CONTACT_TABLE = "contacts";

    static final String CONTACT_ID = "_id";
    static final String CONTACT_NAME = "name";
    static final String CONTACT_EMAIL = "email";

    static final String DB_CREATE = "CREATE TABLE " + CONTACT_TABLE + "("
                                     + CONTACT_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
                                     + CONTACT_NAME + " TEXT, "
                                     + CONTACT_EMAIL + " TEXT" + ");";

    static final String AUTHORITY = "zulfigarov.com.trainingprj.MyContactsProvider";

    static final String CONTACT_PATH = "contacts";

    public static final Uri CONTACT_CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/" + CONTACT_PATH);

    static final String CONTACT_CONTENT_TYPE = "vnd.android.cursor.dir/vnd." + AUTHORITY + "." + CONTACT_PATH;

    static final String CONTACT_CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd." + AUTHORITY + "." + CONTACT_PATH;


    static final int URI_CONTACTS = 1;

    static final int URI_CONTACTS_ID = 2;

    private static final UriMatcher uriMatcher;
    static
    {
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        uriMatcher.addURI(AUTHORITY, CONTACT_PATH, URI_CONTACTS);
        uriMatcher.addURI(AUTHORITY, CONTACT_PATH + "/#", URI_CONTACTS_ID);
    }

    DBHelper dbHelper;
    SQLiteDatabase db;

    @Override
    public boolean onCreate()
    {
        Log.d(LOG_TAG, "onCreate provider");
        dbHelper = new DBHelper(getContext());
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)
    {
        Log.d(LOG_TAG,"query, " + uri.toString());

        switch (uriMatcher.match(uri))
        {
            case URI_CONTACTS:
                Log.d(LOG_TAG, "URI_CONTACTS");
                if(TextUtils.isEmpty(sortOrder))
                {
                    sortOrder = CONTACT_NAME + " ASC";
                }
                break;

            case URI_CONTACTS_ID:
                String id = uri.getLastPathSegment();
                Log.d(LOG_TAG, "URI_CONTACTS_ID");

                if (TextUtils.isEmpty(selection))
                    selection = CONTACT_ID + " = " + id;
                else
                    selection = selection + " AND " + CONTACT_ID + " = " + id;
                break;

            default:
                throw new IllegalArgumentException("Wrong URI: " + uri);
        }

        db = dbHelper.getWritableDatabase();
        Cursor cursor = db.query(CONTACT_TABLE, projection, selection,
                selectionArgs, null, null, sortOrder);

        cursor.setNotificationUri(getContext().getContentResolver(),CONTACT_CONTENT_URI);

        return cursor;
    }

    @Override
    public String getType(Uri uri)
    {
        Log.d(LOG_TAG, "getTYpe, " + uri.toString());
        switch (uriMatcher.match(uri))
        {
            case URI_CONTACTS:
                return CONTACT_CONTENT_TYPE;
            case URI_CONTACTS_ID:
                return CONTACT_CONTENT_ITEM_TYPE;
        }
        return null;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values)
    {
        Log.d(LOG_TAG,"insert, " + uri.toString());

        if(uriMatcher.match(uri) != URI_CONTACTS)
            throw new IllegalArgumentException("Wrong URI: " + uri);

        db = dbHelper.getWritableDatabase();
        long rowID = db.insert(CONTACT_TABLE, null, values);
        Uri resultUri = ContentUris.withAppendedId(CONTACT_CONTENT_URI, rowID);
        getContext().getContentResolver().notifyChange(resultUri, null);

        return resultUri;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs)
    {

        Log.d(LOG_TAG,"delete, " + uri.toString());
        switch (uriMatcher.match(uri))
        {
            case URI_CONTACTS:
                Log.d(LOG_TAG,"URI_CONTACTS");
                break;

            case URI_CONTACTS_ID:
                String id = uri.getLastPathSegment();
                Log.d(LOG_TAG,"URI_CONTACTS_ID, " + id);
                if(TextUtils.isEmpty(selection))
                {
                    selection = CONTACT_ID + " = " + id;
                }
                else
                {
                    selection = selection + " AND " + CONTACT_ID + " = " + id;
                }
                break;

            default:
                throw new IllegalArgumentException("Wrong URI: " + uri);
        }

        db = dbHelper.getWritableDatabase();
        int cnt = db.delete(CONTACT_TABLE, selection, selectionArgs);
        getContext().getContentResolver().notifyChange(uri, null);

        return cnt;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs)
    {
        Log.d(LOG_TAG,"update, " + uri.toString());

        switch (uriMatcher.match(uri))
        {
            case URI_CONTACTS:
                Log.d(LOG_TAG,"URI_CONTACTS");
                break;
            case URI_CONTACTS_ID:
                String id = uri.getLastPathSegment();
                Log.d(LOG_TAG, "URI_CONTACTS_ID");
                if(TextUtils.isEmpty(selection))
                {
                    selection = CONTACT_ID;
                }
                else
                {
                    selection = selection + " AND " + CONTACT_ID + " = " + id;
                }
                break;
            default:
                throw new IllegalArgumentException("Wrong URI: " + uri);
        }
        db = dbHelper.getWritableDatabase();
        int cnt = db.update(CONTACT_TABLE, values, selection, selectionArgs);
        getContext().getContentResolver().notifyChange(uri,null);
        return cnt;
    }

    private class DBHelper extends SQLiteOpenHelper
    {

        public DBHelper(Context context)
        {
            super(context, DB_NAME, null, DB_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db)
        {
            db.execSQL(DB_CREATE);
            ContentValues cv = new ContentValues();

            for (int i = 1; i <= 3; i++)
            {
                cv.put(CONTACT_NAME, "name " + i);
                cv.put(CONTACT_EMAIL, "email " + i);
                db.insert(CONTACT_TABLE, null, cv);
            }
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
        {

        }
    }
}

麻烦的是，当我点击按钮(触发 onClickInsert、onClickUpdate 等 MainActivity 中的方法)时，它会更新数据库，但不更新 Activity 的 ListView。看起来像

getContext().getContentResolver().notifyChange(resultUri, null);

无法正常工作。所以我找不到我哪里错了。

Answer 1

使用 CursorLoaders 加载数据并填充 ListView。

http://developer.android.com/reference/android/content/CursorLoader.html

然后在插入、更新或删除时使用getContext().getContentResolver().notifyChange(resultUri, null);!

如果没有 CursorLoaders，您将不得不使用 ContentObservers

因此，尽管 DB 在后台更新并且您正在使用 notifyChange() 但没有人在听它!