SimpleCursorAdapter的旧构造函数已弃用..真的吗？

Question

这里说它SimpleCursorAdapter的API级别1构造函数已被弃用,建议使用LoaderManager和CursorLoader.

但是深入研究LoaderManager和CursorLoader使用我发现这个例子里面的内部类扩展了一个ListFragment(我认为是Fragment本身的扩展),我们创建了一个CursorLoader.一切似乎确定,不同的是,其实CursorLoader需要一个Uri作为参数.所以这意味着我需要创建一个ContentProvider访问我的数据库的权限.

我必须承认,为了创建一个简单的ListView来自数据库的项目,我们必须完成所有这些操作才能看起来有点过分.特别是如果我不打算将我的数据库数据提供给其他应用程序,并且内容提供商的主要目的是这样做.

那真的值得吗？

特别是在像我这样的情况下,要获取的内容可能会很小.我认真考虑用旧方式做,你怎么说？

Answer 1

我写了一个不需要内容提供者的简单CursorLoader:

import android.content.Context;
import android.database.Cursor;
import android.support.v4.content.AsyncTaskLoader;

/**
 * Used to write apps that run on platforms prior to Android 3.0. When running
 * on Android 3.0 or above, this implementation is still used; it does not try
 * to switch to the framework's implementation. See the framework SDK
 * documentation for a class overview.
 *
 * This was based on the CursorLoader class
 */
public abstract class SimpleCursorLoader extends AsyncTaskLoader<Cursor> {
    private Cursor mCursor;

    public SimpleCursorLoader(Context context) {
        super(context);
    }

    /* Runs on a worker thread */
    @Override
    public abstract Cursor loadInBackground();

    /* Runs on the UI thread */
    @Override
    public void deliverResult(Cursor cursor) {
        if (isReset()) {
            // An async query came in while the loader is stopped
            if (cursor != null) {
                cursor.close();
            }
            return;
        }
        Cursor oldCursor = mCursor;
        mCursor = cursor;

        if (isStarted()) {
            super.deliverResult(cursor);
        }

        if (oldCursor != null && oldCursor != cursor && !oldCursor.isClosed()) {
            oldCursor.close();
        }
    }

    /**
     * Starts an asynchronous load of the contacts list data. When the result is ready the callbacks
     * will be called on the UI thread. If a previous load has been completed and is still valid
     * the result may be passed to the callbacks immediately.
     * <p/>
     * Must be called from the UI thread
     */
    @Override
    protected void onStartLoading() {
        if (mCursor != null) {
            deliverResult(mCursor);
        }
        if (takeContentChanged() || mCursor == null) {
            forceLoad();
        }
    }

    /**
     * Must be called from the UI thread
     */
    @Override
    protected void onStopLoading() {
        // Attempt to cancel the current load task if possible.
        cancelLoad();
    }

    @Override
    public void onCanceled(Cursor cursor) {
        if (cursor != null && !cursor.isClosed()) {
            cursor.close();
        }
    }

    @Override
    protected void onReset() {
        super.onReset();

        // Ensure the loader is stopped
        onStopLoading();

        if (mCursor != null && !mCursor.isClosed()) {
            mCursor.close();
        }
        mCursor = null;
    }
}

它只需要AsyncTaskLoader上课.Android 3.0或更高版本中的一个,或兼容包附带的那个.