se.chalmers.watchme.database.GenericCursorLoader.java Source code

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Here is the source code for se.chalmers.watchme.database.GenericCursorLoader.java

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/**
 *   GenericCursorLoader.java
 *
 *  Static library support version of the framework's
 *  {@link android.content.CursorLoader}. 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.
 * 
 *  A CursorLoader that has a ICursorHelper that calculates the cursor.
 *
 *   @author lisastenberg
 *   @copyright (c) 2012 Johan Brook, Robin Andersson, Lisa Stenberg, Mattias Henriksson
 *   @license MIT
 */

package se.chalmers.watchme.database;

import android.content.Context;
import android.database.ContentObserver;
import android.database.Cursor;
import android.net.Uri;
import android.os.CancellationSignal;
import android.support.v4.content.CursorLoader;

import java.io.FileDescriptor;
import java.io.PrintWriter;

public class GenericCursorLoader extends CursorLoader {

    private final ForceLoadContentObserver mObserver;
    private Uri mUri;

    private String mSortOrder;

    private Cursor mCursor;
    private CancellationSignal mCancellationSignal;

    private ICursorHelper mCursorHelper;

    /**
     * Creates an empty unspecified CursorLoader. You must follow this with
     * calls to {@link #setUri(Uri)}, {@link #setSelection(String)}, etc to
     * specify the query to perform.
     */
    public GenericCursorLoader(Context context) {
        super(context);
        mObserver = new ForceLoadContentObserver();
    }

    /**
     * Creates a CursorLoader with a cursorHelper that is used to calculate the
     * Cursor in loadCursor()
     * 
     * @param context
     *            The context
     * @param cursorHelper
     *            The CursorHelper
     */
    public GenericCursorLoader(Context context, ICursorHelper cursorHelper) {
        super(context);
        mObserver = new ForceLoadContentObserver();
        mCursorHelper = cursorHelper;

        mUri = mCursorHelper.getUri();
        mSortOrder = mCursorHelper.getSortOrder();
    }

    /* Runs on a worker thread */
    @Override
    public Cursor loadInBackground() {
        synchronized (this) {
            mCancellationSignal = new CancellationSignal();
        }
        try {

            Cursor cursor = mCursorHelper.getCursor();
            if (cursor != null) {

                // Ensure the cursor window is filled
                cursor.getCount();
                registerContentObserver(cursor, mObserver);
            }
            return cursor;
        } finally {
            synchronized (this) {
                mCancellationSignal = null;
            }
        }
    }

    /**
     * Registers an observer to get notifications from the content provider when
     * the cursor needs to be refreshed.
     */
    void registerContentObserver(Cursor cursor, ContentObserver observer) {
        cursor.registerContentObserver(mObserver);
    }

    /* 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.
     * 
     * 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;
    }

    @Override
    public Uri getUri() {
        return mUri;
    }

    @Override
    public void setUri(Uri uri) {
        this.mUri = uri;
    }

    @Override
    public String getSortOrder() {
        return mSortOrder;
    }

    @Override
    public void setSortOrder(String sortOrder) {
        mSortOrder = sortOrder;
    }

    @Override
    public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) {
        super.dump(prefix, fd, writer, args);
        writer.print(prefix);
        writer.print("mUri=");
        writer.println(mUri);
        writer.print(prefix);
        writer.print("mSortOrder=");
        writer.println(mSortOrder);
        writer.print(prefix);
        writer.print("mCursor=");
        writer.println(mCursor);
        writer.print(prefix);
    }

}