Android Open Source - streaming_project Media Manager

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License

The source code is released under:

GNU General Public License

Java Source Code

package com.example.streaming.streaming;
//  w w w  .  ja va2s.  com

import android.content.Context;
import android.util.Log;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

// TODO: why do we need this class? Can we just use directly MediaDatabaseHelper instead?
// MediaManager will create a storage mechanism for the Streaming app that uses a database to store
// data about media.
// NOTE: it provides a database API that the rest of the app uses to store and retrieve data
public class MediaManager {
    // For debugging
    private static final String TAG = "MediaManager";

    private static MediaManager sMediaManager;
    private Context mAppContext;
    private MediaDatabaseHelper mHelper;

    // The private constructor forces users to use MediaManager.get(Context)
    private MediaManager(Context appContext) {
        mAppContext = appContext;
        mHelper = new MediaDatabaseHelper(mAppContext);
        // NOTE: every time the app is started, I drop the media Table if it exists and re-create it
        // I do this because I don't want to add the same data over and over again after I start the
        // app
        // TODO: see if I am doing right. See http://stackoverflow.com/questions/20192642/android-onupgrade-not-calling-at-database-upgrade, http://stackoverflow.com/questions/7647566/why-is-onupgrade-not-being-invoked-on-android-sqlite-database
        // TODO: if we go back to MainActivity from MediaListFragment, and then we press the getListFiles button, we will add the same data again in the db
        // TODO: because we are not calling this constructor which destroys the db and re-create it.
        mHelper.onUpgrade(mHelper.getReadableDatabase(), 1, 2);
    }

    public static MediaManager get(Context c) {
        if (sMediaManager == null) {
            // Use the application context to avoid leaking activities
            sMediaManager = new MediaManager(c.getApplicationContext());
        }
        return sMediaManager;
    }

    // Creates and inserts a new Media into the database. More precisely, the JSONObject
    // representing a media file will be used to create an instance of Media that will then be added
    // to the database.
    // TODO: not used anymore. Been replaced by insertListOfMedia.
    public void insertMedia(JSONObject obj) throws JSONException {
        Media media = new Media(obj);
        mHelper.insertMedia(media);
    }

    // TODO: add description
    public void insertListOfMedia(JSONArray array) throws JSONException {
        long startTime = System.currentTimeMillis();
        mHelper.getWritableDatabase().beginTransaction();
        // Convert the JSONObject into an instance of Media and insert the Media object into the
        // database. TODO: Should we use a loader to do the work?
        // TODO: When inserting the media info into the database, the app is not responsive. It freezes while the database is being filled
        for (int i = 0; i < array.length(); i++) {
            Media media = new Media(array.getJSONObject(i));
            mHelper.insertMedia(media);
        }
        mHelper.getWritableDatabase().setTransactionSuccessful();
        mHelper.getWritableDatabase().endTransaction();

        long diff = System.currentTimeMillis() - startTime;
        Log.d(TAG, "Exec Time: " + Long.toString(diff) + "ms");
    }

    // TODO: add description
    public void bulkInsertListOfMedia(JSONArray array) throws JSONException {
        long startTime = System.currentTimeMillis();
        mHelper.getWritableDatabase().beginTransaction();
        // Convert the JSONObject into an instance of Media and insert the Media object into the
        // database. TODO: Should we use a loader to do the work?
        // TODO: When inserting the media info into the database, the app is not responsive. It freezes while the database is being filled
        for (int i = 0; i < array.length(); i++) {
            Media media = new Media(array.getJSONObject(i));
            mHelper.insertMedia(media);
        }
        mHelper.getWritableDatabase().setTransactionSuccessful();
        mHelper.getWritableDatabase().endTransaction();

        long diff = System.currentTimeMillis() - startTime;
        Log.d(TAG, "Exec Time: " + Long.toString(diff) + "ms");
    }

    // Proxy media queries
    // NOTE: it is called in MediaListFragment
    public MediaDatabaseHelper.MediaCursor queryMediaList() {
        return mHelper.queryMediaList();
    }

    // Pulls a media out of the first row of the MediaCursor retrieved from queryMedia()
    public Media getMedia(long id) {
        Media media = null;
        MediaDatabaseHelper.MediaCursor cursor = mHelper.queryMedia(id);
        // Move the MediaCursor to the first row in the results
        cursor.moveToFirst();
        // If you got a row, get a media
        // NOTE: isAfterLast() returns false if there are any results at all
        if (!cursor.isAfterLast())
            // Since there is a result, we can safely ask for a Media for this row
            media = cursor.getMedia();
        // NOTE: Since the caller of this method will not have access to the MediaCursor, you must
        // be careful to call close() on it before returning, so that the database can release any
        // resources associated with the cursor from memory as soon as possible.
        cursor.close();
        return media;
    }
}

Java Source Code List

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