Freezing UI while loading JSON using AsyncTaskLoader

Question

I want to load some data from local database, I am using AsynctaskLoader for that purpose. But while data is loading I cant interact with the screen. Whole UI of freezes. I did some research and found that AsyncTaskLoader should be initialized on the worker thread to move the whole process on the worker thread, I tried working that as well but again im getting is freeze in UI.

Here is my AsyncTaskLoader class

public class ArticleDatabaseLoader extends AsyncTaskLoader<List<Article>> {

private int code = 0;

public ArticleDatabaseLoader(Context context, int code) {
    super(context);
    this.code = code;
}

@Override
public List<Article> loadInBackground() {
    List<Article> articleList = new ArrayList<>();
    ArticleTable articleTable = new ArticleTable(getContext());
    ArticleCategory categoryTable = new ArticleCategory(getContext());
    switch (code) {
        case ArticleList:
            articleTable.open();
            categoryTable.open();
            List<String> selected_category = new ArrayList<>();
            for (int i = 0; i < 5; i++) {   /* saving all the selected categories */
                if (getCategoryStatus(getContext(), categories[i]) == 1) {
                    selected_category.add(categories[i]);
                }
            }
            StringBuilder where_query =  new StringBuilder();
            if (selected_category.size() > 0){  /* building the where query for sql */
                for (int i = 0; i < selected_category.size(); i++) {
                    if (i == selected_category.size() - 1) {
                        where_query.append(String.format("%s = '%s'",
                                DBColumn.ArticleCategoryColumn.category_id,
                                selected_category.get(i)));
                    } else {
                        where_query.append(String.format("%s = '%s' OR ",
                                DBColumn.ArticleCategoryColumn.category_id,
                                selected_category.get(i)));
                    }
                }
                Cursor selectedCursor = categoryTable.getArticles(where_query.toString());
                if (selectedCursor != null && selectedCursor.moveToFirst() && selectedCursor.getCount() > 0) {
                    do {
                        String articleId = selectedCursor.getString(selectedCursor.getColumnIndex(DBColumn.ArticleCategoryColumn.article_id));
                        Cursor articleCursor = articleTable.getArticleById(articleId);
                        if (articleCursor != null && articleCursor.moveToFirst()) {
                            articleList.add(articleTable.articleObject(getContext(),articleCursor));
                        }
                        articleCursor.close();
                    } while (selectedCursor.moveToNext());
                }
                if (selectedCursor != null)
                    selectedCursor.close();
            } else {
                Cursor articleListCursor = articleTable.getAllArticles();
                if (articleListCursor != null && articleListCursor.moveToFirst() && articleListCursor.getCount() > 0) {
                    do {
                        articleList.add(articleTable.articleObject(getContext(),articleListCursor));
                    } while (articleListCursor.moveToNext());
                }
                if (articleListCursor != null)
                    articleListCursor.close();
            }
            articleTable.close();
            categoryTable.close();
            return articleList;
    }

    return null;
}
}

and here is my onCreateMethod

@Override
protected void onCreate(@Nullable final Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    ArticleTable articleTable = new ArticleTable(this);
    articleTable.open();
    if (articleTable.getAllArticles() != null) {
        /* load the data from local database */
        getSupportLoaderManager().initLoader(Loader_ID, null, ArticleListActivity.this).forceLoad();
    } else {
        ApiManager.getArticles(this, this);
    }
    articleTable.close();
}

score 0 · Accepted Answer · answered Apr 07 '18 at 12:46

Create Async task to load data from database, when complete set adapter
MainActivity execute asynctask in oncreate and set adapter in call back method

public class MainActivity extends AppCompatActivity implements
 ArticleDatabaseLoader.ArticleDatabaseLoaderHandler{
{
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        new ArticleDatabaseLoader(MainActivity.this,0).execute();
    }

    @Override
    public void ArticleDatabaseLoaderComplete(List<Article> articleList) {
        if(articleList.size() > 0)
        {
            // refresh your adapter
        }
    }
}

Create ArticleDatabaseLoader class

import android.content.Context;
import android.database.Cursor;
import android.os.AsyncTask;

import java.util.ArrayList;
import java.util.List;


public class ArticleDatabaseLoader extends AsyncTask<String, String, String> {
    private int code = 0;
    List<Article> articleList = new ArrayList<>();
    protected Context mCtx;
    ArticleDatabaseLoaderHandler handler;
    public interface ArticleDatabaseLoaderHandler {
        void ArticleDatabaseLoaderComplete(List<Article> articleList);
    }

    public ArticleDatabaseLoader(Context context, int code) {
        mCtx = context;
        this.code = code;
        this.handler = (ArticleDatabaseLoaderHandler) context;
    }
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // todo display progress bar
    }
    @Override
    protected String doInBackground(String... strings) {
        ArticleTable articleTable = new ArticleTable(mCtx);
        ArticleCategory categoryTable = new ArticleCategory(mCtx);
        switch (code) {
            case ArticleList:
                articleTable.open();
                categoryTable.open();
                List<String> selected_category = new ArrayList<>();
                for (int i = 0; i < 5; i++) {   /* saving all the selected categories */
                    if (getCategoryStatus(mCtx, categories[i]) == 1) {
                        selected_category.add(categories[i]);
                    }
                }
                StringBuilder where_query = new StringBuilder();
                if (selected_category.size() > 0) {  /* building the where query for sql */
                    for (int i = 0; i < selected_category.size(); i++) {
                        if (i == selected_category.size() - 1) {
                            where_query.append(String.format("%s = '%s'",
                                    DBColumn.ArticleCategoryColumn.category_id,
                                    selected_category.get(i)));
                        } else {
                            where_query.append(String.format("%s = '%s' OR ",
                                    DBColumn.ArticleCategoryColumn.category_id,
                                    selected_category.get(i)));
                        }
                    }
                    Cursor selectedCursor = categoryTable.getArticles(where_query.toString());
                    if (selectedCursor != null && selectedCursor.moveToFirst() && selectedCursor.getCount() > 0) {
                        do {
                            String articleId = selectedCursor.getString(selectedCursor.getColumnIndex(DBColumn.ArticleCategoryColumn.article_id));
                            Cursor articleCursor = articleTable.getArticleById(articleId);
                            if (articleCursor != null && articleCursor.moveToFirst()) {
                                articleList.add(articleTable.articleObject(mCtx, articleCursor));
                            }
                            articleCursor.close();
                        } while (selectedCursor.moveToNext());
                    }
                    if (selectedCursor != null)
                        selectedCursor.close();
                } else {
                    Cursor articleListCursor = articleTable.getAllArticles();
                    if (articleListCursor != null && articleListCursor.moveToFirst() && articleListCursor.getCount() > 0) {
                        do {
                            articleList.add(articleTable.articleObject(getContext(), articleListCursor));
                        } while (articleListCursor.moveToNext());
                    }
                    if (articleListCursor != null)
                        articleListCursor.close();
                }
                articleTable.close();
                categoryTable.close();

                return null;

        }
    }
    protected void onPostExecute(String results) {
        // todo dismiss progress bar
        handler.ArticleDatabaseLoaderComplete(articleList);
    }
}

Freezing UI while loading JSON using AsyncTaskLoader

1 Answers1