Android Open Source - GridListViewAdapters Cursor Retaining Fragment

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License

The source code is released under:

Apache License

Java Source Code

/**
 * Copyright 2014-present Biraj Patel/*from w  w  w . j a  va2s  .  co  m*/
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License. You may obtain a
 * copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package com.birin.cursorgridadapter.datasetup;

import android.app.Activity;
import android.app.Fragment;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.os.AsyncTask;
import android.os.Bundle;

import com.birin.gridlistviewadaptersdemo.common.Constants;
import com.birin.gridlistviewadaptersdemo.common.RandomInfoGenerator;

/**
 * Helper fragment class which will be used to hold data across configuration
 * changes of activity life-cycle as mentioned in below link
 */
// http://www.androiddesignpatterns.com/2013/04/retaining-objects-across-config-changes.html
public class CursorRetainingFragment extends Fragment {

  private DummyDataGeneratorCallback mCallbacks;
  private DummyTask mTask;
  private boolean isTaskRunning;
  public static final String KEY_MAX_ITEMS = "KEY_MAX_ITEMS";

  /**
   * Hold a reference to the parent Activity so we can report the task's
   * current progress and results. The Android framework will pass us a
   * reference to the newly created Activity after each configuration change.
   */
  @Override
  public void onAttach(Activity activity) {
    super.onAttach(activity);
    if (activity instanceof DummyDataGeneratorCallback) {
      mCallbacks = (DummyDataGeneratorCallback) activity;
    }
  }

  /**
   * This method will only be called once when the retained Fragment is first
   * created.
   */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Retain this fragment across configuration changes.
    setRetainInstance(true);
    runAddDataTaskToEnsureMinimumData();
  }

  /**
   * Set the callback to null so we don't accidentally leak the Activity
   * instance.
   */
  @Override
  public void onDetach() {
    super.onDetach();
    mCallbacks = null;
  }

  public boolean isTaskRunning() {
    return isTaskRunning;
  }

  private int getMaxAllowedItems() {
    int maxAllowed = Integer.MAX_VALUE;
    Bundle extras = getArguments();
    if (null != extras && extras.containsKey(KEY_MAX_ITEMS)) {
      maxAllowed = extras.getInt(KEY_MAX_ITEMS);
    }
    return maxAllowed;
  }

  private void runAddDataTaskToEnsureMinimumData() {
    runAddDataTaskIfNotRunning(true);
  }

  public void runAddDataTaskOnLoadMoreRequest() {
    runAddDataTaskIfNotRunning(false);
  }

  private void runAddDataTaskIfNotRunning(boolean isEnsureRun) {
    if (isTaskRunning() == false) {
      if (null != mTask) {
        mTask.cancel(true);
        mTask = null;
      }
      // Create and execute the background task.
      mTask = new DummyTask(isEnsureRun);
      mTask.execute();
    }
  }

  public boolean canLoadMoreData(int currentDataSize) {
    return currentDataSize < getMaxAllowedItems();
  }

  /**
   * A dummy task that performs some (dumb) background work and proxies
   * progress updates and results back to the Activity.
   * 
   */
  private class DummyTask extends AsyncTask<Void, Integer, Void> {

    private boolean isEnsureRun;

    public DummyTask(boolean isEnsureRun) {
      this.isEnsureRun = isEnsureRun;
    }

    @Override
    protected void onPreExecute() {
      isTaskRunning = true;
      if (mCallbacks != null) {
        mCallbacks.onDataGeneratorTaskExecuting();
      }
    }

    @Override
    protected Void doInBackground(Void... ignore) {
      Activity activity = getActivity();
      if (null != activity) {
        ContentResolver resolver = activity.getContentResolver();
        Cursor existingData = resolver.query(
            TestContentProvider.CONTENT_URI_EMPLOYEE, null, null,
            null, null);
        int currentSize = existingData == null ? 0 : existingData
            .getCount();
        if (isEnsureRun == false || currentSize <= 0) {
          generateNewDummyDataIfCanLoadMoreData(currentSize, resolver);
        }
      }
      return null;
    }

    private void generateNewDummyDataIfCanLoadMoreData(int currentSize,
        ContentResolver resolver) {
      if (canLoadMoreData(currentSize) == true) {
        generateNewDummyDataAndAddToDB(currentSize, resolver);
      }
    }

    @Override
    protected void onCancelled() {
      isTaskRunning = false;
    }

    @Override
    protected void onPostExecute(Void result) {
      isTaskRunning = false;
    }

  }

  private void generateNewDummyDataAndAddToDB(int currentSize,
      ContentResolver resolver) {
    try {
      Thread.sleep(Constants.DUMMY_DELAY_IN_MILLIS);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
    ContentValues valuesToInsert = new ContentValues();
    for (int i = currentSize; i < (currentSize + 20); i++) {
      valuesToInsert.clear();
      updateValuesToInsert(valuesToInsert, i);
      resolver.insert(TestContentProvider.CONTENT_URI_EMPLOYEE,
          valuesToInsert);
    }
  }

  private void updateValuesToInsert(ContentValues valuesToInsert, int i) {
    valuesToInsert.put(TestContentProviderSqlHelper.EMPLOYEE_NAME, "id:"
        + i);
    valuesToInsert.put(TestContentProviderSqlHelper.EMPLOYEE_COLUMN_CHAR,
        Character.toString(RandomInfoGenerator.getRandomChar()));
    valuesToInsert.put(
        TestContentProviderSqlHelper.EMPLOYEE_COLUMN_CHAR_COLOR,
        RandomInfoGenerator.getRandomColor());

  }

  public interface DummyDataGeneratorCallback {

    public void onDataGeneratorTaskExecuting();
  }

}

Java Source Code List

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