ExDbEndlessAdapter.java

package fahrbot.apps.calculator.ui.widget;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import tiny.lib.log.L;
import tiny.lib.misc.ExFactory;
import tiny.lib.misc.app.IRenderer;
import tiny.lib.misc.utils.ExExecutor;
import tiny.lib.sorm.ex.ExDbAdapter;
import tiny.lib.sorm.ex.IExCursorCollection;
import tiny.lib.sorm.ex.collections.GroupingCursorView;

import java.util.concurrent.atomic.AtomicBoolean;

public class ExDbEndlessAdapter<T> extends ExDbAdapter<T> {
	private final static String TAG = "ExDbEndlessAdapter";
	AtomicBoolean mIsRequestPending;
	private int mProvidedCount;
	private int mPreloadStart = 15;
	private int mRequestSizeMax = 50;

	public ExDbEndlessAdapter(@NotNull Context context,
	                          @Nullable IExCursorCollection<T> objects,
	                          @NotNull IRenderer<T> renderer) {
		super(context, objects, renderer);
		init();
	}

	public ExDbEndlessAdapter(@NotNull Context context,
	                          @Nullable IExCursorCollection<T> objects, int type,
	                          @NotNull IRenderer<T> renderer) {
		super(context, objects, type, renderer);
		init();
	}

	private void init() {
		mIsRequestPending = new AtomicBoolean(false);
		mProvidedCount = mObjects != null ? mObjects.size() : 0;
	}

	public void setPreloadStart(int start) {
		mPreloadStart = start;
	}

	public void setRequestSize(int requestSize) {
		mRequestSizeMax = requestSize;
	}

	@Override
	protected View getViewInternal(int position, View convertView, ViewGroup parent, int type) {
		if (position + mPreloadStart >= mProvidedCount) {
			postRequest();
		}
		return super.getViewInternal(position, convertView, parent, type);
	}

	private void postRequest() {
		if (mObjects != null && !mIsRequestPending.get()) {
			ExExecutor.runBackground(new Runnable() {
				@Override
				public void run() {
					requestNew();
				}
			});
		}
	}

	private void requestNew() {
		if (mObjects instanceof IExCursorCollection && mIsRequestPending.compareAndSet(false, true)) {
			mProvidedCount = mObjects.size();
			int newSize = findNext(mProvidedCount, mRequestSizeMax);
			if (newSize > 0) {
				final int finalNewSize = newSize;
				ExFactory.runOnUiThread(new Runnable() {
					@Override
					public void run() {
						mProvidedCount += finalNewSize;
						notifyDataSetChanged();
						mIsRequestPending.set(false);
					}
				});
			} else {
				mIsRequestPending.set(false);
			}
		}
	}

	private int findNext(int provided, int offset) {
		L.d(TAG, "findNext() provided: %s, offset: %s", provided, offset);
		if (offset == 0) {
			return 0;
		} else if (mObjects.get(provided + offset - 1) != null) {
			return offset;
		}
		return findNext(provided, offset / 2);
	}

	@Override
	public void startUpdating() {
		if (mObjects instanceof GroupingCursorView) {
			((GroupingCursorView)mObjects).invalidate();
		}
		super.startUpdating();
	}

	@Override
	public void onChanged() {
		ExFactory.runOnUiThread(new Runnable() {
			@Override
			public void run() {
				ExDbEndlessAdapter.super.onChanged();
			}
		});

	}

	@Override
	public void onInvalidated() {
		ExFactory.runOnUiThread(new Runnable() {
			@Override
			public void run() {
				ExDbEndlessAdapter.super.onInvalidated();
			}
		});
	}

/* From Adapter */

	@Override
	public T getItem(int position) {
		//L.d(TAG, "getItem(%s)", position);
		return super.getItem(position);
	}

	/* From IAdapterObserver */
	@Override
	public void notifyDataSetChanged() {
		mObjects.get(mProvidedCount > 0 ? mProvidedCount - 1 : mPreloadStart);
		mProvidedCount = mObjects.size();
		super.notifyDataSetChanged();
	}

	/* From IExAdapter */

	@Override
	public int getCount() {
		return mProvidedCount;
	}
}