mirror of https://github.com/tasks/tasks
Use paging library
Alex Baker
6 years ago
parent
3009004dcf
commit
4762a7330f
@ -0,0 +1,97 @@
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package org.tasks.data;
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import android.arch.paging.PositionalDataSource;
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import android.arch.persistence.room.RoomDatabase;
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import android.database.Cursor;
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import android.support.annotation.NonNull;
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import android.support.annotation.Nullable;
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import android.support.annotation.WorkerThread;
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import com.todoroo.astrid.data.Task;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.List;
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public abstract class LimitOffsetDataSource extends PositionalDataSource<Task> {
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private final String mCountQuery;
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private final String mLimitOffsetQuery;
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private final RoomDatabase mDb;
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protected LimitOffsetDataSource(RoomDatabase db, String query) {
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mDb = db;
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mCountQuery = "SELECT COUNT(*) FROM ( " + query + " )";
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mLimitOffsetQuery = "SELECT * FROM ( " + query + " ) LIMIT ? OFFSET ?";
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}
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@WorkerThread
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public int countItems() {
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Cursor cursor = mDb.query(mCountQuery, null);
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try {
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if (cursor.moveToFirst()) {
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return cursor.getInt(0);
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}
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return 0;
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} finally {
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cursor.close();
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}
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}
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@SuppressWarnings("WeakerAccess")
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protected List<Task> convertRows(Cursor cursor) {
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List<Task> result = new ArrayList<>();
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while (cursor.moveToNext()) {
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result.add(new Task(cursor));
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}
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return result;
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}
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@Nullable
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@WorkerThread
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public List<Task> loadRange(int startPosition, int loadCount) {
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Cursor cursor = mDb.query(mLimitOffsetQuery, new Object[] { loadCount, startPosition });
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//noinspection TryFinallyCanBeTryWithResources
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try {
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return convertRows(cursor);
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} finally {
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cursor.close();
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}
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}
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@Override
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public void loadInitial(@NonNull LoadInitialParams params,
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@NonNull LoadInitialCallback<Task> callback) {
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int totalCount = countItems();
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if (totalCount == 0) {
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callback.onResult(Collections.emptyList(), 0, 0);
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return;
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}
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// bound the size requested, based on known count
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final int firstLoadPosition = computeInitialLoadPosition(params, totalCount);
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final int firstLoadSize = computeInitialLoadSize(params, firstLoadPosition, totalCount);
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// convert from legacy behavior
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List<Task> list = loadRange(firstLoadPosition, firstLoadSize);
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if (list != null && list.size() == firstLoadSize) {
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callback.onResult(list, firstLoadPosition, totalCount);
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} else {
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// null list, or size doesn't match request
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// The size check is a WAR for Room 1.0, subsequent versions do the check in Room
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invalidate();
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}
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}
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@WorkerThread
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@Override
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public void loadRange(@NonNull LoadRangeParams params,
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@NonNull LoadRangeCallback<Task> callback) {
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List<Task> list = loadRange(params.startPosition, params.loadSize);
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if (list != null) {
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callback.onResult(list);
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} else {
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invalidate();
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}
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}
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}
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