Java tutorial
/* * Twidere - Twitter client for Android * * Copyright (C) 2012-2015 Mariotaku Lee <mariotaku.lee@gmail.com> * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ package org.mariotaku.twidere.loader.support; import android.content.Context; import android.database.Cursor; import android.net.Uri; import android.support.annotation.NonNull; import android.support.v4.content.AsyncTaskLoader; import android.support.v4.content.LoaderTrojan; import org.mariotaku.twidere.model.ListResponse; import org.mariotaku.twidere.model.ObjectCursor; import java.io.FileDescriptor; import java.io.PrintWriter; import java.lang.reflect.InvocationTargetException; import java.util.Arrays; import java.util.List; /** * Created by mariotaku on 15-7-5. */ public class ObjectCursorLoader<T> extends AsyncTaskLoader<List<T>> { final ForceLoadContentObserver mObserver; final Class<? extends ObjectCursor.CursorIndices<T>> mIndicesClass; Uri mUri; String[] mProjection; String mSelection; String[] mSelectionArgs; String mSortOrder; ObjectCursor<T> mObjects; /* Runs on a worker thread */ @Override public ObjectCursor<T> loadInBackground() { Cursor cursor = getContext().getContentResolver().query(mUri, mProjection, mSelection, mSelectionArgs, mSortOrder); if (cursor != null) { // Ensure the cursor window is filled cursor.getCount(); cursor.registerContentObserver(mObserver); } if (cursor == null) throw new NullPointerException("Cursor is null"); return new ObjectCursor<>(cursor, createIndices(cursor)); } @SuppressWarnings("TryWithIdenticalCatches") @NonNull private ObjectCursor.CursorIndices<T> createIndices(final Cursor cursor) { try { return mIndicesClass.getConstructor(Cursor.class).newInstance(cursor); } catch (NoSuchMethodException e) { throw new RuntimeException(e); } catch (InvocationTargetException e) { throw new RuntimeException(e); } catch (InstantiationException e) { throw new RuntimeException(e); } catch (IllegalAccessException e) { throw new RuntimeException(e); } } /* Runs on the UI thread */ @Override public void deliverResult(List<T> data) { final ObjectCursor<T> cursor = (ObjectCursor<T>) data; if (isReset()) { // An async query came in while the loader is stopped if (cursor != null) { cursor.close(); } return; } ObjectCursor<T> oldCursor = mObjects; mObjects = cursor; if (isStarted()) { super.deliverResult(cursor); } if (oldCursor != null && oldCursor != cursor && !oldCursor.isClosed()) { oldCursor.close(); } } /** * Creates an empty unspecified CursorLoader. You must follow this with * calls to {@link #setUri(Uri)}, {@link #setSelection(String)}, etc * to specify the query to perform. */ public ObjectCursorLoader(Context context, Class<? extends ObjectCursor.CursorIndices<T>> indicesClass) { super(context); mIndicesClass = indicesClass; mObserver = new ForceLoadContentObserver(); } /** * Creates a fully-specified CursorLoader. See * {@link android.content.ContentResolver#query(Uri, String[], String, String[], String) * ContentResolver.query()} for documentation on the meaning of the * parameters. These will be passed as-is to that call. */ public ObjectCursorLoader(Context context, Class<? extends ObjectCursor.CursorIndices<T>> indicesClass, Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { super(context); mIndicesClass = indicesClass; mObserver = new ForceLoadContentObserver(); mUri = uri; mProjection = projection; mSelection = selection; mSelectionArgs = selectionArgs; mSortOrder = sortOrder; } /** * Starts an asynchronous load of the contacts list data. When the result is ready the callbacks * will be called on the UI thread. If a previous load has been completed and is still valid * the result may be passed to the callbacks immediately. * <p/> * Must be called from the UI thread */ @Override protected void onStartLoading() { if (mObjects != null) { deliverResult(mObjects); } if (takeContentChanged() || mObjects == null) { forceLoad(); } } /** * Must be called from the UI thread */ @Override protected void onStopLoading() { // Attempt to cancel the current load task if possible. cancelLoad(); } @Override public void onCanceled(List<T> data) { final ObjectCursor<T> cursor = (ObjectCursor<T>) data; if (cursor != null && !cursor.isClosed()) { cursor.close(); } } @Override protected void onReset() { super.onReset(); // Ensure the loader is stopped onStopLoading(); if (mObjects != null && !mObjects.isClosed()) { mObjects.close(); } mObjects = null; } public Uri getUri() { return mUri; } public void setUri(Uri uri) { mUri = uri; } public String[] getProjection() { return mProjection; } public void setProjection(String[] projection) { mProjection = projection; } public String getSelection() { return mSelection; } public void setSelection(String selection) { mSelection = selection; } public String[] getSelectionArgs() { return mSelectionArgs; } public void setSelectionArgs(String[] selectionArgs) { mSelectionArgs = selectionArgs; } public String getSortOrder() { return mSortOrder; } public void setSortOrder(String sortOrder) { mSortOrder = sortOrder; } @Override public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) { super.dump(prefix, fd, writer, args); writer.print(prefix); writer.print("mUri="); writer.println(mUri); writer.print(prefix); writer.print("mProjection="); writer.println(Arrays.toString(mProjection)); writer.print(prefix); writer.print("mSelection="); writer.println(mSelection); writer.print(prefix); writer.print("mSelectionArgs="); writer.println(Arrays.toString(mSelectionArgs)); writer.print(prefix); writer.print("mSortOrder="); writer.println(mSortOrder); writer.print(prefix); writer.print("mObjects="); writer.println(mObjects); writer.print(prefix); writer.print("mContentChanged="); writer.println(LoaderTrojan.isContentChanged(this)); } }