Java tutorial
/* 50AH-code ========= 50 Android Hacks (http://manning.com/sessa/) book source code Copyright (c) 2012 Manning Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ /* * Copyright (C) 2012 The Android Open Source Project * * 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.manning.androidhacks.hack040; import android.content.Context; import android.content.Intent; import android.os.Bundle; import android.support.v4.app.Fragment; import android.util.Log; import android.util.TypedValue; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuInflater; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.view.ViewGroup.LayoutParams; import android.view.ViewTreeObserver; import android.widget.AbsListView; import android.widget.AdapterView; import android.widget.BaseAdapter; import android.widget.GridView; import android.widget.ImageView; import android.widget.Toast; import com.manning.androidhacks.hack040.provider.Images; import com.manning.androidhacks.hack040.util.ImageCache; import com.manning.androidhacks.hack040.util.ImageCache.ImageCacheParams; import com.manning.androidhacks.hack040.util.ImageFetcher; import com.manning.androidhacks.hack040.util.ImageResizer; import com.manning.androidhacks.hack040.util.Utils; /** * The main fragment that powers the ImageGridActivity screen. Fairly straight * forward GridView implementation with the key addition being the ImageWorker * class w/ImageCache to load children asynchronously, keeping the UI nice and * smooth and caching thumbnails for quick retrieval. The cache is retained over * configuration changes like orientation change so the images are populated * quickly as the user rotates the device. */ public class ImageGridFragment extends Fragment implements AdapterView.OnItemClickListener { private static final String TAG = "ImageGridFragment"; private static final String IMAGE_CACHE_DIR = "thumbs"; private int mImageThumbSize; private int mImageThumbSpacing; private ImageAdapter mAdapter; private ImageResizer mImageWorker; /** * Empty constructor as per the Fragment documentation */ public ImageGridFragment() { } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setHasOptionsMenu(true); mImageThumbSize = getResources().getDimensionPixelSize(R.dimen.image_thumbnail_size); mImageThumbSpacing = getResources().getDimensionPixelSize(R.dimen.image_thumbnail_spacing); mAdapter = new ImageAdapter(getActivity()); ImageCacheParams cacheParams = new ImageCacheParams(IMAGE_CACHE_DIR); // Allocate a third of the per-app memory limit to the bitmap memory cache. // This value // should be chosen carefully based on a number of factors. Refer to the // corresponding // Android Training class for more discussion: // http://developer.android.com/training/displaying-bitmaps/ // In this case, we aren't using memory for much else other than this // activity and the // ImageDetailActivity so a third lets us keep all our sample image // thumbnails in memory // at once. cacheParams.memCacheSize = 1024 * 1024 * Utils.getMemoryClass(getActivity()) / 3; // The ImageWorker takes care of loading images into our ImageView children // asynchronously mImageWorker = new ImageFetcher(getActivity(), mImageThumbSize); mImageWorker.setAdapter(Images.imageThumbWorkerUrlsAdapter); mImageWorker.setLoadingImage(R.drawable.empty_photo); mImageWorker.setImageCache(ImageCache.findOrCreateCache(getActivity(), cacheParams)); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { final View v = inflater.inflate(R.layout.image_grid_fragment, container, false); final GridView mGridView = (GridView) v.findViewById(R.id.gridView); mGridView.setAdapter(mAdapter); mGridView.setOnItemClickListener(this); // This listener is used to get the final width of the GridView and then // calculate the // number of columns and the width of each column. The width of each column // is variable // as the GridView has stretchMode=columnWidth. The column width is used to // set the height // of each view so we get nice square thumbnails. mGridView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() { @Override public void onGlobalLayout() { if (mAdapter.getNumColumns() == 0) { final int numColumns = (int) Math .floor(mGridView.getWidth() / (mImageThumbSize + mImageThumbSpacing)); if (numColumns > 0) { final int columnWidth = (mGridView.getWidth() / numColumns) - mImageThumbSpacing; mAdapter.setNumColumns(numColumns); mAdapter.setItemHeight(columnWidth); if (BuildConfig.DEBUG) { Log.d(TAG, "onCreateView - numColumns set to " + numColumns); } } } } }); return v; } @Override public void onResume() { super.onResume(); mImageWorker.setExitTasksEarly(false); mAdapter.notifyDataSetChanged(); } @Override public void onPause() { super.onPause(); mImageWorker.setExitTasksEarly(true); } @Override public void onItemClick(AdapterView<?> parent, View v, int position, long id) { final Intent i = new Intent(getActivity(), ImageDetailActivity.class); i.putExtra(ImageDetailActivity.EXTRA_IMAGE, (int) id); startActivity(i); } @Override public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) { inflater.inflate(R.menu.main_menu, menu); } @Override public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case R.id.clear_cache: final ImageCache cache = mImageWorker.getImageCache(); if (cache != null) { mImageWorker.getImageCache().clearCaches(); // DiskLruCache.clearCache(getActivity(), ImageFetcher.HTTP_CACHE_DIR); Toast.makeText(getActivity(), R.string.clear_cache_complete, Toast.LENGTH_SHORT).show(); } return true; } return super.onOptionsItemSelected(item); } /** * The main adapter that backs the GridView. This is fairly standard except * the number of columns in the GridView is used to create a fake top row of * empty views as we use a transparent ActionBar and don't want the real top * row of images to start off covered by it. */ private class ImageAdapter extends BaseAdapter { private final Context mContext; private int mItemHeight = 0; private int mNumColumns = 0; private int mActionBarHeight = -1; private GridView.LayoutParams mImageViewLayoutParams; public ImageAdapter(Context context) { super(); mContext = context; mImageViewLayoutParams = new GridView.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT); } @Override public int getCount() { // Size of adapter + number of columns for top empty row return mImageWorker.getAdapter().getSize() + mNumColumns; } @Override public Object getItem(int position) { return position < mNumColumns ? null : mImageWorker.getAdapter().getItem(position - mNumColumns); } @Override public long getItemId(int position) { return position < mNumColumns ? 0 : position - mNumColumns; } @Override public int getViewTypeCount() { // Two types of views, the normal ImageView and the top row of empty views return 2; } @Override public int getItemViewType(int position) { return (position < mNumColumns) ? 1 : 0; } @Override public boolean hasStableIds() { return true; } @Override public View getView(int position, View convertView, ViewGroup container) { // First check if this is the top row if (position < mNumColumns) { if (convertView == null) { convertView = new View(mContext); } // Calculate ActionBar height if (mActionBarHeight < 0) { TypedValue tv = new TypedValue(); if (mContext.getTheme().resolveAttribute(android.R.attr.actionBarSize, tv, true)) { mActionBarHeight = TypedValue.complexToDimensionPixelSize(tv.data, mContext.getResources().getDisplayMetrics()); } else { // No ActionBar style (pre-Honeycomb or ActionBar not in theme) mActionBarHeight = 0; } } // Set empty view with height of ActionBar convertView.setLayoutParams( new AbsListView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, mActionBarHeight)); return convertView; } // Now handle the main ImageView thumbnails ImageView imageView; if (convertView == null) { // if it's not recycled, instantiate and // initialize imageView = new ImageView(mContext); imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); imageView.setLayoutParams(mImageViewLayoutParams); } else { // Otherwise re-use the converted view imageView = (ImageView) convertView; } // Check the height matches our calculated column width if (imageView.getLayoutParams().height != mItemHeight) { imageView.setLayoutParams(mImageViewLayoutParams); } // Finally load the image asynchronously into the ImageView, this also // takes care of // setting a placeholder image while the background thread runs mImageWorker.loadImage(position - mNumColumns, imageView); return imageView; } /** * Sets the item height. Useful for when we know the column width so the * height can be set to match. * * @param height */ public void setItemHeight(int height) { if (height == mItemHeight) { return; } mItemHeight = height; mImageViewLayoutParams = new GridView.LayoutParams(LayoutParams.MATCH_PARENT, mItemHeight); mImageWorker.setImageSize(height); notifyDataSetChanged(); } public void setNumColumns(int numColumns) { mNumColumns = numColumns; } public int getNumColumns() { return mNumColumns; } } }