Java tutorial
/* * 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 mk.apps.soundblog.fragment; import android.annotation.TargetApi; import android.content.Context; import android.os.Build.VERSION_CODES; 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.FrameLayout; import android.widget.GridView; import android.widget.ImageView; import android.widget.TextView; import android.widget.Toast; import mk.apps.soundblog.BuildConfig; import mk.apps.soundblog.R; import mk.apps.soundblog.utils.ImageCache; import mk.apps.soundblog.utils.ImageFetcher; import mk.apps.soundblog.utils.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 if, for example, 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 ImageFetcher mImageFetcher; /** * 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()); ImageCache.ImageCacheParams cacheParams = new ImageCache.ImageCacheParams(getActivity(), IMAGE_CACHE_DIR); cacheParams.setMemCacheSizePercent(0.25f); // Set memory cache to 25% of app memory // The ImageFetcher takes care of loading images into our ImageView children asynchronously mImageFetcher = new ImageFetcher(getActivity(), mImageThumbSize); mImageFetcher.setLoadingImage(R.drawable.empty_photo); mImageFetcher.addImageCache(getActivity().getSupportFragmentManager(), 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); mGridView.setOnScrollListener(new AbsListView.OnScrollListener() { @Override public void onScrollStateChanged(AbsListView absListView, int scrollState) { // Pause fetcher to ensure smoother scrolling when flinging if (scrollState == AbsListView.OnScrollListener.SCROLL_STATE_FLING) { // Before Honeycomb pause image loading on scroll to help with performance if (!Utils.hasHoneycomb()) { mImageFetcher.setPauseWork(true); } } else { mImageFetcher.setPauseWork(false); } } @Override public void onScroll(AbsListView absListView, int firstVisibleItem, int visibleItemCount, int totalItemCount) { } }); // 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() { @TargetApi(VERSION_CODES.JELLY_BEAN) @Override public void onGlobalLayout() { if (mAdapter.getNumColumns() == 0) { // final int numColumns = (int) Math.floor( // mGridView.getWidth() / (mImageThumbSize + mImageThumbSpacing)); final int numColumns = 2; 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); } if (Utils.hasJellyBean()) { mGridView.getViewTreeObserver().removeOnGlobalLayoutListener(this); } else { mGridView.getViewTreeObserver().removeGlobalOnLayoutListener(this); } } } } }); return v; } @Override public void onResume() { super.onResume(); mImageFetcher.setExitTasksEarly(false); mAdapter.notifyDataSetChanged(); } @Override public void onPause() { super.onPause(); mImageFetcher.setPauseWork(false); mImageFetcher.setExitTasksEarly(true); mImageFetcher.flushCache(); } @Override public void onDestroy() { super.onDestroy(); mImageFetcher.closeCache(); } @TargetApi(VERSION_CODES.JELLY_BEAN) @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); // if (Utils.hasJellyBean()) { // // makeThumbnailScaleUpAnimation() looks kind of ugly here as the loading spinner may // // show plus the thumbnail image in GridView is cropped. so using // // makeScaleUpAnimation() instead. // ActivityOptions options = // ActivityOptions.makeScaleUpAnimation(v, 0, 0, v.getWidth(), v.getHeight()); // getActivity().startActivity(i, options.toBundle()); // } else { // 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: mImageFetcher.clearCache(); Toast.makeText(getActivity(), R.string.clear_cache_complete_toast, 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 = 0; private FrameLayout.LayoutParams mImageViewLayoutParams; private LayoutInflater mLayoutInflater; public ImageAdapter(Context context) { super(); mContext = context; mImageViewLayoutParams = new FrameLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT); // Calculate ActionBar height TypedValue tv = new TypedValue(); if (context.getTheme().resolveAttribute(android.R.attr.actionBarSize, tv, true)) { mActionBarHeight = TypedValue.complexToDimensionPixelSize(tv.data, context.getResources().getDisplayMetrics()); } mLayoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); } @Override public int getCount() { // If columns have yet to be determined, return no items if (getNumColumns() == 0) { return 0; } // Size + number of columns for top empty row return 100; } @Override public Object getItem(int position) { // return position < mNumColumns ? // null : Images.imageThumbUrls[position - mNumColumns]; return null; } @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) { //BEGIN_INCLUDE(load_gridview_item) // First check if this is the top row // if (position < mNumColumns) { // if (convertView == null) { // convertView = mLayoutInflater.inflate(R.layout.entry_item, null); // } // // Set empty view with height of ActionBar //// convertView.setLayoutParams(new AbsListView.LayoutParams( //// LayoutParams.MATCH_PARENT, mActionBarHeight)); // return convertView; // } // Now handle the main ImageView thumbnails ImageView imageView; TextView textView; // if (convertView == null) { // if it's not recycled, instantiate and initialize convertView = mLayoutInflater.inflate(R.layout.entry_item, null); // imageView = new RecyclingImageView(mContext); // imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); // imageView.setLayoutParams(mImageViewLayoutParams); // } else { // Otherwise re-use the converted view //// imageView = (ImageView) convertView; // } imageView = (ImageView) convertView.findViewById(R.id.entry_ic); textView = (TextView) convertView.findViewById(R.id.entry_title); textView.setText("update title"); // textView.setLayoutParams( new GridView.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT)); // 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 // mImageFetcher.loadImage(Images.imageThumbUrls[position - mNumColumns], imageView); return convertView; //END_INCLUDE(load_gridview_item) } /** * 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 FrameLayout.LayoutParams(LayoutParams.MATCH_PARENT, mItemHeight); mImageFetcher.setImageSize(height); notifyDataSetChanged(); } public int getNumColumns() { return mNumColumns; } public void setNumColumns(int numColumns) { mNumColumns = numColumns; } } }