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 com.xuwakao.mixture.ui; import android.annotation.TargetApi; import android.app.Activity; import android.app.ActivityOptions; import android.content.Context; import android.content.Intent; import android.os.Bundle; import android.support.v4.app.Fragment; import android.util.Log; 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.xuwakao.mixture.BuildConfig; import com.xuwakao.mixture.R; import com.xuwakao.mixture.framework.AppConfig; import com.xuwakao.mixture.framework.http.HttpTaskRequestParam; import com.xuwakao.mixture.framework.image.ImageCache; import com.xuwakao.mixture.framework.image.ImageFetcher; import com.xuwakao.mixture.framework.image.RecyclingImageView; import com.xuwakao.mixture.framework.test.TestImage; import com.xuwakao.mixture.framework.utils.MLog; import com.xuwakao.mixture.framework.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 void onAttach(Activity activity) { super.onAttach(activity); // ((ActionBarActivity)getActivity()).getSupportActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#00212121")) ); } @Override public void onDetach() { super.onDetach(); } @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) { 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() { @Override public void onGlobalLayout() { final int numColumns = (int) Math .floor(mGridView.getWidth() / (mImageThumbSize + mImageThumbSpacing)); if (numColumns > 0) { final int columnWidth = (mGridView.getWidth() / numColumns) - mImageThumbSpacing; mAdapter.setItemHeight(columnWidth); if (BuildConfig.DEBUG) { Log.d(TAG, "onCreateView - numColumns set to " + numColumns); } } } }); 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(16) @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.color_demo_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 GridView.LayoutParams mImageViewLayoutParams; public ImageAdapter(Context context) { super(); mContext = context; mImageViewLayoutParams = new GridView.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT); } @Override public int getCount() { return TestImage.imageThumbUrls.length; } @Override public Object getItem(int position) { return TestImage.imageThumbUrls[position]; } @Override public long getItemId(int position) { return position; } @Override public int getViewTypeCount() { return 1; } @Override public boolean hasStableIds() { return true; } @Override public View getView(int position, View convertView, ViewGroup container) { // Now handle the main ImageView thumbnails ImageView imageView; if (convertView == null) { // if it's not recycled, instantiate and initialize imageView = new RecyclingImageView(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 HttpTaskRequestParam param = new HttpTaskRequestParam(); param.url = TestImage.imageThumbUrls[position]; MLog.verbose("AtomicInteger", "AtomicInteger getView is " + AppConfig.getView.incrementAndGet()); mImageFetcher.loadImage(param, 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); mImageFetcher.setImageSize(height); notifyDataSetChanged(); } } }