DisplayingBitmaps / src / com.example.android.displayingbitmaps / ui /

ImageGridFragment.java

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/*
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 * Copyright (C) 2012 The Android Open Source Project
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 *      http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package com.example.android.displayingbitmaps.ui;
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import android.annotation.TargetApi;
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import android.app.ActivityOptions;
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import android.content.Context;
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import android.content.Intent;
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import android.os.Build.VERSION_CODES;
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import android.os.Bundle;
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import android.support.v4.app.Fragment;
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import android.util.TypedValue;
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import android.view.LayoutInflater;
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import android.view.Menu;
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import android.view.MenuInflater;
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import android.view.MenuItem;
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import android.view.View;
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import android.view.ViewGroup;
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import android.view.ViewGroup.LayoutParams;
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import android.view.ViewTreeObserver;
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import android.widget.AbsListView;
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import android.widget.AdapterView;
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import android.widget.BaseAdapter;
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import android.widget.GridView;
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import android.widget.ImageView;
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import android.widget.Toast;
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import com.example.android.common.logger.Log;
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import com.example.android.displayingbitmaps.BuildConfig;
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import com.example.android.displayingbitmaps.R;
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import com.example.android.displayingbitmaps.provider.Images;
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import com.example.android.displayingbitmaps.util.ImageCache;
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import com.example.android.displayingbitmaps.util.ImageFetcher;
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import com.example.android.displayingbitmaps.util.Utils;
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/**
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 * The main fragment that powers the ImageGridActivity screen. Fairly straight forward GridView
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 * implementation with the key addition being the ImageWorker class w/ImageCache to load children
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 * asynchronously, keeping the UI nice and smooth and caching thumbnails for quick retrieval. The
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 * cache is retained over configuration changes like orientation change so the images are populated
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 * quickly if, for example, the user rotates the device.
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 */
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public class ImageGridFragment extends Fragment implements AdapterView.OnItemClickListener {
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    private static final String TAG = "ImageGridFragment";
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    private static final String IMAGE_CACHE_DIR = "thumbs";
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    private int mImageThumbSize;
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    private int mImageThumbSpacing;
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    private ImageAdapter mAdapter;
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    private ImageFetcher mImageFetcher;
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    /**
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     * Empty constructor as per the Fragment documentation
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     */
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    public ImageGridFragment() {}
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    @Override
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    public void onCreate(Bundle savedInstanceState) {
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        super.onCreate(savedInstanceState);
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        setHasOptionsMenu(true);
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        mImageThumbSize = getResources().getDimensionPixelSize(R.dimen.image_thumbnail_size);
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        mImageThumbSpacing = getResources().getDimensionPixelSize(R.dimen.image_thumbnail_spacing);
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        mAdapter = new ImageAdapter(getActivity());
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        ImageCache.ImageCacheParams cacheParams =
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                new ImageCache.ImageCacheParams(getActivity(), IMAGE_CACHE_DIR);
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        cacheParams.setMemCacheSizePercent(0.25f); // Set memory cache to 25% of app memory
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        // The ImageFetcher takes care of loading images into our ImageView children asynchronously
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        mImageFetcher = new ImageFetcher(getActivity(), mImageThumbSize);
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        mImageFetcher.setLoadingImage(R.drawable.empty_photo);
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        mImageFetcher.addImageCache(getActivity().getSupportFragmentManager(), cacheParams);
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    }
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    @Override
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    public View onCreateView(
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            LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
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        final View v = inflater.inflate(R.layout.image_grid_fragment, container, false);
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        final GridView mGridView = (GridView) v.findViewById(R.id.gridView);
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        mGridView.setAdapter(mAdapter);
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        mGridView.setOnItemClickListener(this);
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        mGridView.setOnScrollListener(new AbsListView.OnScrollListener() {
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            @Override
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            public void onScrollStateChanged(AbsListView absListView, int scrollState) {
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                // Pause fetcher to ensure smoother scrolling when flinging
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                if (scrollState == AbsListView.OnScrollListener.SCROLL_STATE_FLING) {
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                    // Before Honeycomb pause image loading on scroll to help with performance
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                    if (!Utils.hasHoneycomb()) {
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                        mImageFetcher.setPauseWork(true);
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                    }
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                } else {
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                    mImageFetcher.setPauseWork(false);
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                }
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            }
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            @Override
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            public void onScroll(AbsListView absListView, int firstVisibleItem,
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                    int visibleItemCount, int totalItemCount) {
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            }
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        });
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        // This listener is used to get the final width of the GridView and then calculate the
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        // number of columns and the width of each column. The width of each column is variable
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        // as the GridView has stretchMode=columnWidth. The column width is used to set the height
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        // of each view so we get nice square thumbnails.
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        mGridView.getViewTreeObserver().addOnGlobalLayoutListener(
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                new ViewTreeObserver.OnGlobalLayoutListener() {
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                    @TargetApi(VERSION_CODES.JELLY_BEAN)
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                    @Override
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                    public void onGlobalLayout() {
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                        if (mAdapter.getNumColumns() == 0) {
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                            final int numColumns = (int) Math.floor(
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                                    mGridView.getWidth() / (mImageThumbSize + mImageThumbSpacing));
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                            if (numColumns > 0) {
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                                final int columnWidth =
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                                        (mGridView.getWidth() / numColumns) - mImageThumbSpacing;
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                                mAdapter.setNumColumns(numColumns);
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                                mAdapter.setItemHeight(columnWidth);
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                                if (BuildConfig.DEBUG) {
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                                    Log.d(TAG, "onCreateView - numColumns set to " + numColumns);
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                                }
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                                if (Utils.hasJellyBean()) {
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                                    mGridView.getViewTreeObserver()
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                                            .removeOnGlobalLayoutListener(this);
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                                } else {
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                                    mGridView.getViewTreeObserver()
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                                            .removeGlobalOnLayoutListener(this);
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                                }
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                            }
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                        }
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                    }
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                });
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        return v;
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    }
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    @Override
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    public void onResume() {
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        super.onResume();
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        mImageFetcher.setExitTasksEarly(false);
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        mAdapter.notifyDataSetChanged();
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    }
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    @Override
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    public void onPause() {
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        super.onPause();
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        mImageFetcher.setPauseWork(false);
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        mImageFetcher.setExitTasksEarly(true);
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        mImageFetcher.flushCache();
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    }
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    @Override
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    public void onDestroy() {
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        super.onDestroy();
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        mImageFetcher.closeCache();
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    }
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    @TargetApi(VERSION_CODES.JELLY_BEAN)
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    @Override
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    public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
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        final Intent i = new Intent(getActivity(), ImageDetailActivity.class);
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        i.putExtra(ImageDetailActivity.EXTRA_IMAGE, (int) id);
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        if (Utils.hasJellyBean()) {
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            // makeThumbnailScaleUpAnimation() looks kind of ugly here as the loading spinner may
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            // show plus the thumbnail image in GridView is cropped. so using
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            // makeScaleUpAnimation() instead.
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            ActivityOptions options =
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                    ActivityOptions.makeScaleUpAnimation(v, 0, 0, v.getWidth(), v.getHeight());
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            getActivity().startActivity(i, options.toBundle());
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        } else {
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            startActivity(i);
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        }
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    }
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    @Override
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    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
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        inflater.inflate(R.menu.main_menu, menu);
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    }
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    @Override
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    public boolean onOptionsItemSelected(MenuItem item) {
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        switch (item.getItemId()) {
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            case R.id.clear_cache:
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                mImageFetcher.clearCache();
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                Toast.makeText(getActivity(), R.string.clear_cache_complete_toast,
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                        Toast.LENGTH_SHORT).show();
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                return true;
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        }
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        return super.onOptionsItemSelected(item);
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    }
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    /**
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     * The main adapter that backs the GridView. This is fairly standard except the number of
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     * columns in the GridView is used to create a fake top row of empty views as we use a
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     * transparent ActionBar and don't want the real top row of images to start off covered by it.
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     */
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    private class ImageAdapter extends BaseAdapter {
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        private final Context mContext;
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        private int mItemHeight = 0;
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        private int mNumColumns = 0;
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        private int mActionBarHeight = 0;
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        private GridView.LayoutParams mImageViewLayoutParams;
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        public ImageAdapter(Context context) {
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            super();
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            mContext = context;
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            mImageViewLayoutParams = new GridView.LayoutParams(
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                    LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
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            // Calculate ActionBar height
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            TypedValue tv = new TypedValue();
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            if (context.getTheme().resolveAttribute(
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                    android.R.attr.actionBarSize, tv, true)) {
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                mActionBarHeight = TypedValue.complexToDimensionPixelSize(
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                        tv.data, context.getResources().getDisplayMetrics());
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            }
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        }
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        @Override
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        public int getCount() {
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            // If columns have yet to be determined, return no items
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            if (getNumColumns() == 0) {
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                return 0;
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            }
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            // Size + number of columns for top empty row
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            return Images.imageThumbUrls.length + mNumColumns;
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        }
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        @Override
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        public Object getItem(int position) {
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            return position < mNumColumns ?
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                    null : Images.imageThumbUrls[position - mNumColumns];
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        }
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        @Override
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        public long getItemId(int position) {
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            return position < mNumColumns ? 0 : position - mNumColumns;
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        }
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        @Override
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        public int getViewTypeCount() {
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            // Two types of views, the normal ImageView and the top row of empty views
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            return 2;
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        }
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        @Override
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        public int getItemViewType(int position) {
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            return (position < mNumColumns) ? 1 : 0;
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        }
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        @Override
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        public boolean hasStableIds() {
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            return true;
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        }
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        @Override
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        public View getView(int position, View convertView, ViewGroup container) {
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            // First check if this is the top row
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            if (position < mNumColumns) {
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                if (convertView == null) {
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                    convertView = new View(mContext);
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                }
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                // Set empty view with height of ActionBar
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                convertView.setLayoutParams(new AbsListView.LayoutParams(
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                        LayoutParams.MATCH_PARENT, mActionBarHeight));
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                return convertView;
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            }
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            // Now handle the main ImageView thumbnails
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            ImageView imageView;
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            if (convertView == null) { // if it's not recycled, instantiate and initialize
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                imageView = new RecyclingImageView(mContext);
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                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
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                imageView.setLayoutParams(mImageViewLayoutParams);
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            } else { // Otherwise re-use the converted view
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                imageView = (ImageView) convertView;
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            }
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            // Check the height matches our calculated column width
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            if (imageView.getLayoutParams().height != mItemHeight) {
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                imageView.setLayoutParams(mImageViewLayoutParams);
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            }
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            // Finally load the image asynchronously into the ImageView, this also takes care of
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            // setting a placeholder image while the background thread runs
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            mImageFetcher.loadImage(Images.imageThumbUrls[position - mNumColumns], imageView);
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            return imageView;
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        }
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        /**
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         * Sets the item height. Useful for when we know the column width so the height can be set
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         * to match.
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         *
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         * @param height
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         */
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        public void setItemHeight(int height) {
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            if (height == mItemHeight) {
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                return;
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            }
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            mItemHeight = height;
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            mImageViewLayoutParams =
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                    new GridView.LayoutParams(LayoutParams.MATCH_PARENT, mItemHeight);
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            mImageFetcher.setImageSize(height);
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            notifyDataSetChanged();
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        }
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        public void setNumColumns(int numColumns) {
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            mNumColumns = numColumns;
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        }
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        public int getNumColumns() {
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            return mNumColumns;
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        }
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    }
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}