Java tutorial
/* * Copyright (C) 2014 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.example.android.justforus; import android.content.Context; import android.content.Intent; import android.net.Uri; import android.os.Bundle; import android.support.v4.app.ShareCompat; import android.support.v7.app.ActionBarActivity; import android.text.TextUtils; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.AdapterView; import android.widget.AdapterView.OnItemClickListener; import android.widget.BaseAdapter; import android.widget.GridView; import android.widget.ImageView; import android.widget.TextView; import java.util.ArrayList; import java.util.List; /** * Activity to display a grid of coupons. The number of columns varies based on screen width, * and goes down to a one-column grid on a small device such as a phone. * * <p>A coupon consists of a photo, title, and subtitle. * * <p>Tapping on a coupon to redeem it brings up the Android "share" * dialog with a pre-populated message based on the coupon text. */ public class MainActivity extends ActionBarActivity implements OnItemClickListener { // Name of person giving out these coupons. When the user clicks on a coupon and shares // to another app, this name will be part of the pre-populated text. // TODO: Fill in your name here private static final String SENDER_NAME = ""; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Set activity_main.xml to be the layout for this activity setContentView(R.layout.activity_main); // Fetch the {@link LayoutInflater} service so that new views can be created LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE); // Find the {@link GridView} that was already defined in the XML layout GridView gridView = (GridView) findViewById(R.id.grid); // Initialize the adapter with all the coupons. Set the adapter on the {@link GridView}. gridView.setAdapter(new CouponAdapter(inflater, createAllCoupons())); // Set a click listener for each coupon in the grid gridView.setOnItemClickListener(this); } /** * Generate the list of all coupons. * @return The list of coupons. */ private List<Coupon> createAllCoupons() { // TODO: Customize this list of coupons for your personal use. // You can add a title, subtitle, and a photo (in the assets directory). List<Coupon> coupons = new ArrayList<Coupon>(); coupons.add(new Coupon("Walk in the park" /* title */, "Take a stroll in the flower garden" /* subtitle */, "park.jpg" /* image */)); coupons.add(new Coupon("Trip to the zoo", "See the cute zoo animals", "zoo.jpg")); coupons.add(new Coupon("Watch sunrise", "Drive out to the vista point and watch the sunrise at 6am", "sunrise.jpg")); coupons.add(new Coupon("Hawaii getaway", "Relax in Hawaii by going to the beach and attending luaus", "hawaii.jpg")); coupons.add(new Coupon("Spa day", "Receive a massage and enjoy the peace and quiet", "spa.jpg")); coupons.add(new Coupon("Homemade dinner", "Your favorite meal cooked by yours truly", "dinner.jpg")); coupons.add(new Coupon("Day on the water", "Boat ride down the river on a breezy day", "boat.jpg")); coupons.add(new Coupon("Flowers", "Delivered to your front door", "rose.jpg")); coupons.add(new Coupon("Picnic", "Wine, bread, and cheese at the vineyard", "picnic.jpg")); coupons.add(new Coupon("Surprise gift", "Won't be revealed until redeemed", "present.jpg")); return coupons; } /** * Callback method for a when a coupon is clicked. A new share intent is created with the * coupon title. Then the user can select which app to share the content of the coupon with. * * @param parent The AdapterView where the click happened. * @param view The view within the AdapterView that was clicked (this * will be a view provided by the adapter). * @param position The position of the view in the adapter. * @param id The row id of the item that was clicked. */ @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { // Find coupon that was clicked based off of position in adapter Coupon coupon = (Coupon) parent.getItemAtPosition(position); // Create share intent Intent shareIntent = ShareCompat.IntentBuilder.from(this).setText(getShareText(coupon)) .setType("image/jpeg").setStream(coupon.mImageUri).setChooserTitle(getString(R.string.redeem_using)) .createChooserIntent(); startActivity(shareIntent); } /** * Create the share intent text based on the coupon title, subtitle, and whether or not * there is a {@link #SENDER_NAME}. * * @param coupon to create the intent text for. * @return string to be used in the share intent. */ private String getShareText(Coupon coupon) { // If there is no sender name, just use the coupon title and subtitle if (TextUtils.isEmpty(SENDER_NAME)) { return getString(R.string.message_format_without_sender, coupon.mTitle, coupon.mSubtitle); } else { // Otherwise, use the other string template and pass in the {@link #SENDER_NAME} too return getString(R.string.message_format_with_sender, SENDER_NAME, coupon.mTitle, coupon.mSubtitle); } } /** * Adapter for grid of coupons. */ private static class CouponAdapter extends BaseAdapter { private LayoutInflater mInflater; private List<Coupon> mAllCoupons; /** * Constructs a new {@link CouponAdapter}. * * @param inflater to create new views * @param allCoupons for list of all coupons to be displayed */ public CouponAdapter(LayoutInflater inflater, List<Coupon> allCoupons) { if (allCoupons == null) { throw new IllegalStateException("Can't have null list of coupons"); } mAllCoupons = allCoupons; mInflater = inflater; } @Override public int getCount() { return mAllCoupons.size(); } @Override public Coupon getItem(int position) { return mAllCoupons.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { View result = convertView; if (result == null) { result = mInflater.inflate(R.layout.grid_item, parent, false); } // Try to get view cache or create a new one if needed ViewCache viewCache = (ViewCache) result.getTag(); if (viewCache == null) { viewCache = new ViewCache(result); result.setTag(viewCache); } // Fetch item Coupon coupon = getItem(position); // Bind the data viewCache.mTitleView.setText(coupon.mTitle); viewCache.mSubtitleView.setText(coupon.mSubtitle); viewCache.mImageView.setImageURI(coupon.mImageUri); return result; } } /** * Cache of views in the grid item view to make recycling of views quicker. This avoids * additional {@link View#findViewById(int)} calls after the {@link ViewCache} is first * created for a view. See * {@link CouponAdapter#getView(int position, View convertView, ViewGroup parent)}. */ private static class ViewCache { /** View that displays the title of the coupon */ private final TextView mTitleView; /** View that displays the subtitle of the coupon */ private final TextView mSubtitleView; /** View that displays the image associated with the coupon */ private final ImageView mImageView; /** * Constructs a new {@link ViewCache}. * * @param view which contains children views that should be cached. */ private ViewCache(View view) { mTitleView = (TextView) view.findViewById(R.id.title); mSubtitleView = (TextView) view.findViewById(R.id.subtitle); mImageView = (ImageView) view.findViewById(R.id.image); } } /** * Model object for coupon. */ private static class Coupon { /** Title of the coupon. */ private final String mTitle; /** Description of the coupon. */ private final String mSubtitle; /** Content URI of the image for the coupon. */ private final Uri mImageUri; /** * Constructs a new {@link Coupon}. * * @param titleString is the title * @param subtitleString is the description * @param imageAssetFilePath is the file path from the application's assets folder for * the image associated with this coupon */ private Coupon(String titleString, String subtitleString, String imageAssetFilePath) { mTitle = titleString; mSubtitle = subtitleString; mImageUri = Uri.parse("content://" + AssetProvider.CONTENT_URI + "/" + imageAssetFilePath); } } }