Android example source code file (LookupActivity.java)

This example Android source code file (LookupActivity.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, animation, app, application, back_threshold, keyevent, lookupactivity, lookuptask, os, override, problem, progressbar, stack, string, tag, textview, ui, uri, view, webview

The LookupActivity.java Android example source code

/*
 * Copyright (C) 2009 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.wiktionary;

import com.example.android.wiktionary.SimpleWikiHelper.ApiException;
import com.example.android.wiktionary.SimpleWikiHelper.ParseException;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.SearchManager;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.SystemClock;
import android.text.TextUtils;
import android.text.format.DateUtils;
import android.util.Log;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.view.animation.Animation.AnimationListener;
import android.webkit.WebView;
import android.widget.ProgressBar;
import android.widget.TextView;

import java.util.Stack;

/**
 * Activity that lets users browse through Wiktionary content. This is just the
 * user interface, and all API communication and parsing is handled in
 * {@link ExtendedWikiHelper}.
 */
public class LookupActivity extends Activity implements AnimationListener {
    private static final String TAG = "LookupActivity";

    private View mTitleBar;
    private TextView mTitle;
    private ProgressBar mProgress;
    private WebView mWebView;

    private Animation mSlideIn;
    private Animation mSlideOut;

    /**
     * History stack of previous words browsed in this session. This is
     * referenced when the user taps the "back" key, to possibly intercept and
     * show the last-visited entry, instead of closing the activity.
     */
    private Stack<String> mHistory = new Stack();

    private String mEntryTitle;

    /**
     * Keep track of last time user tapped "back" hard key. When pressed more
     * than once within {@link #BACK_THRESHOLD}, we treat let the back key fall
     * through and close the app.
     */
    private long mLastPress = -1;

    private static final long BACK_THRESHOLD = DateUtils.SECOND_IN_MILLIS / 2;

    /**
     * {@inheritDoc}
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.lookup);

        // Load animations used to show/hide progress bar
        mSlideIn = AnimationUtils.loadAnimation(this, R.anim.slide_in);
        mSlideOut = AnimationUtils.loadAnimation(this, R.anim.slide_out);

        // Listen for the "in" animation so we make the progress bar visible
        // only after the sliding has finished.
        mSlideIn.setAnimationListener(this);

        mTitleBar = findViewById(R.id.title_bar);
        mTitle = (TextView) findViewById(R.id.title);
        mProgress = (ProgressBar) findViewById(R.id.progress);
        mWebView = (WebView) findViewById(R.id.webview);

        // Make the view transparent to show background
        mWebView.setBackgroundColor(0);

        // Prepare User-Agent string for wiki actions
        ExtendedWikiHelper.prepareUserAgent(this);

        // Handle incoming intents as possible searches or links
        onNewIntent(getIntent());
    }

    /**
     * Intercept the back-key to try walking backwards along our word history
     * stack. If we don't have any remaining history, the key behaves normally
     * and closes this activity.
     */
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        // Handle back key as long we have a history stack
        if (keyCode == KeyEvent.KEYCODE_BACK && !mHistory.empty()) {

            // Compare against last pressed time, and if user hit multiple times
            // in quick succession, we should consider bailing out early.
            long currentPress = SystemClock.uptimeMillis();
            if (currentPress - mLastPress < BACK_THRESHOLD) {
                return super.onKeyDown(keyCode, event);
            }
            mLastPress = currentPress;

            // Pop last entry off stack and start loading
            String lastEntry = mHistory.pop();
            startNavigating(lastEntry, false);

            return true;
        }

        // Otherwise fall through to parent
        return super.onKeyDown(keyCode, event);
    }

    /**
     * Start navigating to the given word, pushing any current word onto the
     * history stack if requested. The navigation happens on a background thread
     * and updates the GUI when finished.
     *
     * @param word The dictionary word to navigate to.
     * @param pushHistory If true, push the current word onto history stack.
     */
    private void startNavigating(String word, boolean pushHistory) {
        // Push any current word onto the history stack
        if (!TextUtils.isEmpty(mEntryTitle) && pushHistory) {
            mHistory.add(mEntryTitle);
        }

        // Start lookup for new word in background
        new LookupTask().execute(word);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.lookup, menu);
        return true;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.lookup_search: {
                onSearchRequested();
                return true;
            }
            case R.id.lookup_random: {
                startNavigating(null, true);
                return true;
            }
            case R.id.lookup_about: {
                showAbout();
                return true;
            }
        }
        return false;
    }

    /**
     * Show an about dialog that cites data sources.
     */
    protected void showAbout() {
        // Inflate the about message contents
        View messageView = getLayoutInflater().inflate(R.layout.about, null, false);

        // When linking text, force to always use default color. This works
        // around a pressed color state bug.
        TextView textView = (TextView) messageView.findViewById(R.id.about_credits);
        int defaultColor = textView.getTextColors().getDefaultColor();
        textView.setTextColor(defaultColor);

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setIcon(R.drawable.app_icon);
        builder.setTitle(R.string.app_name);
        builder.setView(messageView);
        builder.create();
        builder.show();
    }

    /**
     * Because we're singleTop, we handle our own new intents. These usually
     * come from the {@link SearchManager} when a search is requested, or from
     * internal links the user clicks on.
     */
    @Override
    public void onNewIntent(Intent intent) {
        final String action = intent.getAction();
        if (Intent.ACTION_SEARCH.equals(action)) {
            // Start query for incoming search request
            String query = intent.getStringExtra(SearchManager.QUERY);
            startNavigating(query, true);

        } else if (Intent.ACTION_VIEW.equals(action)) {
            // Treat as internal link only if valid Uri and host matches
            Uri data = intent.getData();
            if (data != null && ExtendedWikiHelper.WIKI_LOOKUP_HOST
                    .equals(data.getHost())) {
                String query = data.getPathSegments().get(0);
                startNavigating(query, true);
            }

        } else {
            // If not recognized, then start showing random word
            startNavigating(null, true);
        }
    }

    /**
     * Set the title for the current entry.
     */
    protected void setEntryTitle(String entryText) {
        mEntryTitle = entryText;
        mTitle.setText(mEntryTitle);
    }

    /**
     * Set the content for the current entry. This will update our
     * {@link WebView} to show the requested content.
     */
    protected void setEntryContent(String entryContent) {
        mWebView.loadDataWithBaseURL(ExtendedWikiHelper.WIKI_AUTHORITY, entryContent,
                ExtendedWikiHelper.MIME_TYPE, ExtendedWikiHelper.ENCODING, null);
    }

    /**
     * Background task to handle Wiktionary lookups. This correctly shows and
     * hides the loading animation from the GUI thread before starting a
     * background query to the Wiktionary API. When finished, it transitions
     * back to the GUI thread where it updates with the newly-found entry.
     */
    private class LookupTask extends AsyncTask<String, String, String> {
        /**
         * Before jumping into background thread, start sliding in the
         * {@link ProgressBar}. We'll only show it once the animation finishes.
         */
        @Override
        protected void onPreExecute() {
            mTitleBar.startAnimation(mSlideIn);
        }

        /**
         * Perform the background query using {@link ExtendedWikiHelper}, which
         * may return an error message as the result.
         */
        @Override
        protected String doInBackground(String... args) {
            String query = args[0];
            String parsedText = null;

            try {
                // If query word is null, assume request for random word
                if (query == null) {
                    query = ExtendedWikiHelper.getRandomWord();
                }

                if (query != null) {
                    // Push our requested word to the title bar
                    publishProgress(query);
                    String wikiText = ExtendedWikiHelper.getPageContent(query, true);
                    parsedText = ExtendedWikiHelper.formatWikiText(wikiText);
                }
            } catch (ApiException e) {
                Log.e(TAG, "Problem making wiktionary request", e);
            } catch (ParseException e) {
                Log.e(TAG, "Problem making wiktionary request", e);
            }

            if (parsedText == null) {
                parsedText = getString(R.string.empty_result);
            }

            return parsedText;
        }

        /**
         * Our progress update pushes a title bar update.
         */
        @Override
        protected void onProgressUpdate(String... args) {
            String searchWord = args[0];
            setEntryTitle(searchWord);
        }

        /**
         * When finished, push the newly-found entry content into our
         * {@link WebView} and hide the {@link ProgressBar}.
         */
        @Override
        protected void onPostExecute(String parsedText) {
            mTitleBar.startAnimation(mSlideOut);
            mProgress.setVisibility(View.INVISIBLE);

            setEntryContent(parsedText);
        }
    }

    /**
     * Make the {@link ProgressBar} visible when our in-animation finishes.
     */
    public void onAnimationEnd(Animation animation) {
        mProgress.setVisibility(View.VISIBLE);
    }

    public void onAnimationRepeat(Animation animation) {
        // Not interested if the animation repeats
    }

    public void onAnimationStart(Animation animation) {
        // Not interested when the animation starts
    }
}