src/android/src/com/google/android/inputmethod/japanese/preference/MiniBrowserActivity.java

// Copyright 2010-2014, Google Inc.
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package org.mozc.android.inputmethod.japanese.preference;

import org.mozc.android.inputmethod.japanese.resources.R;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Bundle;
import android.view.KeyEvent;
import android.webkit.WebView;
import android.webkit.WebViewClient;

import java.util.regex.Pattern;

/**
 * Mini browser to show licenses.
 *
 * <p>We must show some web sites (e.g. EULA) from preference screen.
 * However in some special environments default browser is not installed so
 * even if an Intent is issued nothing will happen.
 * This mini browser accepts an Intent and shows its content (of which URL is included as
 * Intent's data) like as a browser.
 *
 */
public class MiniBrowserActivity extends Activity {

  // TODO(matsuzakit): "print" link is meaningless. Should be invisible.
  // TODO(matsuzakit): CSS needs to be improved.

  @VisibleForTesting
  static final class MiniBrowserClient extends WebViewClient {
    private final String restrictionPattern;
    private final PackageManager packageManager;
    private final Context context;

    @VisibleForTesting
    MiniBrowserClient(String restrictionPattern, PackageManager packageManager, Context context) {
      Preconditions.checkNotNull(restrictionPattern);
      Preconditions.checkNotNull(packageManager);
      Preconditions.checkNotNull(packageManager);

      this.restrictionPattern = restrictionPattern;
      this.packageManager = packageManager;
      this.context = context;
    }

    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
      try {
        Preconditions.checkNotNull(view);
        Preconditions.checkNotNull(url);

        // Use temporary matcher intentionally.
        // Regex engine is rather heavy to instantiate so use it as less as possible.
        if (!Pattern.matches(restrictionPattern, url)) {
          // If the URL's doesn't match restriction pattern,
          // delegate the operation to the default browser.
          Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
          if (!packageManager.queryIntentActivities(browserIntent, 0).isEmpty()) {
            context.startActivity(browserIntent);
          }
          // If no default browser is available, do nothing.
          return true;
        }
        // Prevent from invoking default browser.
        // In some special environment default browser is not installed.
        return false;
      } catch (Throwable e) {
        // This method might be called from native layer.
        // Therefore throwing something from here causes native crash.
        // To prevent from native crash, catches all here.
        // At least SecurityException must be caught here for Android-TV.
        return true;
      }
    }
  }

  private Optional<WebView> webView = Optional.absent();

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    WebView webView = new WebView(this);
    this.webView = Optional.of(webView);
    webView.setWebViewClient(
        new MiniBrowserClient(getResources().getString(R.string.pref_url_restriction_regex),
                              getPackageManager(), this));
    webView.loadUrl(getIntent().getData().toString());
    setContentView(webView);
  }

  @Override
  protected void onPause() {
    // Clear cache in order to show appropriate website even if system locale is changed.
    if (this.webView.isPresent()) {
      this.webView.get().clearCache(true);
    }
    super.onPause();
  }

  @Override
  public boolean onKeyDown(int keyCode, KeyEvent event) {
    Preconditions.checkNotNull(event);

    // Enable back-key inside the webview.
    // If no history exists, default behavior is executed (finish the activity).
    if (keyCode == KeyEvent.KEYCODE_BACK && webView.isPresent() && webView.get().canGoBack()) {
      webView.get().goBack();
      return true;
    }
    return super.onKeyDown(keyCode, event);
  }
}