WebViewer.java

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// -*- mode: java; c-basic-offset: 2; -*-
// Copyright 2009-2011 Google, All Rights reserved
// Copyright 2011-2020 MIT, All rights reserved
// Released under the Apache License, Version 2.0
// http://www.apache.org/licenses/LICENSE-2.0
 
package com.google.appinventor.components.runtime;
 
import android.Manifest;
import android.graphics.Bitmap;
import android.view.MotionEvent;
import android.view.View;
import android.webkit.CookieManager;
import android.webkit.JavascriptInterface;
import android.webkit.WebView;
import android.webkit.WebViewClient;
 
import com.google.appinventor.components.annotations.DesignerComponent;
import com.google.appinventor.components.annotations.DesignerProperty;
import com.google.appinventor.components.annotations.PropertyCategory;
import com.google.appinventor.components.annotations.SimpleEvent;
import com.google.appinventor.components.annotations.SimpleFunction;
import com.google.appinventor.components.annotations.SimpleObject;
import com.google.appinventor.components.annotations.SimpleProperty;
import com.google.appinventor.components.annotations.UsesPermissions;
import com.google.appinventor.components.common.ComponentCategory;
import com.google.appinventor.components.common.PropertyTypeConstants;
import com.google.appinventor.components.common.YaVersion;
 
import com.google.appinventor.components.runtime.util.EclairUtil;
import com.google.appinventor.components.runtime.util.FroyoUtil;
import com.google.appinventor.components.runtime.util.MediaUtil;
import com.google.appinventor.components.runtime.util.SdkLevel;
 
 
@DesignerComponent(version = YaVersion.WEBVIEWER_COMPONENT_VERSION,
    category = ComponentCategory.USERINTERFACE,
    description = "Component for viewing Web pages.  The Home URL can be " +
        "specified in the Designer or in the Blocks Editor.  The view can be set " +
        "to follow links when they are tapped, and users can fill in Web forms. " +
        "Warning: This is not a full browser.  For example, pressing the phone's " +
        "hardware Back key will exit the app, rather than move back in the " +
        "browser history." +
        "<p />You can use the WebViewer.WebViewString property to communicate " +
        "between your app and Javascript code running in the Webviewer page. " +
        "In the app, you get and set WebViewString.  " +
        "In the WebViewer, you include Javascript that references the window.AppInventor " +
        "object, using the methoods </em getWebViewString()</em> and <em>setWebViewString(text)</em>.  " +
        "<p />For example, if the WebViewer opens to a page that contains the Javascript command " +
        "<br /> <em>document.write(\"The answer is\" + window.AppInventor.getWebViewString());</em> " +
        "<br />and if you set WebView.WebVewString to \"hello\", then the web page will show " +
        "</br ><em>The answer is hello</em>.  " +
        "<br />And if the Web page contains Javascript that executes the command " +
        "<br /><em>window.AppInventor.setWebViewString(\"hello from Javascript\")</em>, " +
        "<br />then the value of the WebViewString property will be " +
        "<br /><em>hello from Javascript</em>. ")
 
// TODO(halabelson): Integrate control of the Back key, when we provide it
 
@SimpleObject
@UsesPermissions(permissionNames = "android.permission.INTERNET")
public final class WebViewer extends AndroidViewComponent {
 
  private final WebView webview;
 
  // URL for the WebViewer to load initially
  private String homeUrl;
 
  // whether or not to follow links when they are tapped
  private boolean followLinks = true;
 
  // Whether or not to prompt for permission in the WebViewer
  private boolean prompt = true;
 
  // ignore SSL Errors (mostly certificate errors. When set
  // self signed certificates should work.
 
  private boolean ignoreSslErrors = false;
 
  // allows passing strings to javascript
  WebViewInterface wvInterface;
 
  // Flag to mark whether we have received permission to read external storage
  private boolean havePermission = false;
 
  public WebViewer(ComponentContainer container) {
    super(container);
 
    webview = new WebView(container.$context());
    resetWebViewClient();       // Set up the web view client
    webview.getSettings().setJavaScriptEnabled(true);
    webview.setFocusable(true);
    // adds a way to send strings to the javascript
    wvInterface = new WebViewInterface();
    webview.addJavascriptInterface(wvInterface, "AppInventor");
    // enable pinch zooming and zoom controls
    webview.getSettings().setBuiltInZoomControls(true);
 
    if (SdkLevel.getLevel() >= SdkLevel.LEVEL_ECLAIR)
      EclairUtil.setupWebViewGeoLoc(this, webview, container.$context());
 
    container.$add(this);
 
    webview.setOnTouchListener(new View.OnTouchListener() {
      @Override
      public boolean onTouch(View v, MotionEvent event) {
        switch (event.getAction()) {
          case MotionEvent.ACTION_DOWN:
          case MotionEvent.ACTION_UP:
            if (!v.hasFocus()) {
              v.requestFocus();
            }
            break;
        }
        return false;
      }
    });
 
    // set the initial default properties.  Height and Width
    // will be fill-parent, which will be the default for the web viewer.
 
    HomeUrl("");
    Width(LENGTH_FILL_PARENT);
    Height(LENGTH_FILL_PARENT);
  }
 
  @SimpleProperty(description = "Gets the WebView's String, which is viewable through " +
      "Javascript in the WebView as the window.AppInventor object",
      category = PropertyCategory.BEHAVIOR)
  public String WebViewString() {
    return wvInterface.getWebViewString();
  }
 
  @SimpleProperty(category = PropertyCategory.BEHAVIOR)
  public void WebViewString(String newString) {
    wvInterface.setWebViewStringFromBlocks(newString);
  }
 
  @Override
  public View getView() {
    return webview;
  }
 
  // Create a class so we can override the default link following behavior.
  // The handler doesn't do anything on its own.  But returning true means that
  // this do nothing will override the default WebView behavior.  Returning
  // false means to let the WebView handle the Url.  In other words, returning
  // true will not follow the link, and returning false will follow the link.
  private class WebViewerClient extends WebViewClient {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
      return !followLinks;
    }
 
    @Override
    public void onPageStarted(WebView view, String url, Bitmap favicon) {
      BeforePageLoad(url);
    }
 
    @Override
    public void onPageFinished(WebView view, String url) {
      PageLoaded(url);
    }
 
    @Override
    public void onReceivedError(WebView view, final int errorCode, final String description, final String failingUrl) {
      container.$form().runOnUiThread(new Runnable() {
        public void run() {
          ErrorOccurred(errorCode, description, failingUrl);
        }
      });
    }
  }
 
  // Components don't normally override Width and Height, but we do it here so that
  // the automatic width and height will be fill parent.
 
  @Override
  @SimpleProperty()
  public void Width(int width) {
    if (width == LENGTH_PREFERRED) {
      width = LENGTH_FILL_PARENT;
    }
    super.Width(width);
  }
 
  @Override
  @SimpleProperty()
  public void Height(int height) {
    if (height == LENGTH_PREFERRED) {
      height = LENGTH_FILL_PARENT;
    }
    super.Height(height);
  }
 
 
  @SimpleProperty(
      description = "URL of the page the WebViewer should initially open to.  " +
          "Setting this will load the page.",
      category = PropertyCategory.BEHAVIOR)
  public String HomeUrl() {
    return homeUrl;
  }
 
  @DesignerProperty(editorType = PropertyTypeConstants.PROPERTY_TYPE_STRING,
      defaultValue = "")
  @SimpleProperty()
  public void HomeUrl(String url) {
    homeUrl = url;
    // clear the history, since changing Home is a kind of reset
    webview.clearHistory();
    loadUrl("HomeUrl", homeUrl);
  }
 
  @SimpleProperty(
      description = "URL of the page currently viewed.   This could be different from the " +
          "Home URL if new pages were visited by following links.",
      category = PropertyCategory.BEHAVIOR)
  public String CurrentUrl() {
    return (webview.getUrl() == null) ? "" : webview.getUrl();
  }
 
  @SimpleProperty(
      description = "Title of the page currently viewed",
      category = PropertyCategory.BEHAVIOR)
  public String CurrentPageTitle() {
    return (webview.getTitle() == null) ? "" : webview.getTitle();
  }
 
 
  @SimpleProperty(
      description = "Determines whether to follow links when they are tapped in the WebViewer.  " +
          "If you follow links, you can use GoBack and GoForward to navigate the browser history. ",
      category = PropertyCategory.BEHAVIOR)
  public boolean FollowLinks() {
    return followLinks;
  }
 
 
  @DesignerProperty(editorType = PropertyTypeConstants.PROPERTY_TYPE_BOOLEAN,
      defaultValue = "True")
  @SimpleProperty()
  public void FollowLinks(boolean follow) {
    followLinks = follow;
    resetWebViewClient();
  }
 
  @SimpleProperty(
      description = "Determine whether or not to ignore SSL errors. Set to true to ignore " +
          "errors. Use this to accept self signed certificates from websites.",
      category = PropertyCategory.BEHAVIOR)
  public boolean IgnoreSslErrors() {
    return ignoreSslErrors;
  }
 
  @DesignerProperty(editorType = PropertyTypeConstants.PROPERTY_TYPE_BOOLEAN,
      defaultValue = "False")
  @SimpleProperty()
  public void IgnoreSslErrors(boolean ignoreSslErrors) {
    this.ignoreSslErrors = ignoreSslErrors;
    resetWebViewClient();
  }
 
  @SimpleFunction(
      description = "Loads the home URL page.  This happens automatically when " +
          "the home URL is changed.")
  public void GoHome() {
    loadUrl("GoHome", homeUrl);
  }
 
  @SimpleFunction(
      description = "Go back to the previous page in the history list.  " +
          "Does nothing if there is no previous page.")
  public void GoBack() {
    if (webview.canGoBack()) {
      webview.goBack();
    }
  }
 
  @SimpleFunction(
      description = "Go forward to the next page in the history list.   " +
          "Does nothing if there is no next page.")
  public void GoForward() {
    if (webview.canGoForward()) {
      webview.goForward();
    }
  }
 
  @SimpleFunction(
      description = "Returns true if the WebViewer can go forward in the history list.")
  public boolean CanGoForward() {
    return webview.canGoForward();
  }
 
 
  @SimpleFunction(
      description = "Returns true if the WebViewer can go back in the history list.")
  public boolean CanGoBack() {
    return webview.canGoBack();
  }
 
 
  @SimpleFunction(
      description = "Load the page at the given URL.")
  public void GoToUrl(String url) {
    loadUrl("GoToUrl", url);
  }
 
  @SimpleFunction(
      description = "Stop loading a page.")
  public void StopLoading() {
    webview.stopLoading();
  }
 
  @SimpleFunction(
      description = "Reload the current page.")
  public void Reload() {
    webview.reload();
  }
 
  @DesignerProperty(editorType = PropertyTypeConstants.PROPERTY_TYPE_BOOLEAN,
      defaultValue = "False")
  @SimpleProperty(userVisible = false,
      description = "Whether or not to give the application permission to use the Javascript geolocation API. " +
          "This property is available only in the designer.")
  public void UsesLocation(boolean uses) {
    // We don't actually do anything here (the work is in the MockWebViewer)
  }
 
  @SimpleProperty(description = "If True, then prompt the user of the WebView to give permission to access the geolocation API. " +
      "If False, then assume permission is granted.")
  public boolean PromptforPermission() {
    return prompt;
  }
 
  @DesignerProperty(editorType = PropertyTypeConstants.PROPERTY_TYPE_BOOLEAN,
      defaultValue = "True")
  @SimpleProperty(userVisible = true)
  public void PromptforPermission(boolean prompt) {
    this.prompt = prompt;
  }
 
  @SimpleFunction(description = "Clear stored location permissions.")
  public void ClearLocations() {
    if (SdkLevel.getLevel() >= SdkLevel.LEVEL_ECLAIR)
      EclairUtil.clearWebViewGeoLoc();
  }
 
  private void resetWebViewClient() {
    if (SdkLevel.getLevel() >= SdkLevel.LEVEL_FROYO) {
      webview.setWebViewClient(FroyoUtil.getWebViewClient(ignoreSslErrors, followLinks, container.$form(), this));
    } else {
      webview.setWebViewClient(new WebViewerClient());
    }
  }
 
  @SimpleFunction(description = "Clear WebView caches.")
  public void ClearCaches() {
    webview.clearCache(true);
  }
 
  @SimpleFunction(description = "Clear WebView cookies.")
  public void ClearCookies() {
    CookieManager cookieManager = CookieManager.getInstance();
    if (SdkLevel.getLevel() >= SdkLevel.LEVEL_LOLLIPOP) {
      cookieManager.removeAllCookies(null);
    } else {
      cookieManager.removeAllCookie();
    }
  }
 
  @SimpleFunction(description = "Run JavaScript in the current page.")
  public void RunJavaScript(String js) {
    // evaluateJavascript() was added in API 19
    // and is therefore not used here for compatibility purposes.
    webview.loadUrl("javascript:(function(){" + js + "})()");
  }
 
  @SimpleEvent(description = "When the JavaScript calls AppInventor.setWebViewString this event is run.")
  public void WebViewStringChange(String value) {
    EventDispatcher.dispatchEvent(this, "WebViewStringChange", value);
  }
 
  @SimpleEvent(description = "When a page is about to load this event is run.")
  public void BeforePageLoad(String url) {
    EventDispatcher.dispatchEvent(this, "BeforePageLoad", url);
  }
 
  @SimpleEvent(description = "When a page is finished loading this event is run.")
  public void PageLoaded(String url) {
    EventDispatcher.dispatchEvent(this, "PageLoaded", url);
  }
 
  @SimpleEvent(description = "When an error occurs this event is run.")
  public void ErrorOccurred(int errorCode, String description, String failingUrl) {
    EventDispatcher.dispatchEvent(this, "ErrorOccurred", errorCode, description, failingUrl);
  }
 
  private void loadUrl(final String caller, final String url) {
    if (!havePermission && MediaUtil.isExternalFileUrl(container.$form(), url)) {
      container.$form().askPermission(Manifest.permission.READ_EXTERNAL_STORAGE,
          new PermissionResultHandler() {
            @Override
            public void HandlePermissionResponse(String permission, boolean granted) {
              if (granted) {
                havePermission = true;
                webview.loadUrl(url);
              } else {
                container.$form().dispatchPermissionDeniedEvent(WebViewer.this, caller,
                    Manifest.permission.READ_EXTERNAL_STORAGE);
              }
            }
          });
      return;
    }
    webview.loadUrl(url);
  }
 
  public class WebViewInterface {
    String webViewString;
 
    WebViewInterface() {
      webViewString = " ";
    }
 
    @JavascriptInterface
    public String getWebViewString() {
      return webViewString;
    }
 
    @JavascriptInterface
    public void setWebViewString(final String newString) {
      webViewString = newString;
 
      container.$form().runOnUiThread(new Runnable() {
        public void run() {
          WebViewStringChange(newString);
        }
      });
    }
 
    public void setWebViewStringFromBlocks(final String newString) {
      webViewString = newString;
    }
 
  }
}