Building a browser for android. The best browsers for Android
In this lesson:
Writing a simple browser
In the last lesson, we saw that if we call Intent With action= ACTION_VIEW and data= Uri- object with http-address, then it starts browser and displays the content of the page at that http address. We can independently make the simplest browser that will respond to such an Intent and simply display the page. To do this, you need to set Intent Filter and use the component webview.
On the first screen of the application, we will have a button that submits an Intent. The second screen will have a WebView.
Let's create a project:
project name: P0321_SimpleBrowser
Build Target: Android 2.3.3
application name: SimpleBrowser
package name: en.startandroid.develop.p0321simplebrowser
Create Activity: MainActivity
We draw main.xml
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
Just a button on the screen
Kodim MainActivity.java:
package
Import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
Public class MainActivity extends Activity(
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState )(
setContentView(R.layout.main) ;
(findViewById(R.id.btnWeb)) .setOnClickListener(new OnClickListener()(
@Override
public void onClick ( View v ) (
startActivity (new Intent (Intent.ACTION_VIEW, Uri.parse ("http://www.ya.ru" ))) ;
}
})
;
}
}
The code is a bit odd. Pay attention, I do not describe the class object anywhere. button. Method findViewById returns view, and this view supports method setOnClickListener which I am calling. And in the method setOnClickListener I create an object that implements an interface OnClickListener and in it I write the code in onClick. Also I create an object Intent not separately, but directly in the method startActivity. There is less code than usual. Maybe this is an option for you.
Let's create a second Activity. First the layout file browser.xml:
android:layout_height="match_parent"
android:orientation="vertical" >
android:layout_width="match_parent"
android:layout_height ="match_parent" >
On screen component webview.
We create BrowserActivity.java:
package en.startandroid.develop.p0321simplebrowser;
Import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.webkit.webview;
Public class BrowserActivity extends Activity(
@Override
protected void onCreate (Bundle savedInstanceState ) (
super .onCreate(savedInstanceState ) ;
setContentView(R.layout.browser) ;
WebView webView = (WebView ) findViewById (R.id.webView ) ;
Uri data = getIntent() .getData() ;
webView.loadUrl(data.toString());
}
}
We define webview, read data from Intent and transfer string in webview.
Now let's write Activity in manifest. To it we will need to add Intent filter, indicate in it action = ACTION_VIEW. And for data we see several options, use Scheme= http.
It means that Uri object in Intent must contain an http address.
Don't forget about Category= Default. label for BrowserActivity specify e.g. MyBrowser.
Also in the manifest you need to add Use Permission = android.permission.INTERNET tab Permissions. For the system to give the application access to the Internet.
Save everything and run the application. We press the button and see the choice: the system offers us a choice system browser and our just made. Those. Intent with a request to view the http address found in the system two Activities that are in their Intent filter declared that they can display http-addresses.
Select our MyBrowser and see the page.
We saw that Activity in our applications can handle Not only our invented action, but also systemic. And, thus, create an alternative to system applications.
But, as you understand, we could easily not use WebView in our Activity and not show the page. It was possible to use a TextView and simply display the address from data as text. Or code an http request that would download this page and display its html content. We could generally score on the http address and show some left picture or just a dark screen.
Those. for Activity, you can create an Intent Filter that will tell the system that the application can do something, but at the same time, there will be some nonsense inside the Activity. These are questions of programming ethics, common sense and adequacy)
Full manifest file code:
In the next lesson:
Storing data with Preferences
Android allows you to create your own window for browsing the web, or even create your own browser clone using the . The element itself uses the WebKit engine and has many properties and methods. We will limit ourselves to a basic example of creating an application with which we can view pages on the Internet. AT latest versions the engine from Chromium is used, but there is not much difference in this for simple tasks.
Let's create a new project MyBrowser and immediately replace the code in the markup file res/layout/activity_main.xml:
Now let's open the activity file MainActivity.java and declare the component , and also initialize it - include Java support Script and specify the page to load.
Private WebView webView; public void onCreate(Bundle savedInstanceState) ( super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); webView = findViewById(R.id.webView); // enable JavaScript webView.getSettings().setJavaScriptEnabled(true) ; // Specify the loading page webView.loadUrl("http://website/android"); )
Since the application will use the Internet, you need to set permission to access the Internet in the manifest file.
In the same place in the manifest, we modify the line for the screen by removing the title from our application (highlighted in bold):
Let's start the application. We have at our disposal the simplest web page viewer, but with one drawback. If you click on any link, your default browser will automatically launch and new page will show up there. More precisely, it was before. On newer devices, launching the app immediately opens the browser.
To solve this problem and open links in your program, you need to override the class WebViewClient and let our application handle the links. Let's add a nested class in the code:
Private class MyWebViewClient extends WebViewClient ( @TargetApi(Build.VERSION_CODES.N) @Override public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) ( view.loadUrl(request.getUrl().toString()); return true; ) // For old devices @Override public boolean shouldOverrideUrlLoading(WebView view, String url) ( view.loadUrl(url); return true; ) )
Then in the method onCreate() define an instance MyWebViewClient. It can be anywhere after the object has been initialized:
WebView.setWebViewClient(new MyWebViewClient());
Now in our application created WebViewClient, which allows any given URL selected in to be loaded into the container itself rather than launching a browser. The method is responsible for this functionality, in which we specify the current and desired URL. Return value true says we don't need to run third party browser, and independently download the content from the link. An overloaded version of the method was added in API version 24, so keep this in mind.
Re-launch the program and check that the links are now loaded in the application itself. But now there is another problem. We cannot return to the previous page. If we press the BACK button on our device, we simply close our application. To solve a new problem, we need to handle pressing the BACK button. Adding a new method:
@Override public void onBackPressed() ( if(webView.canGoBack()) ( webView.goBack(); ) else ( super.onBackPressed(); ) )
We need to check what supports navigation to the previous page. If the condition is true, then the method is called goBack(), which takes us back one step to the previous page. If there are several such pages, then we can sequentially return to the very first page. The method will always return a value. true. When we return to the very first page from which we started our journey on the Internet, the value will return false and the processing of pressing the BACK button will be handled by the system itself, which will close the application screen.
Run the application again. You now have your own web browser that allows you to follow links and return to the previous page. After studying the documentation, you can equip the application with other delicious goodies for your browser.
If you need to open some of the links leading to your site in the browser, and open local links in the application, then use a condition with different return values.
Public class MyWebViewClient extends WebViewClient ( @Override public boolean shouldOverrideUrlLoading(WebView view, String url) ( if(Uri.parse(url).getHost()..ACTION_VIEW, Uri.parse(url)); view.getContext().startActivity (intent); return true; ) )
A universal method that will open all local links in the application, the rest in the browser (we change one line):
Public class MyAppWebViewClient extends WebViewClient ( @Override public boolean shouldOverrideUrlLoading(WebView view, String url) ( if(Uri.parse(url).getHost().length() == 0)( return false; ) Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url)); view.getContext().startActivity(intent); return true; ) )
And now let's complicate the example a bit so that the user has an alternative to standard browsers.
To make it clearer, let's rewrite the example as follows. Create two activities. On the first activity, place a button to navigate to the second activity, and on the second activity, place the .
In the manifest, we prescribe a filter for the second activity.
The code for the button to navigate to the second activity.
Public void onClick(View view) ( Intent intent = new Intent("ru.alexanderklimov.Browser"); intent.setData(Uri.parse("http://site/android/")); startActivity(intent); )
We created our own intent with a filter and provided data - the site address.
The second activity should receive the data:
Package en.alexanderklimov.testapplication; import android.net.Uri; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.webkit.webview; import android.webkit.WebViewClient; public class SecondActivity extends AppCompatActivity ( @Override protected void onCreate(Bundle savedInstanceState) ( super.onCreate(savedInstanceState); setContentView(R.layout.activity_second); Uri url = getIntent().getData(); WebView webView = findViewById(R.id.webView); webView.setWebViewClient(new Callback()); webView.loadUrl(url.toString()); ) private class Callback extends WebViewClient ( @Override public boolean shouldOverrideUrlLoading (WebView view, String url) ( return(false); ) ) )
In the filter for the second activity, we specified two actions.
This means that any activity (read, applications) can trigger your activity with a mini-browser in the same way. Run any old project in the studio in a separate window, or create a new one and add a button to it and write the same code that we used to click the button.
Launch the second application (the first application can be closed) and click on the button. You will not launch the first application with home screen, and immediately the second activity with a mini-browser. Thus, any application can launch a browser without knowing the class name of your activity, but using only the string "en.alexanderklimov.Browser" transmitted to Intent. However, your browser activity must have a default category and data. Let me remind you:
You can represent your string as a string constant and tell all potential users of your browser how they can run it on their own. But Android already has such a ready-made constant ACTION_VIEW, which according to the documentation help is the following:
Public static final java.lang.String ACTION_VIEW = "android.intent.action.VIEW";
Let's rewrite the code for the button of the second application
Intent(android.content.Intent.ACTION_VIEW, Uri.parse("http://site/android/")); startActivity(intent);
What will happen this time? We remember that we have two actions, including and android.intent.action.VIEW. This means that our first application with a browser must also recognize this command when some application at the user uses this code. There is at least one such "Browser" program on the emulator, and now our second activity from the first application has been added to it. A choice of two applications will appear on the screen.
And if you remove all alternative browsers and leave only your program, then there will be no choice. Your browser will become the main one. And if some application wants to launch a web page specified way, your program will open.
A small note. If you replace the last line with this:
StartActivity(Intent.createChooser(intent, "Meow..."));
Then in the program selection window, instead of the top line "Open with" or its local translation, your line will appear. But this is not the main thing. If for some reason there is not a single browser on the device, then this version of the code will not cause the application to crash, unlike the original version. Therefore, use the proposed option for the sake of reliability.
We have already begun to fully provide ourselves with personal software, remember our wonderful calculator and converter. And in this lesson we will learn how to create a simple browser with which to surf the Internet. Agree, surfing the web on your own browser is many times more pleasant than doing it on Opera or Chrome (hardly more convenient, but more pleasant :)). We are creating a new project, traditionally choose the names yourself. Personally, I don’t create everything from scratch every time, but simply open what is and clean up all the code to the original state of Blank Activity. Do what is more convenient for you.
So, let us briefly outline the scope and specifics of the subsequent work. We need to create an element
Let's start. Opening the file activity_main.xml. We create a single element there
The markup window will look like this:
After that, let's deal with the file right away AndroidManifest.xml. Open it and add two lines there, one is permission for the application to use the Internet, the other is changing the style of the application, or rather hiding the "Title" panel of the application (the panel with the title of the application) in order to give the browser window more space to display pages .
Write a permission string to use the Internet before opening tag
Now let's add to the configuration line of our Activity command to hide the header (bottom line in bold, this is also in AndroidManifest.xml):
< activity android: name= ".MainActivity" android: label= android:theme= "@android:style/Theme.NoTitleBar" >Now let's move on to the most important and responsible part of the work - writing java code. Open the MainActivity.java file and write the following (explanations are given in the code after the signs //, who did not notice):
packagehome.myapplication ; import android.app.Activity ; import android.app.AlertDialog ; import android.content.ContentValues ; import android.content.Intent ; import android.database.Cursor ; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.support.v7.app.ActionBarActivity; import android.os.Bundle ; import android.util.Log ; import android.view.KeyEvent ; import android.view.Menu ; import android.view.MenuItem ; import android.view.View ; import android.webkit.WebView ; import android.webkit.WebViewClient ; import android.widget.Button ; import android.widget.EditText ; import android.widget.RadioButton ; import android.widget.TextView ; public class MainActivity extends Activity( // Declaring type variable webview private WebView mWeb; // Create a class of type Web browser (WebViewClient), which we configure // default permission to process all links inside this class, // without referring to third party programs: private class WebViewer extends WebViewClient ( (WebView view , String url ) ( view. loadUrl(url); return true ; ) ) public void onCreate (Bundle savedInstanceState ) ( super. onCreate(savedInstanceState); setContentView(R . layout. activity_main); // Bind the declared variable of the WebView type to the one we created // to the WebView element in the activity_main.xml file: mWeb= (WebView )findViewById(R . id. web); // Enable Java script support for this element: mWeb. getSettings(). setJavaScriptEnabled(true); // Set up the page that will load at startup, you can enter any: mWeb. loadUrl( "http://developeroleg.ucoz.ru/"); // Set up the browser for our WebView element, connect the one we created above // Web client that will be used to view pages: mWeb. setWebViewClient(new WebViewer()); ) // We write the code for handling the back button press on the device, which will allow us when we press // on the back button go to the previous page, not just close applications. // It will be closed with the "Back" button only if we are on the home page // the page specified above:@Override public void onBackPressed () ( if (mWeb. canGoBack()) ( mWeb. goBack();) else ( super. onBackPressed(); ) ) )That's all! In fact, everything is quite simple and after some work we have our own browser, of course it is quite simple and does not have any options, but this is quite enough to understand the essence of creating such applications.
Dear, I am a bca student. I have to do one project in the last semester. So I decided to create a web site that runs on the Android OS, but I am completely for this application. So, can anyone help me with this. I have already installed all necessary tools like jdk, android sdk 3.0, eclipse. But now I have no idea where I should start browser development from. So please help me... I only have 2 months for this project. So is it possible in 2 months or not?
It depends what you have in mind when designing a browser...
Designing a browser + rendering engine from scratch is a lot of work, but you can easily build a browser based on Androids WebView using WebViewClient and create a new user interface by changing the way the user interacts with the browser.
Webview has all sorts of hooks to intercept browser interaction, so you can easily extend it. For example, you can let the user flip pages (like google fastflip), experiment with 3D by mapping the rendered web page in OpenGL space (like sphere browser), etc.
As a starting point, take a look at Alexander Kmetek's blog and his Mosambro project, which expands android browser by adding microformat support.
Sounds like a really big project and that's why you can't just start from scratch and write it down. You have to make a plan on how you want to implement all the parts, write down class diagrams, etc. If you are studying computer science, you must have heard about it in previous semesters.
First you have to ask yourself if this project is possible. as you can see from the comments, most people agree that you shouldn't underestimate this challenge!
I really suggest that you understand the scope of this task, here source Androids browser, giving you an idea of its complexity.
Building a basic browser could be done in a day or two for those with experience android development, just as others have stated that WebView provides just about everything you need to display a web page. There are a few tweaks for JavaScript and other features to check and then after marking the main text field for the URL and the go button which is pretty much the main web browser.
The real work comes in all advanced settings. Building a browser that competes with the big guys might be a bit difficult for one person in a couple of months, but making something of your own that works is very possible. Try!
To create a complete web browser in Android, you use a WebView .
Simple code binding:
WebView wv = (WebView)findViewById(R.id.webview1); wv = (WebView) findViewById(R.id.webView1); wv.loadUrl("http://www.apsmind.com");
