Difference between revisions of "An Android HTML and Web Content Printing Example"

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(→‎Designing the User Interface Layout)
(→‎Printing Dynamic HTML Content)
Line 52: Line 52:
  
 
    String htmlDocument =  
 
    String htmlDocument =  
−
                   "<html><body>== Designing the User Interface Layout ==
+
                   "<html><body><h1>Android Print Test</h1><p>"
 +
            + "This is some sample content.</p></body></html>";
 +
 
 +
    webView.loadDataWithBaseURL(null, htmlDocument,
 +
                  "text/HTML", "UTF-8", null);
 +
   
 +
    myWebView = webView;
 +
}
 +
.
 +
.
 +
.
 +
}
 +
</pre>
 +
 
 +
The code changes begin by declaring a variable named myWebView in which will be stored a reference to the WebView instance used for the printing operation. Within the onCreate() method, an instance of the WebView class is created to which a WebViewClient instance is then assigned.
 +
 
 +
The WebViewClient assigned to the web view object is configured to indicate that loading of the HTML content is to be handled by the WebView instance (by returning false from the  shouldOverrideUrlLoading()) method. More importantly, an onPageFinished() handler method is declared and implemented to call a method named createWebPrintJob(). The onPageFinished() method will be called automatically when all of the HTML content has been loaded into the web view. As outlined in the previous chapter, this step is necessary when printing dynamically created HTML content to ensure that the print job is not started until the content has fully loaded into the WebView.
 +
 
 +
Next, a String object is created containing some HTML to serve as the content and subsequently loaded into the web view. Once the HTML is loaded, the onPageFinished() callback method will trigger. Finally, the method stores a reference to the web view object in the previously declared myWebView variable. Without this vital step, there is a significant risk that the Java runtime system will assume that the application no longer needs the web view object and will discard it to free up memory resulting in the print job terminating before completion.
 +
 
 +
All that remains in this example is to implement the createWebPrintJob() method which is currently configured to be called by the onPageFinished() callback method. Remaining within the HTMLPrintActivity.java file, therefore, implement this method as follows:
 +
 
 +
<pre>
 +
private void createWebPrintJob(WebView webView) {
 +
 
 +
PrintManager printManager = (PrintManager) this
 +
  .getSystemService(Context.PRINT_SERVICE);
 +
 
 +
PrintDocumentAdapter printAdapter =
 +
        webView.createPrintDocumentAdapter();
 +
 
 +
String jobName = getString(R.string.app_name) + " Print Test";
 +
 
 +
printManager.print(jobName, printAdapter,
 +
  new PrintAttributes.Builder().build());
 +
}
 +
</pre>
 +
 
 +
This method obtains a reference to the PrintManager service and instructs the web view instance to create a print adaptor. A new string is created to store the name of the print job (in this case based on the name of the application and the word “Print Test”).
 +
Finally, the print job is started by calling the print() method of the print manager, passing through the job name, print adaptor and a set of default print attributes.
 +
 
 +
Compile and run the application on a device running Android 4.4 or later. Once launched, the printing panel should appear as illustrated in Figure 50-1.
 +
 +
 
 +
[[Image:android_print_example_dialog_cropped.png|The Android Printing Framework Print dialog]]
 +
 
 +
Figure 50-1
 +
 
 +
 
 +
Print to a physical printer if you have one configured, save to Google Drive or, alternatively, select the option to save to a PDF file. Once the print job has been initiated, check the generated output on your chosen destination. Note that when using the Save to PDF option, the system will request a name and location for the PDF file. The Downloads folder makes a good option, the contents of which can be viewed by selecting the Downloads icon located amongst the other app icons on the device. Figure 50-2, for example, shows the PDF output generated by the Save to PDF option viewed on an Android device:
 +
 +
 
 +
[[Image:android_printing_save_to_pdf_reduced.png|PDF output from the Android Printing framework]]
 +
 
 +
Figure 50-2
 +
 
 +
== Creating the Web Page Printing Example ==
 +
 
 +
The second example application to be created in this chapter will provide the user with an Overflow menu option to print the web page currently displayed within a WebView instance. Within the Eclipse environment, begin this example by selecting the File -> New -> Android Application Project… menu option. Name the application and project WebPrint, enter a suitable package name (or com.example.webprint if you do not yet have a domain name) and select API 19 or later for the SDK settings. As with the HTML example, request the creation of a blank activity and the use of the default launcher icons. On the New Blank Activity screen of the New Android Application wizard, set the Activity Name to WebPrintActivity and the Layout Name to activity_web_print.
 +
 
 +
== Designing the User Interface Layout ==
  
 
Load the activity_web_print.xml layout resource file into the Graphical Layout editor if it has not already been loaded and select and delete the “Hello World!” TextView object.  
 
Load the activity_web_print.xml layout resource file into the Graphical Layout editor if it has not already been loaded and select and delete the “Hello World!” TextView object.  

Revision as of 19:16, 6 January 2014





As outlined in the previous chapter, entitled Printing with the Android Printing Framework, the Android Printing framework can be used to print both web pages and dynamically created HTML content. Whilst there is much similarity in these two approaches to printing, there are also some subtle differences that need to be taken into consideration. This chapter will work through the creation of two example applications in order to bring some clarity to these two printing options.


Contents

Creating the HTML Printing Example Application

Begin this example by launching the Eclipse environment and selecting the File -> New -> Android Application Project… menu option. Name the application and project HTMLPrint, enter a suitable package name (or com.example.htmlprint if you do not yet have a domain name) and select API 19 or later for the SDK settings. As with previous examples, request the creation of a blank activity and the use of the default launcher icons. On the New Blank Activity screen of the New Android Application wizard, set the Activity Name to HTMLPrintActivity and the Layout Name to activity_html_print.

Printing Dynamic HTML Content

The first stage of this tutorial is to add code to the project to create some HTML content and send it to the Printing framework in the form of a print job.

Begin by locating the HTMLPrintActivity.java file and loading it into the editing panel. Once loaded, modify the code so that it reads as outlined in the following listing: 

package com.example.htmlprint;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.print.PrintAttributes;
import android.print.PrintDocumentAdapter;
import android.print.PrintManager;
import android.content.Context;

public class HTMLPrintActivity extends Activity {

	private WebView myWebView;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_html_print);
		
	    	WebView webView = new WebView(this);
	    	webView.setWebViewClient(new WebViewClient() {

	           public boolean shouldOverrideUrlLoading(WebView view, 
                              String url) 
		   {
	                return false;     
	           }

	           @Override
	           public void onPageFinished(WebView view, String url) {
	                createWebPrintJob(view);
	                myWebView = null;
	            }
	    });

	    String htmlDocument = 
                   "<html><body><h1>Android Print Test</h1><p>" 
	            + "This is some sample content.</p></body></html>";

	    webView.loadDataWithBaseURL(null, htmlDocument, 
                   "text/HTML", "UTF-8", null);
	    
	    myWebView = webView;
	}
.
.
.
}

The code changes begin by declaring a variable named myWebView in which will be stored a reference to the WebView instance used for the printing operation. Within the onCreate() method, an instance of the WebView class is created to which a WebViewClient instance is then assigned.

The WebViewClient assigned to the web view object is configured to indicate that loading of the HTML content is to be handled by the WebView instance (by returning false from the shouldOverrideUrlLoading()) method. More importantly, an onPageFinished() handler method is declared and implemented to call a method named createWebPrintJob(). The onPageFinished() method will be called automatically when all of the HTML content has been loaded into the web view. As outlined in the previous chapter, this step is necessary when printing dynamically created HTML content to ensure that the print job is not started until the content has fully loaded into the WebView.

Next, a String object is created containing some HTML to serve as the content and subsequently loaded into the web view. Once the HTML is loaded, the onPageFinished() callback method will trigger. Finally, the method stores a reference to the web view object in the previously declared myWebView variable. Without this vital step, there is a significant risk that the Java runtime system will assume that the application no longer needs the web view object and will discard it to free up memory resulting in the print job terminating before completion.

All that remains in this example is to implement the createWebPrintJob() method which is currently configured to be called by the onPageFinished() callback method. Remaining within the HTMLPrintActivity.java file, therefore, implement this method as follows: 

private void createWebPrintJob(WebView webView) {

	PrintManager printManager = (PrintManager) this
		  .getSystemService(Context.PRINT_SERVICE);

	PrintDocumentAdapter printAdapter = 
	         webView.createPrintDocumentAdapter();

	String jobName = getString(R.string.app_name) + " Print Test";

	printManager.print(jobName, printAdapter,
		   new PrintAttributes.Builder().build());
}

This method obtains a reference to the PrintManager service and instructs the web view instance to create a print adaptor. A new string is created to store the name of the print job (in this case based on the name of the application and the word “Print Test”). Finally, the print job is started by calling the print() method of the print manager, passing through the job name, print adaptor and a set of default print attributes.

Compile and run the application on a device running Android 4.4 or later. Once launched, the printing panel should appear as illustrated in Figure 50-1.


The Android Printing Framework Print dialog

Figure 50-1


Print to a physical printer if you have one configured, save to Google Drive or, alternatively, select the option to save to a PDF file. Once the print job has been initiated, check the generated output on your chosen destination. Note that when using the Save to PDF option, the system will request a name and location for the PDF file. The Downloads folder makes a good option, the contents of which can be viewed by selecting the Downloads icon located amongst the other app icons on the device. Figure 50-2, for example, shows the PDF output generated by the Save to PDF option viewed on an Android device:


PDF output from the Android Printing framework

Figure 50-2


Creating the Web Page Printing Example

The second example application to be created in this chapter will provide the user with an Overflow menu option to print the web page currently displayed within a WebView instance. Within the Eclipse environment, begin this example by selecting the File -> New -> Android Application Project… menu option. Name the application and project WebPrint, enter a suitable package name (or com.example.webprint if you do not yet have a domain name) and select API 19 or later for the SDK settings. As with the HTML example, request the creation of a blank activity and the use of the default launcher icons. On the New Blank Activity screen of the New Android Application wizard, set the Activity Name to WebPrintActivity and the Layout Name to activity_web_print.

Designing the User Interface Layout

Load the activity_web_print.xml layout resource file into the Graphical Layout editor if it has not already been loaded and select and delete the “Hello World!” TextView object. Switch to the XML view by clicking on the activity_web_print.xml tab located along the lower edge of the editor panel and remove the padding properties from the file so that the WebView will extend to the edges of the display when added to the layout: 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".WebPrintActivity" >

</RelativeLayout>

Switch back to the graphical layout view and, from the Composite section of the palette, drag and drop a WebView object so that it fills the entire layout canvas as outlined in Figure 50-3:


A WebView object added to the Android web printing example UI

Figure 50-3


Right-click on the newly added WebView instance, select the Edit ID… menu option and change the name of the view to myWebView before clicking on OK to commit the change.

Before proceeding to the next step of this tutorial, an additional permission needs to be added to the project to enable the WebView object to access the internet and download a web page for printing. Add this permission by locating the AndroidManifest.xml file in the Project Explorer panel and double clicking on it to load it into the editing panel. Once loaded, directly edit the XML content by clicking on the AndroidManifest.xml tab located along the bottom edge of the manifest editor panel. Within the XML, add the appropriate permission line as shown in the following listing: 

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.webprint"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-permission android:name="android.permission.INTERNET" />
    
    <uses-sdk
        android:minSdkVersion="19"
        android:targetSdkVersion="19" />
.
.
.
</manifest>

Save both layout and manifest files before proceeding.

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