A Kotlin Android HTML and Web Content Printing Example

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Kotlin - Printing with the Android Printing FrameworkA Kotlin Guide to Android Custom Document Printing


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As outlined in the previous chapter, entitled “An Android HTML and Web Content Printing Example”, the Android Printing framework can be used to print both web pages and dynamically created HTML content. While 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.




Creating the HTML Printing Example Application

Begin this example by launching the Android Studio environment and creating a new project, entering HTMLPrint into the Application name field and ebookfrenzy.com as the Company Domain setting before clicking on the Next button.

On the form factors screen, enable the Phone and Tablet option and set the minimum SDK setting to API 21: Android 5.0 (Lollipop). Continue to proceed through the screens, requesting the creation of an Empty Activity named HTMLPrintActivity with a corresponding layout named 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.kt file (located in the Project tool window under app -> java -> com.ebookfrenzy.htmlprint) and loading it into the editing panel. Once loaded, modify the code so that it reads as outlined in the following listing:

package com.ebookfrenzy.htmlprint
 
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.webkit.WebView
import android.webkit.WebViewClient
import android.webkit.WebResourceRequest
import android.print.PrintAttributes
import android.print.PrintManager
import android.content.Context
 
class HTMLPrintActivity : AppCompatActivity() {
 
    private var myWebView: WebView? = null
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_html_print)
 
        printWebView()
    }
 
    private fun printWebView() {
 
        val webView = WebView(this)
        webView.webViewClient = object : WebViewClient() {
 
            override fun shouldOverrideUrlLoading(view: WebView,
                                request: WebResourceRequest): Boolean {
                return false
            }
 
            override fun onPageFinished(view: WebView, url: String) {
                createWebPrintJob(view)
                myWebView = null
            }
        }
 
        val 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.kt file, therefore, implement this method so that it reads as follows:

private fun createWebPrintJob(webView: WebView) {
 
    val printManager = this
            .getSystemService(Context.PRINT_SERVICE) as PrintManager
 
    val printAdapter = webView.createPrintDocumentAdapter("MyDocument")
 
    val jobName = getString(R.string.app_name) + " Print Test"
 
    printManager.print(jobName, printAdapter,
            PrintAttributes.Builder().build())
}

This method obtains a reference to the PrintManager service and instructs the web view instance to create a print adapter. 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 adapter and a set of default print attributes.

Compile and run the application on a device or emulator running Android 5.0 or later. Once launched, the standard Android printing page should appear as illustrated in Figure 77-1.

As3.0 html print preview.png 

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 (renamed Files on Android 8) located amongst the other app icons on the device.

You are reading a sample chapter from the Android Studio 3.0 / Android 8 Edition book.

Purchase the fully updated Android Studio 3.2 / Android 9 / Jetpack Edition of this publication in eBook ($29.99) or Print ($45.99) format

Android Studio 3.2 Development Essentials - Kotlin Edition Print and eBook (ePub/PDF/Kindle) editions contain 96 chapters and over 800 pages

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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. Create a new project in Android Studio, entering WebPrint into the Application name field and ebookfrenzy.com as the Company Domain setting before clicking on the Next button.

On the form factors screen, enable the Phone and Tablet option and set the minimum SDK setting to API 21: Android 5.0 (Lollipop). Continue to proceed through the screens, requesting the creation of a Basic Activity (since we will be making use of the context menu provided by the Basic Activity template) named WebPrintActivity with the remaining properties set to the default values.

Removing the Floating Action Button

Selecting the Basic Activity template provided a context menu and a floating action button. Since the floating action button is not required by the app it can be removed before proceeding. Load the activity_web_print.xml layout file into the Layout Editor, select the floating action button and tap the keyboard Delete key to remove the object from the layout. Edit the WebPrintActivity.kt file and remove the floating action button code from the onCreate method as follows:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_web_print)
    setSupportActionBar(toolbar)
}

Designing the User Interface Layout

Load the content_web_print.xml layout resource file into the Layout Editor tool if it has not already been loaded and, in Design mode, select and delete the “Hello World!” TextView object. From the Containers section of the palette, drag and drop a WebView object onto the center of the device screen layout. Using the Attributes tool window, change the layout_width and layout_height properties of the WebView to match_constraint so that it fills the entire layout canvas as outlined in Figure 77-2:

As3.0 web print ui.png 

Select the newly added WebView instance and change the ID of the view to myWebView.

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 tool window and double-clicking on it to load it into the editing panel. Once loaded, edit the XML content to 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.ebookfrenzy.webprint" >
 
    <uses-permission android:name="android.permission.INTERNET" />
             
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".WebPrintActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
 
                <category android:name=
                        "android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
 
</manifest>

You are reading a sample chapter from the Android Studio 3.0 / Android 8 Edition book.

Purchase the fully updated Android Studio 3.2 / Android 9 / Jetpack Edition of this publication in eBook ($29.99) or Print ($45.99) format

Android Studio 3.2 Development Essentials - Kotlin Edition Print and eBook (ePub/PDF/Kindle) editions contain 96 chapters and over 800 pages

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Loading the Web Page into the WebView

Before the web page can be printed, it needs to be loaded into the WebView instance. For the purposes of this tutorial, this will be performed by a call to the loadUrl() method of the WebView instance, which will be placed in a method named configureWebView() and called from within the onCreate() method of the WebPrintActivity class. Edit the WebPrintActivity.kt file, therefore, and modify it as follows:

package com.ebookfrenzy.webprint
 
import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import android.view.Menu
import android.view.MenuItem
import android.webkit.WebView
import android.webkit.WebViewClient
import android.webkit.WebResourceRequest
 
import kotlinx.android.synthetic.main.activity_web_print.*
import kotlinx.android.synthetic.main.content_web_print.*
 
class WebPrintActivity : AppCompatActivity() {
 
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_web_print)
        setSupportActionBar(toolbar)
 
        configureWebView()
    }
 
    private fun configureWebView() {
 
        myWebView?.webViewClient = object : WebViewClient() {
            override fun shouldOverrideUrlLoading(
                    view: WebView, request: WebResourceRequest): Boolean {
                return super.shouldOverrideUrlLoading(
                        view, request)
            }
        }
        myWebView?.settings?.javaScriptEnabled = true
        myWebView?.loadUrl(
                "https://developer.android.com/google/index.html")
 
    }
.
.
}

Adding the Print Menu Option

The option to print the web page will now be added to the Overflow menu using the techniques outlined in the chapter entitled “Creating and Managing Overflow Menus on Android”.

The first requirement is a string resource with which to label the menu option. Within the Project tool window, locate the app -> res -> values -> strings.xml file, double-click on it to load it into the editor and modify it to add a new string resource:

<resources>
    <string name="app_name">WebPrint</string>
    <string name="action_settings">Settings</string>
    <string name="print_string">Print</string>
</resources>

Next, load the app -> res -> menu -> menu_web_print.xml file into the menu editor, switch to Text mode and replace the Settings menu option with the print option:

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context="com.ebookfrenzy.webprint.WebPrintActivity" >
    <item android:id="@+id/action_settings"
        android:title="@string/action_settings"
        android:orderInCategory="100"
        app:showAsAction="never" />
 
    <item
        android:id="@+id/action_print"
        android:orderInCategory="100"
        app:showAsAction="never"         
        android:title="@string/print_string"/>
 
</menu>

You are reading a sample chapter from the Android Studio 3.0 / Android 8 Edition book.

Purchase the fully updated Android Studio 3.2 / Android 9 / Jetpack Edition of this publication in eBook ($29.99) or Print ($45.99) format

Android Studio 3.2 Development Essentials - Kotlin Edition Print and eBook (ePub/PDF/Kindle) editions contain 96 chapters and over 800 pages

Buy Print Preview Book

All that remains in terms of configuring the menu option is to modify the onOptionsItemSelected() handler method within the WebPrintActivity.kt file:

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    
    if (item.itemId == R.id.action_print) {
        createWebPrintJob(myWebView)
    }
    return super.onOptionsItemSelected(item)
}

With the onOptionsItemSelected() method implemented, the activity will call a method named createWebPrintJob() when the print menu option is selected from the overflow menu. The implementation of this method is identical to that used in the previous HTMLPrint project and may now be added to the WebPrintActivity.kt file such that it reads as follows:

.
.
import android.print.PrintAttributes
import android.print.PrintManager
import android.content.Context
.
.
class WebPrintActivity : AppCompatActivity() {
.
.
   private fun createWebPrintJob(webView: WebView?) {

        val printManager = this
                .getSystemService(Context.PRINT_SERVICE) as PrintManager

        val printAdapter = webView?.createPrintDocumentAdapter("MyDocument")

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

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

With the code changes complete, run the application on a physical Android device or emulator running Android version 5.0 or later. Once successfully launched, the WebView should be visible with the designated web page loaded. Once the page has loaded, select the Print option from the Overflow menu (Figure 77-3) and use the resulting print panel to print the web page to a suitable destination.

 As3.0 web print page loaded.png 

Summary

The Android Printing framework includes extensions to the WebView class that make it possible to print HTML based content from within an Android application. This content can be in the form of HTML created dynamically within the application at runtime, or a pre-existing web page loaded into a WebView instance. In the case of dynamically created HTML, it is important to use a WebViewClient instance to ensure that printing does not start until the HTML has been fully loaded into the WebView.


You are reading a sample chapter from the Android Studio 3.0 / Android 8 Edition book.

Purchase the fully updated Android Studio 3.2 / Android 9 / Jetpack Edition of this publication in eBook ($29.99) or Print ($45.99) format

Android Studio 3.2 Development Essentials - Kotlin Edition Print and eBook (ePub/PDF/Kindle) editions contain 96 chapters and over 800 pages

Buy Print Preview Book



PreviousTable of ContentsNext
Kotlin - Printing with the Android Printing FrameworkA Kotlin Guide to Android Custom Document Printing