Update: Please note that this tutorial was written over a year ago. ZXing has moved on quite a bit since then as have the Android Developer Tools. I haven’t had time to revisit and update the post but it should give you a good steer in the right direction. Some of the comments at the bottom may be able to help you out if you encounter any troubles.

Edit: Sean Owen, one of the developers for ZXing has posted a comment to this blog warning of the pitfalls of integrating ZXing into your own app; doing so just to avoid having your users take that extra step of installing from the market is not a good reason. I completely agree with this. There are many advantages to using the intent based approach as outlined in his comments. My motivation is for an enterprise app that does not have access to the Android market and involves my client installing zxing manually on thousands of devices before they are able to distribute to its business customers.

So to be clear, do not use this method unless it is absolutely necessary, and if you do have to – make sure that override your intent filters so that other apps that want to use zxing do not end up calling your modified version. Also, if zxing is already installed, then you should use that by default instead of your modified version.

ZXing is one of the most popular barcode scanning applications on the market. They make it very easy for you to integrate into your application via an intent but this means that your users must manually install the application from the market.

Fortunately, the app is also open source so I will show you how to cleanly build this capability into your project.

Please note that the awesome developers of this product have released the src under the Apache v2.o license so please be sure to adhere to the terms of this license and give them full credit for their work. http://www.apache.org/licenses/LICENSE-2.0

Step One: Obtain the zxing src code
The src can be found at http://code.google.com/p/zxing/source/browse/trunk. Specifically you only need the android/ and the core/ projects. Use svn to checkout these to your local hard-drive.

Step Two: Build zxing core using Apache Ant
You will need to build the core project into a jar file using apache ant (download from here http://ant.apache.org/ivy/download.cgi). Using a shell or cmd prompt navigate to the root directory of the downloaded zxing src and execute “ant -f core/build.xml”. This will produce a file core/core.jar which we will use in the next step.

Step Three: Build ZXing Android using Eclipse
Create a New Android Project (File –> New –> Android Project).
Set the project name to ZXing (or similar).
Select the “Create project from existing source” radio button
Click “Browse” and navigate to the android project that you downloaded from zxing and click “OK”
Select “Finish”

The project will not currently build. We need to add the core.jar file (that we produced in the previous step) into our project. Right-click on ZXing project –> properties –> Java Build Path –> Add External Jars –> Navigate to and select core.jar –> Open –> OK.

Actually, while we’re here we should do one more very important thing! Right-click on ZXing project –> properties –> Android –> Scroll down and check/tick the “Is Library” checkbox –> OK.

Step 4: Include ZXing Android into your project.
Within Eclipse,  Right-click on YOURPROJECTNAMEHERE project –> properties –>Android –> Scroll down to Libraries section –> Click Add –> Select ZXing (which should appear as an option as a result of completing previous step).

Next, in some trigger function e.g. button press within your code you should add:

Intent intent = new Intent("com.google.zxing.client.android.SCAN");
intent.putExtra("SCAN_MODE", "QR_CODE_MODE");
startActivityForResult(intent, 0);

In the same activity you’ll need the following to retrieve the results:

public void onActivityResult(int requestCode, int resultCode, Intent intent) {
   if (requestCode == 0) {
      if (resultCode == RESULT_OK) {
         String contents = intent.getStringExtra("SCAN_RESULT");
         String format = intent.getStringExtra("SCAN_RESULT_FORMAT");
         // Handle successful scan
      } else if (resultCode == RESULT_CANCELED) {
         // Handle cancel
      }
   }
}

Almost there! One of the current limitations of Android Library projects is that it will not pull anything from AndroidManifest.xml into your project.
So if we try to invoke the above code we will receive a runtime exception because your Android app has no idea how to handle the scan intent.
To fix this you just need to copy the following into your AndroidManifest.xml:

<activity android:name="com.google.zxing.client.android.CaptureActivity"
   android:screenOrientation="landscape"
   android:configChanges="orientation|keyboardHidden"
   android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
   android:windowSoftInputMode="stateAlwaysHidden">
   <intent-filter>
      <action android:name="android.intent.action.MAIN"/>
      <category android:name="android.intent.category.DEFAULT"/>
   </intent-filter>
   <intent-filter>
      <action android:name="com.google.zxing.client.android.SCAN"/>
      <category android:name="android.intent.category.DEFAULT"/>
    </intent-filter>
</activity>

And as Columbo would say, “Just one more thing!”. Add this permission to the top of your AndroidManifest.xml:

<uses-permission android:name="android.permission.CAMERA"/>

EDIT: You need to do yet one more thing! You need to add the core.jar (produced in Step two) to your new project (Right-click your project –> Properties –> Java Build Path –> Add External JARS… –> Select core.jar –> OK). Thanks to Marco and Markosys in the comments for spotting and pointing out the omission!

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