> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/android/annotation/intercept-annotation-handling.md).

# Customize annotation handling

Customize user actions and notification handling with the Tools library. Learn how to intercept annotation events and get notified after an action. Explore advanced customization options for a seamles

By default, the Tools library will respond to user actions such as a click event on a link or form widget, or a property change event on a selected annotation. It is possible to customize such behavior before it is executed within the Tools library, as well as getting notified of an action after it has happened.

## Intercept annotation events

If you would like to customize the behavior executed in response to user actions **prior** to it being handled by the Tools library, it is possible to do so with the `BasicAnnotationListener.onInterceptAnnotationHandling(Annot, Bundle, int)` API. If this method returns true, then it will intercept executing the default logic.

In `BasicAnnotationListener.onInterceptAnnotationHandling(Annot, Bundle, int)`, the second parameter, `Bundle`, contains the name of the action intercepted by this function, as well as some extra information. You can get the name of the intercepted action by calling `bundle.getString(Tool.METHOD_FROM)`:

{% tabs %}
{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
public boolean onInterceptAnnotationHandling(Annot annot, Bundle extra, ToolMode toolMode) {
    if (extra != null && extra.containsKey(Tool.METHOD_FROM)) {
        String methodCalling = extra.getString(Tool.METHOD_FROM);
    }
}
```

{% endcode %}
{% endtab %}

{% tab title="Kotlin" %}
{% code lineNumbers="true" %}

```kotlin
override fun onInterceptAnnotationHandling(annot: Annot?, extra: Bundle?, toolMode: ToolMode): Boolean {
    if (extra != null && extra.containsKey(Tool.METHOD_FROM)) {
        val methodCalling = extra.getString(Tool.METHOD_FROM)
    }
}
```

{% endcode %}
{% endtab %}
{% endtabs %}

To get extra information, first obtain the information keys by calling `bundle.getStringArray(Tool.KEYS)`:

{% tabs %}
{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
String[] paramKeys = extra.getStringArray(Tool.KEYS)
```

{% endcode %}
{% endtab %}

{% tab title="Kotlin" %}
{% code lineNumbers="true" %}

```kotlin
val paramKeys = extra!!.getStringArray(Tool.KEYS)
```

{% endcode %}
{% endtab %}
{% endtabs %}

Then, you can get the information values by looping on each key obtained above:

{% tabs %}
{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
public boolean onInterceptAnnotationHandling(Annot annot, Bundle extra, ToolMode toolMode) {
    if (extra != null && extra.containsKey(Tool.KEYS)) {
        String[] paramKeys = extra.getStringArray(Tool.KEYS);
        if (paramKeys != null) {
            for (String key : paramKeys) {
                // Gets the information value
                Object param = extra.get(key);
            }
        }
    }
}
```

{% endcode %}
{% endtab %}

{% tab title="Kotlin" %}
{% code lineNumbers="true" %}

```kotlin
override fun onInterceptAnnotationHandling(annot: Annot?, extra: Bundle?, toolMode: ToolMode): Boolean {
    if (extra != null && extra.containsKey(Tool.KEYS)) {
        val paramKeys = extra.getStringArray(Tool.KEYS)
        if (paramKeys != null) {
            for (key in paramKeys) {
                // Gets the information value
                val param = extra.get(key)
            }
        }
    }
}
```

{% endcode %}
{% endtab %}
{% endtabs %}

### Common use cases

#### Links

{% tabs %}
{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
mToolManager.setBasicAnnotationListener(new ToolManager.BasicAnnotationListener() {
    @Override
    public boolean onInterceptAnnotationHandling(Annot annot, Bundle extra, ToolMode toolMode) {
        try {
            // Intercept clicking link annotation by return true
            if (annot.getType() == Annot.e_Link) {
                Log.d("InterceptAnnot", "handling link annotation");
                return true;
            }
        } catch (PDFNetException e) {
            e.printStackTrace();
        }
        // return false so the other events can continue executing
        return false;
    }
});
```

{% endcode %}
{% endtab %}

{% tab title="Kotlin" %}
{% code lineNumbers="true" %}

```kotlin
mToolManager.setBasicAnnotationListener(object : ToolManager.BasicAnnotationListener {
    override fun onInterceptAnnotationHandling(annot: Annot?, extra: Bundle?, toolMode: ToolMode?): Boolean {
        try {
            // Intercept clicking link annotation by return true
            if (annot!!.type == Annot.e_Link) {
                Log.d("InterceptAnnot", "handling link annotation")
                return true
            }
        } catch (e: PDFNetException) {
            e.printStackTrace()
        }
        // return false so the other events can continue executing
        return false
    }
})
```

{% endcode %}
{% endtab %}
{% endtabs %}

#### Form widgets

{% tabs %}
{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
mToolManager.setBasicAnnotationListener(new ToolManager.BasicAnnotationListener() {
    @Override
    public boolean onInterceptAnnotationHandling(Annot annot, Bundle extra, ToolMode toolMode) {
        try {
            // Intercept clicking widget annotation by return true
            if (annot.getType() == Annot.e_Widget) {
                Log.d("InterceptAnnot", "handling widget annotation");
                return true;
            }
        } catch (PDFNetException e) {
            e.printStackTrace();
        }
        // return false so the other events can continue executing
        return false;
    }
});
```

{% endcode %}
{% endtab %}

{% tab title="Kotlin" %}
{% code lineNumbers="true" %}

```kotlin
mToolManager.setBasicAnnotationListener(object : ToolManager.BasicAnnotationListener {
    override fun onInterceptAnnotationHandling(annot: Annot?, extra: Bundle?, toolMode: ToolMode?): Boolean {
        try {
            // Intercept clicking widget annotation by return true
            if (annot!!.type == Annot.e_Widget) {
                Log.d("InterceptAnnot", "handling widget annotation")
                return true
            }
        } catch (e: PDFNetException) {
            e.printStackTrace()
        }
        // return false so the other events can continue executing
        return false
    }
})
```

{% endcode %}
{% endtab %}
{% endtabs %}

#### Full sample code

For example, the following code demonstrates several scenarios and how you can get notified **before** each: clicking on a radio button, changing the annotation opacity, and clicking on a link. See the comments in the code for details.

{% tabs %}
{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
mToolManager.setBasicAnnotationListener(new ToolManager.BasicAnnotationListener() {
    @Override
    public boolean onInterceptAnnotationHandling(Annot annot, Bundle extra, ToolMode toolMode) {
        /*
            For example, when a radio button is clicked, this code will print:
            calling method: handleWidget
            property: OTHER
        */
        if (extra != null && extra.containsKey(Tool.METHOD_FROM)) {
            String methodCalling = extra.getString(Tool.METHOD_FROM);
            Log.d("InterceptAnnot", "calling method " + methodCalling);
            AnnotationProperty.Property property = AnnotationProperty.getProperty(methodCalling);
            Log.d("InterceptAnnot", "property: " + property);
        }
        /*
            For example, when annotation opacity is about to be changed to 50%, this code will print:
            calling method: editOpacity
            property: OPACITY
            key: opacity
            value: 0.5
        */
        if (extra != null && extra.containsKey(Tool.KEYS)) {
            String[] paramKeys = extra.getStringArray(Tool.KEYS);
            if (paramKeys != null) {
                for (String key : paramKeys) {
                    Object param = extra.get(key);
                    Log.d("InterceptAnnot", "key: " + key);
                    Log.d("InterceptAnnot", "value: " + param.toString());
                }
            }
        }
        try {
            // Intercept radio button from clicking by return true
            if(annot.getType() == Annot.e_Widget) {
                Widget w = new Widget(annot);
                Field field = w.getField();
                if (field != null && field.isValid() && field.getType() == Field.e_radio) {
                    return true;
                }
            }
            // Intercept clicking link annotation by return true
            if (annot.getType() == Annot.e_Link) {
                Log.d("InterceptAnnot", "handling link annotation");
            }
        } catch (PDFNetException e) {
            e.printStackTrace();
        }
        // return false so the other events can continue executing
        return false;
    }
});
```

{% endcode %}
{% endtab %}

{% tab title="Kotlin" %}
{% code lineNumbers="true" %}

```kotlin
mToolManager.setBasicAnnotationListener(object : ToolManager.BasicAnnotationListener {
    override fun onInterceptAnnotationHandling(annot: Annot?, extra: Bundle?, toolMode: ToolMode?): Boolean {
        /*
      For example, when a radio button is clicked, this code will print:
      calling method: handleWidget
      property: OTHER
      */
        if (extra != null && extra.containsKey(Tool.METHOD_FROM)) {
            val methodCalling = extra.getString(Tool.METHOD_FROM)
            Log.d("InterceptAnnot", "calling method " + methodCalling)
            val property = AnnotationProperty.getProperty(methodCalling)
            Log.d("InterceptAnnot", "property: " + property)
        }
        /*
      For example, when annotation opacity is about to be changed to 50%, this code will print:
      calling method: editOpacity
      property: OPACITY
      key: opacity
      value: 0.5
      */
        if (extra != null && extra.containsKey(Tool.KEYS)) {
            val paramKeys = extra.getStringArray(Tool.KEYS)
            if (paramKeys != null) {
                for (key in paramKeys) {
                    val param = extra.get(key)
                    Log.d("InterceptAnnot", "key: " + key)
                    Log.d("InterceptAnnot", "value: " + param.toString())
                }
            }
        }
        try {
            // Intercept radio button from clicking by return true
            if (annot!!.type == Annot.e_Widget) {
                val w = Widget(annot)
                val field = w.getField()
                if (field != null && field.isValid() && field.getType() === Field.e_radio) {
                    return true
                }
            }
            // Intercept clicking link annotation by return true
            if (annot!!.type == Annot.e_Link) {
                Log.d("InterceptAnnot", "handling link annotation")
            }
        } catch (e: PDFNetException) {
            e.printStackTrace()
        }
        // return false so the other events can continue executing
        return false
    }
})
```

{% endcode %}
{% endtab %}
{% endtabs %}

## Get notified after an action

If you simply want to get notified **after** the action has happened, you can do so via the `AnnotationModificationListener.onAnnotationsModified(Map<Annot, Integer>)` API. This event callback is raised when an annotation change has occurred. For example, in order to get notified when the value of a checkbox has been changed and when annotation opacity has been changed, do the following:

{% tabs %}
{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
ToolManager.AnnotationModificationListener annotationModificationListener = new ToolManager.AnnotationModificationListener() {
    @Override
    public void onAnnotationsModified(Map<Annot, Integer> annots, Bundle extra) {
        /*
            For example, when a checkbox's value has been changed, this code will print:
            calling method: handleWidget
            property: OTHER
        */
        if (extra != null && extra.containsKey(Tool.METHOD_FROM)) {
            String methodCalling = extra.getString(Tool.METHOD_FROM);
            Log.d("AnnotationsModified", "calling method " + methodCalling);
            AnnotationProperty.Property property = AnnotationProperty.getProperty(methodCalling);
            Log.d("AnnotationsModified", "property: " + property);
        }
        /*
            For example, when annotation opacity is changed to 50%, this code will print:
            calling method: editOpacity
            property: OPACITY
            key: opacity
            value: 0.5
        */
        if (extra != null && extra.containsKey(Tool.KEYS)) {
            String[] paramKeys = extra.getStringArray(Tool.KEYS);
            if (paramKeys != null) {
                for (String key : paramKeys) {
                    Object param = extra.get(key);
                    Log.d("AnnotationsModified", "key: " + key);
                    Log.d("AnnotationsModified", "value: " + param.toString());
                }
            }
        }
    }
};
mToolManager.addAnnotationModificationListener(annotationModificationListener);
```

{% endcode %}
{% endtab %}

{% tab title="Kotlin" %}
{% code lineNumbers="true" %}

```kotlin
val annotationModificationListener: ToolManager.AnnotationModificationListener = object : ToolManager.AnnotationModificationListener {
  override fun onAnnotationsModified(annots: MutableMap<Annot, Int>?, extra: Bundle?) {
    /*
      For example, when a checkbox's value has been changed, this code will print:
      calling method: handleWidget
      property: OTHER
      */
    if (extra != null && extra.containsKey(Tool.METHOD_FROM)) {
      val methodCalling = extra.getString(Tool.METHOD_FROM)
      Log.d("AnnotationsModified", "calling method " + methodCalling)
      val property = AnnotationProperty.getProperty(methodCalling)
      Log.d("AnnotationsModified", "property: " + property)
    }
    /*
      For example, when annotation opacity is changed to 50%, this code will print:
      calling method: editOpacity
      property: OPACITY
      key: opacity
      value: 0.5
      */
    if (extra != null && extra.containsKey(Tool.KEYS)) {
      val paramKeys = extra.getStringArray(Tool.KEYS)
      if (paramKeys != null) {
        for (key in paramKeys) {
          val param = extra.get(key)
          Log.d("AnnotationsModified", "key: " + key)
          Log.d("AnnotationsModified", "value: " + param.toString())
        }
      }
    }
  }
}
mToolManager.addAnnotationModificationListener(annotationModificationListener)
```

{% endcode %}
{% endtab %}
{% endtabs %}

{% tabs %}
{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
ToolManager.AnnotationModificationListener annotationModificationListener = new ToolManager.AnnotationModificationListener() {
    @Override
    public void onAnnotationsModified(Map<Annot, Integer> annots, Bundle extra) {
        /*
            For example, when a checkbox's value has been changed, this code will print:
            calling method: handleWidget
            property: OTHER
        */
        if (extra != null && extra.containsKey(Tool.METHOD_FROM)) {
            String methodCalling = extra.getString(Tool.METHOD_FROM);
            Log.d("AnnotationsModified", "calling method " + methodCalling);
            AnnotationProperty.Property property = AnnotationProperty.getProperty(methodCalling);
            Log.d("AnnotationsModified", "property: " + property);
        }

        /*
            For example, when annotation opacity is changed to 50%, this code will print:
            calling method: editOpacity
            property: OPACITY
            key: opacity
            value: 0.5
        */
        if (extra != null && extra.containsKey(Tool.KEYS)) {
            String[] paramKeys = extra.getStringArray(Tool.KEYS);
            if (paramKeys != null) {
                for (String key : paramKeys) {
                    Object param = extra.get(key);
                    Log.d("AnnotationsModified", "key: " + key);
                    Log.d("AnnotationsModified", "value: " + param.toString());
                }
            }
        }
    }
};
mToolManager.addAnnotationModificationListener(annotationModificationListener);
```

{% endcode %}
{% endtab %}

{% tab title="Kotlin" %}
{% code lineNumbers="true" %}

```kotlin
val annotationModificationListener: ToolManager.AnnotationModificationListener = object : ToolManager.AnnotationModificationListener {
  override fun onAnnotationsModified(annots: MutableMap<Annot, Int>?, extra: Bundle?) {
    /*
      For example, when a checkbox's value has been changed, this code will print:
      calling method: handleWidget
      property: OTHER
      */
    if (extra != null && extra.containsKey(Tool.METHOD_FROM)) {
      val methodCalling = extra.getString(Tool.METHOD_FROM)
      Log.d("AnnotationsModified", "calling method " + methodCalling)
      val property = AnnotationProperty.getProperty(methodCalling)
      Log.d("AnnotationsModified", "property: " + property)
    }
    /*
      For example, when annotation opacity is changed to 50%, this code will print:
      calling method: editOpacity
      property: OPACITY
      key: opacity
      value: 0.5
      */
    if (extra != null && extra.containsKey(Tool.KEYS)) {
      val paramKeys = extra.getStringArray(Tool.KEYS)
      if (paramKeys != null) {
        for (key in paramKeys) {
          val param = extra.get(key)
          Log.d("AnnotationsModified", "key: " + key)
          Log.d("AnnotationsModified", "value: " + param.toString())
        }
      }
    }
  }
}
mToolManager.addAnnotationModificationListener(annotationModificationListener)
```

{% endcode %}
{% endtab %}
{% endtabs %}

When finished with the callback, do:

{% tabs %}
{% tab title="Java" %}
{% code lineNumbers="true" %}

```java
mToolManager.removeAnnotationModificationListener(annotationModificationListener);
```

{% endcode %}
{% endtab %}

{% tab title="Kotlin" %}
{% code lineNumbers="true" %}

```kotlin
mToolManager.removeAnnotationModificationListener(annotationModificationListener)
```

{% endcode %}
{% endtab %}
{% endtabs %}

We are always interested in expanding the customization options through APIs, and will be adding more options in the future. If you would like to suggest changes, please don't hesitate to [get in touch](https://apryse.com/form/feature-request).


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