如何获得前台的活动窗口？

Question

my Q is pretty straightforward.

I can't figure the way to modify properties of the currently active window from my service. I saw some threads here on stack, also elsewhere, but none of them really answers. The foreground (active) activity can be just anything. I have no access to it.

This guys seems to ask same Q, getting no A... How to get the foreground activity instance?

Many thanx in advance !

Answer 1

Unfortunatelly Android seems not to support such demand, to modify window of top app, from service running on background.

I found this as the best appropriate do far:

http://developer.android.com/guide/components/services.html

" Sending Notifications to the User Once running, a service can notify the user of events using Toast Notifications or Status Bar Notifications.

A toast notification is a message that appears on the surface of the current window for a moment then disappears, while a status bar notification provides an icon in the status bar with a message, which the user can select in order to take an action (such as start an activity).

Usually, a status bar notification is the best technique when some background work has completed (such as a file completed downloading) and the user can now act on it. When the user selects the notification from the expanded view, the notification can start an activity (such as to view the downloaded file).

See the Toast Notifications or Status Bar Notifications developer guides for more information."

Answer 2

Accessibility services provide a means to interact with the foregroung Service. It is kind of like a workaround but still effective.

To make use of this, extend the Accessibility Service and create a new class. Listen for AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED event. This event is triggered whenever the foreground activity is changed. The current foreground process name is available from the event object.

AccessibilityService.java

public class AccessibilityService extends android.accessibilityservice.AccessibilityService{
    public static AccessibilityService instance;
    @Override
    public void onAccessibilityEvent(AccessibilityEvent accessibilityEvent) {
        // Note : This event is sometimes called more than one for a foreground service
        if (accessibilityEvent.getEventType() == AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED){
            Log.d("Event","TYPE_WINDOW_STATE_CHANGED");
            Log.d("Pkg",accessibilityEvent.getPackageName().toString());

            // Check PackageName matching here and continue with code
            // Here we prevent whatsapp from opening
            // Each time it launches we simulate the press of back button
            if (accessibilityEvent.getPackageName().equals("com.whatsapp")){
                doAction();
            }

        }

    }

    @Override
    public void onInterrupt() {

    }

    @Override
    protected void onServiceConnected() {
        super.onServiceConnected();
        Log.d("Accessibility","Service Connected");
    }

    public void doAction(){
        performGlobalAction(GLOBAL_ACTION_BACK);
    }
}

Here I check if the foreground service is Whatsapp and then continue with my code if it is.

In addition to this class, this service has to be declared in the manifest file in the application section along with a config file in the res/xml folder

<service android:name=".AccessibilityService"
            android:permission="android.permission.BIND_ACCESSIBILITY_SERVICE">
            <intent-filter>
                <action android:name="android.accessibilityservice.AccessibilityService" />
            </intent-filter>
            <meta-data
            android:name="android.accessibilityservice"
            android:resource="@xml/serviceconfig"/>
</service>

serviceconfig.xml

<?xml version="1.0" encoding="utf-8"?>
<accessibility-service
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:accessibilityEventTypes="typeAllMask"
    android:accessibilityFeedbackType="feedbackAllMask"
    android:accessibilityFlags="flagDefault"
    android:notificationTimeout="100"
    android:canRetrieveWindowContent="true"
    />

Also ensure accessibility services permission is allowed by the user.
The complete code for sample app to log the foreground process name is available at https://github.com/abinpaul1/Android-Snippets/tree/master/GetForegroundService