Detect 'home button pressed' event in andr

问题:

In facebook chatheads, that are part of the facebook messenger app, I noticed the following behavior: As far as I can see, the chat head itself and the opened chat screen are all parts of a service. No activity is involved.

How can I be sure? After I press home on the opened chat screen, it gets minimized back to a chat head, and I can immediately reopen the chat screen. If the chat screen was an activity, then reopening the activity via startActivity(intent) after the home button was pressed, would delay the start of the activity, as specified here: Starting an activity from a service after HOME button pressed without the 5 seconds delay

and here: Reason for 5 sec delay to show an activity on pressing the home button?

in my service onCreate method, i use the following code to display a UI from service:

public class ServiceTest extends Service {
...
    @Override 
    public void onCreate() {
        super.onCreate();

        windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);

        WindowManager.LayoutParams params = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.TYPE_PHONE,
            WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
            PixelFormat.TRANSLUCENT);

        windowManager.addView(someView, params);
    }
....
}

Does anyone have an idea how can I receive the 'home button pressed' event directly from a service displaying a UI? I would like to minimize my view (similar to facebook chat heads) when the user presses the home button.

回答1:

well after doing my own research about that issue, I've came with the following conclusions:

Facebook "intercepting" the navigation buttons by providing the flag TYPE_SYSTEM_OVERLAY attribute. look on this post answer provided by @jawsware

doing what he advices not to do - will lead to the "affect" of controling the navigation buttons

using this flag provides focus on your overlay, and takes the focus from the activity behind.

with the onFocusChangedListener view callback or the OnKey listener they reacts to it with closing the full screen mode of the overlay.

that's also explains how they reacts to it from the 3 navigation buttons - home / back / recent tasks

回答2:

You can achieve it by overriding View.onCloseSystemDialogs(). You may need to check View.java because this method is not visible in API doc.

Obviously, we can not detect 'Home button pressed' in general. In most cases, the window is created by startActivity(). And CloseSystemDialogs routine, which is caused by 'Home button pressed', is handled by internal class of android framework, PhoneWindow.DecorView as a view ancestor of ViewRootImpl. But when we add views to window manager directly, view ancestor of ViewRootImpl is being our custom view but PhoneWindow.DecorView. Checking the source code of ViewRootImpl.java might be easier to understand.

KeyEvent.KEYCODE_APP_SWITCH causes closeSystemDialogs routine, too. This explains how facebook chatheads works.

回答3:

ok complete edit of my answer,

Override below method in your activity.

 @Override
    public void onAttachedToWindow() {
        super.onAttachedToWindow();
        this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);           
    }

After overriding above method, now you can easily listen HOME Key press in your activity using onKeyDown() method.

  @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {     

        if(keyCode == KeyEvent.KEYCODE_HOME)
        {
           //The Code Want to Perform. 
        }
    });

try this hope it helps

回答4:

You can monitor (e.g. check every 200 ms) the top running activity, and see if it is your activity or some other activity, and know when it changes. This will also let you handle cases like an incoming call.

ActivityManager am = (ActivityManager) context.getSystemService(Activity.ACTIVITY_SERVICE);
am.getRunningTasks(1).get(0).topActivity...

回答5:

This is my way. It work fine. Put it in onReceive() function.

if (intent.getAction().equals(Intent.ACTION_CLOSE_SYSTEM_DIALOGS))
    {
        String reason = intent.getStringExtra(SYSTEM_REASON);

        //Toast.makeText(context,"ACTION_CLOSE_SYSTEM_DIALOGS : Reason : " + reason ,Toast.LENGTH_LONG).show();

        // Detect home screen key press or "recent app" key pressed when screen is in unlocked state
        if (reason != null)
        {
            if (reason.equals(SYSTEM_HOME_KEY))
            {
            // For Home press
            }
            else if (reason.equals(SYSTEM_RECENT_APPS))
            {
            // For long press
            }
        }
    }

回答6:

I'm fairly sure facebook doesn't listen for home button presses, because their logic requires the chat heads to show up regardless of what app is visible, as long as it isn't facebook.

A simple and crude way to do this would be to maintain a static flag visible in your Application singleton, and modify it from every Activity you have. In the onPause(), set it to false, and in onResume() and onCreate() set it to true.

Then simply check the state of this flag, and act accordingly. If its true, it means your app is visible.

You might want to add a small pause before you act on it to prevent your injected Views from flickering each time an Activity is changed.

回答7:

Here is working sample code.

mLinear =  new LinearLayout(getApplicationContext()) {

          //home or recent button
          public void onCloseSystemDialogs(String reason) {
              //The Code Want to Perform. 
          }

          @Override
          public boolean dispatchKeyEvent(KeyEvent event) {
              if (event.getKeyCode() == KeyEvent.KEYCODE_BACK
                || event.getKeyCode() == KeyEvent.KEYCODE_VOLUME_UP
                || event.getKeyCode() == KeyEvent.KEYCODE_VOLUME_DOWN
                || event.getKeyCode() == KeyEvent.KEYCODE_CAMERA ) {

              //The Code Want to Perform.
              }
          return super.dispatchKeyEvent(event);
          }
};

mLinear.setFocusable(true);

View mView = inflate.inflate(R.layout.floating_panel_layout, mLinear);
WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);

//params
WindowManager.LayoutParams params = new WindowManager.LayoutParams(
             width,
             height,
             WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
             WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
                    | WindowManager.LayoutParams.FLAG_FULLSCREEN
                    | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN
                    | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON,
              PixelFormat.TRANSLUCENT);
params.gravity = Gravity.LEFT | Gravity.CENTER_VERTICAL;
wm.addView(mView, params);

回答8:

You can add the category HOME to your manifest file.