Examples of listening and intercepting Home keys in Android

First of all, you should first understand one situation, that is, Android cannot intercept the Home button in the application. Today we will take you to see the three situations of the Home button.

1. Logical processing of pressing the Home key in the application

When we press the Home key in the application, the interface will start to the desktop. We can see its implementation principle in the frameworks\base\policy\src\com\android\internal\policy\impl\ class, it is nothing more than calling the following code.

  Intent mHomeIntent;
  mHomeIntent = new Intent(Intent.ACTION_MAIN, null);
  (Intent.CATEGORY_HOME);
  (Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);

  startActivity(mHomeIntent);

Create an Intent that starts to the desktop.

2. Listen to the Home button in the application

If you want to monitor the Home key in Android applications, you can use the broadcast mechanism, which is also reflected in the source code.

static public final String SYSTEM_DIALOG_REASON_KEY = "reason";
  static public final String SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS = "globalactions";
  static public final String SYSTEM_DIALOG_REASON_RECENT_APPS = "recentapps";
  static public final String SYSTEM_DIALOG_REASON_HOME_KEY = "homekey";
  static public final String SYSTEM_DIALOG_REASON_ASSIST = "assist";

  @Override
  public void onReceive(Context arg0, Intent arg1) {
    String action = ();
    // Pressing the Home button will send ACTION_CLOSE_SYSTEM_DIALOGS broadcast    if ((Intent.ACTION_CLOSE_SYSTEM_DIALOGS)) {

      String reason = (SYSTEM_DIALOG_REASON_KEY);
      if (reason != null) {
        if ((SYSTEM_DIALOG_REASON_HOME_KEY)) {
          // Short press the home button          (arg0, "Short press Home button", Toast.LENGTH_SHORT).show();
        } else if ((SYSTEM_DIALOG_REASON_RECENT_APPS)) {
          // RECENT_APPS key          (arg0, "RECENT_APPS", Toast.LENGTH_SHORT).show();
        }
      }
    }
  }

This will monitor whether the Home is pressed.

3. Intercept Home keys in the Frameworks layer

In the frameworks\base\policy\src\com\android\internal\policy\impl\file, we first look at the interceptKeyBeforeDispatching() method.

public long interceptKeyBeforeDispatching(WindowState win, KeyEvent event, int policyFlags) {

  //......
  if (keyCode == KeyEvent.KEYCODE_HOME) {

    //......
    handleShortPressOnHome();
  }
}

//Enter handleShortPressOnHomeprivate void handleShortPressOnHome() {
    // If there's a dream running then use home to escape the dream
    // but don't actually go home.
    if (mDreamManagerInternal != null &amp;&amp; ()) {
      (false /*immediate*/);
      return;
    }

    // Go home!
    launchHomeFromHotKey();
  }

Enter the launchHomeFromHotKey method.

static public final String SYSTEM_DIALOG_REASON_KEY = "reason";
  static public final String SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS = "globalactions";
  static public final String SYSTEM_DIALOG_REASON_RECENT_APPS = "recentapps";
  static public final String SYSTEM_DIALOG_REASON_HOME_KEY = "homekey";
  static public final String SYSTEM_DIALOG_REASON_ASSIST = "assist";

void launchHomeFromHotKey() {
    if (isKeyguardShowingAndNotOccluded()) {
      // don't launch home if keyguard showing
    } else if (!mHideLockScreen &amp;&amp; ()) {
      // when in keyguard restricted mode, must first verify unlock
      // before launching home
      (new OnKeyguardExitResult() {
        @Override
        public void onKeyguardExitResult(boolean success) {
          if (success) {
            try {
              ().stopAppSwitches();
            } catch (RemoteException e) {
            }
            sendCloseSystemWindows(SYSTEM_DIALOG_REASON_HOME_KEY);
            startDockOrHome();
          }
        }
      });
    } else {
      // no keyguard stuff to worry about, just launch home!
      try {
        ().stopAppSwitches();
      } catch (RemoteException e) {
      }
      if (mRecentsVisible) {
        // Hide Recents and notify it to launch Home
        awakenDreams();
        sendCloseSystemWindows(SYSTEM_DIALOG_REASON_HOME_KEY);
        hideRecentApps(false, true);
      } else {
        // Otherwise, just launch Home
        sendCloseSystemWindows(SYSTEM_DIALOG_REASON_HOME_KEY);
        //Start Launcher interface        startDockOrHome();
      }
    }
  }

The above method can handle the interception operation of Home keys. Next, we enter the startDockOrHome method.

void startDockOrHome() {

    if (OptConfig.LC_RAM_SUPPORT) {
      try {
        ().startHomePre();
      } catch (RemoteException re) {

      }
    }

    awakenDreams();

    Intent dock = createHomeDockIntent();
    if (dock != null) {
      try {
        startActivityAsUser(dock, );
        return;
      } catch (ActivityNotFoundException e) {
      }
    }

    //Intent related settings    mHomeIntent = new Intent(Intent.ACTION_MAIN, null);
    (Intent.CATEGORY_HOME);
    (Intent.FLAG_ACTIVITY_NEW_TASK
        | Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);

    startActivityAsUser(mHomeIntent, );
  }

OK, here we will simply monitor and intercept the Home button.

The above is all the content of this article. I hope it will be helpful to everyone's study and I hope everyone will support me more.