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问题 I have only one activity and multiple fragments in my application. Two main fragment A(left) and B(right). Fragment A1 called from A B1 called from B B2 called from B1 All fragments have individual back buttons. So when I press back button of fragment A1 , it should go back to A , similarly when Back button from B2 is pressed, B1 appears and from B1 to B and so on. How to implement this type of functionality? 回答1: public void onBackPressed() { FragmentManager fm = getActivity()

问题 I use an async task to upload an image and get some results. While uploading the image I see a progress dialog, written in onPreExecute() method like this: protected void onPreExecute() { uploadingDialog = new ProgressDialog(MyActivity.this); uploadingDialog.setMessage(\"uploading\"); uploadingDialog.setCancelable(true); uploadingDialog.show(); } Ok when I press the back button, obviously the dialog disappears because of the setCancelable(true). But (obviously) the async task doesn\'t stop.

问题 On pressing the back button, I\'d like my application to go into the stopped state, rather than the destroyed state. In the Android docs it states: ...not all activities have the behavior that they are destroyed when BACK is pressed. When the user starts playing music in the Music application and then presses BACK, the application overrides the normal back behavior, preventing the player activity from being destroyed, and continues playing music, even though its activity is no longer visible

问题 How to disable back button in android while logging out the application? 回答1: Override the onBackPressed method and do nothing if you meant to handle the back button on the device. @Override public void onBackPressed() { if (!shouldAllowBack()) { doSomething(); } else { super.onBackPressed(); } } 回答2: If looking for a higher api level 2.0 and above this will work great @Override public void onBackPressed() { // Do Here what ever you want do on back press; } If looking for android api level

问题 How do you definitively detect whether or not the user has pressed the back button in the browser? How do you enforce the use of an in-page back button inside a single page web application using a #URL system? Why on earth don\'t browser back buttons fire their own events!? 回答1: (Note: As per Sharky's feedback, I've included code to detect backspaces) So, I've seen these questions frequently on SO, and have recently run into the issue of controlling back button functionality myself. After a