Fragment回退站

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

int backStackEntryCount = getSupportFragmentManager().getBackStackEntryCount();
//只有在首页才响应退出
if (backStackEntryCount == 1) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
long secondTime = System.currentTimeMillis();
if (secondTime - firstTime > 2000) {
firstTime = secondTime;
return true;
} else {
//显示退出dialog
showExitDialog();
}
}
} else {
//弹出除首页外的所有fragment
List<Fragment> fragments = getSupportFragmentManager().getFragments();
for (Fragment fragment : fragments) {
if (!(fragment instanceof MainFragment)) {
getSupportFragmentManager().popBackStack();
}
}
bottom_zc_radioBtn.setChecked(false);
bottom_srys_radioBtn.setChecked(false);
bottom_user_radioBtn.setChecked(false);
bottom_index_radioBtn.setChecked(true);
}
return false;
}