在FragmentActivity重写onKeyDown方法：
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
// TODO Auto-generated method stub
if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN) {
//if no more history in stack
if (this.getSupportFragmentManager().getBackStackEntryCount() == 0) {
new AlertDialog.Builder(this).setMessage("退出程序？").setNegativeButton("取消", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
}
})
.setPositiveButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
})
.create().show();
return true;
}
}
return super.onKeyDown(keyCode, event);
}