![](/img/trans.png)
[英]Android Studio open navigation Drawer using fragment and handle back button press
[英]Navigation drawer back button to primary fragment
阅读本文并搜索Android文档后,我放弃了,并决定在这里提问。 我正在尝试在Navigation Drawer
设置一个后退按钮,以便该应用程序仅从Home
片段关闭,而其他任何片段都将把我们带回到Home
。 例如,如果我们从Home
片段开始并导航到导航抽屉中的其他片段,则单击“后退”按钮将进入Home
片段,而如果从Home片段返回,则将退出应用程序。
我试图像这样实现它:
public void onNavigationDrawerItemSelected(int position) {
...
// If the next fragment is Home, clear the backstack.
if (frag instanceof Home) {
getSupportFragmentManager().popBackStack();
fragmentManager.beginTransaction().replace(R.id.container, frag)
.commit();
}
// If the backstack already contains a transaction, replace the current fragment
else if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
fragmentManager.beginTransaction().replace(R.id.container, frag)
.commit();
}
// If the backstack is empty, insert the Home -> Fragment transaction
else {
fragmentManager.beginTransaction().replace(R.id.container, frag)
.addToBackStack("").commit();
}
...
}
...
@Override
public void onBackPressed() {
if (drawerLayout.isDrawerOpen(Gravity.START)) {
drawerLayout.closeDrawer(Gravity.LEFT);
} else {
super.onBackPressed();
// If returning back to Home fragment, restore action bar title.
if (getSupportFragmentManager().getBackStackEntryCount() > 0)
onSectionAttached(0);
}
}
我附加的链接无法正常工作,并且我实现的方式不一致。 例如,如果我从“首页”导航到其他片段,然后返回首页(无需按“后退”按钮),则我的片段会彼此重叠。
我只是找到了一种使这项工作相当容易的方法,所以我决定将其发布在这里:
// Are we in Home fragment?
private boolean homeFrag = true;
...
@Override
public void onNavigationDrawerItemSelected(int position) {
...
// Next fragment is Home?
if (frag instanceof Home)
homeFrag = true;
else
homeFrag = false;
fragmentManager.beginTransaction().replace(R.id.container, frag)
.commit();
onSectionAttached(position);
}
...
@Override
public void onBackPressed() {
// Close navigation drawer if open
if (drawerLayout.isDrawerOpen(Gravity.START)) {
drawerLayout.closeDrawer(Gravity.LEFT);
} else {
// If not in Home, move back to Home.
if (!homeFrag) {
onNavigationDrawerItemSelected(0);
} else
super.onBackPressed();
}
}
我想听听您对这个解决方案的想法。
我认为您对super.onBackPressed()
方法中的super.onBackPressed()
的调用应该是else块中的最后一个代码。 原因是方法调用可能会影响getBackStackEntryCount()中的计数。 我认为这些电话已经太多了。
我已经为您提供了管理碎片和后退堆栈的方法。
/**
* Change the current displayed fragment managing fragment backstack
*
* @param frag the fragment to display
* @param saveInBackstack true if you want the previous to be in backstack
*/
private void changeFragment(Fragment frag, boolean saveInBackstack) {
String backStateName = ((Object) frag).getClass().getName();
try {
FragmentManager manager = getSupportFragmentManager();
boolean fragmentPopped = manager.popBackStackImmediate(backStateName, 0);
if (!fragmentPopped && manager.findFragmentByTag(backStateName) == null) { //fragment not in back stack, create it.
FragmentTransaction transaction = manager.beginTransaction();
transaction.replace(R.id.main_fragment_container, frag, ((Object) frag).getClass().getName());
if (saveInBackstack) {
Log.d(TAG, "Change Fragment : addToBackTack");
transaction.addToBackStack(backStateName);
} else {
Log.d(TAG, "Change Fragment : NO addToBackTack");
}
transaction.commit();
} else {
Log.d(TAG, "Change Fragment : nothing to do");
// custom effect if fragment is already instanciated
}
} catch (IllegalStateException exception) {
Log.e(TAG, "Unable to commit fragment, could be activity as been killed in background. " + exception.toString());
}
}
同样在您的活动中,覆盖onBackPressed:
@Override
public void onBackPressed() {
int fragments = getFragmentManager().getBackStackEntryCount();
if (fragments == 1) {
finish();
}
super.onBackPressed();
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.