我创建了一个演示应用程序，它包含菜单抽屉和使用抽屉布局在同一窗口中的选项卡式活动。问题是当我在抽屉菜单中选择片段时，它会重定向其相关的片段页面，但是当点击后退按钮时标签式活动自动消失，我的应用程序出来了。我如何解决这个问题？这是我的主要活动代码
import android.content.Intent;
import android.support.design.widget.NavigationView;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
DrawerLayout mDrawerLayout;
NavigationView mNavigationView;
FragmentManager mFragmentManager;
FragmentTransaction mFragmentTransaction;
//Button signIn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
mNavigationView = (NavigationView) findViewById(R.id.shitstuff) ;
/**
* Lets inflate the very first fragment
* Here , we are inflating the TabFragment as the first Fragment
*/
mFragmentManager = getSupportFragmentManager();
mFragmentTransaction = mFragmentManager.beginTransaction();
mFragmentTransaction.replace(R.id.containerView,new TabFragment()).commit();
/**
* Setup click events on the Navigation View Items.
*/
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
mDrawerLayout.closeDrawers();
if (menuItem.getItemId() == R.id.nav_item_income) {
FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.containerView,new IncomeFragment()).commit();
}
if (menuItem.getItemId() == R.id.nav_item_expence) {
FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
xfragmentTransaction.replace(R.id.containerView,new TabFragment()).commit();
}
return false;
}
});
/**
* Setup Drawer Toggle of the Toolbar
*/
android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(this,mDrawerLayout, toolbar,R.string.app_name,
R.string.app_name);
mDrawerLayout.setDrawerListener(mDrawerToggle);
mDrawerToggle.syncState();
}
}
这是我的标签活动
package com.example.arunbhaskar.seconddemo;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
/**
* Created by arun.bhaskar on 2/9/2017.
*/
public class TabFragment extends Fragment {
public static TabLayout tabLayout;
public static ViewPager viewPager;
public static int int_items = 3 ;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
/**
*Inflate tab_layout and setup Views.
*/
View x = inflater.inflate(R.layout.tablayout,null);
tabLayout = (TabLayout) x.findViewById(R.id.tabs);
viewPager = (ViewPager) x.findViewById(R.id.viewpager);
/**
*Set an Apater for the View Pager
*/
viewPager.setAdapter(new MyAdapter(getChildFragmentManager()));
/**
* Now , this is a workaround ,
* The setupWithViewPager dose't works without the runnable .
* Maybe a Support Library Bug .
*/
tabLayout.post(new Runnable() {
@Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
}
});
return x;
}
class MyAdapter extends FragmentPagerAdapter {
public MyAdapter(FragmentManager fm) {
super(fm);
}
/**
* Return fragment with respect to Position .
*/
@Override
public Fragment getItem(int position)
{
switch (position){
case 0 : return new Pie chart();
case 1 : return new Graph();
case 2 : return new Transaction();
}
return null;
}
@Override
public int getCount() {
return int_items;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position){
case 0 :
return "pie-chart";
case 1 :
return "Graph";
case 2 :
return "Transactions";
}
return null;
}
}
}
答案 0 :(得分：1)
首先在backStack中添加你的片段：
if (menuItem.getItemId() == R.id.nav_item_income) {
FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(null) //this line is needed
fragmentTransaction.replace(R.id.containerView,new IncomeFragment()).commit();
}
现在进入您的活动：覆盖onBackPressed()方法
@Override
public void onBackPressed() {
FragmentManager fm = getSupportFragmentManager();
if (fm.getBackStackEntryCount() > 0) {
Log.i("MainActivity", "popping backstack");
fm.popBackStack();
} else {
Log.i("MainActivity", "nothing on backstack, calling super");
new AlertDialog.Builder(this)
.setMessage("Are you sure you want to exit?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
finishAffinity();
}
})
.setNegativeButton("No", null)
.show();
}
}
答案 1 :(得分：0)
当你调用任何片段时，你必须添加它。如下所示
mFragmentTransaction.addToBackStack("your_fregment_tag").commit();
和背压时。这段代码
@Override
public void onBackPressed() {
try {
int backStackEntryCount = getSupportFragmentManager().getBackStackEntryCount();
if (mDrawerLayout.isDrawerOpen(GravityCompat.END)) {
mDrawerLayout.closeDrawer(GravityCompat.END);
return;
} else {
if (backStackEntryCount == 0) { // last fragment
android.app.AlertDialog.Builder alertDialog = new android.app.AlertDialog.Builder(DashboardActivity.this);
alertDialog.setTitle("Exit");
alertDialog.setMessage("Are you sure you want to Exit?");
alertDialog.setPositiveButton("YES",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
//finish();
//System.exit(0);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
finishAffinity();
}else{
finish();
System.exit(0);
}
}
});
alertDialog.setNegativeButton("NO",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
alertDialog.show();
return;
}
}
} catch (Exception e) {
e.printStackTrace();
}
super.onBackPressed();
}
尝试使用backStack。你必须触发它。请检查我的代码
答案 2 :(得分：0)
创建一个onbackpress函数作为您的主要活动 例如像这样
@Override
public void onBackPressed() {
if (count == 1) {
if (exit) {
super.onBackPressed();
return;
} else {
Toast.makeText(this, "Press Back again to Exit.", Toast.LENGTH_SHORT).show();
exit = true;
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
exit = false;
}
}, 2000);
}
}else {
toolbar.setTitle("Home");
mDrawerLayout.closeDrawers();
count=1;
display(0);
}
}
将您的主片段的计数设置为“1”，将其他片段的其他片段设置为
答案 3 :(得分：0)
用此更新您的NavigationItemSelectedListener。
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
mDrawerLayout.closeDrawers();
if (menuItem.getItemId() == R.id.nav_item_income) {
FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
IncomeFragment fragment = new IncomeFragment();
String fragClassName = fragment.getClass().getName();
fragmentTransaction.replace(R.id.containerView, fragment).addToBackStack(fragClassName).commit();
}
if (menuItem.getItemId() == R.id.nav_item_expence) {
FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
TabFragment fragment = new TabFragment();
String fragClassName = fragment.getClass().getName();
xfragmentTransaction.replace(R.id.containerView, fragment).addToBackStack(fragClassName).commit();
}
return false;
}
});