我在带有视图寻呼机和导航抽屉的选项卡中显示多个片段。 我定义了一个控制所有片段的TabFragment 我想展示退出对话并完成应用程序 但是当我按下Back Button时显示空白屏幕 我甚至评论了onbackpressed方法，但是当我按下后退按钮时它仍显示空白屏幕 我试过这个：Android onBackPressed() not working但不能。
主要活动
public class MainActivity extends AppCompatActivity {
Toolbar toolbar;
DrawerLayout mDrawerLayout;
NavigationView mNavigationView;
FragmentManager mFragmentManager;
FragmentTransaction mFragmentTransaction;
SharedPreferences preferences;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
preferences = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
toolbar = (Toolbar) findViewById(R.id.toolbar);
if (toolbar != null) {
setSupportActionBar(toolbar);
}
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mNavigationView = (NavigationView) findViewById(R.id.main_drawer);
View headerView = LayoutInflater.from(this).inflate(R.layout.drawer_header, null);
mNavigationView.addHeaderView(headerView);
mNavigationView.getHeaderView(0).setVisibility(View.GONE);
int width = getResources().getDisplayMetrics().widthPixels / 2;
DrawerLayout.LayoutParams params = (android.support.v4.widget.DrawerLayout.LayoutParams) mNavigationView.getLayoutParams();
params.width = width;
mNavigationView.setLayoutParams(params);
mFragmentTransaction = mFragmentManager.beginTransaction();
mFragmentTransaction.replace(R.id.frame_container, new TabFragment()).commit();
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
menuItem.setChecked(true);
mDrawerLayout.closeDrawers();
if (menuItem.getItemId() == R.id.Top) {
FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frame_container, new TabFragment()).commit();
}
if (menuItem.getItemId() == R.id.Latest) {
FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frame_container, new Fragment1()).commit();
}
return false;
}
});
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, toolbar, R.string.drawer_open, R.string.drawer_close);
mDrawerLayout.setDrawerListener(mDrawerToggle);
mDrawerToggle.syncState();
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
ExitDialogue();
super.onBackPressed();
}
}
public void ExitDialogue() {
AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setTitle(R.string.app_name);
builder.setIcon(R.mipmap.ic_launcher);
builder.setMessage("Do you want to exit?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
finish();
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
}
}
Tab Fragment实际上会在带有视图寻呼机的选项卡中加载2个片段。
标签片段
public class TabFragment extends Fragment {
private TabLayout tabLayout;
private ViewPager viewPager;
private static int int_items = 2;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.tab_layout, container, false);
tabLayout = (TabLayout) v.findViewById(R.id.tabs);
viewPager = (ViewPager) v.findViewById(R.id.viewpager);
viewPager.setAdapter(new MyAdapter(getChildFragmentManager()));
viewPager.setOffscreenPageLimit(int_items - 1);
viewPager.setPageTransformer(true, new DepthPageTransformer());
tabLayout.post(new Runnable() {
@Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
}
});
return v;
}
class MyAdapter extends FragmentPagerAdapter {
MyAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new Fragment1();
case 1:
return new Fragment2();
}
return null;
}
@Override
public int getCount() {
return int_items;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return getResources().getString(R.string.tab1);
case 1:
return getResources().getString(R.string.tab2);
}
return null;
}
}
}
答案 0 :(得分：1)
**CREATE YOUR MAINACTIVITY SUCH AS:**
public class MainActivity extends AppCompatActivity {
public ViewPager viewPager;
private ArrayList<Fragment> allPagerData;
private MainactivityPagerAdapter mainAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.addTab(tabLayout.newTab().setText("Fragment1"));
tabLayout.addTab(tabLayout.newTab().setText("Fragment1"));
tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
viewPager = (ViewPager) findViewById(R.id.viewPager);
final PagerAdapter adapter = new PagerAdapter
(this.getSupportFragmentManager(), tabLayout.getTabCount());
viewPager.setAdapter(adapter);
viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
Log.e("onTabReselected: ",":"+tab);
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
Log.e("onTabReselected: ",":"+tab);
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
Log.e("onTabReselected: ",":"+tab);
}
});
initViews();
}
public void initViews(){
createPager();
mainAdapter = new MainactivityPagerAdapter(this.getSupportFragmentManager(), allPagerData);
viewPage.setAdapter(mainAdapter);
viewPager.setCurrentItem(0);
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
if (position == allPagerData.size() - 1) {
}
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
}
@Override
public void createPager() {
allPagerData = new ArrayList<>();
Fragment1 fragment1 = new Fragment1();
allPagerData.add(fragment1);
Fragment2 fragment2 = new Fragment2();
allPagerData.add(fragment2);
}
@Override
public void onBackPressed() {
if (viewPager.getCurrentItem() != 0) {
viewPager.setCurrentItem(viewPager.getCurrentItem() - 1);
}else {
super.onBackPressed();
// do whatever want to do if you want finished activity you can
}
}
}
=============================================== ===============
Your MainactivityPagerAdapter
public class MainactivityPagerAdapter extends FragmentPagerAdapter {
private final ArrayList<Fragment> allFragments;
public MainactivityPagerAdapter(FragmentManager fm, ArrayList<Fragment> allFragments) {
super(fm);
this.allFragments = allFragments;
}
/**
* Return the Fragment associated with a specified position.
*
* @param position
*/
@Override
public Fragment getItem(int position) {
return allFragments.get(position);
}
/**
* Return the number of views available.
*/
@Override
public int getCount() {
return (allFragments != null) ? allFragments.size() : 0;
}
}
=============================================== ========================== 你的PagerAdapter
public class PagerAdapter extends FragmentStatePagerAdapter {
int mNumOfTabs;
public PagerAdapter(FragmentManager fm, int NumOfTabs) {
super(fm);
this.mNumOfTabs = NumOfTabs;
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
Fragment1 tab1 = new Fragment1();
return tab1;
case 1:
Fragment2 tab2 = new Fragment2();
return tab2;
default:
return null;
}
}
@Override
public int getItemPosition(Object object) {
return super.getItemPosition(object);
}
@Override
public int getCount() {
return mNumOfTabs;
}
}
答案 1 :(得分：0)
从onBackPressed（）中删除destinationController并尝试。
答案 2 :(得分：0)
<强>问题
当我按下Back Button时显示空白屏幕。
试试这个。
undefined答案 3 :(得分：0)
让你的MainActivity是一个处理你的Tabfragment的父Activity，问题是你的父片段无法处理你的子tabfragment，所以onbackpress在这里不起作用。
答案 4 :(得分：0)
由于您尚未发布日志，因此您可以查看这些内容。