使用溢出菜单实现 App Bar 时禁用向上箭头
Up Arrow disabled on implementing App Bar with overflow menu
我正在开发一个运动计时器应用程序,并且是 android 编程的新手。我已经实现了溢出菜单。我面临两个问题:
- 面对层次结构中向上导航所需的消失向上箭头。选择其中一个溢出菜单后,向上箭头就会消失。
- 由于缺少向上箭头,我按下了后退按钮,但屏幕变空,只显示应用栏中的标题。
我刚刚查看了 SO 和外部关于这个缺失的向上箭头的各种帖子。但是无法获得解决此问题的任何线索。我看不出我拥有的代码和给出的解决方案之间有任何区别。对于空白屏幕,根本没有任何线索。
我经常来SO求助,确实得到了很多。请求 SOians 在这里帮助我。谢谢。
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:visibility="visible"
tools:context=".MainActivity">
<TextView
android:id="@+id/textView"
android:layout_width="215dp"
android:layout_height="48dp"
android:background="@color/teal_200"
android:text="@string/app_name"
android:textAlignment="center"
android:textAllCaps="true"
android:textColor="@color/black"
android:textSize="48sp"
android:textStyle="bold"
android:visibility="visible"
app:layout_anchor="@+id/toolbar"
app:layout_anchorGravity="center" />
<androidx.appcompat.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="69dp"
android:background="@color/white"
app:popupTheme="@style/Theme.PTimer.PopupOverlay" />
<include
android:id="@+id/include"
layout="@layout/content_main"
android:layout_height="match_parent"
app:layout_anchor="@+id/include"
app:layout_anchorGravity="center" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
主要activity的java代码如下
package com.example.ptimer;
import android.content.Intent;
import android.os.Bundle;
import com.google.android.material.snackbar.Snackbar;
import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;
import android.view.View;
import androidx.fragment.app.Fragment;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.fragment.NavHostFragment;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;
import com.example.ptimer.databinding.ActivityMainBinding;
import android.view.Menu;
import android.view.MenuItem;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.FrameLayout;
import android.widget.ImageButton;
import android.widget.Toast;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;
public class MainActivity extends AppCompatActivity {
private AppBarConfiguration appBarConfiguration;
private ActivityMainBinding binding;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = ActivityMainBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());
getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
setSupportActionBar(binding.toolbar);
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main);
appBarConfiguration = new AppBarConfiguration.Builder(navController.getGraph()).build();
NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getMenuInflater().inflate(R.menu.menu_main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
FragmentManager fragmentManager = this.getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
switch (id) {
case R.id.action_settings:
Fragment fragmentS = new SettingsFragment();
fragmentTransaction.replace(R.id.nav_host_fragment_content_main, fragmentS);
fragmentTransaction.setReorderingAllowed(true);
fragmentTransaction.addToBackStack(null);
break;
case R.id.action_kyc:
Fragment fragmentK = new KnowYourCapacity_Fragment();
fragmentTransaction.replace(R.id.nav_host_fragment_content_main, fragmentK);
break;
case R.id.action_about:
Fragment fragmentA = new HelpFragment();
Bundle bundle = new Bundle();
bundle.putString("help_desc", getResources().getString(R.string.pBasics_desc));
bundle.putString("help_image","basic");
fragmentA.setArguments(bundle);
fragmentTransaction.replace(R.id.nav_host_fragment_content_main, fragmentA);
break;
default:
break;
}
fragmentTransaction.commit();
return super.onOptionsItemSelected(item);
}
@Override
public boolean onSupportNavigateUp() {
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main);
onBackPressed();
return NavigationUI.navigateUp(navController, appBarConfiguration)
|| super.onSupportNavigateUp();
}
@Override
public void onDestroy() {
super.onDestroy();
}
}
Blank screen and missing up arrow image of the emulator is given as a link below (not allowed to post the image as such by SO)
编辑 1:将 getSupportActionBar().setDisplayHomeAsUpEnabled(true);
语句移动到 onCreateOptionsMenu
后显示向上箭头。但是单击向上箭头按钮显示空白屏幕。我的问题 #2 仍然存在。这里需要帮助。谢谢。
我找到了
的解决方案
问题 1:添加 getSupportActionBar().setDisplayHomeAsUpEnabled(true);在 onCreateOptionsMenu 中
问题 2:
我在 https://medium.com/mobile-app-development-publication/learn-android-navigation-component-through-coding-79dc47b240b3 中遇到了一个解决方案,它工作得很好,解决了白屏问题,也没有使用片段管理器的显式方法遍历到另一个片段。它是关于将菜单项链接到导航图。
我正在开发一个运动计时器应用程序,并且是 android 编程的新手。我已经实现了溢出菜单。我面临两个问题:
- 面对层次结构中向上导航所需的消失向上箭头。选择其中一个溢出菜单后,向上箭头就会消失。
- 由于缺少向上箭头,我按下了后退按钮,但屏幕变空,只显示应用栏中的标题。
我刚刚查看了 SO 和外部关于这个缺失的向上箭头的各种帖子。但是无法获得解决此问题的任何线索。我看不出我拥有的代码和给出的解决方案之间有任何区别。对于空白屏幕,根本没有任何线索。
我经常来SO求助,确实得到了很多。请求 SOians 在这里帮助我。谢谢。
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:visibility="visible"
tools:context=".MainActivity">
<TextView
android:id="@+id/textView"
android:layout_width="215dp"
android:layout_height="48dp"
android:background="@color/teal_200"
android:text="@string/app_name"
android:textAlignment="center"
android:textAllCaps="true"
android:textColor="@color/black"
android:textSize="48sp"
android:textStyle="bold"
android:visibility="visible"
app:layout_anchor="@+id/toolbar"
app:layout_anchorGravity="center" />
<androidx.appcompat.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="69dp"
android:background="@color/white"
app:popupTheme="@style/Theme.PTimer.PopupOverlay" />
<include
android:id="@+id/include"
layout="@layout/content_main"
android:layout_height="match_parent"
app:layout_anchor="@+id/include"
app:layout_anchorGravity="center" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
主要activity的java代码如下
package com.example.ptimer;
import android.content.Intent;
import android.os.Bundle;
import com.google.android.material.snackbar.Snackbar;
import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;
import android.view.View;
import androidx.fragment.app.Fragment;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.fragment.NavHostFragment;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;
import com.example.ptimer.databinding.ActivityMainBinding;
import android.view.Menu;
import android.view.MenuItem;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.FrameLayout;
import android.widget.ImageButton;
import android.widget.Toast;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;
public class MainActivity extends AppCompatActivity {
private AppBarConfiguration appBarConfiguration;
private ActivityMainBinding binding;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = ActivityMainBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());
getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
setSupportActionBar(binding.toolbar);
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main);
appBarConfiguration = new AppBarConfiguration.Builder(navController.getGraph()).build();
NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getMenuInflater().inflate(R.menu.menu_main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
FragmentManager fragmentManager = this.getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
switch (id) {
case R.id.action_settings:
Fragment fragmentS = new SettingsFragment();
fragmentTransaction.replace(R.id.nav_host_fragment_content_main, fragmentS);
fragmentTransaction.setReorderingAllowed(true);
fragmentTransaction.addToBackStack(null);
break;
case R.id.action_kyc:
Fragment fragmentK = new KnowYourCapacity_Fragment();
fragmentTransaction.replace(R.id.nav_host_fragment_content_main, fragmentK);
break;
case R.id.action_about:
Fragment fragmentA = new HelpFragment();
Bundle bundle = new Bundle();
bundle.putString("help_desc", getResources().getString(R.string.pBasics_desc));
bundle.putString("help_image","basic");
fragmentA.setArguments(bundle);
fragmentTransaction.replace(R.id.nav_host_fragment_content_main, fragmentA);
break;
default:
break;
}
fragmentTransaction.commit();
return super.onOptionsItemSelected(item);
}
@Override
public boolean onSupportNavigateUp() {
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main);
onBackPressed();
return NavigationUI.navigateUp(navController, appBarConfiguration)
|| super.onSupportNavigateUp();
}
@Override
public void onDestroy() {
super.onDestroy();
}
}
Blank screen and missing up arrow image of the emulator is given as a link below (not allowed to post the image as such by SO)
编辑 1:将 getSupportActionBar().setDisplayHomeAsUpEnabled(true);
语句移动到 onCreateOptionsMenu
后显示向上箭头。但是单击向上箭头按钮显示空白屏幕。我的问题 #2 仍然存在。这里需要帮助。谢谢。
我找到了
的解决方案问题 1:添加 getSupportActionBar().setDisplayHomeAsUpEnabled(true);在 onCreateOptionsMenu 中 问题 2: 我在 https://medium.com/mobile-app-development-publication/learn-android-navigation-component-through-coding-79dc47b240b3 中遇到了一个解决方案,它工作得很好,解决了白屏问题,也没有使用片段管理器的显式方法遍历到另一个片段。它是关于将菜单项链接到导航图。