我已经实现了一个Material Navigation Drawer，我想在选择导航抽屉中的一个菜单项而不是Profile Activity的一个片段时启动一个Activity。我不想在ProfileActivity中显示导航抽屉。我只想在从导航抽屉中选择菜单项时启动ProfileActivity。其他菜单项打开了我很好的片段。如果我在switch case语句中调用Intent，应用程序崩溃，因为我正在替换片段。
我目前使用的方法是
我打开FragmentProfile并在该Fragment中启动一个打开Profileactivity的Intent。
主要活动
公共类MainActivity扩展了AppCompatActivity {
private DrawerLayout mDrawerLayout;
@Optional @InjectView(R.id.username)
TextView _username;
public String Username;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.inject(this);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
final ActionBar ab = getSupportActionBar();
ab.setHomeAsUpIndicator(R.drawable.ic_menu);
ab.setDisplayHomeAsUpEnabled(true);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
if (navigationView != null) {
setupDrawerContent(navigationView);
}
navigationView.getMenu().performIdentifierAction(R.id.nav_dashboard, 0);
Username = SingletonName.instance().Username;
_username.setText(Username);
}
private void setupDrawerContent(NavigationView navigationView) {
navigationView.setNavigationItemSelectedListener(
new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
selectDrawerItem(menuItem);
return true;
}
});
}
public void selectDrawerItem(MenuItem menuItem) {
// Create a new fragment and specify the planet to show based on
// position
Fragment fragment = null;
Class fragmentClass = null;
switch (menuItem.getItemId()) {
case R.id.nav_dashboard:
fragmentClass = DashboardActivity.class;
// Intent dashboard = new Intent(this, DashboardActivity.class);
// startActivity(dashboard);
break;
case R.id.nav_history:
Intent historyintent = new Intent(this, HistoryActivity.class);
startActivity(historyintent);
break;
case R.id.nav_Flags:
// fragmentClass = ThirdFragment.class;
break;
case R.id.nav_Profile:
fragmentClass = FragmentProfile.class;
break;
case R.id.nav_Contacts:
fragmentClass = FragmentContact.class;
break;
case R.id.nav_Alerts:
break;
case R.id.nav_Logout:
Intent loginintent = new Intent(this, LoginActivity.class);
startActivity(loginintent);
break;
default:
fragmentClass = DashboardActivity.class;
}
try {
fragment = (Fragment) fragmentClass.newInstance();
} catch (Exception e) {
e.printStackTrace();
}
// Insert the fragment by replacing any existing fragment
FragmentManager fragmentManager = this.getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.flContent, fragment).commit();
// Highlight the selected item, update the title, and close the drawer
menuItem.setChecked(true);
setTitle(menuItem.getTitle());
mDrawerLayout.closeDrawers();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
switch (item.getItemId()) {
case android.R.id.home:
mDrawerLayout.openDrawer(GravityCompat.START);
return true;
}
//noinspection SimplifiableIfStatement
// if (id == R.id.action_settings) {
// return true;
// }
return super.onOptionsItemSelected(item);
}
}
FragmentProfile 片段 公共类FragmentProfile扩展了Fragment {
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
Intent profile = new Intent(getActivity(), ProfileActivity.class);
startActivity(profile);
return super.onCreateView(inflater, container, savedInstanceState);
}
}
/ ** *创建于2015-07-01，获取s210121629。 * / ProfileActivity 公共类ProfileActivity扩展了ActionBarActivity {
// Declaring Your View and Variables
Toolbar toolbar;
ViewPager pager;
ViewPagerAdapter adapter;
SlidingTabLayout tabs;
CharSequence Titles[] = {"Personal Info", "Medical Info", "Contact Info"};
int Numboftabs = 3;
String username;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_profile);
// Creating The Toolbar and setting it as the Toolbar for the activity
toolbar = (Toolbar) findViewById(R.id.tool_bar);
setSupportActionBar(toolbar);
final ActionBar ab = getSupportActionBar();
ab.setHomeAsUpIndicator(R.mipmap.ic_action_back);
ab.setDisplayHomeAsUpEnabled(true);
// Creating The ViewPagerAdapter and Passing Fragment Manager, Titles fot the Tabs and Number Of Tabs.
adapter = new ViewPagerAdapter(getSupportFragmentManager(), Titles, Numboftabs);
// Assigning ViewPager View and setting the adapter
pager = (ViewPager) findViewById(R.id.pager);
pager.setAdapter(adapter);
// Assiging the Sliding Tab Layout View
tabs = (SlidingTabLayout) findViewById(R.id.tabs);
tabs.setDistributeEvenly(true); // To make the Tabs Fixed set this true, This makes the tabs Space Evenly in Available width
username = getIntent().getStringExtra("username");
// Setting Custom Color for the Scroll bar indicator of the Tab View
tabs.setCustomTabColorizer(new SlidingTabLayout.TabColorizer() {
@Override
public int getIndicatorColor(int position) {
return getResources().getColor(R.color.md_cyan_900);
}
});
// Setting the ViewPager For the SlidingTabsLayout
tabs.setViewPager(pager);
Bundle extras = getIntent().getExtras();
if (extras != null) {
String value = extras.getString("new_variable_name");
Bundle bundle = new Bundle();
bundle.putString("message", value );
PersonalinfoFragment fragInfo = new PersonalinfoFragment();
fragInfo.setArguments(bundle);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
// int id = item.getItemId();
switch (item.getItemId()) {
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
}
有没有更简单，更简洁的方法。
当前错误
Process: com.example.s210121629.myhealth, PID: 31073
java.lang.NullPointerException
at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:417)
at android.support.v4.app.BackStackRecord.replace(BackStackRecord.java:452)
at android.support.v4.app.BackStackRecord.replace(BackStackRecord.java:444)
at com.example.s210121629.myhealth.MainActivity.selectDrawerItem(MainActivity.java:151)
at com.example.s210121629.myhealth.MainActivity$1.onNavigationItemSelected(MainActivity.java:72)
at android.support.design.widget.NavigationView$1.onMenuItemSelected(NavigationView.java:136)
at android.support.v7.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:811)
at android.support.v7.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:153)
at android.support.v7.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:958)
at android.support.design.internal.NavigationMenuPresenter.onItemClick(NavigationMenuPresenter.java:179)
at android.widget.AdapterView.performItemClick(AdapterView.java:308)
at android.widget.AbsListView.performItemClick(AbsListView.java:1524)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3531)
at android.widget.AbsListView$3.run(AbsListView.java:4898)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
答案 0 :(得分：1)
有一种更为简单的方法可以做到这一点。
IMO是的，但在这个阶段需要大量的重写。关于快速修复，从代码的外观来看，解决方案可能涉及此部分：
try {
fragment = (Fragment) fragmentClass.newInstance();
} catch (Exception e) {
e.printStackTrace();
}
FragmentManager = this.getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.flContent, fragment).commit();
使用null支票进行环绕：
if (fragment != null) {
//...
}
由于fragment永远不会赋值，因此应跳过实际加载片段的部分。
答案 1 :(得分：1)
而不是在切换案例结束时使用片段管理器。我改变了每个案例中的每个片段。
public void selectDrawerItem(MenuItem menuItem) {
switch (menuItem.getItemId()) {
case R.id.nav_dashboard:
getSupportFragmentManager().beginTransaction()
.replace(R.id.flContent, new DashboardActivity())
.commit();
break;
// case R.id.nav_history:
//
//
// Intent historyintent = new Intent(this, HistoryActivity.class);
// startActivity(historyintent);
// break;
case R.id.nav_Flags:
// fragmentClass = ThirdFragment.class;
break;
case R.id.nav_Profile:
Intent profileActivity = new Intent(getApplicationContext(), ProfileActivity.class);
startActivity(profileActivity);
break;
case R.id.nav_Contacts:
getSupportFragmentManager().beginTransaction()
.replace(R.id.flContent, new FragmentContact())
.commit();
break;
case R.id.nav_Alerts:
break;
case R.id.nav_Logout:
Intent loginintent = new Intent(this, LoginActivity.class);
startActivity(loginintent);
break;
default:
getSupportFragmentManager().beginTransaction()
.replace(R.id.flContent, new DashboardActivity())
.commit();
}