【发布时间】：2017-08-11 22:22:16
【问题描述】：
下面是我在使用导航抽屉导航时在 Android Studio 中遇到的错误的 StackTrace。这是一个新错误，因为它以前没有发生过。所以我不确定如果我改变了什么。
08-11 23:16:37.823 15951-15951/com.example.aids.a09application
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.aids.a09application, PID: 15951
java.lang.NullPointerException: Attempt to read from field 'int android.support.v4.app.Fragment.mContainerId' on a null object reference
at android.support.v4.app.FragmentTransition.addToFirstInLastOut(FragmentTransition.java:1017)
at android.support.v4.app.FragmentTransition.calculateFragments(FragmentTransition.java:976)
at android.support.v4.app.FragmentTransition.startTransitions(FragmentTransition.java:95)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2146)
at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2103)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2013)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:710)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6692)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358)
下面是我的导航抽屉的片段事务的 Java 类。
public class MainActivity extends AppCompatActivity {
DrawerLayout drawerLayout;
Toolbar toolbar;
ActionBarDrawerToggle actionBarDrawerToggle;
FragmentTransaction fragmentTransaction;
NavigationView navigationView;
Intent intent;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
actionBarDrawerToggle = new ActionBarDrawerToggle(this, drawerLayout, toolbar, R.string.drawer_open, R.string.drawer_close);
drawerLayout.addDrawerListener(actionBarDrawerToggle);
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.add(R.id.main_container, new HomeFragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle("Drift Fan");
navigationView = (NavigationView) findViewById(R.id.navigation_view);
navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.Home:
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_container, new HomeFragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle("Home Fragment");
item.setCheckable(true);
drawerLayout.closeDrawers();
break;
case R.id.my_account:
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_container, new myAccountFragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle("My Account");
item.setCheckable(true);
drawerLayout.closeDrawers();
break;
case R.id.nav_about:
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_container, new AboutDriftingFragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle("About Drifting");
item.setCheckable(true);
drawerLayout.closeDrawers();
break;
case R.id.nav_shop:
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_container, new ShopFragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle("Shop");
item.setCheckable(true);
drawerLayout.closeDrawers();
break;
case R.id.nav_news:
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_container, new NewsFragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle("News");
item.setCheckable(true);
drawerLayout.closeDrawers();
break;
case R.id.nav_media:
intent = new Intent(MainActivity.this, media_main.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
MainActivity.this.startActivity(intent);
break;
case R.id.nav_results:
fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_container, new ResultsFragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle("Results");
item.setCheckable(true);
drawerLayout.closeDrawers();
break;
}
return false;
}
});
}
@Override
protected void onPostCreate(@Nullable Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
actionBarDrawerToggle.syncState();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater menuInflater = getMenuInflater();
menuInflater.inflate(R.menu.drawer_menu, menu);
return true;
}
}
【问题讨论】：
-
包含容器 ID 的 Activity 的布局是什么？它看起来是在尝试提交片段事务时找不到与容器 Id 关联的视图。
-
它是在开始时出现还是在单击其中一项后出现？
标签： java android android-fragments