我是android studio的新手，我有这个问题，当我点击导航抽屉中的菜单时...使用Activity，它只是工作正常，它显示布局。但是当我使用Fragments时它会崩溃。
继承人我的主要活动：
public class MainActivity extends AppCompatActivity{
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mToggle;
private Toolbar mToolbar;
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mToolbar=(Toolbar)findViewById(R.id.nav_act);
setSupportActionBar(mToolbar);
NavigationView navigationView;
mDrawerLayout=(DrawerLayout)findViewById(R.id.main_content);
mToggle= new ActionBarDrawerToggle(this, mDrawerLayout,R.string.open,R.string.close);
mDrawerLayout.addDrawerListener(mToggle);
mToggle.syncState();
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
//drawers functions
navigationView=(NavigationView)findViewById(R.id.navigation_view);
navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()){
case R.id.nav_ac:
startActivity(new Intent(MainActivity.this,pop.class));
mDrawerLayout.closeDrawers();
break;
case R.id.nav_off:
startActivity(new Intent(MainActivity.this,no.class));
mDrawerLayout.closeDrawers();
break;
case R.id.nav_am:
startActivity(new Intent(MainActivity.this,am.class));
mDrawerLayout.closeDrawers();
break;
case R.id.nav_ab:
startActivity(new Intent(MainActivity.this,ab.class));
mDrawerLayout.closeDrawers();
break;
}
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.
if(mToggle.onOptionsItemSelected(item)){
return true;}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
public PlaceholderFragment() {
}
/**
* Returns a new instance of this fragment for the given section
* number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position){
switch(position)
{
case 0:
Tab1 tab1 = new Tab1();
return tab1;
case 1:
Tab2 tab2 = new Tab2();
return tab2;
case 2:
Tab3 tab3 = new Tab3();
return tab3;
case 3:
Tab4 tab4= new Tab4();
return tab4;
}
return null;
}
@Override
public int getCount() {
// Show 3 total pages.
return 4;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Massage";
case 1:
return "Add Ons";
case 2:
return "Foot&Nail Care";
case 3:
return "Benefits";
}
return null;
}
}
}
然后是错误：
4-13 23:21:33.081 15239-15239/com.example.jackreynaldo.tab E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.jackreynaldo.tab, PID: 15239
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.jackreynaldo.tab/com.example.jackreynaldo.tab.no}: java.lang.ClassCastException: com.example.jackreynaldo.tab.no cannot be cast to android.app.Activity
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2249)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2413)
at android.app.ActivityThread.access$800(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5357)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:952)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
Caused by: java.lang.ClassCastException: com.example.jackreynaldo.tab.no cannot be cast to android.app.Activity
at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2239)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2413)
at android.app.ActivityThread.access$800(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5357)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:952)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
而且我的没有上课：
public class no extends Fragment {
public no(){
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.no, container, false);
}
}
答案 0 :(得分：0)
startActivity（new Intent（MainActivity.this，no.class））;
no.class是活动吗？ no.class应该是活动并在清单文件中声明
您可以在MainActivity中添加框架布局，然后根据项目Id重新启动片段，如下所示：
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.frame, new no())
.commit();