我的android应用程序在启动后开始给我这个（logcat）错误。
我的主要活动是：
import android.app.Activity;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.support.v4.widget.DrawerLayout;
public class MainActivity extends AppCompatActivity
implements my.app.NavigationDrawerFragment.NavigationDrawerCallbacks {
/**
* Fragment managing the behaviors, interactions and presentation of the navigation drawer.
*/
private my.app.NavigationDrawerFragment mNavigationDrawerFragment;
/**
* Used to store the last screen title. For use in {@link #restoreActionBar()}.
*/
private CharSequence mTitle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mNavigationDrawerFragment = (my.app.NavigationDrawerFragment)
getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
mTitle = getTitle();
// Set up the drawer.
mNavigationDrawerFragment.setUp(
R.id.navigation_drawer,
(DrawerLayout) findViewById(R.id.drawer_layout));
}
@Override
public void onNavigationDrawerItemSelected(int position) {
Fragment myFragment = null;
switch (position) {
case 0:
myFragment = new First_Fragment();
break;
case 1:
myFragment = new Second_Fragment();
break;
case 2:
myFragment = new Third_Fragment();
break;
case 3:
myFragment = new Fourth_Fragment();
break;
//case 3:
// myFragment = new Caseopen_Fragment();
// break;
}
// update the main content by replacing fragments
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.container, myFragment)
.commit();
}
public void onSectionAttached(int number) {
switch (number) {
case 1:
mTitle = getString(R.string.title_section1);
break;
case 2:
mTitle = getString(R.string.title_section2);
break;
case 3:
mTitle = getString(R.string.title_section3);
break;
case 4:
mTitle = getString(R.string.title_section4);
break;
//case 4:
// mTitle = getString(R.string.title_caseopen);
// break;
}
}
public void restoreActionBar() {
ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
actionBar.setDisplayShowTitleEnabled(true);
actionBar.setTitle(mTitle);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
if (!mNavigationDrawerFragment.isDrawerOpen()) {
// Only show items in the action bar relevant to this screen
// if the drawer is not showing. Otherwise, let the drawer
// decide what to show in the action bar.
getMenuInflater().inflate(R.menu.main, menu);
restoreActionBar();
return true;
}
return super.onCreateOptionsMenu(menu);
}
@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();
//noinspection SimplifiableIfStatement
// if (id == R.id.action_settings) {
// 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";
/**
* 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;
}
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
return rootView;
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
((MainActivity) activity).onSectionAttached(
getArguments().getInt(ARG_SECTION_NUMBER));
}
}
}
主活动xml此处
我在谷歌上搜索了很多，唯一的东西，我找到了（使用extend FragmentActivity），但我的restoreActionBar()不起作用。在我运行应用程序之前，安卓工作室不会显示任何错误。
谢谢。
从你的评论中，我只有一个建议。
pixelsquad.csgohandbook.NavigationDrawerFragment中的Java片段代码是可疑的。为了隔离问题，你能尝试另一个片段代码吗？
创建"活动"时，您需要调试NavigationDrawerFragment，就像该片段的onCreate一样。如果该片段不在同一个项目中，那么调试就会更加困难，这是一个警告。
从logcat错误中，深入阅读，我认为没有找到类。错误：
导致原因：java.lang.ClassNotFoundException：找不到类"pixelsquad.csgohandbook.NavigationDrawerFragment"
如果是这样，那么在系统Java路径中根本找不到类、JAR或APK文件。
我已经解决了这个问题。我把属性android:name改为class。（虽然在Android文档上，他们说这些属性是相同的，但它有效！！）
因此，它应该从
android:name="pixelsquad.csgohandbook.NavigationDrawerFragment"
至
class="pixelsquad.csgohandbook.NavigationDrawerFragment"
所以，新的布局应该是：
<FrameLayout android:id="@+id/container" android:layout_width="match_parent"
android:layout_height="match_parent" />
<!-- android:layout_gravity="start" tells DrawerLayout to treat
this as a sliding drawer on the left side for left-to-right
languages and on the right side for right-to-left languages.
If you're not building against API 17 or higher, use
android:layout_gravity="left" instead. -->
<!-- The drawer is given a fixed width in dp and extends the full height of
the container. -->
<fragment android:id="@+id/navigation_drawer"
android:layout_width="@dimen/navigation_drawer_width" android:layout_height="match_parent"
android:layout_gravity="start"
class ="pixelsquad.csgohandbook.NavigationDrawerFragment"
tools:layout="@layout/fragment_navigation_drawer" />
希望得到帮助：）