Question

我正致力于片段活动，以便在姜饼OS上工作。当我试图在姜饼模拟器上运行应用程序时，由于ClassNotFound错误，应用程序被强制关闭。我在下面提供我的主要片段活动代码

和平的帮助将是可观的。

  package com.example.android.effectivenavigation;
import android.annotation.SuppressLint;
import android.annotation.TargetApi;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@SuppressLint("NewApi")
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {

/**
 * The {@link android.support.v4.view.PagerAdapter} that will provide fragments for each of the
 * three primary sections of the app. We use a {@link android.support.v4.app.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}.
 */
AppSectionsPagerAdapter mAppSectionsPagerAdapter;

/**
 * The {@link ViewPager} that will display the three primary sections of the app, one at a
 * time.
 */
ViewPager mViewPager;

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@SuppressLint("NewApi")
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Create the adapter that will return a fragment for each of the three primary sections
    // of the app.
    mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());

    // Set up the action bar.
    final ActionBar actionBar = getActionBar();

    // Specify that the Home/Up button should not be enabled, since there is no hierarchical
    // parent.
    actionBar.setHomeButtonEnabled(false);

    // Specify that we will be displaying tabs in the action bar.
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    // Set up the ViewPager, attaching the adapter and setting up a listener for when the
    // user swipes between sections.
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mAppSectionsPagerAdapter);
    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
        @SuppressLint("NewApi")
        @Override
        public void onPageSelected(int position) {
            // When swiping between different app sections, select the corresponding tab.
            // We can also use ActionBar.Tab#select() to do this if we have a reference to the
            // Tab.
            actionBar.setSelectedNavigationItem(position);
        }
    });

    // For each of the sections in the app, add a tab to the action bar.
    for (int i = 0; i < mAppSectionsPagerAdapter.getCount(); i++) {
        // Create a tab with text corresponding to the page title defined by the adapter.
        // Also specify this Activity object, which implements the TabListener interface, as the
        // listener for when this tab is selected.
        actionBar.addTab(
                actionBar.newTab()
                        .setText(mAppSectionsPagerAdapter.getPageTitle(i))
                        .setTabListener(this));
    }
}

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}

@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    // When the given tab is selected, switch to the corresponding page in the ViewPager.
    mViewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}

/**
 * A {@link FragmentPagerAdapter} that returns a fragment corresponding to one of the primary
 * sections of the app.
 */
public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {

    public AppSectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int i) {
        switch (i) {
            case 0:
                // The first section of the app is the most interesting -- it offers
                // a launchpad into the other demonstrations in this example application.
                return new LaunchpadSectionFragment();

            default:
                // The other sections of the app are dummy placeholders.
                Fragment fragment = new DummySectionFragment();
                Bundle args = new Bundle();
                args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, i + 1);
                fragment.setArguments(args);
                return fragment;
        }
    }

    @Override
    public int getCount() {
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return "Section " + (position + 1);
    }
}

/**
 * A fragment that launches other parts of the demo application.
 */
public static class LaunchpadSectionFragment extends Fragment {
    ArrayAdapter<String> adapter;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_section_launchpad, container, false);
        ListView listView = (ListView)rootView.findViewById(R.id.listview);
        String[] values = new String[] {"Akshay Borgave","Pramod Mahake","Vishal Lokhande","Vivek Chaudhari","Rahul Borole","Neha Gadekar"};


      adapter = new ArrayAdapter<String>(getActivity(),android.R.layout.simple_list_item_2, android.R.id.text1, values);


        listView.setAdapter(adapter);
        // Demonstration of a collection-browsing activity.
        /*rootView.findViewById(R.id.demo_collection_button)
                .setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        Intent intent = new Intent(getActivity(), CollectionDemoActivity.class);
                        startActivity(intent);
                    }
                });*/

        // Demonstration of navigating to external activities.
       /* rootView.findViewById(R.id.demo_external_activity)
                .setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        // Create an intent that asks the user to pick a photo, but using
                        // FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET, ensures that relaunching
                        // the application from the device home screen does not return
                        // to the external activity.
                        Intent externalActivityIntent = new Intent(Intent.ACTION_PICK);
                        externalActivityIntent.setType("image/*");
                        externalActivityIntent.addFlags(
                                Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);
                        startActivity(externalActivityIntent);
                    }
                });*/

        return rootView;
    }
}

/**
 * A dummy fragment representing a section of the app, but that simply displays dummy text.
 */
public static class DummySectionFragment extends Fragment {

    public static final String ARG_SECTION_NUMBER = "section_number";

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
        Bundle args = getArguments();
        ((TextView) rootView.findViewById(android.R.id.text1)).setText(
                getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
        return rootView;
    }
}
}

Manifest看起来像这样

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.android.effectivenavigation"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk android:minSdkVersion="9" 
    android:targetSdkVersion="10"/>

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.WithActionBar" >
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".CollectionDemoActivity"
        android:label="@string/demo_collection" />
</application>

logcat是

06-12 16:37:17.099: E/AndroidRuntime(378): FATAL EXCEPTION: main
06-12 16:37:17.099: E/AndroidRuntime(378): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.android.effectivenavigation/com.example.android.effectivenavigation.MainActivity}: java.lang.ClassNotFoundException: com.example.android.effectivenavigation.MainActivity in loader dalvik.system.PathClassLoader[/data/app/com.example.android.effectivenavigation-1.apk]
06-12 16:37:17.099: E/AndroidRuntime(378):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569)
06-12 16:37:17.099: E/AndroidRuntime(378):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
06-12 16:37:17.099: E/AndroidRuntime(378):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
06-12 16:37:17.099: E/AndroidRuntime(378):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
06-12 16:37:17.099: E/AndroidRuntime(378):  at android.os.Handler.dispatchMessage(Handler.java:99)
06-12 16:37:17.099: E/AndroidRuntime(378):  at android.os.Looper.loop(Looper.java:123)
06-12 16:37:17.099: E/AndroidRuntime(378):  at android.app.ActivityThread.main(ActivityThread.java:3683)
06-12 16:37:17.099: E/AndroidRuntime(378):  at java.lang.reflect.Method.invokeNative(Native Method)
06-12 16:37:17.099: E/AndroidRuntime(378):  at java.lang.reflect.Method.invoke(Method.java:507)
06-12 16:37:17.099: E/AndroidRuntime(378):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-12 16:37:17.099: E/AndroidRuntime(378):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-12 16:37:17.099: E/AndroidRuntime(378):  at dalvik.system.NativeStart.main(Native Method)
06-12 16:37:17.099: E/AndroidRuntime(378): Caused by: java.lang.ClassNotFoundException: com.example.android.effectivenavigation.MainActivity in loader dalvik.system.PathClassLoader[/data/app/com.example.android.effectivenavigation-1.apk]
06-12 16:37:17.099: E/AndroidRuntime(378):  at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240)
06-12 16:37:17.099: E/AndroidRuntime(378):  at java.lang.ClassLoader.loadClass(ClassLoader.java:551)
06-12 16:37:17.099: E/AndroidRuntime(378):  at  java.lang.ClassLoader.loadClass(ClassLoader.java:511)
06-12 16:37:17.099: E/AndroidRuntime(378):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
06-12 16:37:17.099: E/AndroidRuntime(378):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561)
06-12 16:37:17.099: E/AndroidRuntime(378):  ... 11 more

片段活动的Xml布局文件如下

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent" />

再次感谢

Answer 1

在你的mainfest.xml中

<uses-sdk android:minSdkVersion="9" 
    android:targetSdkVersion="10"/>

Fragments 是在 API等级11 中引入的，即Android 3.0。我认为你得到的是ClassNotFoundException，因为系统对较低版本的Fragment类一无所知。

因此，您需要使用 Android Support Library 来使用较低API级别的片段。

Answer 2

代码看似正确，听起来像构建系统的问题。尝试刷新/清除工作区（如果使用eclipse）并确保在构建APK时添加支持库

class not found for android for fragment activity

2 个答案: