android - 按下后退按钮后的Android ViewPager异常

我有一个viewpager，它包含3个片段，运行良好。我从viewpager中的任何片段启动一个活动并显示该活动。之后，当我按下后退按钮时，我的应用程序将崩溃，出现以下异常：

FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to resume activity {AppName.Activities/AppName.Activities.ViewPagerActivity}: java.lang.IndexOutOfBoundsException: Invalid index 2, size is 0
    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2120)
    at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2135)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:957)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:123)
    at android.app.ActivityThread.main(ActivityThread.java:3683)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:507)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IndexOutOfBoundsException: Invalid index 2, size is 0
    at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:257)
    at java.util.ArrayList.set(ArrayList.java:484)
    at android.support.v4.app.FragmentStatePagerAdapter.destroyItem(FragmentStatePagerAdapter.java:97)
    at android.support.v4.view.ViewPager.populate(ViewPager.java:415)
    at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:271)
    at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:244)
    at AppName.Activities.ViewPagerActivity.setUpView(ViewPagerActivity.java:36)
    at AppName.Activities.ViewPagerActivity.onStart(ViewPagerActivity.java:28)
    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129)
    at android.app.Activity.performStart(Activity.java:3791)
    at android.app.Activity.performRestart(Activity.java:3821)
    at android.app.Activity.performResume(Activity.java:3826)
    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2110)

以下是扩展FragmentActivity的ViewPageActivity的代码：

public class ViewPagerActivity extends FragmentActivity
{
    private ViewPager mViewPager;
    private ViewPagerAdapter adapter;
    boolean flag = false;

    @Override
    protected void onCreate(Bundle arg0)
    {
        super.onCreate(arg0);
        setContentView(R.layout.view_pager);
    }

    @Override
    protected void onStart()
    {
        super.onStart();
        setUpView();
    }

    private void setUpView()
    {
        mViewPager = (ViewPager) findViewById(R.id.viewPager);
        adapter = new ViewPagerAdapter(getApplicationContext(),getSupportFragmentManager());
        mViewPager.setAdapter(adapter);
        mViewPager.setCurrentItem(0);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        switch (item.getItemId())
        {
            case R.id.settings:
                startActivity(new Intent(this, AppSettingsActivity.class));
                return true;
            case R.id.addSituationMenu:
                Intent i = new Intent(this, MainLayout.class);
                i.putExtra("parentActivity", "SplashScreenLayout");
                startActivity(i);
                return true;
            case R.id.historyActivity:
                startActivity(new Intent(this, HistoryActivity.class));
                return true;
            case R.id.chartActivity:
                startActivity(new Intent(this, ViewPagerActivity.class));
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

}

行mviewpager.setcurrentitem（0）；导致崩溃。
这是viewPageRadapter代码：

public class ViewPagerAdapter extends FragmentStatePagerAdapter
{
    private final Context context;
    ArrayList<ArrayList<Object>> data;
    int totalMoodEntries = 0;
    static Fragment f = null;

    public ViewPagerAdapter(Context mcontext, FragmentManager fm)
    {
        super(fm);
        context = mcontext;
    }

    @Override
    public Fragment getItem(int position)
    {
        switch (position)
        {
            case 0:
            {
                f = new ChartFragment(context, totalMoodEntries, data);
                break;
            }
            case 1:
            {
                f = new ViewRecordsFragment(context, data);
                break;
            }
            case 2:
            {
                f = new LearnMoreFragment(context);
                break;
            }
        }
        return f;
    }

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

最佳答案

您可以尝试在onCreate()方法中移动以下行：

mViewPager = (ViewPager) findViewById(R.id.viewPager);
adapter = new ViewPagerAdapter(getApplicationContext(),getSupportFragmentManager());
mViewPager.setAdapter(adapter);