FragmentActivity 中的 Android PagerAdapter IllegalStateException

Question

我收到以下错误，但我无法弄清楚它发生的原因。我没有关于该错误的更多信息。

我有一个包含 50 个项目的 Android ListView。当您单击一个项目，然后打开第二个屏幕（带有分页器的片段活动）时，此片段活动显示片段中的所有项目，从 ListView 中单击的项目到最后一个项目，可以向左或向右滑动。

java.lang.IllegalStateException: 
  at android.support.v4.view.ViewPager.populate(ViewPager.java:1167)
  at android.support.v4.view.ViewPager.populate(ViewPager.java:1116)
  at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1642)
  at android.view.View.measure(View.java:17951)
  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5797)
  at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
  at android.view.View.measure(View.java:17951)
  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5797)
  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
  at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
  at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
  at android.view.View.measure(View.java:17951)
  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5797)
  at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
  at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2910)
  at android.view.View.measure(View.java:17951)
  at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2048)
  at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1185)
  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1406)
  at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1073)
  at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5988)
  at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
  at android.view.Choreographer.doCallbacks(Choreographer.java:580)
  at android.view.Choreographer.doFrame(Choreographer.java:550)
  at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
  at android.os.Handler.handleCallback(Handler.java:739)
  at android.os.Handler.dispatchMessage(Handler.java:95)
  at android.os.Looper.loop(Looper.java:135)
  at android.app.ActivityThread.main(ActivityThread.java:5910)
  at java.lang.reflect.Method.invoke(Native Method:0)
  at java.lang.reflect.Method.invoke(Method.java:372)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1405)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1200)

Answer 1

public class ScreenSlidePagerActivity extends FragmentActivity {
    /**
     * The number of pages (wizard steps) to show in this demo.
     */
    public static int NUM_PAGES = 50;

    /**
     * The pager widget, which handles animation and allows swiping horizontally to access previous
     * and next wizard steps.
     */
    private ViewPager mPager;

    /**
     * The pager adapter, which provides the pages to the view pager widget.
     */
    private PagerAdapter mPagerAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_screen_slide);

        // Instantiate a ViewPager and a PagerAdapter.
        mPager = (ViewPager) findViewById(R.id.pager);
        mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
        mPager.setAdapter(mPagerAdapter);

    }

    @Override
    public void onBackPressed() {
        if (mPager.getCurrentItem() <= 0) {

           //start an intent
        } else {
            // Otherwise, select the previous step.
            mPager.setCurrentItem(mPager.getCurrentItem() - 1);
        }
    }

    private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
        public ScreenSlidePagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {

            Bundle bundle = new Bundle();
            bundle.putSerializable("content", "bla bla content" );

            MyFragment fragmentObj= new MyFragment();
            fragmentObj.setArguments(bundle);
            return fragmentObj;
        }

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

    }


}