IllegalStateException：指定的孩子已经有一个父母

Question

当切换回我已经看到的视图时，Activity 崩溃并抛出 IllegalStateException: The specified child has a parent。您必须先在孩子的父母上调用 removeView()。

堆栈跟踪：

02-23 23:59:22.685    9254-9254/ldellabella3.gatech.edu.sustainability_in_computer_science E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: ldellabella3.gatech.edu.sustainability_in_computer_science, PID: 9254
    java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
            at android.view.ViewGroup.addViewInner(ViewGroup.java:3770)
            at android.view.ViewGroup.addView(ViewGroup.java:3623)
            at android.view.ViewGroup.addView(ViewGroup.java:3568)
            at android.view.ViewGroup.addView(ViewGroup.java:3544)
            at android.support.v4.app.NoSaveStateFrameLayout.wrap(NoSaveStateFrameLayout.java:40)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:951)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
            at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:486)
            at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:163)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:1073)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:919)
            at android.support.v4.view.ViewPager$3.run(ViewPager.java:249)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:812)
            at android.view.Choreographer.doCallbacks(Choreographer.java:612)
            at android.view.Choreographer.doFrame(Choreographer.java:581)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:798)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5487)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
            at dalvik.system.NativeStart.main(Native Method)
02-24 00:02:57.133    9800-9800/ldellabella3.gatech.edu.sustainability_in_computer_science E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: ldellabella3.gatech.edu.sustainability_in_computer_science, PID: 9800
    java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
            at android.view.ViewGroup.addViewInner(ViewGroup.java:3770)
            at android.view.ViewGroup.addView(ViewGroup.java:3623)
            at android.view.ViewGroup.addView(ViewGroup.java:3568)
            at android.view.ViewGroup.addView(ViewGroup.java:3544)
            at android.support.v4.app.NoSaveStateFrameLayout.wrap(NoSaveStateFrameLayout.java:40)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:951)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
            at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:486)
            at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:163)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:1073)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:919)
            at android.support.v4.view.ViewPager$3.run(ViewPager.java:249)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:812)
            at android.view.Choreographer.doCallbacks(Choreographer.java:612)
            at android.view.Choreographer.doFrame(Choreographer.java:581)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:798)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:146)
            at android.app.ActivityThread.main(ActivityThread.java:5487)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
            at dalvik.system.NativeStart.main(Native Method)

我传递给 setContentView() 的 xml 很简单

<?xml version="1.0" encoding="utf-8"?>
<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" />

这是不断崩溃的活动：

public class LearnMoreSlidesActivity extends FragmentActivity {

    private ViewPager viewPager;
    private PagerAdapter pagerAdapter;
    private ImageView[] slidesArray;

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

        viewPager = (ViewPager) findViewById(R.id.pager);
        pagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
        viewPager.setAdapter(pagerAdapter);

        slidesArray = new ImageView[]{
                new ImageView(this),
                new ImageView(this),
                new ImageView(this)
        };

        slidesArray[0].setImageResource(R.drawable.earthzineimg);
        slidesArray[1].setImageResource(R.drawable.computingsustainability);
        slidesArray[2].setImageResource(R.drawable.computingandsustainability);

    }

    @Override
    public void onBackPressed() {
        if (viewPager.getCurrentItem() == 0) {
            // If the user is currently looking at the first step, allow the system to handle the
            // Back button. This calls finish() on this activity and pops the back stack.
            super.onBackPressed();
        } else {
            // Otherwise, select the previous step.
            viewPager.setCurrentItem(viewPager.getCurrentItem() - 1);
        }
    }

    private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {

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

        //this is where we "inflate" fragment_learn_more with our ldellabella3.gatech.edu.sustainability_in_computer_science.ScreenSlideFragment
        @Override
        public Fragment getItem(int position) {
            ScreenSlideFragment slideFragment = new ScreenSlideFragment();
            slideFragment.setMySlide(slidesArray[position]);
            return slideFragment;
        }

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

我的 ScreenSlideFragmentClass

public class ScreenSlideFragment extends Fragment {

    private ImageView myImg;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return myImg;
    }

    public void setMySlide(ImageView img) {
        myImg = img;
    }
}

Answer 1

在您的片段中添加以下代码。

@Override
public void onDestroyView() {
    super.onDestroyView();
    if (myImg != null) {
        ViewGroup parentViewGroup = (ViewGroup) myImg.getParent();
        if (parentViewGroup != null) {
            parentViewGroup.removeAllViews();
        }
    }
}