Android AuthAdapter无法重写FragmentStatePagerAdapter中的getItem（int），返回类型AuthFragment与Fragment不兼容

我有一个关于授权的片段。代码如下所示：

public abstract class AuthFragment extends Fragment {

    protected Callback callback;

    @BindView(R.id.caption)
    protected VerticalTextView caption;

    @BindView(R.id.root)
    protected ViewGroup parent;

    protected boolean lock;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View root = inflater.inflate(authLayout(), container, false);
        ButterKnife.bind(this, root);
        KeyboardVisibilityEvent.setEventListener(getActivity(), isOpen -> {
            callback.scale(isOpen);
            if (!isOpen) {
                clearFocus();
            }
        });
        return root;
    }

    public void setCallback(@NonNull Callback callback) {
        this.callback = callback;
    }

    @LayoutRes
    public abstract int authLayout();

    public abstract void fold();

    public abstract void clearFocus();

    @RequiresApi(api = Build.VERSION_CODES.M)
    @OnClick(R.id.root)
    public void unfold() {
        if (!lock) {
            caption.setVerticalText(false);
            caption.requestLayout();
            Rotate transition = new Rotate();
            transition.setStartAngle(-90f);
            transition.setEndAngle(0f);
            transition.addTarget(caption);
            TransitionSet set = new TransitionSet();
            set.setDuration(getResources().getInteger(R.integer.duration));
            ChangeBounds changeBounds = new ChangeBounds();
            set.addTransition(changeBounds);
            set.addTransition(transition);
            TextSizeTransition sizeTransition = new TextSizeTransition();
            sizeTransition.addTarget(caption);
            set.addTransition(sizeTransition);
            set.setOrdering(TransitionSet.ORDERING_TOGETHER);
            caption.post(() -> {
                TransitionManager.beginDelayedTransition(parent, set);
                caption.setTextSize(TypedValue.COMPLEX_UNIT_PX, getResources().getDimension(R.dimen.unfolded_size));
                caption.setTextColor(ContextCompat.getColor(getContext(), R.color.color_label));
                caption.setTranslationX(0);
                ConstraintLayout.LayoutParams params = getParams();
                params.rightToRight = ConstraintLayout.LayoutParams.PARENT_ID;
                params.leftToLeft = ConstraintLayout.LayoutParams.PARENT_ID;
                params.verticalBias = 0.78f;
                caption.setLayoutParams(params);
            });
            callback.show(this);
            lock = true;
        }
    }

    protected ConstraintLayout.LayoutParams getParams() {
        return ConstraintLayout.LayoutParams.class.cast(caption.getLayoutParams());
    }

    public interface Callback {
        void show(AuthFragment fragment);

        void scale(boolean hasFocus);
    }

}  

public abstract class AuthAdapter extends FragmentStatePagerAdapter implements AuthFragment.Callback {

    private final AnimatedViewPager pager;
    private final SparseArray<AuthFragment> authArray;
    private final List<ImageView> sharedElements;
    private final ImageView authBackground;
    private float factor;

    public AuthAdapter(FragmentManager manager,
                       AnimatedViewPager pager,
                       ImageView authBackground,
                       List<ImageView> sharedElements) {
        super(manager);
        this.authBackground = authBackground;
        this.pager = pager;
        this.authArray = new SparseArray<>(getCount());
        this.sharedElements = sharedElements;
        pager.setDuration(350);
        final float textSize = pager.getResources().getDimension(R.dimen.folded_size);
        final float textPadding = pager.getResources().getDimension(R.dimen.folded_label_padding);
        factor = 1 - (textSize + textPadding) / (pager.getWidth());
    }

    @Override
    public AuthFragment getItem(int position) {
        AuthFragment fragment = authArray.get(position);
        if (fragment == null) {
            fragment = position != 1 ? new LogInFragment() : new SignUpFragment();
            authArray.put(position, fragment);
            fragment.setCallback(this);
        }
        return fragment;
    }

    @Override
    public void show(AuthFragment fragment) {
        final int index = authArray.keyAt(authArray.indexOfValue(fragment));
        pager.setCurrentItem(index, true);
        shiftSharedElements(getPageOffsetX(fragment), index == 1);
        for (int jIndex = 0; jIndex < authArray.size(); jIndex++) {
            if (jIndex != index) {
                authArray.get(jIndex).fold();
            }
        }
    }

    private float getPageOffsetX(AuthFragment fragment) {
        int pageWidth = fragment.getView().getWidth();
        return pageWidth - pageWidth * factor;
    }

    private void shiftSharedElements(float pageOffsetX, boolean forward) {
        final Context context = pager.getContext();
        //since we're clipping the page, we have to adjust the shared elements
        AnimatorSet shiftAnimator = new AnimatorSet();
        for (View view : sharedElements) {
            float translationX = forward ? pageOffsetX : -pageOffsetX;
            float temp = view.getWidth() / 3f;
            translationX -= forward ? temp : -temp;
            ObjectAnimator shift = ObjectAnimator.ofFloat(view, View.TRANSLATION_X, 0, translationX);
            shiftAnimator.playTogether(shift);
        }

        int color = ContextCompat.getColor(context, forward ? R.color.color_logo_sign_up : R.color.color_logo_log_in);
        DrawableCompat.setTint(sharedElements.get(0).getDrawable(), color);
        //scroll the background by x
        int offset = authBackground.getWidth() / 2;
        ObjectAnimator scrollAnimator = ObjectAnimator.ofInt(authBackground, "scrollX", forward ? offset : -offset);
        shiftAnimator.playTogether(scrollAnimator);
        shiftAnimator.setInterpolator(new AccelerateDecelerateInterpolator());
        shiftAnimator.setDuration(pager.getResources().getInteger(R.integer.duration) / 2);
        shiftAnimator.start();
    }

    @Override
    public void scale(boolean hasFocus) {

        final float scale = hasFocus ? 1 : 1.4f;
        final float logoScale = hasFocus ? 0.75f : 1f;
        View logo = sharedElements.get(0);

        AnimatorSet scaleAnimation = new AnimatorSet();
        scaleAnimation.playTogether(ObjectAnimator.ofFloat(logo, View.SCALE_X, logoScale));
        scaleAnimation.playTogether(ObjectAnimator.ofFloat(logo, View.SCALE_Y, logoScale));
        scaleAnimation.playTogether(ObjectAnimator.ofFloat(authBackground, View.SCALE_X, scale));
        scaleAnimation.playTogether(ObjectAnimator.ofFloat(authBackground, View.SCALE_Y, scale));
        scaleAnimation.setDuration(200);
        scaleAnimation.setInterpolator(new AccelerateDecelerateInterpolator());
        scaleAnimation.start();
    }

    @Override
    public float getPageWidth(int position) {
        return factor;
    }

    @Override
    public int getCount() {
        return 2;
    }
}  

我有一个适配器，它使用上述片段的

回调

接口。代码如下所示：

public abstract class AuthFragment extends Fragment {

    protected Callback callback;

    @BindView(R.id.caption)
    protected VerticalTextView caption;

    @BindView(R.id.root)
    protected ViewGroup parent;

    protected boolean lock;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View root = inflater.inflate(authLayout(), container, false);
        ButterKnife.bind(this, root);
        KeyboardVisibilityEvent.setEventListener(getActivity(), isOpen -> {
            callback.scale(isOpen);
            if (!isOpen) {
                clearFocus();
            }
        });
        return root;
    }

    public void setCallback(@NonNull Callback callback) {
        this.callback = callback;
    }

    @LayoutRes
    public abstract int authLayout();

    public abstract void fold();

    public abstract void clearFocus();

    @RequiresApi(api = Build.VERSION_CODES.M)
    @OnClick(R.id.root)
    public void unfold() {
        if (!lock) {
            caption.setVerticalText(false);
            caption.requestLayout();
            Rotate transition = new Rotate();
            transition.setStartAngle(-90f);
            transition.setEndAngle(0f);
            transition.addTarget(caption);
            TransitionSet set = new TransitionSet();
            set.setDuration(getResources().getInteger(R.integer.duration));
            ChangeBounds changeBounds = new ChangeBounds();
            set.addTransition(changeBounds);
            set.addTransition(transition);
            TextSizeTransition sizeTransition = new TextSizeTransition();
            sizeTransition.addTarget(caption);
            set.addTransition(sizeTransition);
            set.setOrdering(TransitionSet.ORDERING_TOGETHER);
            caption.post(() -> {
                TransitionManager.beginDelayedTransition(parent, set);
                caption.setTextSize(TypedValue.COMPLEX_UNIT_PX, getResources().getDimension(R.dimen.unfolded_size));
                caption.setTextColor(ContextCompat.getColor(getContext(), R.color.color_label));
                caption.setTranslationX(0);
                ConstraintLayout.LayoutParams params = getParams();
                params.rightToRight = ConstraintLayout.LayoutParams.PARENT_ID;
                params.leftToLeft = ConstraintLayout.LayoutParams.PARENT_ID;
                params.verticalBias = 0.78f;
                caption.setLayoutParams(params);
            });
            callback.show(this);
            lock = true;
        }
    }

    protected ConstraintLayout.LayoutParams getParams() {
        return ConstraintLayout.LayoutParams.class.cast(caption.getLayoutParams());
    }

    public interface Callback {
        void show(AuthFragment fragment);

        void scale(boolean hasFocus);
    }

}  

public abstract class AuthAdapter extends FragmentStatePagerAdapter implements AuthFragment.Callback {

    private final AnimatedViewPager pager;
    private final SparseArray<AuthFragment> authArray;
    private final List<ImageView> sharedElements;
    private final ImageView authBackground;
    private float factor;

    public AuthAdapter(FragmentManager manager,
                       AnimatedViewPager pager,
                       ImageView authBackground,
                       List<ImageView> sharedElements) {
        super(manager);
        this.authBackground = authBackground;
        this.pager = pager;
        this.authArray = new SparseArray<>(getCount());
        this.sharedElements = sharedElements;
        pager.setDuration(350);
        final float textSize = pager.getResources().getDimension(R.dimen.folded_size);
        final float textPadding = pager.getResources().getDimension(R.dimen.folded_label_padding);
        factor = 1 - (textSize + textPadding) / (pager.getWidth());
    }

    @Override
    public AuthFragment getItem(int position) {
        AuthFragment fragment = authArray.get(position);
        if (fragment == null) {
            fragment = position != 1 ? new LogInFragment() : new SignUpFragment();
            authArray.put(position, fragment);
            fragment.setCallback(this);
        }
        return fragment;
    }

    @Override
    public void show(AuthFragment fragment) {
        final int index = authArray.keyAt(authArray.indexOfValue(fragment));
        pager.setCurrentItem(index, true);
        shiftSharedElements(getPageOffsetX(fragment), index == 1);
        for (int jIndex = 0; jIndex < authArray.size(); jIndex++) {
            if (jIndex != index) {
                authArray.get(jIndex).fold();
            }
        }
    }

    private float getPageOffsetX(AuthFragment fragment) {
        int pageWidth = fragment.getView().getWidth();
        return pageWidth - pageWidth * factor;
    }

    private void shiftSharedElements(float pageOffsetX, boolean forward) {
        final Context context = pager.getContext();
        //since we're clipping the page, we have to adjust the shared elements
        AnimatorSet shiftAnimator = new AnimatorSet();
        for (View view : sharedElements) {
            float translationX = forward ? pageOffsetX : -pageOffsetX;
            float temp = view.getWidth() / 3f;
            translationX -= forward ? temp : -temp;
            ObjectAnimator shift = ObjectAnimator.ofFloat(view, View.TRANSLATION_X, 0, translationX);
            shiftAnimator.playTogether(shift);
        }

        int color = ContextCompat.getColor(context, forward ? R.color.color_logo_sign_up : R.color.color_logo_log_in);
        DrawableCompat.setTint(sharedElements.get(0).getDrawable(), color);
        //scroll the background by x
        int offset = authBackground.getWidth() / 2;
        ObjectAnimator scrollAnimator = ObjectAnimator.ofInt(authBackground, "scrollX", forward ? offset : -offset);
        shiftAnimator.playTogether(scrollAnimator);
        shiftAnimator.setInterpolator(new AccelerateDecelerateInterpolator());
        shiftAnimator.setDuration(pager.getResources().getInteger(R.integer.duration) / 2);
        shiftAnimator.start();
    }

    @Override
    public void scale(boolean hasFocus) {

        final float scale = hasFocus ? 1 : 1.4f;
        final float logoScale = hasFocus ? 0.75f : 1f;
        View logo = sharedElements.get(0);

        AnimatorSet scaleAnimation = new AnimatorSet();
        scaleAnimation.playTogether(ObjectAnimator.ofFloat(logo, View.SCALE_X, logoScale));
        scaleAnimation.playTogether(ObjectAnimator.ofFloat(logo, View.SCALE_Y, logoScale));
        scaleAnimation.playTogether(ObjectAnimator.ofFloat(authBackground, View.SCALE_X, scale));
        scaleAnimation.playTogether(ObjectAnimator.ofFloat(authBackground, View.SCALE_Y, scale));
        scaleAnimation.setDuration(200);
        scaleAnimation.setInterpolator(new AccelerateDecelerateInterpolator());
        scaleAnimation.start();
    }

    @Override
    public float getPageWidth(int position) {
        return factor;
    }

    @Override
    public int getCount() {
        return 2;
    }
}  

公共抽象类AuthAdapter扩展了FragmentStatePagerAdapter，实现了AuthFragment.Callback{ 私人最终动画视图寻呼机； 私有最终Sparsarray authArray； 私人最终股东名单； 私有最终图像视图背景； 私人浮动系数； 公共AuthAdapter（碎片管理器， 动画视图寻呼机， ImageView authBackground， 列表共享（删除）{ 高级经理； this.authBackground=authBackground； this.pager=寻呼机； this.authArray=new SparseArray（getCount（））； this.sharedElements=sharedElements； 寻呼机设置持续时间（350）； final float textSize=pager.getResources（）.getDimension（R.dimen.folded_size）； 最终浮点文本填充=pager.getResources（）.getDimension（R.dimen.folded\u label\u padding）； 系数=1-（textSize+textPadding）/（pager.getWidth（））； } @凌驾 公共AuthFragment getItem（int位置）{ AuthFragment fragment=authArray.get（位置）； if（片段==null）{ 片段=位置！=1？新登录片段（）：新注册片段（）； 放置（位置，片段）； setCallback（this）； } 返回片段； } @凌驾 公共无效显示（AuthFragment片段）{ final int index=authArray.keyAt（authArray.indexOfValue（fragment））； pager.setCurrentItem（索引，true）； 移位共享元素（getPageOffsetX（片段），索引==1）； 对于（int jIndex=0；jIndex 当我尝试运行代码时，会出现以下错误：

错误：AuthAdapter中的getItem（int）无法覆盖FragmentStatePagerAdapter中的getItem（int）
返回类型AuthFragment与Fragment不兼容
错误：方法不重写或实现超类型中的方法

---

如果我让

getItem

返回

android.support.v4.Fragment

，那么我会得到

不兼容类型

错误。我怎样才能解决这个问题

在将应用程序从Android-O操作系统移植到Android-p移植时，我遇到了同样的问题 这个问题是因为V4、V7旧库用于旧代码。 现在在androidp中，它已经迁移到androidandroidx库。 因此，请将源文件中所有必要的导入从V4、V7、V13更改为androidx 更改文件：导入androidx.legacy\u legacy-support-v13\ 如下所示-旧版本V4/V7/V13包括最新的androidx遗留库，如下图所示。Android.mk文件更改如下：-

        LOCAL_STATIC_ANDROID_LIBRARIES += \
        androidx.car_car \
        androidx.legacy_legacy-support-v4 \
        androidx.legacy_legacy-support-v13 \
        android-support-design 
    #   android-support-v4
    #   android-support-v13 \

In source code If you are extending V13 or V4 change it to latest androidx classes :
refere below  https://developer.android.com/topic/libraries/support-library/refactor for changed V4/V7/V13 libraries changed to corresponding androidx....
i did like below in my case for same error.

Before :-


     private class ScreenSlidePagerAdapter extends 
        android.support.v13.app.FragmentStatePagerAdapter {}

After :- added import androidx.legacy.app.FragmentStatePagerAdapter;

private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {}

this change worked for me.

---

为什么投票否决？？？确保所有类中所有与

片段

相关的导入都来自

android.support.v4.app

，包括

FragmentStatePagerAdapter

。