Java 如何将fragment和AppCompatActivity扩展到同一个类？

我有一个类。我将Fragment扩展到这个类，因为我在开发导航抽屉时使用了Fragment

代码如下

public class aboutSLFragment extends Fragment  {

public aboutSLFragment() {
    // Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_about_sl, container, false);
}

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    //you can set the title for your toolbar here for different fragments different titles
    getActivity().setTitle("About Sri Lanka");
}

}

现在我想给这个类添加一个图像滑块

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    viewPager = (ViewPager) findViewById(R.id.viewPager);

    sliderDotspanel = (LinearLayout) findViewById(R.id.SliderDots);

    ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter(this);

    viewPager.setAdapter(viewPagerAdapter);

    dotscount = viewPagerAdapter.getCount();
    dots = new ImageView[dotscount];

    for(int i = 0; i < dotscount; i++){

        dots[i] = new ImageView(this);
        dots[i].setImageDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.non_active_dot));

        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);

        params.setMargins(8, 0, 8, 0);

        sliderDotspanel.addView(dots[i], params);

    }

    dots[0].setImageDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.active_dot));

    viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {

            for(int i = 0; i< dotscount; i++){
                dots[i].setImageDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.non_active_dot));
            }

            dots[position].setImageDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.active_dot));

        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });

}

正如我所知，我们不能继承两个类。那么我应该如何解决它呢？请帮帮我？如果有人修改我的代码，我们将不胜感激

我已经在aboutSLFragment.java中添加了一个图像滑块，但是有一些错误我无法修复。我是android新手，所以请有人告诉我如何修复这些错误。我已将错误加粗

public class aboutSLFragment extends Fragment{

ViewPager viewPager;
LinearLayout sliderDotspanel;
private int dotscount;
private ImageView[] dots;


public aboutSLFragment() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    viewPager = (ViewPager) **findViewById**(R.id.viewPager);

    sliderDotspanel = (LinearLayout) **findViewById**(R.id.SliderDots);

    ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter(**this**);

    viewPager.setAdapter(viewPagerAdapter);

    dotscount = viewPagerAdapter.getCount();
    dots = new ImageView[dotscount];

    for(int i = 0; i < dotscount; i++){

        dots[i] = new ImageView(**this**);
        dots[i].setImageDrawable(ContextCompat.getDrawable(**getApplicationContext()**, R.drawable.non_active_dot));

        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);

        params.setMargins(8, 0, 8, 0);

        sliderDotspanel.addView(dots[i], params);

    }

    dots[0].setImageDrawable(ContextCompat.getDrawable(**getApplicationContext()**, R.drawable.active_dot));

    viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {

            for(int i = 0; i< dotscount; i++){
                dots[i].setImageDrawable(ContextCompat.getDrawable(**getApplicationContext()**, R.drawable.non_active_dot));
            }

            dots[position].setImageDrawable(ContextCompat.getDrawable(**getApplicationContext()**, R.drawable.active_dot));

        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });

    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_about_sl, container, false);
}

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    //you can set the title for your toolbar here for different fragments different titles
    getActivity().setTitle("About Sri Lanka");
}

public类aboutSLFragment扩展了Fragment{
查看页面查看页面；
线性布局滑道；
私人互联网公司；
私有图像视图[]点；
公众关于碎片（）{
//必需的空公共构造函数
}
@凌驾
创建视图上的公共视图（布局、充气机、视图组容器、，
Bundle savedInstanceState）{
viewPager=（viewPager）**findViewById**（R.id.viewPager）；
sliderDotspanel=（线性布局）**findViewById**（R.id.SliderDots）；
ViewPagerAdapter ViewPagerAdapter=新ViewPagerAdapter（**此**）；
viewPager.setAdapter（viewPagerAdapter）；
dotscont=viewPagerAdapter.getCount（）；
dots=新图像视图[DOTSCONT]；
for（int i=0；i

---

}我已更改了您的代码。问题是：

findViewById（）

。活动已具有

findViewById（）

方法，因此您可以在活动中调用它。但是

Fragment

没有这个方法。在

Fragment

中，您必须通过

View.findViewById（）

方法找到一个视图，这里

View

将是您在

onCreateView（）中膨胀的视图

新建ViewPagerAdapter（此）

。要创建视图，必须提供活动上下文。在这里，您传递的是

this

它是您的片段实例，而不是活动上下文

ContextCompat.getDrawable（）

此方法还接受上下文<代码>getApplicationContext（）在片段中不可用。您必须从片段中调用

getActivity（）

或

getContext（）

，以获取活动的上下文

public class aboutSLFragment extends Fragment{

ViewPager viewPager;
LinearLayout sliderDotspanel;
private int dotscount;
private ImageView[] dots;

public aboutSLFragment() {
  // Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                     Bundle savedInstanceState) {

View rootView = inflater.inflate(R.layout.fragment_about_sl, container, false);
viewPager = (ViewPager) rootView .findViewById(R.id.viewPager);

sliderDotspanel = (LinearLayout)rootView.findViewById(R.id.SliderDots);

ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter(getContext());

viewPager.setAdapter(viewPagerAdapter);

dotscount = viewPagerAdapter.getCount();
dots = new ImageView[dotscount];

for(int i = 0; i < dotscount; i++){

    dots[i] = new ImageView(getContext());
    dots[i].setImageDrawable(ContextCompat.getDrawable(getContext(), R.drawable.non_active_dot));

    LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);

    params.setMargins(8, 0, 8, 0);

    sliderDotspanel.addView(dots[i], params);

}

dots[0].setImageDrawable(ContextCompat.getDrawable(getContext(), R.drawable.active_dot));

viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

    }

    @Override
    public void onPageSelected(int position) {

        for(int i = 0; i< dotscount; i++){
            dots[i].setImageDrawable(ContextCompat.getDrawable(getContext(), R.drawable.non_active_dot));
        }

        dots[position].setImageDrawable(ContextCompat.getDrawable(getContext(), R.drawable.active_dot));

    }

    @Override
    public void onPageScrollStateChanged(int state) {

    }
});

 // Inflate the layout for this fragment
 return rootView;
}

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
  super.onViewCreated(view, savedInstanceState);
  //you can set the title for your toolbar here for different fragments different titles
  getActivity().setTitle("About Sri Lanka");
 }

}

public类aboutSLFragment扩展了Fragment{
查看页面查看页面；
线性布局滑道；
私人互联网公司；
私有图像视图[]点；
公众关于碎片（）{
//必需的空公共构造函数
}
@凌驾
创建视图上的公共视图（布局、充气机、视图组容器、，
Bundle savedInstanceState）{
视图根视图=充气机。充气（R.layout.fragment\u about\u sl，container，false）；
viewPager=（viewPager）rootView.findViewById（R.id.viewPager）；
sliderDotspanel=（LinearLayout）rootView.findViewById（R.id.SliderDots）；
ViewPagerAdapter ViewPagerAdapter=新的ViewPagerAdapter（getContext（））；
viewPager.setAdapter（viewPagerAdapter）；
dotscont=viewPagerAdapter.getCount（）；
dots=新图像视图[DOTSCONT]；
for（int i=0；ipublic class aboutSLFragment extends Fragment{

ViewPager viewPager;
LinearLayout sliderDotspanel;
private int dotscount;
private ImageView[] dots;


public aboutSLFragment() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    viewPager = (ViewPager) **findViewById**(R.id.viewPager);

    sliderDotspanel = (LinearLayout) **findViewById**(R.id.SliderDots);

    ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter(**this**);

    viewPager.setAdapter(viewPagerAdapter);

    dotscount = viewPagerAdapter.getCount();
    dots = new ImageView[dotscount];

    for(int i = 0; i < dotscount; i++){

        dots[i] = new ImageView(**this**);
        dots[i].setImageDrawable(ContextCompat.getDrawable(**getApplicationContext()**, R.drawable.non_active_dot));

        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);

        params.setMargins(8, 0, 8, 0);

        sliderDotspanel.addView(dots[i], params);

    }

    dots[0].setImageDrawable(ContextCompat.getDrawable(**getApplicationContext()**, R.drawable.active_dot));

    viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {

            for(int i = 0; i< dotscount; i++){
                dots[i].setImageDrawable(ContextCompat.getDrawable(**getApplicationContext()**, R.drawable.non_active_dot));
            }

            dots[position].setImageDrawable(ContextCompat.getDrawable(**getApplicationContext()**, R.drawable.active_dot));

        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });

    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_about_sl, container, false);
}

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    //you can set the title for your toolbar here for different fragments different titles
    getActivity().setTitle("About Sri Lanka");
}

public class aboutSLFragment extends Fragment{

ViewPager viewPager;
LinearLayout sliderDotspanel;
private int dotscount;
private ImageView[] dots;

public aboutSLFragment() {
  // Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                     Bundle savedInstanceState) {

View rootView = inflater.inflate(R.layout.fragment_about_sl, container, false);
viewPager = (ViewPager) rootView .findViewById(R.id.viewPager);

sliderDotspanel = (LinearLayout)rootView.findViewById(R.id.SliderDots);

ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter(getContext());

viewPager.setAdapter(viewPagerAdapter);

dotscount = viewPagerAdapter.getCount();
dots = new ImageView[dotscount];

for(int i = 0; i < dotscount; i++){

    dots[i] = new ImageView(getContext());
    dots[i].setImageDrawable(ContextCompat.getDrawable(getContext(), R.drawable.non_active_dot));

    LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);

    params.setMargins(8, 0, 8, 0);

    sliderDotspanel.addView(dots[i], params);

}

dots[0].setImageDrawable(ContextCompat.getDrawable(getContext(), R.drawable.active_dot));

viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

    }

    @Override
    public void onPageSelected(int position) {

        for(int i = 0; i< dotscount; i++){
            dots[i].setImageDrawable(ContextCompat.getDrawable(getContext(), R.drawable.non_active_dot));
        }

        dots[position].setImageDrawable(ContextCompat.getDrawable(getContext(), R.drawable.active_dot));

    }

    @Override
    public void onPageScrollStateChanged(int state) {

    }
});

 // Inflate the layout for this fragment
 return rootView;
}

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
  super.onViewCreated(view, savedInstanceState);
  //you can set the title for your toolbar here for different fragments different titles
  getActivity().setTitle("About Sri Lanka");
 }

}