Android如何将Activity转化为View

在Android中怎样实现ViewPager+Activity，就是实现页面之间的滑动切换，而且每个Activity都编写了Java代码

        直接给你贴代码吧，有什么问题再问我
            ArrayList<View> list = new ArrayList<View>();
    Intent intent1 = new Intent(this, t1Activity.class);
    list.add(getView("t1", intent1));
    Intent intent2 = new Intent(this, t2Activity.class);
    list.add(getView("t2", intent2));
    Intent intent3 = new Intent(this, t3Activity.class);
    list.add(getView("t3", intent3));
    Intent intent4 = new Intent(this, t4Activity.class);
    list.add(getView("t4", intent4));
    viewpage.setAdapter(new MyPagerAdapter(list));
    viewpage.setCurrentItem(currentPage);
    viewpage.setOnPageChangeListener(new MyOnPageChangeListener());

如果要实现页面之间的滑动切换，比较好的实现方式 是ViewPager+Fragment。外层是Activity，就像是某些新闻阅读app首页一样可以左右滑动查看一样

final Window w = mLocalActivityManager.startActivity(
mTag, mIntent);
final View wd = w != null ? w.getDecorView() : null;

public class ViewPagerActivity2 extends AppCompatActivity {
private List views=new ArrayList<>();
private LocalActivityManager manager;
private ViewPager vp_view_page_image;

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

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

    manager = new LocalActivityManager((Activity) this,true);
    manager.dispatchCreate(savedInstanceState);

    Intent intentItem = new Intent(getApplicationContext(),ItemActivity.class);
    //views.add(manager.startActivity("ItemActivity",intentItem).getDecorView());
    Intent intentExpandable =new Intent(getApplicationContext(),ExpandableActivity.class);
    //views.add(manager.startActivity("ExpandableActivity",intentExpandable).getDecorView());
    views.add(activityToView(this,intentItem));//这一行报错
    views.add(activityToView(this,intentExpandable));
    vp_view_page_image.setAdapter(new MyAdapter());
}

@Override
protected void onPause() {
    super.onPause();
    manager.dispatchPause(isFinishing());
}

@Override
protected void onResume() {
    super.onResume();
    manager.dispatchResume();
}

public View activityToView(Context parent,Intent intent){
    Window w= manager.startActivity(parent.getClass().getName(),intent);//这一行报错
    View wd = w !=null ? w.getDecorView() :null;
    if(wd!=null){
        wd.setVisibility(View.VISIBLE);
        wd.setFocusableInTouchMode(true);
        ((ViewGroup)wd).setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
    }
    return wd;
}

class MyAdapter extends PagerAdapter {

    @Override
    public int getCount() {
        return views.size();
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view==object;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        View v=views.get(position);
        container.addView(v);

        return v;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        View v=views.get(position);
        container.removeView(v);
    }


}

}

请大神指出代码的错误，错误的两行已经在注释中写出

已经解决了，是因为没有在AndroidManifests文件中配置Activity