如何通過ViewPager在布局中使用setText

Question

我嘗試在ViewPager的布局中設置文本，但是如果執行此操作，將拋出NullPointerException：

    private ViewPager viewPager;
    private ViewPagerAdapter viewPagerAdapter;
    private LinearLayout dotsLayout;
    private TextView[] dots;
    private int[] layouts;
    private Button btnNext;



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


        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);


        setContentView(R.layout.activity_slider);



        viewPager = (ViewPager) findViewById(R.id.view_pager);
        dotsLayout = (LinearLayout) findViewById(R.id.layoutDots);
        //btnSkip = (Button) findViewById(R.id.btn_skip);
        btnNext = (Button) findViewById(R.id.btn_next);



        layouts = new int[]{
                R.layout.slide_header_bild_text,
                R.layout.slide_header_bild_text_2,
                R.layout.slide_01_03,
                R.layout.slide_01_04,
                R.layout.slide_01_05,
                R.layout.slide_01_06,
                R.layout.startquiz_layout};

//These two lines are the Problem
TextView t1 = (TextView) findViewByID(R.id.header_text);
t1.setText("Test")

        // adding bottom dots
        addBottomDots(0);

        viewPagerAdapter = new ViewPagerAdapter();
        viewPager.setAdapter(viewPagerAdapter);
        viewPager.addOnPageChangeListener(viewPagerPageChangeListener);



    }

    public void btnQuizStart(View v){
        Intent intent = new Intent(this, Quiz.class);
        this.startActivity(intent);
    }



    public  void btnNextClick(View v)
    {
        // checking for last page
        // if last page home screen will be launched
        int current = getItem(1);
        if (current < layouts.length) {
            // move to next screen
            viewPager.setCurrentItem(current);
        } else {
            launchHomeScreen();
        }
    }


    ViewPager.OnPageChangeListener viewPagerPageChangeListener = new ViewPager.OnPageChangeListener() {

        @Override
        public void onPageSelected(int position) {
            addBottomDots(position);

            // changing the next button text 'NEXT' / 'GOT IT'
            if (position == layouts.length - 1) {
                // last page. make button text to GOT IT
                btnNext.setText(getString(R.string.start));

            } else {
                // still pages are left
                btnNext.setText(getString(R.string.next));
            }
        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {

        }

        @Override
        public void onPageScrollStateChanged(int arg0) {

        }
    };


    private void addBottomDots(int currentPage) {
        dots = new TextView[layouts.length];

        dotsLayout.removeAllViews();
        for (int i = 0; i < dots.length; i++) {
            dots[i] = new TextView(this);
            dots[i].setText(Html.fromHtml("&#8226;"));
            dots[i].setTextSize(35);
            dots[i].setTextColor(getResources().getColor(R.color.inactive_dots));
            dotsLayout.addView(dots[i]);
        }

        if (dots.length > 0)
            dots[currentPage].setTextColor(getResources().getColor(R.color.active_dots));
    }


    private int getItem(int i) {
        return viewPager.getCurrentItem() + i;
    }

    private void launchHomeScreen() {
        startActivity(new Intent(this, MainActivity.class));
        finish();
    }

    public class ViewPagerAdapter extends PagerAdapter {
        private LayoutInflater layoutInflater;


        public ViewPagerAdapter() {

        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            layoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            View view = layoutInflater.inflate(layouts[position], container, false);
            container.addView(view);

            return view;
        }

        @Override
        public int getCount() {
            return layouts.length;
        }

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


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

我有包含七個頁面的ViewPager。 我認為將找不到布局，因此TextView為Null。 我還讀到我必須配置InstantiateItem方法，並在其中添加TextView和setter。 有人可以幫忙嗎？

Answer 1

findViewByID（R.layout.header_text）

TaxtView不能是布局。

Answer 2

哦，這也是一個失敗，但不是我所尋找的。 我在viewpager中遇到的問題是我沒有布局，因此布局的元素為null。 我修復了InstantiateItem方法，以便任何布局都將特定於初始化：

public Object instantiateItem(ViewGroup container, int position) {
        layoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);



        View one = layoutInflater.inflate(R.layout.slide_type_a, container, false);


        WebView header_1_a = (WebView) one.findViewById(R.id.header_slide_type_a_1);
        loadHTLMContentHeader(getString(R.string.Historie1_header),header_1_a);

        ImageView image_1_a = (ImageView) one.findViewById(R.id.image_slide_type_a_1);
        image_1_a.setImageResource(R.drawable.picture_kap01_01);
        WebView text_1_a = (WebView) one.findViewById(R.id.text_slide_type_a_1);
        loadHTLMContentText(getString(R.string.Historie1), text_1_a);


        View two = layoutInflater.inflate(R.layout.slide_type_a, container, false);

        View three = layoutInflater.inflate(R.layout.slide_type_a, container, false);
        View four = layoutInflater.inflate(R.layout.slide_type_b, container, false);

        View five = layoutInflater.inflate(R.layout.slide_type_b, container, false);

        View six = layoutInflater.inflate(R.layout.slide_type_b, container, false);

        View seven = layoutInflater.inflate(R.layout.slide_type_b, container, false);

        View eight = layoutInflater.inflate(R.layout.startquiz_layout, container, false);
        View viewarr[] = {one, two, three, four, five, six, seven, eight};
        container.addView(viewarr[position]);


        return viewarr[position];

    }

因此，在啟動布局之后，我可以獲取xml元素並更改其內容。