android - 为什么 ViewPager 中的第一个 View 显示为空？

Question

我有一个使用以下适配器的 viewpager，加载后第一个 View 显示为空，但事实并非如此。如果我滚动到下一个 View 然后向后滚动，我可以看到内容。

import android.content.Context;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.widget.TextView;
import java.util.ArrayList;

public class MyPagerAdapter extends PagerAdapter {

    Context context;

    public ArrayList<TextView> mViews;

    int layoutResourceId;

    public MyPagerAdapter(Context context) {
        mViews = new ArrayList<TextView>();

    }

    @Override
    public void destroyItem(View view, int arg1, Object object) {
        ((ViewPager)view).removeView((View)object);
    }

    @Override
    public void finishUpdate(View arg0) {

    }

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

    @Override
    public Object instantiateItem(View view, int position) {
        View myView = mViews.get(position);
        ((ViewPager)view).addView(myView);
        return myView;
    }

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

    @Override
    public void restoreState(Parcelable arg0, ClassLoader arg1) {

    }

    @Override
    public Parcelable saveState() {
        return null;
    }

    @Override
    public void startUpdate(View arg0) {

    }

    @Override
    public int getItemPosition(Object object) {
        return POSITION_NONE;
    }

}

这是从我的 Activity 中实现它的代码...

public void resetPages() {
    if (mPageText == null)
        return;
    mPagerAdapter.mViews.clear();
    for (int i = 0; i < mPageText.size(); i++) {
        TextView tv = new TextView(this);
        tv.setTextSize(mSelectedFontSize);
        tv.setText(mPageText.get(i));
        tv.setId(i);
        tv.setTag(i);
        tv.invalidate();
        mPagerAdapter.mViews.add(tv);
    }

mPagerAdapter.notifyDataSetChanged();
mViewPager.refreshDrawableState();
}

Answer 1

尝试添加 followind onCreate 方法并且我的代码有效(启动时出现“TEXT 0”)。也许只是因为在不合适的时间调用了 resetPages()？

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mPageText = new LinkedList<CharSequence>();
    for (int i=0; i<10; i++) {
        mPageText.add("TEXT "+i);
    }
    this.mPagerAdapter = new MyPagerAdapter(this);
    this.mViewPager = (ViewPager)this.findViewById(R.id.viewpager);
    this.mViewPager.setAdapter(mPagerAdapter);
    resetPages();
}