java - Android Viewpager 为空

Question

遇到一个小问题。我像以前一样制作了一个 ViewPager，看不出与我上次所做的代码有什么真正的区别，但它不会显示出来。没有错误或警告。只是一个空白的 Viewpager。这是代码:

MainActivity.java:

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;

public class MainActivity extends BaseActivity {

public ViewPager viewPager;
public PagerAdapter viewPagerAdapter;

private String strTitle = "Werkstatt";

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

    viewPager = (ViewPager) findViewById(R.id.CatPager);
    viewPagerAdapter = new CatPagerAdapter(getSupportFragmentManager());
    viewPager.setAdapter(viewPagerAdapter);
}

private class CatPagerAdapter extends FragmentPagerAdapter
{

public CatPagerAdapter(FragmentManager fm) {
    super(fm);
    // TODO Auto-generated constructor stub
}

@Override
public Fragment getItem(int arg0) {
    // TODO Auto-generated method stub
    Fragment fragment = new FragmentCat();

    return fragment;
}

@Override
public int getCount() {
    // TODO Auto-generated method stub
    return 0;
}}}

FragmentCat.java

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;


public class FragmentCat extends Fragment{

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // Inflate the layout for this fragment


    View rootView = (View) inflater.inflate(R.layout.fragment_cat, container, false);
    return rootView;
}   
}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" 
>
<android.support.v4.view.ViewPager
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/CatPager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
     />    
</LinearLayout>

fragment_cat.xml:

<?xml version="1.0" encoding="utf-8"?>
<!-- fragment_screen_slide_page.xml -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"

>

<TextView
    android:id="@+id/textView1"
    android:layout_width="247dp"
    android:layout_height="33dp"
    android:background="#0F0"
    android:text="Something happens" />

<ListView
    android:id="@+id/catListFrag"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginTop="20dp"
    android:paddingLeft="25dp"
    android:paddingRight="25dp"
    android:background="#F00" >
</ListView>
</LinearLayout>

这里没有找到解决方案。希望您能帮忙。

谢谢

Answer 1

它是空的，因为

@Override
public int getCount() {
    // TODO Auto-generated method stub
    return 0;
}

getCount 返回可用 View 数。如果返回 0，则意味着没有可用的 View ，因此永远不会调用 getItem。