从 MainActivity 获取 ViewPager 视图

Question

我正在开发一个应用程序，它使用 ViewPager 和两个滑动视图（first_page.xml 和 second_page.xml）并有一个活动（activity_main.xml）。

当我在主活动类中尝试使用findViewById 访问TextView（位于first_page.xml 中）时，找不到它。

这是我的 activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >
    <android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</RelativeLayout>

这是我的 first_page.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="match_parent"
    android:orientation="vertical" >
    <TextView
        android:id="@+id/someText"
        android:text="example"
        android:textSize="42sp" >
    </TextView>
</LinearLayout>

这是我的 customPagerAdapter

public class CustomPagerAdapter extends PagerAdapter {

    public Object instantiateItem(View collection, int position) {
    LayoutInflater inflater = (LayoutInflater) collection.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    int resId = 0;
    switch (position) {
    case 0: {
        resId = R.layout.first_page;
        break;
    }
    case 1: {
        resId = R.layout.second_page;
        break;
    }
    }
    View view = inflater.inflate(resId, null);
    ((ViewPager) collection).addView(view, 0);
    return view;
}

@Override
public void destroyItem(View arg0, int arg1, Object arg2) {
    ((ViewPager) arg0).removeView((View) arg2);
}

@Override
public boolean isViewFromObject(View arg0, Object arg1) {
    return arg0 == ((View) arg1);
}

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

@Override
public int getCount() {
    return 2;
}
}

这是我的MainActivity，我想在其中获取 first_page 布局，找到名为 someText 的 TextView，并设置新的自定义字体。

public class MainActivity extends Activity {

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // Create and set adapter
    CustomPagerAdapter adapter = new CustomPagerAdapter();
    ViewPager myPager = (ViewPager) findViewById(R.id.pager);
    myPager.setAdapter(adapter);
    myPager.setCurrentItem(0);

    /*
     *  Here i want to set a new custom font but it seems the someText can't
     *  be found because the Activity searches for it in the 
     *  layout.activity_main and not in the layout.first_page
    */
    TextView textView = (TextView) findViewById(R.id.someText);
    Typeface font = Typeface.createFromAsset(getAssets(), "roboto_thin.ttf");  
    textView.setTypeface(font);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}
}

我为这个问题苦苦挣扎了两天。

有什么建议吗？

Answer 1

textview被封装在fragment的容器中。如果您获得对正确片段的引用并获得对容器的引用，您可以调用 findViewById(R.id.someid)。

---

示例代码：

// TODO cast checks
int item = mViewPager.getCurrentItem();
Fragment frag = (Fragment) mPagerAdapter.getItem(item);
View container = frag.getView();
TextView searchTextView = (TextView) container.findViewById(R.id.someid);

或者是你的情况：

// TODO add null + cast checks
TextView textView = (TextView) ((Fragment)adapter.getItem(0)).getView().findViewById(R.id.someText);