如何获取水平 ViewPager 的 PagerAdapter 项目 ID？

Question

我已经实现了带有自定义 PagerAdapter 的 Horizo​​ntal ViewPager，就像附加在屏幕上一样。 我想要实现的是从 list 中获取 First item 的 Id 。 这是迄今为止所有内容的代码。

寻呼机适配器：

private static final String TAG = ViewPagerAdapter.class.getSimpleName();
private Context context;
private LayoutInflater layoutInflater;
private ArrayList<QuickActionItem> quickActionItems;

public ViewPagerAdapter(Context context, ArrayList<QuickActionItem> items) {
    this.context = context;
    this.quickActionItems = items;   
}

@Override
public float getPageWidth(int position) {
    return 0.25f;
}

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

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

@Override
public Object instantiateItem(final ViewGroup container, final int position) {

    layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    View view = layoutInflater.inflate(R.layout.item_page_slide, null);

    ImageView actionImage = view.findViewById(R.id.img_action);

    TextView actionText = view.findViewById(R.id.title_action_value);
actionImage.setImageResource(quickActionItems.get(position).getActionDrawableImage());

    actionText.setText(quickActionItems.get(position).getActionName());

    ViewPager vp = (ViewPager) container;
    vp.addView(view, 0);

    view.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View view) {

            if (quickActionItems.get(position).getActionName().equals(context.getString(R.string.quick_add_property))) {
                Log.d(TAG, "Add Property ");


            } else if (quickActionItems.get(position).getActionName().equals(context.getString(R.string.quick_add_tenant))) {
                Log.d(TAG, "Add Tenant ");

                context.startActivity(targetIntent);
            } else if (quickActionItems.get(position).getActionName().equals(context.getString(R.string.quick_add_income))) {
                Log.d(TAG, "Add Income ");

                context.startActivity(targetIntent);
            } else if (quickActionItems.get(position).getActionName().equals(context.getString(R.string.quick_add_expense))) {
                Log.d(TAG, "Add Expense ");

            }

        }
    });

    return view;
}


@Override
public void destroyItem(ViewGroup container, int position, Object object) {

      ViewPager vp = (ViewPager) container;
      View view = (View) object;
      vp.removeView(view);
     }
   }

快速操作项

public class QuickActionItem {

    private String actionName;
    private int actionDrawableImage;
}

主片段

    quickActionPager = fragmentView.findViewById(R.id.quick_actions_pager);
    sliderDotsPanel = fragmentView.findViewById(R.id.SliderDots);

    quickActionItems = new ArrayList<>();
    quickActionItems.add(new QuickActionItem(getString(R.string.quick_add_property), R.drawable.ic_add_property));
    quickActionItems.add(new QuickActionItem(getString(R.string.quick_add_tenant), R.drawable.ic_add_tenant));
    quickActionItems.add(new QuickActionItem(getString(R.string.quick_add_income), R.drawable.ic_add_income));
    quickActionItems.add(new QuickActionItem(getString(R.string.quick_add_expense), R.drawable.ic_add_expense));


    viewPagerAdapter = new ViewPagerAdapter(getActivity(), quickActionItems);
    quickActionPager.setAdapter(viewPagerAdapter);

我只分享 MainFragment 代码的必要部分，因为它很长，无论我想实现什么。

问题：

1) 第一个项目是否有可能获得任何类型的 ID？ 在我的情况下，“添加属性”项目的 ID

2）如果可能，那么如何获取该 Id 以及我能否在其上调用 findViewById ？

如果您需要任何其他信息或代码，也请告诉我。

任何帮助，将不胜感激。

Answer 1

请尝试以下操作：

因此，您需要在 viewPager 中获取某个页面的布局，然后使用findViewById()获取布局视图。 您可以通过将每个膨胀的布局放入TreeMap中的instantiateItem()并在destroyItem()销毁时从TreeMap 中删除布局来实现这一点。 然后你可以通过使用treeMap.get(position)来获得一定的页面布局 下面是一个例子：

主活动类

public class MainActivity extends AppCompatActivity {

private final String TAG = MainActivity.class.getSimpleName();
private ViewPager vp;
private ViewPagerAdapter viewPagerAdapter = null;
private Button b;
private List<String> data = new ArrayList<>();
private List<Integer> color = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    vp = (ViewPager) findViewById(R.id.vp);

    b = (Button) findViewById(R.id.b);
    b.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            /**
             * use viewPagerAdapter.getLayout(int position) to get the layout for a certain page
             * then use findViewById() to get a certain view inside that layout
             */
            View layout = viewPagerAdapter.getLayout(vp.getCurrentItem());
            if (layout != null) {
                TextView tv = (TextView) layout.findViewById(R.id.tv);
                tv.setTextColor(color.get(vp.getCurrentItem()));
            }
        }
    });
    color.add(Color.RED);

    color.add(Color.GRAY);
    color.add(Color.BLUE);
    color.add(Color.YELLOW);
    color.add(Color.MAGENTA);
    color.add(Color.CYAN);
    color.add(Color.LTGRAY);
    color.add(Color.DKGRAY);
    for(int i=0; i<8; i++){
        data.add("Page " + (i+1));
    }
    viewPagerAdapter = new ViewPagerAdapter(MainActivity.this, data);
    vp.setAdapter(viewPagerAdapter);
}

}

ViewPagerAdapter.class

public class ViewPagerAdapter extends PagerAdapter {

private static final String TAG = ViewPagerAdapter.class.getSimpleName();
private Context context;
private LayoutInflater layoutInflater;
private List<String> data;
private TreeMap<Integer, View> layout;

public ViewPagerAdapter(Context context, List<String> data) {
    this.context = context;
    this.data = data;
    this.layout = new TreeMap<>();
}

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

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

@Override
@NonNull
public Object instantiateItem(@NonNull final ViewGroup container, final int position) {
    layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View view = layoutInflater.inflate(R.layout.page_item, container, false);
    TextView tv = (TextView) view.findViewById(R.id.tv);
    tv.setText(data.get(position));
    /**
     * put the inflated layout inside TreeMap with key being the position
     */
    this.layout.put(position, view);
    container.addView(view);
    return view;
}


@Override
public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
    ViewPager vp = (ViewPager) container;
    View view = (View) object;
    /**
     * remove a layout with key position
     */
    this.layout.remove(position);
    vp.removeView(view);
}

/**
 * used to get a layout
 * @return TreeMap
 */
public TreeMap<Integer, View> getLayout() {
    return this.layout;
}

/**
 *
 * @param position
 * @return View at position
 */
public View getLayout(int position) {
    return this.layout.get(position);
}


}

活动_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:weightSum="100"
android:orientation="vertical">

<android.support.v4.view.ViewPager
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="80"
    android:id="@+id/vp">
</android.support.v4.view.ViewPager>

<Button
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/b"
    android:layout_weight="20"
    android:text="Change Text View Color">
</Button>

</LinearLayout>

page_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:id="@+id/ll"
android:layout_marginStart="20dp"
android:layout_marginRight="20dp"
android:layout_marginLeft="20dp"
android:layout_marginEnd="20dp"
android:layout_marginTop="20dp"
android:layout_marginBottom="20dp"
android:background="@color/colorAccent"
android:layout_height="match_parent">

<TextView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/tv"
    android:gravity="center"
    android:layout_gravity="center"
    android:textSize="24sp"
    android:textColor="@android:color/black">
</TextView>

</LinearLayout>