当片段显示在屏幕上时，片段代码不是运行

Question

我已经开始在我的应用程序中创建 inflated 使用侧边菜单的片段。问题是 none 个片段，其中 1 个是使用 android studio 模板自动生成时的样子，似乎正在执行任何代码。

这可能是我遗漏了一些明显的情况，我们将不胜感激。

这是我的 MainActivity:

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.*;

import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;


public class MainActivity extends ActionBarActivity
    implements NavigationDrawerFragment.NavigationDrawerCallbacks {

/**
 * Fragment managing the behaviors, interactions and presentation of the  navigation drawer.
 */
private NavigationDrawerFragment mNavigationDrawerFragment;

/**
 * Used to store the last screen title. For use in {@link #restoreActionBar()}.
 */
private CharSequence mTitle;

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

    mNavigationDrawerFragment = (NavigationDrawerFragment)
            getSupportFragmentManager().findFragmentById (R.id.navigation_drawer);
    mTitle = getTitle();

    // Set up the drawer.
    mNavigationDrawerFragment.setUp(
            R.id.navigation_drawer,
            (DrawerLayout) findViewById(R.id.drawer_layout));
}

/*    @Override
public void onNavigationDrawerItemSelected(int position) {
    // update the main content by replacing fragments
    FragmentManager fragmentManager = getSupportFragmentManager();
    fragmentManager.beginTransaction()
            .replace(R.id.container, PlaceholderFragment.newInstance(position + 1))
            .commit();
}*/

@Override
public void onNavigationDrawerItemSelected(int position) {
    android.support.v4.app.FragmentManager fragmentManager = getSupportFragmentManager();
    android.support.v4.app.FragmentTransaction transaction = fragmentManager.beginTransaction();

    switch (position) {
        case 1:
    BlogFragment blogFragment = new BlogFragment();
    transaction.replace(R.id.action_bar, blogFragment);
    }

}

public void onSectionAttached(int number) {
    switch (number) {
        case 1:
            mTitle = getString(R.string.title_section1);
            break;
        case 2:
            mTitle = getString(R.string.title_section2);
            break;
        case 3:
            mTitle = getString(R.string.title_section3);
            break;
    }
}

public void restoreActionBar() {
    ActionBar actionBar = getSupportActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
    actionBar.setDisplayShowTitleEnabled(true);
    actionBar.setTitle(mTitle);
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    if (!mNavigationDrawerFragment.isDrawerOpen()) {
        // Only show items in the action bar relevant to this screen
        // if the drawer is not showing. Otherwise, let the drawer
        // decide what to show in the action bar.
        getMenuInflater().inflate(R.menu.main, menu);
        restoreActionBar();
        return true;
    }
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";

    /**
     * Returns a new instance of this fragment for the given section
     * number.
     */
    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = null;
        rootView = inflater.inflate(R.layout.fragment_home, container, false);
        switch(getArguments().getInt(ARG_SECTION_NUMBER)) {
            case 1:
                rootView = inflater.inflate(R.layout.fragment_home, container, false);
                break;
            case 2:
                rootView = inflater.inflate(R.layout.fragment_blog, container, false);
                break;
            case 3:
                rootView = inflater.inflate(R.layout.fragment_test, container, false);
                break;
            case 4:
                //rootView = inflater.inflate(R.layout.fragment_info, container, false);
                break;
            default:
                Log.e("TAG", "Unrecognized section: " + getArguments().getInt(ARG_SECTION_NUMBER));

        }
        return rootView;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        ((MainActivity) activity).onSectionAttached(
                getArguments().getInt(ARG_SECTION_NUMBER));
    }
}

}

这是博客片段，它试图打开 webview:

import android.app.Activity;
import android.app.Fragment;
import android.net.Uri;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;


 /**
* A simple {@link Fragment} subclass.
* Activities that contain this fragment must implement the
* {@link BlogFragment.OnFragmentInteractionListener} interface
* to handle interaction events.
* Use the {@link BlogFragment#newInstance} factory method to
* create an instance of this fragment.
*/
public class BlogFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";

// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;

private OnFragmentInteractionListener mListener;

 /**
 * Use this factory method to create a new instance of
 * this fragment using the provided parameters.
 *
 * @param param1 Parameter 1.
 * @param param2 Parameter 2.
 * @return A new instance of fragment blog.
 */
// TODO: Rename and change types and number of parameters
public static BlogFragment newInstance(String param1, String param2) {
    BlogFragment fragment = new BlogFragment();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    args.putString(ARG_PARAM2, param2);
    fragment.setArguments(args);
    return fragment;
}

public BlogFragment() {
    // Required empty public constructor
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (getArguments() != null) {
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
    }
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    WebView wv;

    View view=inflater.inflate(R.layout.fragment_blog, null);

    wv = (WebView) view.findViewById(R.id.webview);
    WebSettings settings = wv.getSettings();
    wv.setWebChromeClient(new WebChromeClient() {
    });
    final String mimeType = "text/html";
    final String encoding = "UTF-8";
    String html = getHTML();
    settings.setJavaScriptEnabled(true);
    wv.loadDataWithBaseURL("", html, mimeType, encoding, "");

    return view;

}

// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
    if (mListener != null) {
        mListener.onFragmentInteraction(uri);
    }
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    try {
        mListener = (OnFragmentInteractionListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
}

public String getHTML() {
    String html = "<iframe width=\"100%\" height=\"100%\" src=\"http://www.bbc.co.uk\" frameborder=\"0\" allowfullscreen></iframe>";
    return html;
}


/**
 * This interface must be implemented by activities that contain this
 * fragment to allow an interaction in this fragment to be communicated
 * to the activity and potentially other fragments contained in that
 * activity.
 * <p/>
 * See the Android Training lesson <a href=
 * "http://developer.android.com/training/basics/fragments/communicating.html"
 * >Communicating with Other Fragments</a> for more information.
 */
public interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    public void onFragmentInteraction(Uri uri);
}

}

提前致谢。

Answer 1

要查明错误，您应该在 switch 语句中添加一个默认块：

    switch(getArguments().getInt(ARG_SECTION_NUMBER)) {
        case 1:
            rootView = inflater.inflate(R.layout.fragment_home, container, false);
            break;
        case 2:
            rootView = inflater.inflate(R.layout.fragment_blog, container, false);
            break;
        case 3:
            rootView = inflater.inflate(R.layout.fragment_test, container, false);
            break;
        case 4:
            //rootView = inflater.inflate(R.layout.fragment_info, container, false);
            break;
        default:
            Log.e("TAG", "Unrecognized section: " + getArguments().getInt(ARG_SECTION_NUMBER));
    }

在我看来，调用 onCreateView 时未设置参数。如果未设置，则 getInt() returns 0，这不属于您的 switch 语句中的任何情况。

编辑：

经过仔细检查，我相信您应该可以使用更简单的抽屉项目选择侦听器：

@Override
public void onNavigationDrawerItemSelected(int position) {
    FragmentManager fragmentManager = getSupportFragmentManager();
    FragmentTransaction transation = fragmentManager.beginTransaction();
    switch (position) {
        case 1:
            HomeFragment homeFragment = new HomeFragment();
            homeFragment.setArguments(someArgs);
            transation.replace(R.id.container, homeFragment);
            break;
        case 2:
            BlogFragment blogFragment = new BlogFragment();
            blogFragment.setArguments(someArgs);
            transation.replace(R.id.container, blogFragment);
            break;
        case 3:
            TestFragment testFragment = new TestFragment();
            testFragment.setArguments(someArgs);
            transation.replace(R.id.container, testFragment);
            break;
        case 4:
            //rootView = inflater.inflate(R.layout.fragment_info, container, false);
            break;
        default:
            return;
    }
    transation.commit();
}

当片段显示在屏幕上时，片段代码不是运行

Fragment code not being run when fragment is displayed on screen

android

android-fragments

android-actionbaractivity

当片段显示在屏幕上时，片段代码不是 运行

Fragment code not being run when fragment is displayed on screen

android

android-fragments

android-actionbaractivity

当片段显示在屏幕上时，片段代码不是运行