Question

我正在创建一个应用程序。我有一个登录页面。登录后，我显示从firebase中检索到的用户列表，点击任何用户，显示聊天屏幕。我使用Fragments完成了这个。我有UsersListFragment.java和ChatFragment.java，活动为HomeActivity.java。

我的应用程序适用于手机。我现在正试图为平板电脑制作它。对于手机，我在不同的屏幕上显示用户列表和聊天。但是对于平板电脑，我希望它们都在同一个屏幕上。当我点击某个用户时，该用户的相应聊天应显示在另一个片段中。

我已经提到了这一切。但是我仍然无法得到如何继续。

1）https://developer.android.com/training/basics/fragments/fragment-ui.html#AddAtRuntime

2）https://developer.android.com/training/basics/fragments/communicating.html#Deliver

3）https://developer.android.com/guide/components/fragments.html#CommunicatingWithActivity

4）http://www.vogella.com/tutorials/AndroidFragments/article.html

参考代码。

actvity_home.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal"
android:background="#FFFFFF"
tools:context=".Activity.HomeActivity">

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:id="@+id/framecontainerMain"
    android:layout_weight="1"
    android:orientation="horizontal"
    >
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:id="@+id/framecontainer"
    android:layout_gravity="left"
    android:layout_weight="0.5"
    android:orientation="horizontal"
    >

</FrameLayout>

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:id="@+id/framecontainerTab"
    android:layout_weight="0.5"
    android:layout_gravity="right"
    android:orientation="horizontal"
    >

</FrameLayout>
</LinearLayout>


</LinearLayout>

HomeActivity.java

DisplayMetrics displaymetrics = new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
    int height = displaymetrics.heightPixels;
    int width = displaymetrics.widthPixels;
    Log.d(TAG,String.valueOf(height));
    if (width > 1023 || height > 1184){
        //code for big screen (like tablet)

        FrameLayout layout1 = (FrameLayout) findViewById(R.id.framecontainer);
        layout1.setVisibility(View.VISIBLE);

        FrameLayout layout2 = (FrameLayout) findViewById(R.id.framecontainerTab);
        layout2.setVisibility(View.VISIBLE);

        mItemsFragment = new UsersListFragment();
        mItemsFragment.initlizeval(this);

        android.support.v4.app.FragmentTransaction fts = getSupportFragmentManager().beginTransaction();
        fts.add(R.id.framecontainer, mItemsFragment).commit();

        //Instantiate some stuff here like view components
        Fragment fragmentOne = new ChatFragment();
        android.support.v4.app.FragmentTransaction ft = getSupportFragmentManager().beginTransaction();

        ft.add(R.id.framecontainerTab, fragmentOne).commit();


    }else{
        FrameLayout layout1 = (FrameLayout) findViewById(R.id.framecontainer);
        layout1.setVisibility(View.GONE);
        FrameLayout layout2 = (FrameLayout) findViewById(R.id.framecontainerTab);
        layout2.setVisibility(View.GONE);
        layout2.removeAllViews();

        mItemsFragment = new UsersListFragment();
        mItemsFragment.initlizeval(this);
        setFragment(mItemsFragment);

        //code for small screen (like smartphone)
    }


}

public void setFragment(Fragment frag)
{
    android.support.v4.app.FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
    ft.add(R.id.framecontainerMain, frag).commit();

}
@Override
public void onFragmentInteraction(String uri) {
    FrameLayout layout1 = (FrameLayout) findViewById(R.id.framecontainer);
    layout1.setVisibility(View.GONE);
    FrameLayout layout2 = (FrameLayout) findViewById(R.id.framecontainerTab);
    layout2.setVisibility(View.GONE);
}

@Override
public void onBackPressed() {
    super.onBackPressed();

    DisplayMetrics displaymetrics = new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
    int height = displaymetrics.heightPixels;
    int width = displaymetrics.widthPixels;
    if (width > 1023 || height > 1184) {
        Fragment fragmentOne = new ChatFragment();
        FrameLayout layout1 = (FrameLayout) findViewById(R.id.framecontainer);
        layout1.setVisibility(View.VISIBLE);
        FrameLayout layout2 = (FrameLayout) findViewById(R.id.framecontainerTab);
        layout2.setVisibility(View.VISIBLE);

    }

}

UsersListFragment.java

public void onButtonPressed(Uri uri) {
    if (mListener != null) {
        String val = "'";
        mListener.onFragmentInteraction(val);

    }
}

 public void initlizeval(Context context) {

    mListener = (OnFragmentInteractionListener) context;
}
@Override
public void onAttach(Context context) {
    super.onAttach(context);
    if (context instanceof OnFragmentInteractionListener) {
        mListener = (OnFragmentInteractionListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

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

public interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    void onFragmentInteraction(String val);
}

ChatFragment.java

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
  chatMessages = new ArrayList<>();
    view = inflater.inflate(R.layout.fragment_chat, container, false);
    listView = (ListView) view.findViewById(R.id.list_msg);

    adapter = new MessageAdapter(getActivity(), R.layout.item_chat_left, chatMessages);

    listView.setAdapter(adapter);
    setHasOptionsMenu(true);

    actionBar = ((AppCompatActivity) getActivity()).getSupportActionBar();
    if (actionBar != null) {
        actionBar.setDisplayUseLogoEnabled(false);
        ColorDrawable colorDrawable = new ColorDrawable(Color.parseColor("#72B94F"));
        actionBar.setBackgroundDrawable(colorDrawable);
        actionBar.setHomeAsUpIndicator(R.drawable.ic_backarrow);
        actionBar.setDisplayHomeAsUpEnabled(true);
        actionBar.setDisplayShowTitleEnabled(true);
        actionBar.setHomeButtonEnabled(true);
    }

    String[] strings = {Global.getInstance().someData, Global.getInstance().ownerId};
    Arrays.sort(strings);
    Arrays.sort(strings);
    String first = strings[0];
    String second = strings[1];
    chatKey = first + "_" + second;

    final FirebaseUtil utils = new FirebaseUtil(getContext());

    String timeaTab = Global.getInstance().time;
    chatMessages.clear();
    utils.startListeningMsgs(chatKey, timeaTab, new CallBack() {
        @Override
        public void onCallback(Map<String, Object> response, String Success) {
            Map<String, Object> sentByMe = (Map<String, Object>) response.get("value");


            Double chat_time = (Double) response.get("last_sent");
            // String timeString = String.valueOf(chat_time);

            String sentBy = (String) sentByMe.get("sent_by");
            String ownerId = Global.getInstance().ownerId;
            synchronized (this) {
                ChatMessage chat;
                if (sentBy.equals(ownerId)) {

                    String msg = (String) sentByMe.get("msg");
                    chat = new ChatMessage();
                    chat.setContent(msg);
                    String mine = "false";
                    chat.setIsMine(mine);
                    chat.setTime(chat_time);

                } else {
                    String msg = (String) sentByMe.get("msg");
                    chat = new ChatMessage();
                    chat.setContent(msg);
                    String mine = "true";
                    chat.setIsMine(mine);
                    chat.setTime(chat_time);

                }
                chatMessages.add(chat);
            }
            adapter.notifyDataSetChanged();
        }
    });

    mEmailSignInButton = (Button) view.findViewById(R.id.btn_chat_send);

    editText = (EditText) view.findViewById(R.id.msg_type);

    //event for button SEND
    mEmailSignInButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {


            Toast.makeText(getActivity(), String.valueOf( Global.getInstance().unreadMessageUsers.size()) , Toast.LENGTH_SHORT).show();
            if (editText.getText().toString().trim().equals("")) {
                Toast.makeText(getActivity(), "Type some message...", Toast.LENGTH_SHORT).show();
            } else {
                Map<String, Object> val = new HashMap<String, Object>();
                val.put("msg", editText.getText().toString());
                val.put("sent_by", Global.getInstance().ownerId);
                val.put("sent_to", Global.getInstance().someData);
                val.put("type", "chat");
                FirebaseUtil utilMsg = new FirebaseUtil(getContext());
                utilMsg.setNewMessageNotification(Global.getInstance().ownerId, Global.getInstance().someData, "chat");
                utilMsg.sendMessageRequestChatKeyValue(chatKey, val);
                editText.setText("");
            }
        }
    });
    return view;
}
 }

对于平板电脑，登录应用程序崩溃后。我猜我无法设置视图。

日志

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.rider.project/com.rider.project.Activity.HomeActivity}: java.lang.NullPointerException: rhs == null
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                  at android.app.ActivityThread.-wrap11(ActivityThread.java)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:148)
                  at android.app.ActivityThread.main(ActivityThread.java:5417)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
               Caused by: java.lang.NullPointerException: rhs == null
                  at java.lang.String.compareTo(Native Method)
                  at java.lang.String.compareTo(String.java:335)
                  at java.util.ComparableTimSort.countRunAndMakeAscending(ComparableTimSort.java:286)
                  at java.util.ComparableTimSort.sort(ComparableTimSort.java:153)
                  at java.util.ComparableTimSort.sort(ComparableTimSort.java:142)
                  at java.util.Arrays.sort(Arrays.java:1957)
                  at com.rider.project.Fragments.ChatFragment.onCreateView(ChatFragment.java:189)
                  at android.support.v4.app.Fragment.performCreateView(Fragment.java:2080)
                  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1108)
                  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1290)
                  at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
                  at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1677)
                  at android.support.v4.app.FragmentController.execPendingActions(FragmentController.java:388)
                  at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:604)
                  at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:178)
                  at com.rider.project.Activity.HomeActivity.onStart(HomeActivity.java:172)
                  at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1237)
                  at android.app.Activity.performStart(Activity.java:6253)
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                  at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                  at android.os.Handler.dispatchMessage(Handler.java:102) 
                  at android.os.Looper.loop(Looper.java:148) 
                  at android.app.ActivityThread.main(ActivityThread.java:5417) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

请有人告诉我，我能做些什么。新的android。提前谢谢。

Answer 1

试试这个：

2个不同的布局文件夹：layout，其中包含智能手机的actvity_home.xml，片段布局等; layout-large，包含用于平板电脑的actvity_home.xml。

在HomeActivity.java中，用以下内容替换您发布的代码：

    // Part of onCreate()
    setContentView(R.layout.activity_home);
    FrameLayout layout1 = (FrameLayout) findViewById(R.id.framecontainer);
    FrameLayout layout2 = (FrameLayout) findViewById(R.id.framecontainerTab);

    android.support.v4.app.FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
    // Initialize UserListFragment
    // and setTag, UserList. [Both smartphone and tablet]
    mItemsFragment = new UsersListFragment();
    mItemsFragment.initlizeval(this);
    ft.add(R.id.framecontainer, frag, "UserList").commit();

    if (layout2 != null){
        // Tablet, initiallly no user selected and layout is GONE.
        layout2.setVisibility(View.GONE);
    }
}

@Override
public void onFragmentInteraction(String uri) {
    FrameLayout layout2 = (FrameLayout) findViewById(R.id.framecontainerTab);
    android.support.v4.app.FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
    ChatFragment fragmentOne = new ChatFragment();
    if(layout2 == null){ // Smartphone, replace fragment.
        ft.replace(R.id.framecontainer, fragmentOne, "Chat");
        ft.addToBackStack(null);
        ft.commit();
    }else{ // Tablet, add fragment and show on UI.
        ft.add(R.id.framecontainerTab, fragmentOne, "Chat").commit();
        layout2.setVisibility(View.VISIBLE);
    }
}

@Override
public void onBackPressed() {
    super.onBackPressed();
    FrameLayout layout2 = (FrameLayout) findViewById(R.id.framecontainerTab);
    if (layout2 != null) { // Tablet
        if(layout2.isShown()){
            android.support.v4.app.FragmentManager fm = getSupportFragmentManager();
            ChatFragment fragmentOne = (ChatFragment) fm.findFragmentByTag("Chat");
            fm.beginTransaction().remove(fragmentOne).commit();
            layout2.setVisibility(View.GONE);
        }
    }
}

希望有所帮助！

Answer 2

您是否已将HomeActivity添加到清单文件中

两个片段在相同的活动和相同的屏幕

2 个答案: