从主要活动以外的活动访问片段

Question

我有一个尝试修改的现有应用程序，确实可以使用一些帮助。

这是一个聊天应用程序。 该应用程序的原始流程如下：启动->启动画面活动-> MainActivity（扩展了Actionbar Sherlock）

一旦进入主活动，默认片段就是ChatRoomFragment。 从那里您可以选择不同的选项卡并与应用程序进行交互。

我要更改的流程如下：启动->启动画面活动->服务/签名条款-> MainMenu-> MainActivity

我创建了mainmenu布局以包含4个按钮。 加入，搜索，个人资料，设置

这是问题所在。 我的加入按钮可以正常工作，onClick只需触发启动MainActivity的意图，然后聊天室就会加载。 在此屏幕上，您可以访问应用程序中的不同选项卡和片段。

但是，我现在想将“搜索”按钮设置为打开对话框。 具有editText字段和搜索按钮。 单击搜索后，应将搜索字符串传递给PlacesSearchFragment并填充结果。

我从通常完成此搜索的应用程序中复制了代码（在ChatRoomsFragment内部，但是在我的mainMenu活动中无法使用）。

如何从菜单活动中启动新片段？

下面的代码：

  menuActivity.java
package com.peekatucorp.peekatu;

//import android.support.v7.app.ActionBarActivity;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.v4.app.FragmentTransaction;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.actionbarsherlock.app.ActionBar;
import com.loopj.android.http.AsyncHttpClient;
import com.loopj.android.http.AsyncHttpResponseHandler;
import com.loopj.android.http.RequestParams;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;


public class menuActivity extends Activity implements ActionBar.TabListener {
    Button b1;
    Button b2;
    Button b3;
    EditText txtsearch;
    final private static int DIALOG_LOGIN = 1;
    final private static int DIALOG_FORGET = 2;
    final private static int DIALOG_SEARCH = 3;
    private android.app.FragmentTransaction ft;



@Override
public void onCreate(Bundle savedInstanceState) {

SharedPreferences preferences = this.getSharedPreferences("MyPreferences", MODE_PRIVATE);

SharedPreferences.Editor editor = preferences.edit();


super.onCreate(savedInstanceState);
setContentView(R.layout.mainmenu);

if(preferences.getString("Username", "").length()<=0 || preferences.getString("loggedin_user", "").length()<=0){
    showDialog(DIALOG_LOGIN);

}

b1= (Button) this.findViewById(R.id.joinbutton);

b1.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {

        Intent intent = new Intent(menuActivity.this, MainActivity.class);
        menuActivity.this.startActivity(intent);

        SharedPreferences preferences = getSharedPreferences("MyPreferences", MODE_PRIVATE);

        SharedPreferences.Editor editor = preferences.edit();
        editor.putString("loadMain", "1");
        editor.commit();
        }

});
b2= (Button) this.findViewById(R.id.searchbutton);

b2.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            showDialog(DIALOG_SEARCH);
        }

    }

);





}

@Override
protected Dialog onCreateDialog(int id) {

    AlertDialog dialogDetails = null;

    switch (id) {


    case DIALOG_LOGIN:
                if(true){
....some code}


         break;
            case DIALOG_FORGET:
                if(true){
...some code
}
                break;
            case DIALOG_SEARCH:
            if(true){
                LayoutInflater inflater = LayoutInflater.from(this);
                View dialogview = inflater.inflate(R.layout.menusearch_layout, null);

                AlertDialog.Builder dialogbuilder = new AlertDialog.Builder(this);

                dialogbuilder.setTitle("Where ya headed?");
                dialogbuilder.setView(dialogview);
                dialogDetails = dialogbuilder.create();
            }
    }

    return dialogDetails;
}
 @Override
    protected void onPrepareDialog(int id, Dialog dialog) {

        switch (id) {
        case DIALOG_LOGIN:
...some code
break;

case DIALOG_SEARCH:
                final AlertDialog alertDialog3 = (AlertDialog) dialog;
                final Button btnLocalsearch = (Button) alertDialog3
                        .findViewById(R.id.local_search);
                final Button btnSearch = (Button) alertDialog3
                        .findViewById(R.id.btn_search);
                final EditText txtsearch = (EditText) alertDialog3
                        .findViewById(R.id.txtsearch);

                btnSearch.setOnClickListener(new View.OnClickListener() {

                    @Override
                    public void onClick(final View v) {
                        //showDialog(DIALOG_FORGET);
                        //alertDialog3.dismiss();
                                // TODO Auto-generated method stub
                               menuActivity m = com.peekatucorp.peekatu.menuActivity.this;
                                final TabInfo tab = com.peekatucorp.peekatu.menuActivity.this.getCurrentTabInfo();
                                final PlacesSearchFragment fragment = new PlacesSearchFragment().setNAV(m).setSearch(txtsearch.getText().toString(),"1");
                                // fragment.setText(characters[position]);

                                // second, you push the fragment. It becomes visible and the up button is
                                // shown
                                m.pushFragment(tab, fragment);


                            }



        });
    }

mainmenu.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="65dp"
        android:layout_marginLeft="10dip"
        android:src="@drawable/registration_banner3"
        android:id="@+id/imageView" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Join Chat"
        android:id="@+id/joinbutton"
        android:layout_below="@+id/imageView"
        android:layout_alignLeft="@+id/imageView"
        android:layout_alignStart="@+id/imageView"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Search"
        android:id="@+id/searchbutton"
        android:layout_below="@+id/joinbutton"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="55dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Profile"
        android:id="@+id/prfbutton"
        android:layout_below="@+id/searchbutton"
        android:layout_marginTop="72dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_alignLeft="@+id/searchbutton"
        android:layout_alignStart="@+id/searchbutton" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Settings"
        android:id="@+id/settingsbutton"
        android:layout_below="@+id/prfbutton"
        android:layout_marginTop="51dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
    <LinearLayout android:id="@+id/footer"
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="@layout/footer_repeat"
        android:layout_alignParentBottom="true">



    </LinearLayout>
</RelativeLayout>

ChatRoomsFragment.java（工作片段）

public class ChatRoomsFragment extends SherlockFragment implements OnItemSelectedListener{
    String[] items;
    List<String> list;
    Spinner my_spin;
     RadioButton mainRoom;
     RadioButton customRoom;
     RadioButton GPSRoom;
     EditText privateRoom;
     EditText GPSsearch;
     TextView GPSaddress;
     String selected_public;
     Context contexxt;
     ImageLoader imageLoader;
     public AbstractTabStackNavigationActivity navact;
    @Override

      public View onCreateView(final LayoutInflater inflater, final ViewGroup container, final Bundle savedInstanceState) {
          setRetainInstance(true);

          final View v = inflater.inflate(R.layout.chatrooms_layout, container, false);
          contexxt = v.getContext();
         // setRetainInstance(true);
          SharedPreferences preferences = v.getContext().getSharedPreferences("MyPreferences", this.getActivity().MODE_PRIVATE);
          my_spin=(Spinner)v.findViewById(R.id.spinner1);
          my_spin.setOnItemSelectedListener(this);
          selected_public = preferences.getString("selected_room", "Adult Lobby");
          AsyncHttpClient  client = new AsyncHttpClient();
            RequestParams params = new RequestParams();

            GPSsearch = (EditText)v.findViewById(R.id.cr_gps_search);
            GPSaddress = (TextView)v.findViewById(R.id.cr_gps_address);
            GPSaddress.setText(preferences.getString("user_location", ""));
            Button search_go = (Button)v.findViewById(R.id.cr_go_search);
            Button address_go = (Button)v.findViewById(R.id.cr_go_address);
            Button changeroom = (Button)v.findViewById(R.id.cr_changeroom);
            //Button changeroom2 = (Button)v.findViewById(R.id.cr_changeRoom2);


    search_go.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                 MainActivity m = (MainActivity)getActivity();
                 final TabInfo tab = m.getCurrentTabInfo();
                    final PlacesSearchFragment fragment = new PlacesSearchFragment().setNAV(m).setSearch(GPSsearch.getText().toString(),"1");
                   // fragment.setText(characters[position]);

                    // second, you push the fragment. It becomes visible and the up button is
                    // shown
                    m.pushFragment(tab, fragment);  
            }
        });

有人可以向我解释如何获取它来加载片段。 谢谢。 让我知道是否遗漏了任何相关代码。 我收到一个空指针异常作为我的错误。

Answer 1

好吧，首先，这是我在评论中谈论的代码：

 btnSearch.setOnClickListener(new View.OnClickListener() {
     @Override
     public void onClick(final View v) {
         menuActivity m = dialog.getOwningActivity();
         final TabInfo tab = m.getCurrentTabInfo();
         final PlacesSearchFragment fragment = new PlacesSearchFragment().setNAV(m).setSearch(txtsearch.getText().toString(),"1");
         m.pushFragment(tab, fragment);
         ...

但是，既然我输入了该信息，就没有NPE像您所说的那样正在调用pushFragment了。 如果活动外部类引用确实是空指针，那么它应该早些崩溃，调用getCurrentTabInfo。 因此，我认为此代码更改无济于事。 请再看一下您所看到的堆栈，并告诉我NPE发生在哪条线上。