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使用Tabbed活動中的片段的網格視圖的適配器為null

[英]Adapter is null for grid view using fragment in Tabbed activity

 原文  2018-02-18 06:45:17  6   1    java/ android/ xml/ android-fragments/ android-gridview

問題描述

我在android 3.0.1中使用TabbedActivity我想在名稱為fragment_simple.java的片段Java類的選項卡1中顯示網格視圖，所有三個選項卡都可以正常工作，但是當我嘗試顯示選項卡1的網格視圖時，我的應用程序崩潰了我設置了一些xml文件和自定義的Grid Adapter。這里是以下文件

activity_main.xml中 

<?xml version="1.0" encoding="utf-8"?>
 <android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="com.mobdev.birthdaycakesquotes.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/appbar_padding_top"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:layout_weight="1"
            android:background="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|enterAlways"
            app:popupTheme="@style/AppTheme.PopupOverlay"
            app:title="@string/app_name">

        </android.support.v7.widget.Toolbar>

        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

            <android.support.design.widget.TabItem
                android:id="@+id/tabItem"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/tab_text_1" />

            <android.support.design.widget.TabItem
                android:id="@+id/tabItem2"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/tab_text_2" />

            <android.support.design.widget.TabItem
                android:id="@+id/tabItem3"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/tab_text_3" />

        </android.support.design.widget.TabLayout>
    </android.support.design.widget.AppBarLayout>

    <android.support.v4.view.ViewPager
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="501dp"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />


</android.support.design.widget.CoordinatorLayout>

fragment_simple_cake.xml 

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout 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="com.mobdev.birthdaycakesquotes.Simple_cakes">
        <GridView android:id="@+id/MyGrid"
            android:stretchMode="columnWidth"
            android:horizontalSpacing="10dp"
            android:verticalSpacing="10dp"
            android:numColumns="auto_fit"
            android:columnWidth="150dp"
            android:layout_height="fill_parent"
            android:layout_width="fill_parent"
            xmlns:android="http://schemas.android.com/apk/res/android"/>


 </LinearLayout>

custom_layout.xml 

<?xml version="1.0" encoding="utf-8"?>
        <LinearLayout
            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"
            android:orientation="vertical">
            <FrameLayout android:layout_height="200dp"
                android:layout_width="fill_parent" android:layout_margin="1dp">
                <!--150-->
                <FrameLayout android:layout_height="fill_parent"
                    android:layout_width="fill_parent">
                    <ImageView
                        android:id="@+id/imageView"
                        android:layout_width="fill_parent"
                        android:layout_height="match_parent"
                        android:scaleType="fitCenter"
                        android:layout_gravity="center"
                        android:contentDescription="@string/cake"
                        android:src="@mipmap/birthday_cake_01" />

                </FrameLayout>
            </FrameLayout>

        </LinearLayout>

GridAdapter.java 

package com.mobdev.birthdaycakesquotes;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;

import static android.content.Context.LAYOUT_INFLATER_SERVICE;


public class GridAdapter extends ArrayAdapter {
private Integer[] Image;
private int resource;
private LayoutInflater inflater;

public GridAdapter(Context context, int resource, Integer[] image) {
    super(context, resource, image);
    Image = image;
    this.resource = resource;
    inflater = (LayoutInflater)context.getSystemService(LAYOUT_INFLATER_SERVICE);
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    ViewHolder Holder = null;

    if (convertView == null) {
        Holder = new ViewHolder();
        convertView = inflater.inflate(resource, null);
        Holder.IMAGE = (ImageView) convertView.findViewById(R.id.imageView);
        convertView.setTag(Holder);
    } else {
        Holder = (ViewHolder)convertView.getTag();
    }
    Holder.IMAGE.setImageResource(Image[position]);
    Holder.IMAGE.setScaleType(ImageView.ScaleType.CENTER_CROP);

    return convertView;
}

class ViewHolder {
    private ImageView IMAGE;
}
}

Simple_cakes.java 

package com.mobdev.birthdaycakesquotes;

import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import static android.content.Context.LAYOUT_INFLATER_SERVICE;


public class Simple_cakes extends Fragment {
GridView gridView;
GridAdapter adapter;
TextView textView;
Integer[] image = new Integer[]{R.mipmap.birthday_cake_01, 
R.mipmap.birthday_cake_02, R.mipmap.birthday_cake_03,
        R.mipmap.birthday_cake_04, R.mipmap.birthday_cake_05,R.mipmap.birthday_cake_04};




@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View view =inflater.inflate(R.layout.fragment_supreme_cakes,container,false);
    //view.setBackgroundColor(getResources().getColor(android.R.color.holo_green_light));

    gridView=(GridView) view.findViewById(R.id.MyGrid);
    adapter = new GridAdapter(getActivity(),R.layout.custom_layout,image);
   /* gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
            Toast.makeText(getActivity(),"Clicked",Toast.LENGTH_LONG).show();
        }
    });*/




    gridView.setAdapter(adapter);

    return view;
}


}

MainActivity.java 

        package com.mobdev.birthdaycakesquotes;

        import android.app.TaskStackBuilder;
        import android.support.design.widget.TabLayout;
        import android.support.design.widget.FloatingActionButton;
        import android.support.design.widget.Snackbar;
        import android.support.v4.app.FragmentTransaction;
        import android.support.v7.app.ActionBar;
        import android.support.v7.app.AppCompatActivity;
        import android.support.v7.widget.Toolbar;

        import android.support.v4.app.Fragment;
        import android.support.v4.app.FragmentManager;
        import android.support.v4.app.FragmentPagerAdapter;
        import android.support.v4.view.ViewPager;
        import android.os.Bundle;
        import android.view.LayoutInflater;
        import android.view.Menu;
        import android.view.MenuItem;
        import android.view.View;
        import android.view.ViewGroup;

        import android.widget.GridView;
        import android.widget.TextView;

 public class MainActivity extends AppCompatActivity {

/**
 * The {@link android.support.v4.view.PagerAdapter} that will provide
 * fragments for each of the sections. We use a
 * {@link FragmentPagerAdapter} derivative, which will keep every
 * loaded fragment in memory. If this becomes too memory intensive, it
 * may be best to switch to a
 * {@link android.support.v4.app.FragmentStatePagerAdapter}.
 */
private SectionsPagerAdapter mSectionsPagerAdapter;

/**
 * The {@link ViewPager} that will host the section contents.
 */
private ViewPager mViewPager;

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


    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    // Create the adapter that will return a fragment for each of the three
    // primary sections of the activity.
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);



    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);

    mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));


}


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

@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);
}




public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
        //return PlaceholderFragment.newInstance(position + 1);

        switch (position){
            case 0:

                Simple_cakes simple_cakes=new Simple_cakes();
                return simple_cakes;

            case 1:
                Special_cakes special_cakes=new Special_cakes();
                return special_cakes;

            case 2:
                Supreme_cakes supreme_cakes=new Supreme_cakes();
                return supreme_cakes;
            default:
                return null;
        }



    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {

        switch (position){
            case 0:
               return "Simple";

            case 1:
                return "Special";

            case 2:
               return "Supreme";
            default:
                return null;
        }
    }
}
}

空指針異常錯誤 

  E/AndroidRuntime: FATAL EXCEPTION: main
  Process: com.mobdev.birthdaycakesquotes, PID: 25821
  java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.GridView.setAdapter(android.widget.ListAdapter)' on a null object reference
                  at com.mobdev.birthdaycakesquotes.Simple_cakes.onCreateView(Simple_cakes.java:49)
                  at android.support.v4.app.Fragment.performCreateView(Fragment.java:2354)
                  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1419)
                  at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1740)
                  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1809)
                  at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:799)
                  at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580)
                  at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)
                  at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
                  at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:2199)
                  at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:651)
                  at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:145)
                  at android.support.v4.view.ViewPager.populate(ViewPager.java:1236)
                  at android.support.v4.view.ViewPager.populate(ViewPager.java:1084)
                  at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1614)
                  at android.view.View.measure(View.java:19147)
                  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6113)
                  at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:714)
                  at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:786)
                  at android.view.View.measure(View.java:19147)
                  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6113)
                  at android.widget.FrameLayout.onMeasure(FrameLayout.java:223)
                  at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139)
                  at android.view.View.measure(View.java:19147)
                  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6113)
                  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1723)
                  at android.widget.LinearLayout.measureVertical(LinearLayout.java:788)
                  at android.widget.LinearLayout.onMeasure(LinearLayout.java:648)
                  at android.view.View.measure(View.java:19147)
                  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6113)
                  at android.widget.FrameLayout.onMeasure(FrameLayout.java:223)
                  at android.view.View.measure(View.java:19147)
                  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6113)
                  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1723)
                  at android.widget.LinearLayout.measureVertical(LinearLayout.java:788)
                  at android.widget.LinearLayout.onMeasure(LinearLayout.java:648)
                  at android.view.View.measure(View.java:19147)
                  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6113)
                  at android.widget.FrameLayout.onMeasure(FrameLayout.java:223)
                  at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2693)
                  at android.view.View.measure(View.java:19147)
                  at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2481)
                  at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1440)
                  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1694)
                  at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1321)
                  at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6708)
                  at android.view.Choreographer$CallbackRecord.run(Choreographer.java:894)
                  at android.view.Choreographer.doCallbacks(Choreographer.java:696)
                  at android.view.Choreographer.doFrame(Choreographer.java:631)
                  at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:880)
                  at android.os.Handler.handleCallback(Handler.java:815)
                  at android.os.Handler.dispatchMessage(Handler.java:104)
                  at android.os.Looper.loop(Looper.java:2

           I/System: FinalizerDaemon: finalize objects = 1
           I/Process: Sending signal. PID: 25821 SIG: 9
           Application terminated.

1 個解決方案

解決方案1
 1 已采納  2018-02-18 06:49:41

看來您誇大了錯誤的布局。 

View view =inflater.inflate(R.layout.fragment_supreme_cakes,container,false);

嘗試將其更改為fragment_simple_cake

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