Question

此适配器类始终正常工作;但是，当我添加启动画面并启动启动画面作为启动器活动时，此适配器类在getView函数上提供nullpointerexception。

MYADAPTER.JAVA

package com.zoopoo.a_man.zoopoo;
import android.content.Context;    
import android.view.LayoutInflater;    
import android.view.View;    
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

public class MyAdapter extends BaseAdapter {
    Context context;
    String[] listItems;
    int[] images = {R.drawable.home, R.drawable.notification, R.drawable.gallery, R.drawable.about};

    public MyAdapter(Context context) {
        this.context = context;
        listItems = context.getResources().getStringArray(R.array.list_item);
    }

    @Override
    public int getCount() {
        return listItems.length;
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        View row = null;
        if (view == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE);
            row = inflater.inflate(R.layout.custom_list, viewGroup, false);
        } else {
            row = viewGroup;
        }
        ImageView iv = (ImageView) row.findViewById(R.id.iv);
        TextView tv = (TextView) row.findViewById(R.id.tv);
        tv.setText(listItems[i]);  // error comes here..!!
        iv.setImageResource(images[i]);
        return row;
    }

    @Override
    public long getItemId(int i) {
        return i;
    }

    @Override
    public Object getItem(int i) {
        return listItems[i];
    }
}

SPLASH.JAVA

package com.zoopoo.a_man.zoopoo;
import android.content.Intent;
import android.graphics.Typeface;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.WindowManager;
import android.widget.TextView;

public class Splash extends ActionBarActivity {
    TextView tvsplash;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.splash);
        tvsplash = (TextView)findViewById(R.id.tvsplash);
        Typeface typeface = Typeface.createFromAsset(getAssets(),"fonts/DroidSerif-BoldItalic.ttf");
        tvsplash.setTypeface(typeface);

        Thread wait = new Thread(){
            public void run(){
                try{
                   sleep(3000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }finally {
                    Intent register = new Intent("com.zoopoo.a_man.zoopoo.MAINACTIVITY");
                    startActivity(register);
                }
            }
        };
        wait.start();
    }
}

的AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.zoopoo.a_man.zoopoo">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">
        <activity
            android:name=".Splash"
            android:label="@string/app_name"
            android:theme="@style/FullScreen">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity
            android:name=".GcmRegister"
            android:label="zooPoo"
            android:theme="@android:style/Theme.NoTitleBar">
            <intent-filter>
                <action android:name="com.zoopoo.a_man.zoopoo.GCMREGISTER" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>

        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme">`enter code here`

<!-- Whenever i set this as launcher activity app runs fine, but when i launch this from splash activity, app crashes at MyAdapter's getView. -->

            <intent-filter>
                <action android:name="com.zoopoo.a_man.zoopoo.MAINACTIVITY" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
    </application>

</manifest>

LOGCAT OUTPUT

07-22 09:20:19.613    5043-5043/com.zoopoo.a_man.zoopoo E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.NullPointerException
            at com.zoopoo.a_man.zoopoo.MyAdapter.getView(MyAdapter.java:40)
            at android.widget.AbsListView.obtainView(AbsListView.java:2054)
            at android.widget.ListView.makeAndAddView(ListView.java:2004)
            at android.widget.ListView.fillSpecific(ListView.java:1550)
            at android.widget.ListView.layoutChildren(ListView.java:1835)
            at android.widget.AbsListView.onLayout(AbsListView.java:1905)
            at android.view.View.layout(View.java:11359)
            at android.view.ViewGroup.layout(ViewGroup.java:4531)
            at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:914)
            at android.view.View.layout(View.java:11359)
            at android.view.ViewGroup.layout(ViewGroup.java:4531)
            at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
            at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
            at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
            at android.view.View.layout(View.java:11359)
            at android.view.ViewGroup.layout(ViewGroup.java:4531)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
            at android.view.View.layout(View.java:11359)
            at android.view.ViewGroup.layout(ViewGroup.java:4531)
            at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
            at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
            at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
            at android.view.View.layout(View.java:11359)
            at android.view.ViewGroup.layout(ViewGroup.java:4531)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
            at android.view.View.layout(View.java:11359)
            at android.view.ViewGroup.layout(ViewGroup.java:4531)
            at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
            at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
            at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
            at android.view.View.layout(View.java:11359)
            at android.view.ViewGroup.layout(ViewGroup.java:4531)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
            at android.view.View.layout(View.java:11359)
            at android.view.ViewGroup.layout(ViewGroup.java:4531)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1665)
            at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2695)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:156)
            at android.app.ActivityThread.main(ActivityThread.java:4987)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

适配器的getView（）存在问题。您正在row = viewGroup;但它应该是row = view;。如下，

    if (view == null) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE);
        row = inflater.inflate(R.layout.custom_list, viewGroup, false);
    } else {
        row = view; // CHECK THIS LINE!!!!!!
    }

view是转到getView进行回收的convertView实例，如果它不为null则可以重复使用，这就是你的代码的意图！

当您执行row = viewGroup;，然后尝试row.findViewById(R.id.tv)时，它会返回null，当您尝试setText()时，您会获得NPE！

希望这会有所帮助。：）

添加启动画面后，在我的自定义适配器的getView上出现NullPointerException

1 个答案: