java - BaseAdapter 应用程序崩溃

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我的应用程序已构建，但崩溃了，我不知道为什么。基本上我在 MainActivity 中实现 BaseAdapter，稍后我会将它放在另一个类中

这是MainActivity.java

public class MainActivity extends Activity {

    ListView mListView;
    String[] mTitle={"item1","item2"};
    String[] mDetail={"info1","info2"};
    int[] mImage ={R.drawable.ic_launcher,R.drawable.ic_launcher};


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mListView=(ListView)findViewById(R.id.list);
        mListView.setAdapter(new dataListAdapter(mTitle, mDetail, mImage, this));
    }

    class dataListAdapter extends BaseAdapter {

        String[] Title, Detail;
        int[] imge;

        dataListAdapter() {
            Title = null;
            Detail = null;
            imge=null;
            context = null;
        }

        public dataListAdapter(String[] text, String[] text1,int[] text3, Context ctx) {
            Title = text;
            Detail = text1;
            imge = text3;
            context = ctx;
        }

        public final Context context;

        public dataListAdapter(Context mContext){
            this.context = mContext;
        }

        public int getCount() {
            // TODO Auto-generated method stub
            return Title.length;
        }

        public Object getItem(int arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        public long getItemId(int position) {
            // TODO Auto-generated method stub
            return position;
        }

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



            TextView titleView, detailView;
            ImageView imageView;

            if(convertView == null){
                convertView = LayoutInflater.from(context).inflate(R.layout.custom, parent,false);

                titleView = (TextView) convertView.findViewById(R.id.title);
                detailView = (TextView) convertView.findViewById(R.id.detail);
                imageView = (ImageView) convertView.findViewById(R.id.image);
                convertView.setTag(R.id.title, titleView);
                convertView.setTag(R.id.detail, detailView);
                convertView.setTag(R.id.image, imageView);
            }else{
                titleView = (TextView) convertView.getTag(R.id.title);
                detailView = (TextView) convertView.getTag(R.id.detail);
                imageView = (ImageView) convertView.getTag(R.id.image);
            }


            titleView.setText(Title[position]);
            detailView.setText(Detail[position]);
            imageView.setImageDrawable(context.getResources().getDrawable(imge[position]));

            return convertView;
        }
}

日志猫:

01-10 21:20:43.290  26874-26874/com.robigroza.justlisttest E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
        at com.robigroza.justlisttest.MainActivity$dataListAdapter.getView(MainActivity.java:91)
        at android.widget.AbsListView.obtainView(AbsListView.java:2465)
        at android.widget.ListView.measureHeightOfChildren(ListView.java:1250)
        at android.widget.ListView.onMeasure(ListView.java:1162)
        at android.view.View.measure(View.java:15371)
        at android.widget.RelativeLayout.measureChild(RelativeLayout.java:602)
        at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:415)
        at android.view.View.measure(View.java:15371)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4876)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.view.View.measure(View.java:15371)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4876)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1396)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
        at android.view.View.measure(View.java:15371)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4876)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2423)
        at android.view.View.measure(View.java:15371)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2011)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1250)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1425)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1143)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4674)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
        at android.view.Choreographer.doCallbacks(Choreographer.java:555)
        at android.view.Choreographer.doFrame(Choreographer.java:525)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
        at android.os.Handler.handleCallback(Handler.java:615)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4960)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
        at dalvik.system.NativeStart.main(Native Method)

这是custom.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:orientation="vertical"
          android:layout_width="match_parent"
          android:layout_height="match_parent">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

    <LinearLayout
        android:layout_width="255dp"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >

            <TextView
                android:id="@+id/title"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Video1"
                android:textAppearance="?android:attr/textAppearanceLarge"
                android:textColor="#339966"
                android:textStyle="bold" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >

            <TextView
                android:id="@+id/detail"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="video1"
                android:textColor="#606060" />
        </LinearLayout>
    </LinearLayout>

    <ImageView
        android:id="@+id/img"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher" />

</LinearLayout>

这是 main.xml

    <RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
            android:paddingRight="@dimen/activity_horizontal_margin"
            android:paddingTop="@dimen/activity_vertical_margin"
            android:paddingBottom="@dimen/activity_vertical_margin"
            tools:context=".MainActivity">

<ListView
    android:id="@+id/list"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true" >

</ListView>

Answer 1

您的 custom.xml 应包含 2 个 TextView(标题和详细信息)和一个 ImageView(图像)。

例如像这样的东西:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent">
    <TextView
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <TextView
        android:id="@+id/detail"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <ImageView
        android:id="@+id/image"
        android:layout_width="50dp"
        android:layout_height="50dp"/>
</LinearLayout>