Question

我正在使用gridview，我想使用适配器在gridview中显示图像和文本，但我无法理解为什么它会崩溃。 GridAdapter.java.and中存在错误我不知道为什么这段代码会给我一个带有gridview的NullPointerException

以下是我的代码：

GridAdapter.java

    public class GridAdapter extends BaseAdapter {
    private Context mContext;
    private final String[] web;
    private final int[] Imageid;

    public GridAdapter(Context c,String[] web,int[] Imageid ) {
        mContext = c;
        this.Imageid = Imageid;
        this.web = web;
    }

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

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

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        View grid;
        LayoutInflater inflater = (LayoutInflater) mContext
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        if (convertView == null) {

            grid = new View(mContext);
            grid = inflater.inflate(R.layout.grid_item, null);
            TextView textView = (TextView) grid.findViewById(R.id.product_name);
            ImageView imageView = (ImageView)grid.findViewById(R.id.pic);
            textView.setText(web[position]);
            imageView.setImageResource(Imageid[position]);
        } else {
            grid = (View) convertView;
        }

        return grid;
    }
}

GridActivity.java

public class GridActivity extends Activity {
GridView simpleGrid;
String[] web = {"Google", "Github", "Instagram", "Facebook"} ;
int[] imageId = {R.drawable.product_imag,R.drawable.product_imag,R.drawable.product_imag,R.drawable.product_imag};
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_gridview);
    simpleGrid = (GridView) findViewById(R.id.gv);

    GridAdapter adapter = new GridAdapter(GridActivity.this, web, imageId);
    simpleGrid.setAdapter(adapter);
    simpleGrid.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {
            Toast.makeText(GridActivity.this, "You Clicked at " +web[+ position], Toast.LENGTH_SHORT).show();

        }
    });

}

}

编辑Griditem.xml

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="#e6e6e6"
    android:orientation="vertical"
    android:padding="1dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/white"
        android:orientation="vertical"
        android:padding="1.5dp">

        <ImageView
            android:id="@+id/pic"
            android:layout_width="150dp"
            android:layout_height="250dp"
            android:layout_gravity="top|center"
            android:padding="5dp"
            android:src="@drawable/product_imag"/>

        <view
            android:layout_width="match_parent"
            android:layout_height="1.5dp"
            android:background="#e6e6e6"/>

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|center_horizontal">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/product_name"
                android:layout_alignParentLeft="true"
                android:layout_alignParentStart="true"
                android:layout_alignParentTop="true"
                android:layout_marginTop="2dp"
                android:text="New text"/>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/product_price"
                android:layout_alignParentEnd="true"
                android:layout_alignParentRight="true"
                android:layout_alignParentTop="true"
                android:text="New Text"/>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/product_other"
                android:layout_alignParentLeft="true"
                android:layout_alignParentStart="true"
                android:layout_below="@+id/product_name"
                android:text="New Text" />
        </RelativeLayout>
    </LinearLayout>

</LinearLayout>

activity_gridview.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:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <!-- Vertical space between grid items -->
    <GridView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:columnWidth="100dp"
        android:numColumns="2"
        android:gravity="center"
        android:paddingBottom="5dp"
        android:paddingLeft="10dp"
        android:paddingRight="10dp"
        android:paddingTop="5dp"
        android:stretchMode="columnWidth"
        android:horizontalSpacing="10dp"
        android:id="@+id/gv"
        android:verticalSpacing="50dp"></GridView>

</LinearLayout>

这是我的LogCat

FATAL EXCEPTION: main
Process: android.mendonca.averdapp, PID: 6640

android.view.InflateException: Binary XML file line #24: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:761)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:858)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:861)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:518)
at android.view.LayoutInflater.inflate(LayoutInflater.java:426)
at android.view.LayoutInflater.inflate(LayoutInflater.java:377)
at android.mendonca.averdapp.activity.GridAdapter.getView(GridAdapter.java:55)
at android.widget.AbsListView.obtainView(AbsListView.java:2427)
at android.widget.GridView.onMeasure(GridView.java:1065)
at android.view.View.measure(View.java:19881)

Answer 1

尝试在第24行的grid_item.xml中使用View元素而不是view。

Answer 2

Maby您需要覆盖方法

  @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return web[position];
    }

 @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return Imageid[position];
    }

GridAdapter导致java.lang.NullPointerException

2 个答案: