Spinner加载自定义Adapter

最新推荐文章于 2025-05-26 14:59:35 发布

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最新推荐文章于 2025-05-26 14:59:35 发布

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分类专栏： Android 文章标签： android

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本文详细介绍了如何在Android应用中利用Spinner组件结合自定义Item布局展示商品信息，包括XML布局文件的编写、数据适配器的实现以及异常处理策略。通过实例演示了从创建Commodity类到适配器MyAdapter的完整流程，确保了界面的正确加载与显示。

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直接贴代码：

activity_main.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="match_parent"
    android:orientation="vertical"
    android:padding="10dp">

    <Spinner
        android:id="@+id/spinner"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
    </Spinner>

</LinearLayout>

item.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="match_parent">

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

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

        <TextView
            android:id="@+id/tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_toRightOf="@id/iv"
            android:text="商品" />
    </RelativeLayout>

</LinearLayout>

这里注意：item.xml文件中根布局不能写为RelativeLayout，否则会报空指针异常

Commodity.java

public class Commodity {
    private int icon;
    private String name;

    public int getIcon() {
        return icon;
    }

    public void setIcon(int icon) {
        this.icon = icon;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private Spinner spinner;
    private MyAdapter adapter;

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

        spinner = (Spinner) findViewById(R.id.spinner);

        List<Commodity> list = new ArrayList<>();

        for (int i = 1; i <= 30; i ++) {
            Commodity commodity = new Commodity();
            commodity.setIcon(R.mipmap.ic_launcher);
            commodity.setName("商品 " + i);
            list.add(commodity);
        }

        adapter = new MyAdapter(this, list);

        spinner.setAdapter(adapter);
    }

    private class MyAdapter extends BaseAdapter {

        private Context mContext;
        private List<Commodity> mList;

        public MyAdapter(Context context, List<Commodity> list) {
            this.mContext = context;
            this.mList = list;
        }

        @Override
        public int getCount() {
            return mList.size();
        }

        @Override
        public Object getItem(int position) {
            return mList.get(position);
        }

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

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

            ViewHolder holder = null;

            if (convertView == null) {
                convertView = View.inflate(MainActivity.this, R.layout.item, null);

                holder = new ViewHolder();

                holder.iv = (ImageView) convertView.findViewById(R.id.iv);
                holder.tv = (TextView) convertView.findViewById(R.id.tv);

                convertView.setTag(holder);
            } else {
                holder = (ViewHolder) convertView.getTag();
            }

            holder.iv.setImageResource(mList.get(position).getIcon());
            holder.tv.setText(mList.get(position).getName());

            return convertView;
        }
    }

    static class ViewHolder {
        private ImageView iv;
        private TextView tv;
    }
}

运行结果

将item.xml文件修改为如下代码运行一下

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

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

    <TextView
        android:id="@+id/tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_toRightOf="@id/iv"
        android:text="商品" />

</RelativeLayout>

异常信息如下：

03-17 12:37:36.719 6241-6241/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                 java.lang.NullPointerException
                                                     at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:559)
                                                     at android.view.View.measure(View.java:15518)
                                                     at android.support.v7.internal.widget.ListViewCompat.measureHeightOfChildrenCompat(ListViewCompat.java:301)
                                                     at android.support.v7.widget.ListPopupWindow.buildDropDown(ListPopupWindow.java:1200)
                                                     at android.support.v7.widget.ListPopupWindow.show(ListPopupWindow.java:584)
                                                     at android.support.v7.widget.AppCompatSpinner$DropdownPopup.show(AppCompatSpinner.java:766)
                                                     at android.support.v7.widget.AppCompatSpinner.performClick(AppCompatSpinner.java:424)
                                                     at android.view.View$PerformClick.run(View.java:17355)
                                                     at android.os.Handler.handleCallback(Handler.java:725)
                                                     at android.os.Handler.dispatchMessage(Handler.java:92)
                                                     at android.os.Looper.loop(Looper.java:137)
                                                     at android.app.ActivityThread.main(ActivityThread.java:5041)
                                                     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:793)
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
                                                     at dalvik.system.NativeStart.main(Native Method)
03-17 12:37:40.603 410-837/? E/JavaBinder: !!! FAILED BINDER TRANSACTION !!!
03-17 12:37:40.603 410-837/? E/JavaBinder: !!! FAILED BINDER TRANSACTION !!!