java - 带有按钮和静态字符串数组的 ListView

Question

我想创建一个 ListView，其中每个 row 都有两个按钮。 Button1 和 Button2。

我已经阅读了一些关于如何创建 CustomAdapter 或扩展 BaseAdapter 的教程，但没有一个对我有用，这就是为什么我要提出一个新问题在这里。

我的 strings.xml 中有一个静态(未更改)字符串数组:

 <string-array name="locations_array">
   <item>Item1</item>
   <item>Item2</item>
 </string-array>

我想在我的 ListView 中使用这个数组(我设法创建一个带有 onClick 事件的普通 ListView，但现在我想向每一行添加按钮)并向每一行添加两个按钮，每个按钮都有自己的 onClick 事件.

我已按照 this answers here 中的步骤操作和网络上的其他一些教程，但我在尝试 setText 时总是得到 NullPointerException。

CustomAdapter.java:

public class CustomAdapter extends BaseAdapter implements ListAdapter {
    private ArrayList<String> list = new ArrayList<>();
    private Context ctx;

    public CustomAdapter(ArrayList<String> list, Context ctx){
        this.list = list;
        this.ctx = ctx;
    }

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

    @Override
    public Object getItem(int position) {
        Log.d("TAG", list.get(position));
        return list.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = convertView;
        if(view == null){
            LayoutInflater inflater = (LayoutInflater) ctx.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = inflater.inflate(R.layout.layout_listview,null);
        }
        Log.d("TAG", list.get(position));
        TextView listItemText = (TextView) view.findViewById(R.id.list_item_string);
        listItemText.setText(list.get(position));

        Button localData = (Button) view.findViewById(R.id.button1);
        Button onlineData = (Button) view.findViewById(R.id.button2);

        localData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });

        onlineData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });

        return view;
    }
}

在这里，我在 fragment 中使用适配器:

locationsArray = getResources().getStringArray(R.array.locations_array);
ArrayList<String> data = new ArrayList<>(Arrays.asList(locationsArray));
CustomAdapter adapter = new CustomAdapter(data,getActivity());
listView.setAdapter(adapter);

但这行不通。所有教程都专注于我需要的其他东西。我只需要简单地在每一行上放置两个按钮，并使用现有的字符串数组。我不想动态添加任何内容等。只需使用我已经创建的字符串数组即可。

编辑(添加我忘记的 XML 文件!)

R.layout.layout_listview(EditText用于过滤List):

<?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">
    <EditText
        android:id="@+id/et_filter"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:hint="Search Location">
    </EditText>
    <ListView
        android:id="@+id/list"
        android:layout_height="wrap_content"
        android:layout_width="match_parent">
    </ListView>


</LinearLayout>

R.layout.layout_listview_buttons:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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/list_item_string"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_alignParentLeft="true"
        android:paddingLeft="8dp"
        android:textSize="18sp"
        android:textStyle="bold" />

    <Button
        android:id="@+id/button1"
        android:layout_width="80dp"
        android:layout_height="40dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:focusable="false"
        android:focusableInTouchMode="false"
        android:text="Online Data"

        android:textColor="#0099CC" />

    <Button
        android:id="@+id/button2"
        android:layout_width="80dp"
        android:layout_height="40dp"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/button1"
        android:layout_marginTop="3dp"
        android:focusable="false"
        android:focusableInTouchMode="false"
        android:text="Local Data"
        android:textColor="#0099CC" />



</RelativeLayout>

LogCat 异常:

12-15 11:24:10.852  14626-14626/com.inodroid.myweatherapp E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.inodroid.myweatherapp, PID: 14626
    java.lang.NullPointerException
            at com.inodroid.myweatherapp.Data.CustomAdapter.getView(CustomAdapter.java:59)

代码行:

listItemText.setText(list.get(position));

希望有人能帮帮我。

干杯

Answer 1

请尝试以下操作:

主.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" >

<ListView
    android:id="@+id/lvItems"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
</ListView>

</LinearLayout>

主要 Activity .java:

public class MainActivity extends Activity {

private ListView lvItems;

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

    lvItems = (ListView) findViewById(R.id.lvItems);
    String[] locationsArray = getResources().getStringArray(
            R.array.locations_array);
    CustomAdapter adapter = new CustomAdapter(this, locationsArray);
    lvItems.setAdapter(adapter);

lvItems.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {
            ViewHolder holder = (ViewHolder) view.getTag();
            String item = holder.getItem();
            // Do what ever with your Item.
            // If You need the position, you can take it from above
            // position.
        }
    });
}

}

列表项.xml:

<?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"
android:orientation="vertical"
android:padding="5dp" >

<Button
    android:id="@+id/btnLocalData"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="local Data" />

<TextView
    android:id="@+id/tvItem"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignBottom="@+id/btnLocalData"
    android:layout_alignTop="@+id/btnOnlineData"
    android:layout_toLeftOf="@+id/btnOnlineData"
    android:layout_toRightOf="@+id/btnLocalData"
    android:gravity="center"
    android:text="Item"
    android:textSize="16dp"
    android:textStyle="bold" />

<Button
    android:id="@+id/btnOnlineData"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentRight="true"
    android:text="Online Data" />

</RelativeLayout>

自定义适配器.java :

public class CustomAdapter extends ArrayAdapter<String> {

private LayoutInflater lf;

public CustomAdapter(Context context, String[] objects) {
    super(context, 0, objects);
    lf = LayoutInflater.from(context);
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder = null;
    if (convertView == null) {
        convertView = lf.inflate(R.layout.list_item, parent, false);
        holder = new ViewHolder();
        holder.btnLocalData = (Button) convertView
                .findViewById(R.id.btnLocalData);
        holder.btnOnlineData = (Button) convertView
                .findViewById(R.id.btnOnlineData);
        holder.tvItem = (TextView) convertView.findViewById(R.id.tvItem);
        holder.initListeners();
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    holder.setData(getItem(position));

    return convertView;
}

public static class ViewHolder {
    TextView tvItem;
    Button btnOnlineData;
    Button btnLocalData;
    String mItem;

    public String getItem(){
        return mItem;
    }

    public void setData(String item) {
        mItem = item;
        tvItem.setText(item);
    }

    public void initListeners() {
        btnLocalData.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                Toast.makeText(v.getContext(),
                        "Local Data Clicked : " + mItem, Toast.LENGTH_LONG)
                        .show();
            }
        });
        btnOnlineData.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                Toast.makeText(v.getContext(),
                        "Online Data Clicked : " + mItem, Toast.LENGTH_LONG)
                        .show();
            }
        });
    }

}

}