android - 带有文本和图像的自定义 ListView 未显示在 Activity 中

Question

我是 Android 的新手，我正在尝试基于自定义适配器使用 ImageView 和 TextView 创建一个 ListView。

当我尝试运行我的应用程序时，它似乎不会以某种方式将 ListView 显示在屏幕上。不过也不异常(exception)。也许我遗漏了一些非常明显的东西。如果有人可以查看我的代码，那就太好了:

MyActivity.java:

public class MyActivity extends Activity {

    public static final String[] countries = new String[] {"Germany", "USA", "Great Britain", "Japan", "Korea"};
    public static final int[] images = new int[]{R.drawable.de, R.drawable.us, R.drawable.kr, R.drawable.jp, R.drawable.kr};
    ListView listView;
    List<MyListObject> values;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
        TextView textView = (TextView) findViewById(R.id.textView);

        values = new ArrayList<MyListObject>();
        for (int i = 0; i < countries.length; i++) {
            MyListObject item = new MyListObject();
            item.setCountry(countries[i]);
            item.setImage(images[i]);
            values.add(item);
        }

        listView = (ListView) findViewById(R.id.list);
        MySimpleArrayAdapter adapter = new MySimpleArrayAdapter(this, R.layout.rowlayout, values);
        listView.setAdapter(adapter);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.my, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

MySimpleArrayAdapter.java:

public class MySimpleArrayAdapter extends ArrayAdapter<MyListObject> {
    private final Context context;
    private final List<MyListObject> values;

    public MySimpleArrayAdapter(Context context, int resourceID, List<MyListObject> values) {
        super(context, resourceID, values);
        this.context = context;
        this.values = values;
    }

    private class ViewHolder {
        ImageView imageView;
        TextView textView;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        MyListObject rowItem = getItem(position);

        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.rowlayout, null);


        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder = new ViewHolder();
        holder.textView = (TextView) convertView.findViewById(R.id.countryName);
        holder.imageView = (ImageView) convertView.findViewById(R.id.countryImage);


        holder.textView.setText(rowItem.getCountry());
        holder.imageView.setImageResource(rowItem.getImage());

        return convertView;
    }

    @Override
    public MyListObject getItem(int position) {
        return values.get(position);
    }

}

activity_my.xml:

<LinearLayout 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=".MyActivity">

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/textView"/>

    <ListView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/list"
        android:layout_weight="1" />
</LinearLayout>

行布局.xml:

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="fill_parent"
    android:layout_height="wrap_content" android:gravity="center_vertical" >

    <ImageView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingRight="10dp"
        android:id="@+id/countryImage" />
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:id="@+id/countryName"
        android:text="@+id/countryName" />

</LinearLayout>

MyListObject.java:

public class MyListObject {
    private int image;
    private String country;

    public int getImage() {
        return image;
    }

    public void setImage(int image) {
        this.image = image;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }
}

Answer 1

在activity_my的最上面的linearlayout应该有android:orientation="vertical"属性

在你的 rowlayout 父布局是 Horizo​​ntal LinearLayout 和 android:layout_width 对于 ImageView 和 TextView 是 fill_parent。所以，只有 ImageView 是可见的，因为在 LinearLayout 子位置一个接一个地线性变化。改变 rowlayout 像这样

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center_vertical"
    android:padding="8dp"
    android:orientation="horizontal" >

    <ImageView
        android:id="@+id/countryImage"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:paddingRight="10dp" />

    <TextView
        android:id="@+id/countryName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="countryName" />

</LinearLayout>

你也需要改变你的适配器

MySimpleArrayAdapter

public class MySimpleArrayAdapter extends ArrayAdapter<MyListObject> {
    private final Context context;
    private final List<MyListObject> values;
    private int resourceID;

    public MySimpleArrayAdapter(Context context, int resourceID, List<MyListObject> values) {
        super(context, resourceID, values);
        this.context = context;
        this.resourceID = resourceID;
        this.values = values;
    }

    private class ViewHolder {
        ImageView imageView;
        TextView textView;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;       
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(resourceID, null);
            holder = new ViewHolder();
            holder.textView = (TextView) convertView.findViewById(R.id.countryName);
            holder.imageView = (ImageView) convertView.findViewById(R.id.countryImage);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        MyListObject rowItem = (MyListObject) values.get(position); 
        holder.textView.setText(rowItem.getCountry());
        holder.imageView.setImageResource(rowItem.getImage());

        return convertView;
    }

}

截图: