Android之ArrayAdapter（数组适配器）

一、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"
    >

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

</LinearLayout>

二、list_item.xml

<?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">

    <ImageView
        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" />

</LinearLayout>

三、MainActivity.java

package com.example.arrayadaptertest;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class MainActivity extends AppCompatActivity {

    private static String[] names = {"功能1", "功能2", "功能3", "功能4", "功能5"};

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

        ListView lv = (ListView) findViewById(R.id.lv);
        lv.setAdapter(new ArrayAdapter<String>(this, R.layout.list_item,
                R.id.tv, names));


    }
}

四、运行结果

五、ArrayAdapter的构造函数较多，其中的参数的含义可以参见源代码

 /**
     * Constructor
     *
     * @param context The current context.
     * @param resource The resource ID for a layout file containing a TextView to use when
     *                 instantiating views.
     */
    public ArrayAdapter(@NonNull Context context, @LayoutRes int resource) {
        this(context, resource, 0, new ArrayList<>());
    }

    /**
     * Constructor
     *
     * @param context The current context.
     * @param resource The resource ID for a layout file containing a layout to use when
     *                 instantiating views.
     * @param textViewResourceId The id of the TextView within the layout resource to be populated
     */
    public ArrayAdapter(@NonNull Context context, @LayoutRes int resource,
            @IdRes int textViewResourceId) {
        this(context, resource, textViewResourceId, new ArrayList<>());
    }

    /**
     * Constructor. This constructor will result in the underlying data collection being
     * immutable, so methods such as {@link #clear()} will throw an exception.
     *
     * @param context The current context.
     * @param resource The resource ID for a layout file containing a TextView to use when
     *                 instantiating views.
     * @param objects The objects to represent in the ListView.
     */
    public ArrayAdapter(@NonNull Context context, @LayoutRes int resource, @NonNull T[] objects) {
        this(context, resource, 0, Arrays.asList(objects));
    }

    /**
     * Constructor. This constructor will result in the underlying data collection being
     * immutable, so methods such as {@link #clear()} will throw an exception.
     *
     * @param context The current context.
     * @param resource The resource ID for a layout file containing a layout to use when
     *                 instantiating views.
     * @param textViewResourceId The id of the TextView within the layout resource to be populated
     * @param objects The objects to represent in the ListView.
     */
    public ArrayAdapter(@NonNull Context context, @LayoutRes int resource,
            @IdRes int textViewResourceId, @NonNull T[] objects) {
        this(context, resource, textViewResourceId, Arrays.asList(objects));
    }

    /**
     * Constructor
     *
     * @param context The current context.
     * @param resource The resource ID for a layout file containing a TextView to use when
     *                 instantiating views.
     * @param objects The objects to represent in the ListView.
     */
    public ArrayAdapter(@NonNull Context context, @LayoutRes int resource,
            @NonNull List<T> objects) {
        this(context, resource, 0, objects);
    }

    /**
     * Constructor
     *
     * @param context The current context.
     * @param resource The resource ID for a layout file containing a layout to use when
     *                 instantiating views.
     * @param textViewResourceId The id of the TextView within the layout resource to be populated
     * @param objects The objects to represent in the ListView.
     */
    public ArrayAdapter(@NonNull Context context, @LayoutRes int resource,
            @IdRes int textViewResourceId, @NonNull List<T> objects) {
        this(context, resource, textViewResourceId, objects, false);
    }

    private ArrayAdapter(@NonNull Context context, @LayoutRes int resource,
            @IdRes int textViewResourceId, @NonNull List<T> objects, boolean objsFromResources) {
        mContext = context;
        mInflater = LayoutInflater.from(context);
        mResource = mDropDownResource = resource;
        mObjects = objects;
        mObjectsFromResources = objsFromResources;
        mFieldId = textViewResourceId;
    }