如何使用列表适配器

Question

我的应用程序显示ListView中数据库的信息。

在ListView中，还有一个VideoView应该从我的网站加载和播放视频。

在一个只有这个功能的独立应用程序中，我开始工作了。不同之处在于，在工作应用中，视频视图位于 activity_main.xml 文件中，而在我的新应用中，视频视图位于单独的list_item.xml文件中，该文件被加载到activity_main.xml中作为ListView。

另一个堆栈溢出用户告诉我，因为VideoView不在activity_main.xml中，所以我必须创建一个ListAdapter并让列表适配器的getView（）方法引用我的list_item.xml布局文件。 / p>

我找到了关于ListAdapters的教程，但似乎上下文与我想要实现的内容完全不同，以便能够使其适应我的使用。

有人可以帮助我了解如何实现可与我当前代码一起使用的ListAdapter吗？

在此先感谢，我非常感谢您的帮助。

以下是我的文件

activity_main.xml中：

<?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="fill_parent"
android:orientation="vertical">
<!-- Main ListView 
     Always give id value as list(@android:id/list)
-->
<ListView
    android:id="@android:id/list"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>

</LinearLayout>

list_item.xml：

<?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:orientation="vertical" >

<!-- Name Label -->
<TextView
    android:id="@+id/name"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:paddingTop="6dip"
    android:paddingLeft="6dip"
    android:textSize="17dip"
    android:textStyle="bold" />

    <VideoView
     android:id="@+id/videoView"
     android:layout_width="100dp"
     android:layout_height="100dp"
     />

            <ImageButton
    android:id="@+id/imageButton2"
    android:layout_width="60dp"
    android:layout_height="60dp"
    android:src="@drawable/ic_videobutton"
    android:onClick="sendMessage" />

</LinearLayout>

AllProductsActivity.java：

package com.example.androidhive;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.MediaController;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.VideoView;

public class AllProductsActivity extends ListActivity {

// Progress Dialog
private ProgressDialog pDialog;

// Creating JSON Parser object
JSONParser jParser = new JSONParser();

ArrayList<HashMap<String, String>> productsList;

// get video url
private static final String MOVIE_URL ="http://mywebsite.com/mycameraapp/android_connect/videos/testvideo.mkv";

// url to get all products list
private static String url_all_products = "http://mywebsite.com/mycameraapp/android_connect/get_all_products.php";

// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "products";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
private static final String TAG_DESCRIPTION = "description";

// products JSONArray
JSONArray products = null;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.all_products);



    // **MY VIDEOVIEW CODE THAT DOESN'T WORK BECAUSE THIS VIDEOVIEW IS IN list_item.xml**
    VideoView vid = (VideoView) findViewById(R.id.videoView);
    Uri video = Uri.parse(MOVIE_URL);
    vid.setMediaController(new MediaController(this));
    vid.setVideoURI(video);
    vid.start();
    vid.requestFocus();



    // Hashmap for ListView
    productsList = new ArrayList<HashMap<String, String>>();

    // Loading products in Background Thread
    new LoadAllProducts().execute();

    // Get listview
    ListView lv = getListView();

    // on seleting single product
    // launching Edit Product Screen
    lv.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {
            // getting values from selected ListItem
            String pid = ((TextView) view.findViewById(R.id.pid)).getText()
                    .toString();

            // Starting new intent
            Intent in = new Intent(getApplicationContext(),
                    EditProductActivity.class);
            // sending pid to next activity
            in.putExtra(TAG_PID, pid);

            // starting new activity and expecting some response back
            startActivityForResult(in, 100);
        }
    });


}

/** CALLED WHEN THE USER CLICKS THE RECORD BUTTON */
public void sendMessage(View view) {
    Intent videoIntent = new Intent(this, PhotoIntentActivity.class);
    startActivity(videoIntent);
}

// Response from Edit Product Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    // if result code 100
    if (resultCode == 100) {
        // if result code 100 is received 
        // means user edited/deleted product
        // reload this screen again
        Intent intent = getIntent();
        finish();
        startActivity(intent);
    }

}

/**
 * Background Async Task to Load all product by making HTTP Request
 * */
class LoadAllProducts extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(AllProductsActivity.this);
        pDialog.setMessage("Loading products. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
    }

    /**
     * getting All products from url
     * */
    protected String doInBackground(String... args) {
        // Building Parameters
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        // getting JSON string from URL
        JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);

        // Check your log cat for JSON reponse
        Log.d("All Products: ", json.toString());

        try {
            // Checking for SUCCESS TAG
            int success = json.getInt(TAG_SUCCESS);

            if (success == 1) {
                // products found
                // Getting Array of Products
                products = json.getJSONArray(TAG_PRODUCTS);

                // looping through All Products
                for (int i = 0; i < products.length(); i++) {
                    JSONObject c = products.getJSONObject(i);

                    // Storing each json item in variable
                    String id = c.getString(TAG_PID);
                    String name = c.getString(TAG_NAME);
                    String description = c.getString(TAG_DESCRIPTION);

                    // creating new HashMap
                    HashMap<String, String> map = new HashMap<String, String>();

                    // adding each child node to HashMap key => value
                    map.put(TAG_PID, id);
                    map.put(TAG_NAME, name);
                    map.put(TAG_DESCRIPTION, description);

                    // adding HashList to ArrayList
                    productsList.add(map);
                }
            } else {
                // no products found
                // Launch Add New product Activity
                Intent i = new Intent(getApplicationContext(),
                        NewProductActivity.class);
                // Closing all previous activities
                i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(i);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog after getting all products
        pDialog.dismiss();
        // updating UI from Background Thread
        runOnUiThread(new Runnable() {
            public void run() {
                /**
                 * Updating parsed JSON data into ListView
                 * */
                ListAdapter adapter = new SimpleAdapter(
                        AllProductsActivity.this, productsList,
                        R.layout.list_item, new String[] { TAG_PID, TAG_NAME, TAG_DESCRIPTION},
                        new int[] { R.id.pid, R.id.name, R.id.description });
                // updating listview
                setListAdapter(adapter);

            }


        });

    }

}

}

Answer 1

适配器用于将数据绑定到ListView。您应该创建一个新类来表示ListView中的每个项目，而不是使用HashMaps列表。

public class MyAdapter extends ArrayAdapter<MyItem>
{
    private final List<MyItem>     mItems;
    private final Context          mContext;
    private final LayoutInflater   mInflater;

    public MyAdapter (Context context, int resourceId, ArrayList<MyItem> items)
    {
        super(context, resourceId, rescues);

        mContext = context;
        mItems = items;
        inflater = (LayoutInflater)mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent)
    {
        ViewHolder holder;
        if (convertView == null)
        {
            convertView = inflater.inflate(R.layout.list_item, null);
            holder = new ViewHolder();
            holder.name = (TextView)convertView.findViewById(R.id.name);
            holder.video = (VideoView)convertView.findViewById(R.id.videoView);
            holder.button = (ImageButton)convertView.findViewById(R.id.imageButton2);
            convertView.setTag(holder);
        }
        else
        {
            holder = (ViewHolder)convertView.getTag();
        }

        MyItem item = getItem(position);
        if (item != null)
        {
            // This is where you set up the views.
            // This is just an example of what you could do.
            holder.text.setText(item.getName());
            holder.video.setMediaController(new MediaController(mContext));
            holder.button.setImageDrawable(item.getImageDrawable());
            holder.button.setOnClickListener(
                new View.OnClickListener()
                {
                    @Override
                    public void onClick(View view)
                    {
                        holder.video.setVideoURI(item.getURI());
                        holder.video.start();
                    }
                }
            );
        }

        return convertView;
    }

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

    @Override
    public MyItem getItem(int position)
    {
        return mItems.get(position);
    }

    public class ViewHolder
    {
        TextView    text;
        VideoView   video;
        ImageButton button;
    }
}

在AllProductsActivity类中：

/**
 * After completing background task Dismiss the progress dialog
 * **/
protected void onPostExecute(String file_url) {
    // dismiss the dialog after getting all products
    pDialog.dismiss();
    // updating UI from Background Thread
    runOnUiThread(new Runnable() {
        public void run() {
            /**
             * Updating parsed JSON data into ListView
             * */
            MyAdapter adapter = new MyAdapter(AllProductsActivity.this,
                R.layout.list_item, productsList);

            // updating listview
            setListAdapter(adapter);

        }