java - 如何在ListView Activity中实现自定义适配器

Question

我想要在textview之前显示图像，并且想要在每一行中自定义TextView，但我很难实现它，因为已经内置了xml这样的布局文件simple_list_item_1。请帮助我如何实现它。

这是 simple_list_item 编码

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (C) 2006 The Android Open Source Project

     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
     You may obtain a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

     Unless required by applicable law or agreed to in writing, software
     distributed under the License is distributed on an "AS IS" BASIS,
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
-->

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/text1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
        android:textSize="20sp"
            android:textStyle="bold"
    android:textAppearance="?android:attr/textAppearanceListItemSmall"
    android:gravity="center_vertical"
    android:paddingStart="?android:attr/listPreferredItemPaddingStart"
    android:paddingEnd="?android:attr/listPreferredItemPaddingEnd"
    android:minHeight="?android:attr/listPreferredItemHeightSmall"
/>

主要 Activity

public class MainActivity extends ListActivity {

    private ListActivity activity;
    final static String ScreenName = "google";
    final static String LOG_TAG = "rnc";
     ListView listview;
      TextView text;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.twit_list);


          listview = this.getListView();

         activity = this;

        downloadTweets();


          listview.setOnItemClickListener(new OnItemClickListener() {
              @Override
              public void onItemClick(AdapterView<?> parent, View view,
                           int position, long id) {   
                 // selected item
                 String lst_txt = parent.getItemAtPosition(position).toString().trim();


                 // Launching new Activity on selecting single List Item
                 Intent i = new Intent(MainActivity.this, SingleListItem.class);
                 // sending data to new activity
                 i.putExtra("product",lst_txt );
                 startActivity(i);
               }
            });
    }

    // download twitter timeline after first checking to see if there is a network connection
    public void downloadTweets() {
        ConnectivityManager connMgr = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();

        if (networkInfo != null && networkInfo.isConnected()) {
            new DownloadTwitterTask().execute(ScreenName);
        } else {
            Log.v(LOG_TAG, "No network connection available.");
        }
    }

    // Uses an AsyncTask to download a Twitter user's timeline
    private class DownloadTwitterTask extends AsyncTask<String, Void, String> {
        final static String CONSUMER_KEY = "keyvaluexxxxx";
        final static String CONSUMER_SECRET = "secretkeyxxxxxxx";
        final static String TwitterTokenURL = "https://api.twitter.com/oauth2/token";
        final static String TwitterStreamURL = "https://api.twitter.com/1.1/statuses/user_timeline.json?screen_name=";


        private ProgressDialog progressDialog;  
        @Override
        // can use UI thread here
        protected void onPreExecute() {
        //this.progressDialog = ProgressDialog.show(Boys.this, ""," Look whose back !! Ok Let me see what i have for you ");  
            try{
            progressDialog = new ProgressDialog(MainActivity.this,AlertDialog.THEME_HOLO_DARK);
            progressDialog.setIndeterminate(true);
            progressDialog.setIndeterminateDrawable(getResources().getDrawable(R.drawable.loader_2));
            progressDialog.setMessage("Please Wait ! Unwrapping Something for You...");
            progressDialog.show();
            progressDialog.setCancelable(false);
            progressDialog.setCanceledOnTouchOutside(false);
            }
            catch(Exception e)
            {
                this.progressDialog.dismiss();
                Toast.makeText(getApplicationContext(),e.toString(), Toast.LENGTH_LONG).show();

            }
        }

        @Override
        protected String doInBackground(String... screenNames) {
            String result = null;

            if (screenNames.length > 0) {
                result = getTwitterStream(screenNames[0]);
            }
            return result;
        }

        // onPostExecute convert the JSON results into a Twitter object (which is an Array list of tweets
        @Override
        protected void onPostExecute(String result) {
            Twitter twits = jsonToTwitter(result);

            // lets write the results to the console as well
            for (Tweet tweet : twits) {
                Log.i(LOG_TAG, tweet.getText());
            }

            // send the tweets to the adapter for rendering
            ArrayAdapter<Tweet> adapter = new ArrayAdapter<Tweet>(activity, android.R.layout.simple_list_item_1, twits);
            setListAdapter(adapter);
            this.progressDialog.dismiss();
        }

        // converts a string of JSON data into a Twitter object
        private Twitter jsonToTwitter(String result) {
            Twitter twits = null;
            if (result != null && result.length() > 0) {
                try {
                    Gson gson = new Gson();
                    twits = gson.fromJson(result, Twitter.class);
                } catch (IllegalStateException ex) {
                    // just eat the exception
                }
            }
            return twits;
        }

        // convert a JSON authentication object into an Authenticated object
        private Authenticated jsonToAuthenticated(String rawAuthorization) {
            Authenticated auth = null;
            if (rawAuthorization != null && rawAuthorization.length() > 0) {
                try {
                    Gson gson = new Gson();
                    auth = gson.fromJson(rawAuthorization, Authenticated.class);
                } catch (IllegalStateException ex) {
                    // just eat the exception
                }
            }
            return auth;
        }

        private String getResponseBody(HttpRequestBase request) {
            StringBuilder sb = new StringBuilder();
            try {

                DefaultHttpClient httpClient = new DefaultHttpClient(new BasicHttpParams());
                HttpResponse response = httpClient.execute(request);
                int statusCode = response.getStatusLine().getStatusCode();
                String reason = response.getStatusLine().getReasonPhrase();

                if (statusCode == 200) {

                    HttpEntity entity = response.getEntity();
                    InputStream inputStream = entity.getContent();

                    BufferedReader bReader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
                    String line = null;
                    while ((line = bReader.readLine()) != null) {
                        sb.append(line);
                    }
                } else {
                    sb.append(reason);
                }
            } catch (UnsupportedEncodingException ex) {
            } catch (ClientProtocolException ex1) {
            } catch (IOException ex2) {
            }
            return sb.toString();
        }

        private String getTwitterStream(String screenName) {
            String results = null;

            // Step 1: Encode consumer key and secret
            try {
                // URL encode the consumer key and secret
                String urlApiKey = URLEncoder.encode(CONSUMER_KEY, "UTF-8");
                String urlApiSecret = URLEncoder.encode(CONSUMER_SECRET, "UTF-8");

                // Concatenate the encoded consumer key, a colon character, and the
                // encoded consumer secret
                String combined = urlApiKey + ":" + urlApiSecret;

                // Base64 encode the string
                String base64Encoded = Base64.encodeToString(combined.getBytes(), Base64.NO_WRAP);

                // Step 2: Obtain a bearer token
                HttpPost httpPost = new HttpPost(TwitterTokenURL);
                httpPost.setHeader("Authorization", "Basic " + base64Encoded);
                httpPost.setHeader("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8");
                httpPost.setEntity(new StringEntity("grant_type=client_credentials"));
                String rawAuthorization = getResponseBody(httpPost);
                Authenticated auth = jsonToAuthenticated(rawAuthorization);

                // Applications should verify that the value associated with the
                // token_type key of the returned object is bearer
                if (auth != null && auth.token_type.equals("bearer")) {

                    // Step 3: Authenticate API requests with bearer token
                    HttpGet httpGet = new HttpGet(TwitterStreamURL + screenName);

                    // construct a normal HTTPS request and include an Authorization
                    // header with the value of Bearer <>
                    httpGet.setHeader("Authorization", "Bearer " + auth.access_token);
                    httpGet.setHeader("Content-Type", "application/json");
                    // update the results with the body of the response
                    results = getResponseBody(httpGet);
                }
            } catch (UnsupportedEncodingException ex) {
            } catch (IllegalStateException ex1) {
            }
            return results;
        }
    }
}

这里twit_list.xml附加了MainActivity.java

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
    android:background="@drawable/bis" 

        >

<ListView  
          android:id="@android:id/list"
          android:layout_width="match_parent"
          android:layout_height="wrap_content">

</ListView>


</LinearLayout>

Answer 1

在布局文件夹内创建一个custom_item

<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:orientation="horizontal" >

    <ImageView
        android:id="@+id/listItemImgView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:contentDescription="@string/done"
        android:src="@drawable/ic_launcher" />

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

</LinearLayout>

创建一个像这样的自定义适配器

public class CustomAdapter extends ArrayAdapter<Tweet> {

    private Context mContext;
    private int layoutId;
    private ArrayList<Tweet> dataList;

    public CustomAdapter(Context context, int resourceId,
            ArrayList<Tweet> objects) {
        super(context, resourceId, objects);
        // TODO Auto-generated constructor stub
        mContext = context;
        layoutId = resourceId;
        dataList = objects;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        ViewHolder viewHolder;
        if(convertView == null) {
            LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(layoutId, null);
            viewHolder = new ViewHolder();
            viewHolder.listItemTxtView = (TextView) convertView.findViewById(R.id.listItemTxtView);
            viewHolder.listItemImgView = (ImageView) convertView.findViewById(R.id.listItemImgView);

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

        viewHolder.listItemTxtView.setText(dataList.get(position).toString());
        //place picasso jar into libs folder of your project and use it for download and  set images like this
        Picasso.with(context).load("url of image you want to load").into(viewHolder.listItemImgView);
        return convertView;
    }

    private class ViewHolder {
        TextView listItemTxtView;
        ImageView listItemImgView;
    }
}

download picasso jar from here

而不是这个

ArrayAdapter<Tweet> adapter = new ArrayAdapter<Tweet>(activity, android.R.layout.simple_list_item_1, twits);
setListAdapter(adapter);

使用这个

CustomAdapter adapter = new CustomAdapter(MainActivity.this, R.layout.custom_item, twits);
setListAdapter(adapter);