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Android网络框架-Volley实践使用Volley打造自定义ListView

發布時間：2023/12/18 Android 37 豆豆

生活随笔收集整理的這篇文章主要介紹了 Android网络框架-Volley实践使用Volley打造自定义ListView 小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

這篇文章翻譯自Ravi Tamada博客中的Android Custom ListView with Image and Text using Volley

最終效果

這個ListView呈現了一些影視信息，每一行是一個影片的信息，每一行中有一張電影的圖片，電影的名字、評分、類型、年份等信息。

1.json數據

我們通過解析json然后拿到數據，這個json數據包括json數組，每個json數組中是一個json對象，json對象中包括了電影的圖片url地址、標題、年份、評分、類型等信息

JSON Url:http://api.androidhive.info/json/movies.json

[{"title": "Dawn of the Planet of the Apes","image": "http://api.androidhive.info/json/movies/1.jpg","rating": 8.3,"releaseYear": 2014,"genre": ["Action", "Drama", "Sci-Fi"]},........]

?來自CODE的代碼片 json

2.下載Volley庫（volley.jar）

如果你第一次使用Volley框架，我建議你去我之前的文章看一下Android網絡框架-Volley(一) 工作原理分析?。然后到百度上下載一個volley.jar。添加到項目的lib文件夾里面

3.布局分析

我選擇了RelativeLayout來實現這個布局，圖片我們使用volley提供的NetworkImageView

現在我們來新建一個Android項目

4.創建一個新的項目

1.打開eclipse，點擊File-->New-->Android Application Project。填好基本信息后，我們把包名命名為info.androidhive.customlistviewvolley

2.將volley.jar添加到項目的lib文件夾下

3.我們先把包建好，我們一共分為4個包：?adapter,?app,?model?和?util? 。現在我們項目結構如下：

info.androidhive.customlistviewvolley.adater
info.androidhive.customlistviewvolley.app
info.androidhive.customlistviewvolley.model
info.androidhive.customlistviewvolley.util

4.打開res/values/colors.xml。如果沒有colors.xml，我們就自己創建一個。然后添加如下代碼

<?xml version="1.0" encoding="utf-8"?><resources> <color name="genre">#666666</color> <color name="year">#888888</color> <color name="list_divider">#d9d9d9</color> <color name="list_row_start_color">#ffffff</color> <color name="list_row_end_color">#ffffff</color> <color name="list_row_hover_start_color">#ebeef0</color> <color name="list_row_hover_end_color">#ebeef0</color> </resources>

?來自CODE的代碼片 colors.xml

5.打開res/values/dimens.xml。添加如下代碼

?來自CODE的代碼片 dimens.xml

6.在寫jsva代碼之前，我們先完成UI部分，在res下新建一個drawable文件夾，在res/drawable中新建3個xml文件：list_row_bg.xml、list_row_bg_hover.xml?、list_row_selector.xml?。
list_row_bg.xml?-沒有被點擊時listview的樣式

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"android:shape="rectangle"><gradientandroid:startColor="@color/list_row_start_color"android:endColor="@color/list_row_end_color"android:angle="270" /></shape>

?來自CODE的代碼片 list_row_bg.xml-

list_row_bg_hover.xml?-被點擊后listview的樣式

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle" > <gradient android:angle="270" android:endColor="@color/list_row_hover_end_color" android:startColor="@color/list_row_hover_start_color" /> </shape>

?來自CODE的代碼片 list_row_bg_hover.xml

list_row_selector.xml?-切換兩種樣式的slector文件

<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:drawable="@drawable/list_row_bg" android:state_pressed="false" android:state_selected="false"/> <item android:drawable="@drawable/list_row_bg_hover" android:state_pressed="true"/> <item android:drawable="@drawable/list_row_bg_hover" android:state_pressed="false" android:state_selected="true"/> </selector>

?來自CODE的代碼片 list_row_selector.xml

7.打開activity_main.xml?添加listview

?來自CODE的代碼片 activity_main.xml

8.創建每個item的布局文件list_row.xml

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="wrap_content" android:background="@drawable/list_row_selector" android:padding="8dp" >  <com.android.volley.toolbox.NetworkImageView android:id="@+id/thumbnail" android:layout_width="80dp" android:layout_height="80dp" android:layout_alignParentLeft="true" android:layout_marginRight="8dp" />  <TextView android:id="@+id/title" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignTop="@+id/thumbnail" android:layout_toRightOf="@+id/thumbnail" android:textSize="@dimen/title" android:textStyle="bold" />  <TextView android:id="@+id/rating" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_below="@id/title" android:layout_marginTop="1dip" android:layout_toRightOf="@+id/thumbnail" android:textSize="@dimen/rating" />  <TextView android:id="@+id/genre" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_below="@id/rating" android:layout_marginTop="5dp" android:layout_toRightOf="@+id/thumbnail" android:textColor="@color/genre" android:textSize="@dimen/genre" />  <TextView android:id="@+id/releaseYear" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:layout_alignParentRight="true" android:textColor="@color/year" android:textSize="@dimen/year" /> </RelativeLayout>

?來自CODE的代碼片 list_row.xml

UI部分我們已經完成了，接下來是java代碼部分 9.在util包下新建LruBitmapCache.java? 這個類是用來緩存圖片的，這個類我們在之前文章中已經分析過了。參見Android網絡框架-Volley(二) RequestQueue源碼分析以及建立一個RequestQueue

package info.androidhive.customlistviewvolley.util; import com.android.volley.toolbox.ImageLoader.ImageCache; import android.graphics.Bitmap;import android.support.v4.util.LruCache; public class LruBitmapCache extends LruCache<String, Bitmap> implements ImageCache { public static int getDefaultLruCacheSize() { final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024); final int cacheSize = maxMemory / 2; return cacheSize; } public LruBitmapCache() { this(getDefaultLruCacheSize()); } public LruBitmapCache(int sizeInKiloBytes) { super(sizeInKiloBytes); } @Override protected int sizeOf(String key, Bitmap value) { return value.getRowBytes() * value.getHeight() / 1024; } @Override public Bitmap getBitmap(String url) { return get(url); } @Override public void putBitmap(String url, Bitmap bitmap) { put(url, bitmap); }}

?來自CODE的代碼片 LruBitmapCache.java

10.在app包下新建AppController.java? 這個類是用來創建一個單例RequestQueue的，以及初始化一些volley核心對象

package info.androidhive.customlistviewvolley.app; import info.androidhive.customlistviewvolley.util.LruBitmapCache;import android.app.Application;import android.text.TextUtils; import com.android.volley.Request;import com.android.volley.RequestQueue;import com.android.volley.toolbox.ImageLoader;import com.android.volley.toolbox.Volley; public class AppController extends Application { public static final String TAG = AppController.class.getSimpleName(); private RequestQueue mRequestQueue; private ImageLoader mImageLoader; private static AppController mInstance; @Override public void onCreate() { super.onCreate(); mInstance = this; } public static synchronized AppController getInstance() { return mInstance; } public RequestQueue getRequestQueue() { if (mRequestQueue == null) { mRequestQueue = Volley.newRequestQueue(getApplicationContext()); } return mRequestQueue; } public ImageLoader getImageLoader() { getRequestQueue(); if (mImageLoader == null) { mImageLoader = new ImageLoader(this.mRequestQueue, new LruBitmapCache()); } return this.mImageLoader; } public <T> void addToRequestQueue(Request<T> req, String tag) { // set the default tag if tag is empty req.setTag(TextUtils.isEmpty(tag) ? TAG : tag); getRequestQueue().add(req); } public <T> void addToRequestQueue(Request<T> req) { req.setTag(TAG); getRequestQueue().add(req); } public void cancelPendingRequests(Object tag) { if (mRequestQueue != null) { mRequestQueue.cancelAll(tag); } }}

?來自CODE的代碼片 AppController.java

11.現在我們要在?AndroidManifest.xml? 中注冊這個AppController，并且添加上網絡權限

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" package="info.androidhive.customlistviewvolley" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="11" android:targetSdkVersion="18" /> <uses-permission android:name="android.permission.INTERNET" /> <application android:name="info.androidhive.customlistviewvolley.app.AppController" android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="info.androidhive.customlistviewvolley.MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>

?來自CODE的代碼片 AndroidManifest.xml

12.現在在model包下創建一個Movie實體類，解析完的json數據會保存到這個實體類中

package info.androidhive.customlistviewvolley.model; import java.util.ArrayList; public class Movie { //title=標題， thumbnailUrl=圖片地址 private String title, thumbnailUrl; //年份 private int year; //評分 private double rating; //類別 private ArrayList<String> genre; public Movie() { } public Movie(String name, String thumbnailUrl, int year, double rating, ArrayList<String> genre) { this.title = name; this.thumbnailUrl = thumbnailUrl; this.year = year; this.rating = rating; this.genre = genre; } public String getTitle() { return title; } public void setTitle(String name) { this.title = name; } public String getThumbnailUrl() { return thumbnailUrl; } public void setThumbnailUrl(String thumbnailUrl) { this.thumbnailUrl = thumbnailUrl; } public int getYear() { return year; } public void setYear(int year) { this.year = year; } public double getRating() { return rating; } public void setRating(double rating) { this.rating = rating; } public ArrayList<String> getGenre() { return genre; } public void setGenre(ArrayList<String> genre) { this.genre = genre; } }

?來自CODE的代碼片 Movie.java

13.在adapter包下新建一個?CustomListAdapter.java? adapter會將item布局加載出來，并且將數據顯示到listview上面

package info.androidhive.customlistviewvolley.adater; import info.androidhive.customlistviewvolley.R;import info.androidhive.customlistviewvolley.app.AppController;import info.androidhive.customlistviewvolley.model.Movie; import java.util.List; import android.app.Activity;import android.content.Context;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.TextView; import com.android.volley.toolbox.ImageLoader;import com.android.volley.toolbox.NetworkImageView; public class CustomListAdapter extends BaseAdapter { private Activity activity; private LayoutInflater inflater; private List<Movie> movieItems; ImageLoader imageLoader = AppController.getInstance().getImageLoader(); public CustomListAdapter(Activity activity, List<Movie> movieItems) { this.activity = activity; this.movieItems = movieItems; } @Override public int getCount() { return movieItems.size(); } @Override public Object getItem(int location) { return movieItems.get(location); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { if (inflater == null) inflater = (LayoutInflater) activity .getSystemService(Context.LAYOUT_INFLATER_SERVICE); if (convertView == null) convertView = inflater.inflate(R.layout.list_row, null); if (imageLoader == null) imageLoader = AppController.getInstance().getImageLoader(); NetworkImageView thumbNail = (NetworkImageView) convertView .findViewById(R.id.thumbnail); TextView title = (TextView) convertView.findViewById(R.id.title); TextView rating = (TextView) convertView.findViewById(R.id.rating); TextView genre = (TextView) convertView.findViewById(R.id.genre); TextView year = (TextView) convertView.findViewById(R.id.releaseYear); // getting movie data for the row Movie m = movieItems.get(position); // thumbnail image thumbNail.setImageUrl(m.getThumbnailUrl(), imageLoader); // title title.setText(m.getTitle()); // rating rating.setText("Rating: " + String.valueOf(m.getRating())); // genre String genreStr = ""; for (String str : m.getGenre()) { genreStr += str + ", "; } genreStr = genreStr.length() > 0 ? genreStr.substring(0, genreStr.length() - 2) : genreStr; genre.setText(genreStr); // release year year.setText(String.valueOf(m.getYear())); return convertView; } }

?來自CODE的代碼片 CustomListAdapter.java

14.打開我們的MainActivity.java。添加如下代碼，我們使用JsonArrayRequest來發送請求，發送json請求我們在Android網絡框架-Volley(四) 使用get和post方法發送json請求?已經講過了。我們將解析來的Movie對象存儲在一個ArrayList中，調用notifyDataSetChanged()方法通知listview去更新我們的數據。

package info.androidhive.customlistviewvolley; import info.androidhive.customlistviewvolley.adater.CustomListAdapter;import info.androidhive.customlistviewvolley.app.AppController;import info.androidhive.customlistviewvolley.model.Movie; import java.util.ArrayList;import java.util.List; import org.json.JSONArray;import org.json.JSONException;import org.json.JSONObject; import android.app.Activity;import android.app.ProgressDialog;import android.graphics.Color;import android.graphics.drawable.ColorDrawable;import android.os.Bundle;import android.util.Log;import android.view.Menu;import android.widget.ListView; import com.android.volley.Response;import com.android.volley.VolleyError;import com.android.volley.VolleyLog;import com.android.volley.toolbox.JsonArrayRequest; public class MainActivity extends Activity { // 用來打Log日志的TAG private static final String TAG = MainActivity.class.getSimpleName(); // JSON地址 private static final String url = "http://api.androidhive.info/json/movies.json"; private ProgressDialog pDialog; //用來存儲Movie對象的list private List<Movie> movieList = new ArrayList<Movie>(); private ListView listView; private CustomListAdapter adapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); listView = (ListView) findViewById(R.id.list); adapter = new CustomListAdapter(this, movieList); listView.setAdapter(adapter); pDialog = new ProgressDialog(this); // 加載框 pDialog.setMessage("Loading..."); pDialog.show(); // 發送一個Json請求 JsonArrayRequest movieReq = new JsonArrayRequest(url, new Response.Listener<JSONArray>() { @Override public void onResponse(JSONArray response) { Log.d(TAG, response.toString()); hidePDialog(); // 解析json數據 for (int i = 0; i < response.length(); i++) { try { JSONObject obj = response.getJSONObject(i); Movie movie = new Movie(); movie.setTitle(obj.getString("title")); movie.setThumbnailUrl(obj.getString("image")); movie.setRating(((Number) obj.get("rating")) .doubleValue()); movie.setYear(obj.getInt("releaseYear")); // Genre是一個json數組 JSONArray genreArry = obj.getJSONArray("genre"); ArrayList<String> genre = new ArrayList<String>(); for (int j = 0; j < genreArry.length(); j++) { genre.add((String) genreArry.get(j)); } movie.setGenre(genre); // 將解析好的一個movie對象添加到list中 movieList.add(movie); } catch (JSONException e) { e.printStackTrace(); } } // 通知listview我們的數據已經改變，現在更新 adapter.notifyDataSetChanged(); } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { VolleyLog.d(TAG, "Error: " + error.getMessage()); hidePDialog(); } }); // 將request添加到requestQueue中 AppController.getInstance().addToRequestQueue(movieReq); } @Override public void onDestroy() { super.onDestroy(); hidePDialog(); } private void hidePDialog() { if (pDialog != null) { pDialog.dismiss(); pDialog = null; } } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } }

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