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1、界面布局
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="horizontal" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center"> <ImageView android:id="@+id/image" android:src="@mipmap/ic_launcher" android:layout_width="60dp" android:layout_height="60dp" /> <LinearLayout android:orientation="vertical" android:layout_marginLeft="10dp" android:layout_width="match_parent" android:layout_height="wrap_content"> <TextView android:id="@+id/title_tv" android:text="TITLE" android:textSize="15dp" android:maxLines="1" android:layout_width="match_parent" android:layout_height="wrap_content" /> <TextView android:id="@+id/content_tv" android:text="CONTENT" android:textSize="10dp" android:maxLines="3" android:layout_width="match_parent" android:layout_height="wrap_content" /> </LinearLayout> </LinearLayout><?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.example.leixiansheng.news.MainActivity"> <ListView android:id="@+id/list_view" android:layout_width="match_parent" android:layout_height="match_parent"> </ListView> </RelativeLayout>2、开启异步解析数据
package com.example.leixiansheng.news; public class NewsBean { public String viewUrl; public String title; public String content; } package com.example.leixiansheng.news; import android.os.AsyncTask; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.widget.ListView; import org.json.JSONArray; import org.json.JSONException; import org.json.JSONObject; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.UnsupportedEncodingException; import java.net.URL; import java.util.ArrayList; import java.util.List; public class MainActivity extends AppCompatActivity { private ListView listView; private static String URL = "http://www.imooc.com/api/teacher?type=4&num=30"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); listView = (ListView) findViewById(R.id.list_view); new NewsAsyncTask().execute(URL); } / public class NewsAdapter extends BaseAdapter implements AbsListView.OnScrollListener{ private List<NewsBean> newsBeanList; private LayoutInflater inflater; private ImageLoader imageLoader; //图片加载 private int start; //第一个元素 private int end; //最后一个元素 private boolean isFirstIn; //是否第一次进入 public static String[] URLS; //所有资源 public NewsAdapter(Context context, List<NewsBean> newsBeanList, ListView listView) { this.newsBeanList = newsBeanList; inflater = LayoutInflater.from(context); imageLoader = new ImageLoader(listView); URLS = new String[newsBeanList.size()]; for (int i = 0; i < newsBeanList.size(); i++) { URLS[i] = newsBeanList.get(i).viewUrl; } isFirstIn = true; listView.setOnScrollListener(this); } @Override public int getCount() { return newsBeanList.size(); } @Override public Object getItem(int i) { return newsBeanList.get(i); } @Override public long getItemId(int i) { return i; } @Override public View getView(int i, View view, ViewGroup viewGroup) { ViewHolder viewHolder = null; if (view == null) { viewHolder = new ViewHolder(); view = inflater.inflate(R.layout.item, null); viewHolder.imageView = (ImageView) view.findViewById(R.id.image); viewHolder.title = (TextView) view.findViewById(R.id.title_tv); viewHolder.content = (TextView) view.findViewById(R.id.content_tv); view.setTag(viewHolder); } else { viewHolder = (ViewHolder) view.getTag(); } String url = newsBeanList.get(i).viewUrl; viewHolder.imageView.setImageResource(R.mipmap.ic_launcher); / @Override public void onScroll(AbsListView absListView, int i, int i1, int i2) { start = i; end = i + i1; //第一次进入需要手动加载 if (isFirstIn && i1 > 0) { imageLoader.loadImages(start, end); isFirstIn = false; } } }package com.example.leixiansheng.news; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.AsyncTask; import android.os.Handler; import android.os.Message; import android.util.LruCache; import android.widget.ImageView; import android.widget.ListView; import java.io.BufferedInputStream; import java.io.IOException; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; import java.util.HashSet; import java.util.Set; public class ImageLoader { private ImageView mImageView; private String mUrl; //*&*创建缓存 private LruCache<String, Bitmap> lruCache; private ListView listview; private Set<NewsAsyncTask> mTask; public ImageLoader(ListView listview) { this.listview = listview; mTask = new HashSet<>(); //*&*获取最大内存 int maxMemory = (int) Runtime.getRuntime().maxMemory(); //设置缓存大小 int lruCacheSize = maxMemory / 4; lruCache = new LruCache<String, Bitmap>(lruCacheSize) { @Override protected int sizeOf(String key, Bitmap value) { //获取每个数据大小 return value.getByteCount(); } }; } //添加数据到缓存 public void addBitmapToLruCache(String url, Bitmap bitmap) { if (getBitmapFromLruCache(url) == null) { lruCache.put(url, bitmap); } } //从缓存中获取数据 public Bitmap getBitmapFromLruCache(String url) { return lruCache.get(url); } private Handler handler = new Handler() { @Override public void handleMessage(Message msg) { super.handleMessage(msg); if (mImageView.getTag().equals(mUrl)) { mImageView.setImageBitmap((Bitmap) msg.obj); } } }; public void showImageByThread(ImageView imageView, final String url) { mImageView = imageView; mUrl = url; new Thread() { @Override public void run() { super.run(); Bitmap bitmap = getBitmapFromURL(url); Message message = Message.obtain(); message.obj = bitmap; handler.sendMessage(message); } }.start(); } public Bitmap getBitmapFromURL(String urlString) { Bitmap bitmap; InputStream is = null; try { URL url = new URL(urlString); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); is = new BufferedInputStream(connection.getInputStream()); bitmap = BitmapFactory.decodeStream(is); connection.disconnect(); //模拟网速卡顿时 // try { // Thread.sleep(1000); // } catch (InterruptedException e) { // e.printStackTrace(); // } return bitmap; } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } return null; } public void showImageViewByAsyncTask(ImageView imageView, String url) { //判断是否已经缓存 Bitmap bitmap = getBitmapFromLruCache(url); //没有缓存则从新下载 if (bitmap == null) { imageView.setImageResource(R.mipmap.ic_launcher); } else { imageView.setImageBitmap(bitmap); } } //加载从start到end的所有图片 public void loadImages(int start, int end) { for (int i = start; i < end; i++) { String url = NewsAdapter.URLS[i]; //判断是否已经缓存 Bitmap bitmap = getBitmapFromLruCache(url); //没有缓存则从新下载 if (bitmap == null) { NewsAsyncTask task = new NewsAsyncTask(url); task.execute(url); mTask.add(task); } else { ImageView imageView = (ImageView) listview.findViewWithTag(url); imageView.setImageBitmap(bitmap); } } } public void cancelAllTasks() { if (mTask != null) { for (NewsAsyncTask task : mTask) { task.cancel(false); } } } private class NewsAsyncTask extends AsyncTask<String, Void, Bitmap> { // private ImageView imageView; private String url; public NewsAsyncTask(String url) { // this.imageView = imageView; this.url = url; } @Override protected Bitmap doInBackground(String... strings) { String url = strings[0]; //从网络获取图片 Bitmap bitmap = getBitmapFromURL(url); if (bitmap != null) { //将不在缓存中的图片加入到缓存 addBitmapToLruCache(url, bitmap); } return bitmap; } @Override protected void onPostExecute(Bitmap bitmap) { super.onPostExecute(bitmap); ImageView imageView = (ImageView) listview.findViewWithTag(url); if (imageView != null && bitmap != null) { imageView.setImageBitmap(bitmap); } mTask.remove(this); } } }4、注册声明权限
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.leixiansheng.news"> <uses-permission android:name="android.permission.INTERNET"/> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:supportsRtl="true" android:theme="@style/AppTheme"> <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>关于怎么Android应用中实现一个APP显示界面滑动优化就分享到这里了，希望以上内容可以对大家有一定的帮助，可以学到更多知识。如果觉得文章不错，可以把它分享出去让更多的人看到。
