android异步请求服务器数据示例这篇文章主要介绍了android异步请求服务器数据示例,需要的朋友可以参考下
1、在android4.0以后的版本,主线程(UI线程)不在支持网络请求,原因大概是影响主线程,速度太慢,容易卡机,所以需要开启新的线程请求数据; 复制代码 代码如下: thread1 = new Thread(){ @Override public void run() { try { URL url = new URL(WebUrlManager.CARSEVER_GetCarsServlet); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); BufferedInputStream bis = new BufferedInputStream(conn.getInputStream()); //缓冲读取 byte[] data = new byte[1024]; int len = 0; String bufferString = ""; while((len = bis.read(data)) != -1){ bufferString+=new String(data, 0, len); } carList = new JSONArray(bufferString.trim()); //System.out.println(carList); /* for(int i=0;i 2、新线程完成后一启动,发现报错,空指针 nullpointerexception,要等待线程完毕后才能得到数据,下面是两种解决方法: 1)要么判断线程是否还活着; 2)要么在线程中设置一flag,结束后,更改其状态 复制代码 代码如下: /* //等待线程thread1执行完毕 while(true){ if(thread1.isAlive()){ try { Thread.sleep(500); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } }else{ break; } } */ //当线程还没结束,就睡500毫秒ms while(!flag){ try { Thread.sleep(500); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }}} 3、处理返回的json数据 复制代码 代码如下: URL url = new URL(WebUrlManager.CARSEVER_GetCarsServlet); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); BufferedInputStream bis = new BufferedInputStream(conn.getInputStream()); 2)解析Json数据 复制代码 代码如下: JSONObject car = (JSONObject) getItem(position); try { //this.pic.setImageBitmap(carImageArray.get(position)); this.title.setText(car.getString("title")); this.describe.setText(car.getString("describe")); this.updateTime.setText(car.getString("updateTime")); this.price.setText(String.format("%.1f", car.getDouble("price"))+"万"); this.pic.setTag(WebUrlManager.CARSERVER_CAR_IMAGE+car.getString("image")); new AsyncViewTask().execute(this.pic); } catch (JSONException e1) { e1.printStackTrace(); } 4、图片加载通常很慢,最好异步请求 复制代码 代码如下: import java.io.InputStream; import java.lang.ref.SoftReference; import java.net.HttpURLConnection; import java.net.URL; import java.util.HashMap; import android.graphics.drawable.Drawable; import android.os.AsyncTask; import android.util.Log; import android.view.View; import android.webkit.URLUtil; import android.widget.ImageView; public class AsyncViewTask extends AsyncTask { private View mView; private HashMap> imageCache; public AsyncViewTask() { |
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