AsyncTask onPostExecute 未执行问题

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在android4.0以下设备上onPostExecute不执行，doInBackground也无抛出异常。

在android4.2以上设备上onPostExecute是执行的，没问题。

那么问题就来了，一路查寻，牵扯出好多问题。

以下是我个人遇到的情况，新建个测试AsyncTask项目没有问题，但是在原项目下问题就来了。

AndroidManifest.xml里加入了android:launchMode="singleTask"

得在UI线程里调用execute；在onCreate中调用，onPostExecute是不执行的。

android-support-v4.jar低版本下，在FragmentActivity下调用，onPostExecute是不执行的。

关键在MAINActivity onCreate中添加

try {

Class.forName("android.os.AsyncTask");

} catch (ClassNotFoundException e) {

e.printStackTrace();

}

以下是案例，有关HTTP请求，需要加入gson.jar

package com.example.asynctasktest;import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.view.View.OnClickListener;public class MainActivity extends Activity {private Button button;  private ProgressBar progressBar;  private TextView textView;  @Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);button = (Button)findViewById(R.id.button03);  progressBar = (ProgressBar)findViewById(R.id.progressBar02);  textView = (TextView)findViewById(R.id.textView01);  button.setOnClickListener(new OnClickListener() {  @Override  public void onClick(View v) {  startGetArea();}  });  ProgressBarAsyncTask asyncTask = new ProgressBarAsyncTask(textView, progressBar);  asyncTask.execute("http://www.xxx.com/getAreaList.htm");}public void startGetArea(){Message msg = mhandler.obtainMessage();msg.what = 1;mhandler.sendMessage(msg);}/*** handler处理消息机制*/protected Handler mhandler = new Handler() {public void handleMessage(Message message) {switch (message.what) {case 1:new ProgressBarAsyncTask(textView, progressBar).execute("http://www.xxx.com/getAreaList.htm");break;}}};@Overridepublic 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;}}

package com.example.asynctasktest;import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;import org.apache.http.HttpEntity;
import org.apache.http.util.EntityUtils;import android.os.AsyncTask;  
import android.util.Log;
import android.widget.ProgressBar;  
import android.widget.TextView;import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;/**  * 生成该类的对象，并调用execute方法之后  * 首先执行的是onProExecute方法  * 其次执行doInBackgroup方法  *  */  
public class ProgressBarAsyncTask extends AsyncTask<String, Integer, List<AllArea>> {  private TextView textView;  private ProgressBar progressBar;  private static Gson gson = new GsonBuilder().setVersion(1).create();List<String> listnames = new ArrayList<String>();List<String> listid = new ArrayList<String>();public ProgressBarAsyncTask(TextView textView, ProgressBar progressBar) {  super();  this.textView = textView;  this.progressBar = progressBar;  }  /**  * 这里的String参数对应AsyncTask中的第一个参数   * 这里的List<AllArea>返回值对应AsyncTask的第三个参数  * 该方法并不运行在UI线程当中，主要用于异步操作，所有在该方法中不能对UI当中的空间进行设置和修改  * 但是可以调用publishProgress方法触发onProgressUpdate对UI进行操作  */@Overrideprotected List<AllArea> doInBackground(String... params) {// TODO Auto-generated method stubList<AllArea> areaList = null;HttpEntity entity;try {entity = HttpUtil.send(HttpUtil.METHOD_GET, params[0], null);String json=EntityUtils.toString(entity);Type type = new TypeToken<List<AllArea>>() {}.getType();areaList = gson.fromJson(json, type);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}return areaList;}/**  * 这里的String参数对应AsyncTask中的第三个参数（也就是接收doInBackground的返回值）  * 在doInBackground方法执行结束之后在运行，并且运行在UI线程当中 可以对UI空间进行设置  */  @Overrideprotected void onPostExecute(List<AllArea> result) {// TODO Auto-generated method stubsuper.onPostExecute(result);textView.setText("异步操作执行结束" + result);if(result == null){Log.e("", "result == null");}else{Log.e("", "result != null"+result.size());for(int i = 0;i<result.size();i++){listnames.add(result.get(i).getIndustryName());listid.add(result.get(i).getId()+"");}}}/*** 该方法运行在UI线程当中,并且运行在UI线程当中 可以对UI空间进行设置 */@Override  protected void onPreExecute() {  textView.setText("开始执行异步线程");  }  /**  * 这里的Intege参数对应AsyncTask中的第二个参数  * 在doInBackground方法当中，，每次调用publishProgress方法都会触发onProgressUpdate执行  * onProgressUpdate是在UI线程中执行，所有可以对UI空间进行操作  */  @Override  protected void onProgressUpdate(Integer... values) {  int vlaue = values[0];  progressBar.setProgress(vlaue);  } 
}  

package com.example.asynctasktest;import java.util.ArrayList;import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;import android.util.Log;/***	HTTP请求方式类* @author Administrator**/
public class HttpUtil {public static final int METHOD_GET=0;public static final int METHOD_POST=1;/*** * @param method GET请求* @param url 请求路径* @param pairs 提交参数* @return* @throws Exception*/public static HttpEntity send(int method,String url,ArrayList<NameValuePair> pairs)throws Exception{HttpClient client=new DefaultHttpClient();HttpResponse resp=null;switch(method){case METHOD_GET:Log.i("send", url);HttpGet get=new HttpGet(url);resp=client.execute(get);Log.i("send", resp.toString());break;case METHOD_POST:HttpPost post=new HttpPost(url);HttpEntity entity=new UrlEncodedFormEntity(pairs,"utf-8");post.setEntity(entity);post.setHeader("Content-Type", "x-www-form-urlencoded");resp=client.execute(post);break;}return resp.getEntity();}
}

package com.example.asynctasktest;import java.io.Serializable;public class AllArea implements Serializable{/*** */private static final long serialVersionUID = -8325422695071123262L;private int id;private int type;private int parentId;private String areaName;private String areaNo;public int getId() {return id;}public void setId(int id) {this.id = id;}public int getType() {return type;}public void setType(int type) {this.type = type;}public int getParentId() {return parentId;}public void setParentId(int parentId) {this.parentId = parentId;}public String getIndustryName() {return areaName;}public void setIndustryName(String industryName) {this.areaName = industryName;}public String getIndustryDesc() {return areaNo;}public void setIndustryDesc(String industryDesc) {this.areaNo = industryDesc;}}

[{"state":1,"type":1,"seq":1,"parentId":1,"areaNo":"3601","areaName”:”东城区”,”id”:11},{“state":1,"type":1,"seq":2,"parentId":1,"areaNo":"3602","areaName”:”西城区”,”id”:22},{“state":1,"type":1,"seq":3,"parentId":1,"areaNo":"3603","areaName”:”海淀区”,”id”:33},{“state":1,"type":1,"seq":4,"parentId":1,"areaNo":"3604","areaName”:”朝阳区”,”id”:44},{“state":1,"type":1,"seq":5,"parentId":1,"areaNo":"3605","areaName”:”昌平区”,”id”:55},{“state":1,"type":1,"seq":6,"parentId":1,"areaNo":"3606","areaName”:”丰台区”,”id”:66}]

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