AsyncTask onPostExecute 未执行问题
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;
@Override
protected 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;
}
}
};
@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;
}
}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> {
private TextView textView;
private ProgressBar progressBar;
private static Gson gson = new GsonBuilder().setVersion(1).create();
List listnames = new ArrayList();
List listid = new ArrayList();
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
*/
@Override
protected List doInBackground(String... params) {
// TODO Auto-generated method stub
List areaList = null;
HttpEntity entity;
try {
entity = HttpUtil.send(HttpUtil.METHOD_GET, params[0], null);
String json=EntityUtils.toString(entity);
Type type = new TypeToken>() {}.getType();
areaList = gson.fromJson(json, type);
} catch (Exception e) {
// TODO Auto-generated catch block
e.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
*/
@Override
protected void onPostExecute(List result) {
// TODO Auto-generated method stub
super.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 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 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}]