Question

您好，因为我在从mysql获取数据时在活动类中使用了Asynctask。但它显示错误仍然可以看到并帮助我做错了什么？我已检查连接问题他们没问题，但我认为代码中的错误。我没有使用Android开发的经验，请帮助!!

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;

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.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONObject;

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class Day extends Activity {

    String dt="";
    String mc="";
    String bc="";
    ImageView dateimg;
    String name;
    String date;
    String targetmonth;
    InputStream is=null;
    String result=null;
    String line=null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.day_lay);
        getCurrDate();
        new LongOperation().execute();
        dateimg = (ImageView) findViewById(R.id.img);



        dateimg.setOnClickListener(new OnClickListener()
        {
                public void onClick(View v)
                 {  
                    //getCurrDate();

                    }

        });



    }


    public String getCurrDate()
    {

        Date cal = Calendar.getInstance().getTime();
        dt = cal.toLocaleString();

        mc = dt.substring(0, dt.length() - 17);
        bc=mc.substring(4);
        System.out.println("Date is"+bc);
        date=bc;
        return dt;

    }
    private class LongOperation extends AsyncTask<Void, Void, Void> {

        private ProgressDialog progressDialog;


        protected void onPreExecute() {
            this.progressDialog = ProgressDialog.show(Day.this, ""," Can you just see your roof...");  
            }

        @Override
        protected void onPostExecute(Void result) {
            TextView txt = (TextView) findViewById(R.id.status_id);
            txt.setText("Executed"); // txt.setText(result);
            // might want to change "executed" for the returned string passed
            // into onPostExecute() but that is upto you
        }


        @Override
        protected Void doInBackground(Void... arg0) {
            // TODO Auto-generated method stub

            ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();

            nameValuePairs.add(new BasicNameValuePair("date",date));

                try
                {
                HttpClient httpclient = new DefaultHttpClient();
                    HttpPost httppost = new HttpPost("http://10.0.1.2/wp-content/themes/app/day.php");
                    httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
                    HttpResponse response = httpclient.execute(httppost); 
                    HttpEntity entity = response.getEntity();
                    is = entity.getContent();
                    Log.e("pass 1", "connection success ");
            }
                catch(Exception e)
            {
                    Log.e("Fail 1", e.toString());
                    Toast.makeText(getApplicationContext(), "Invalid IP Address",
                    Toast.LENGTH_LONG).show();
            }     

                try
                {
                    BufferedReader reader = new BufferedReader
                        (new InputStreamReader(is,"iso-8859-1"),8);
                        StringBuilder sb = new StringBuilder();
                        while ((line = reader.readLine()) != null)
                {
                        sb.append(line + "\n");
                    }
                        is.close();
                        result = sb.toString();
                    Log.e("pass 2", "connection success ");
                    System.out.println("Mainu pata hai"+result);
            }
                catch(Exception e)
                {
                Log.e("Fail 2", e.toString());
            }     

            try
                {
                    JSONObject json_data = new JSONObject(result);
                    targetmonth=(json_data.getString("targetmonth"));
                Toast.makeText(getBaseContext(), "Name : "+targetmonth,
                    Toast.LENGTH_SHORT).show();
                //System.out.println("Mainu pata hai"+name);
                }
                catch(Exception e)
                {
                    Log.e("Fail 3", e.toString());
                }

            return null;
        }




    }

}

//数据库选择

<?php
    $host='127.0.0.1';
    $uname='root';
    $pwd='password';
    $db="android";

    $con = mysql_connect($host,$uname,$pwd) or die("connection failed");
    mysql_select_db($db,$con) or die("db selection failed");

    $date=$_REQUEST['date'];

    $r=mysql_query("select mat from vicks where date='$date'",$con);

    while($row=mysql_fetch_array($r))
    {
        $flag[name]=$row[name];
    }

    print(json_encode($flag));
    mysql_close($con);
?>

// logcat的

05-24 20:41:48.173: I/System.out(691): Date is24
05-24 20:42:01.749: E/pass 1(691): connection success 
05-24 20:42:01.969: E/pass 2(691): connection success 
05-24 20:42:01.969: I/System.out(691): Mainu pata hai{"name":"ollow the rhythm of your heart and you'll find out where your going"}
05-24 20:42:02.438: E/Fail 3(691): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
05-24 20:42:02.438: D/AndroidRuntime(691): Shutting down VM
05-24 20:42:02.438: W/dalvikvm(691): threadid=1: thread exiting with uncaught exception (group=0x409961f8)
05-24 20:42:02.498: E/AndroidRuntime(691): FATAL EXCEPTION: main
05-24 20:42:02.498: E/AndroidRuntime(691): java.lang.NullPointerException
05-24 20:42:02.498: E/AndroidRuntime(691):  at com.status.what.Day$LongOperation.onPostExecute(Day.java:93)
05-24 20:42:02.498: E/AndroidRuntime(691):  at com.status.what.Day$LongOperation.onPostExecute(Day.java:1)
05-24 20:42:02.498: E/AndroidRuntime(691):  at android.os.AsyncTask.finish(AsyncTask.java:602)
05-24 20:42:02.498: E/AndroidRuntime(691):  at android.os.AsyncTask.access$600(AsyncTask.java:156)
05-24 20:42:02.498: E/AndroidRuntime(691):  at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:615)
05-24 20:42:02.498: E/AndroidRuntime(691):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-24 20:42:02.498: E/AndroidRuntime(691):  at android.os.Looper.loop(Looper.java:137)
05-24 20:42:02.498: E/AndroidRuntime(691):  at android.app.ActivityThread.main(ActivityThread.java:4340)
05-24 20:42:02.498: E/AndroidRuntime(691):  at java.lang.reflect.Method.invokeNative(Native Method)
05-24 20:42:02.498: E/AndroidRuntime(691):  at java.lang.reflect.Method.invoke(Method.java:511)
05-24 20:42:02.498: E/AndroidRuntime(691):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
05-24 20:42:02.498: E/AndroidRuntime(691):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
05-24 20:42:02.498: E/AndroidRuntime(691):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

你想在Android代码中得到targetmonth，这不在你的JSON文件中请检查此行

  targetmonth=(json_data.getString("targetmonth"));

Answer 2

targetMonth的Jsonfield为null，您在

的代码中使用此null值

Toast.makeText(getBaseContext(), "Name : "+targetmonth,
                Toast.LENGTH_SHORT).show();

Answer 3

正如我已经看到您的网络服务代码。你没有在你的json中传递“targetmonth”作为键。你在php端的json中创建了“name”键。所以在android端而不是访问targetmonth访问“名称”

要获得准确答案，请提供您从网络服务

获得的json值

从mysql获取数据时Asynctask出错

3 个答案: