Question

我是Android编程的新手，我可能只是错过了一个明显的错误，但我现在还没有看到它。

这一点实际上非常简单。我有一个工作的HttpGet方法，只是为了尝试我将其改为HttpPost方法。但它没有成功。

有趣的部分是＆＃34; lastTweet＆＃34;方法。我只是评论了Post-Request，但就像我说的，如果我从应用程序更改为帖子，应用程序崩溃。

如果有人能解释我做错了什么，我真的很感激。谢谢。

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
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 org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends Activity {

TextView Text;
HttpClient client;
JSONObject json;

final static String URL = "http://www.openligadb.de/api/getmatchdata/bl1/2014/15";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Text = (TextView)findViewById(R.id.myTextView);
    client = new DefaultHttpClient();
    new Read().execute("MatchID");
}

public JSONObject lastTweet(String username) throws ClientProtocolException, IOException, JSONException {
    HttpGet get = new HttpGet(URL);
    //HttpPost post = new HttpPost(URL);

    /*
    List<NameValuePair> pairs = new ArrayList<NameValuePair>();
    pairs.add(new BasicNameValuePair("key1", "value1"));
    pairs.add(new BasicNameValuePair("key2", "value2"));
    post.setEntity(new UrlEncodedFormEntity(pairs));
    */

    HttpResponse r = client.execute(get);
    //HttpResponse r = client.execute(post);
    int status = r.getStatusLine().getStatusCode();

    if (status == 200) {
        HttpEntity e = r.getEntity();
        String data = EntityUtils.toString(e);
        JSONArray timeline = new JSONArray(data);
        JSONObject last = timeline.getJSONObject(0);
        return last;
    }
    else {
        Toast.makeText(MainActivity.this, "error", Toast.LENGTH_LONG).show();
        return null;
    }
}

public class Read extends AsyncTask<String, Integer, String>{

    @Override
    protected String doInBackground(String... params) {
        try {
            json = lastTweet("wurst");
            return json.getString(params[0]);
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }

    @Override
    protected void onPostExecute(String s) {
        Text.setText(s);
    }
}

}

感谢您的快速回复。正如greenapps对Logcat的要求：

    Local Branch:
    Remote Branch:
    Local Patches:
    Reconstruct Branch:
04-29 16:55:02.764    2642-2642/com.example.itsme.jsonnb2 D/OpenGLRenderer﹕ Enabling debug mode 0
04-29 16:55:04.116    2642-2855/com.example.itsme.jsonnb2 W/dalvikvm﹕ threadid=11: thread exiting with uncaught exception (group=0x418a1da0)
04-29 16:55:04.146    2642-2855/com.example.itsme.jsonnb2 E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
    Process: com.example.itsme.jsonnb2, PID: 2642
    java.lang.RuntimeException: An error occured while executing doInBackground()
            at android.os.AsyncTask$3.done(AsyncTask.java:300)
            at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
            at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
            at java.util.concurrent.FutureTask.run(FutureTask.java:242)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
            at java.lang.Thread.run(Thread.java:841)
     Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
            at android.os.Handler.<init>(Handler.java:200)
            at android.os.Handler.<init>(Handler.java:114)
            at android.widget.Toast$TN.<init>(Toast.java:384)
            at android.widget.Toast.<init>(Toast.java:113)
            at android.widget.Toast.makeText(Toast.java:272)
            at com.example.itsme.jsonnb2.MainActivity.lastTweet(MainActivity.java:68)
            at com.example.itsme.jsonnb2.MainActivity$Read.doInBackground(MainActivity.java:78)
            at com.example.itsme.jsonnb2.MainActivity$Read.doInBackground(MainActivity.java:73)
            at android.os.AsyncTask$2.call(AsyncTask.java:288)
            at java.util.concurrent.FutureTask.run(FutureTask.java:237)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
            at java.lang.Thread.run(Thread.java:841)

Answer 1

在doInBackGround中，您无法使用Toast（）。你在lastTweet（）中使用Toast（），因此在doInBackGround中使用。将Toast bij替换为Log.d（）。您还可以在AsyncTask的私有String中留言，并在.. Toast（）中的onPostExecute中显示该字符串。研究logcat，你会看到。

      json = lastTweet("wurst");
      return json.getString(params[0]);

因为lastTweet（）可以返回null，因此json == null以下语句json.getString（params [0]）;将导致NullPointerException。所以当json == null时不要执行该语句。

更改为

     json = lastTweet("wurst");
      if ( json == null )
         return null;
      return json.getString(params[0]);

在onPostExcute参数中，s可以为null。因此，检查该参数是否为null，并显示一个toast，如果为null，则显示为。

使用HttpGet的Android HttpPost失败

1 个答案: