Android HttpPost 与工作 HttpGet 失败

Question

我是 android 编程新手，我可能只是错过了一个明显的错误，但我现在看不到它。

重点其实很简单。我有一个有效的 HttpGet 方法，只是为了尝试我将它更改为 HttpPost 方法。但没有成功。

有趣的部分是“lastTweet”方法。我刚刚评论了 Post-Request，但就像我说的，如果我从 get 更改为 post，应用程序就会崩溃。

因此，如果有人能解释我做错了什么，我将不胜感激。 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。 根据 greenapps 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 中不能使用 Toast()。您在 lastTweet() 中使用 Toast()，因此在 doInBackGround 中。将 Toast bij 替换为 Log.d()。您还可以在 AsyncTask 的私有字符串中留下消息，并在 .. Toast() 中的 onPostExecute 中显示该字符串。研究一下logcat，你就会明白。

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

由于 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。

改成

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

在onPostExcute 参数s 可以为null。因此，请检查该参数是否为 null，并在为 null 时显示一个 toast。