当你在工作线程中，你不能直接操作Android上的UI元素。

当你使用AsyncTask时，请理解回调方法。

例如:

public class MyAyncTask extends AsyncTask<Void, Void, Void>{

    @Override
    protected void onPreExecute() {
        // Here you can show progress bar or something on the similar lines.
        // Since you are in a UI thread here.
        super.onPreExecute();
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);
        // After completing execution of given task, control will return here.
        // Hence if you want to populate UI elements with fetched data, do it here.
    }

    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
        // You can track you progress update here
    }

    @Override
    protected Void doInBackground(Void... params) {
        // Here you are in the worker thread and you are not allowed to access UI thread from here.
        // Here you can perform network operations or any heavy operations you want.
        return null;
    }
}

仅供参考: 要从工作线程访问UI线程，您可以在视图上使用runOnUiThread()方法或post方法。

例如:

runOnUiThread(new Runnable() {
    textView.setText("something.");
});

or
    yourview.post(new Runnable() {
    yourview.setText("something");
});

这将帮助你更好地了解事情。因此在你的情况下，你需要在onPostExecute()方法中设置你的textview。

当一个异步任务执行时，该任务经过四个步骤:

onPreExecute () doInBackground (Params…) onProgressUpdate(进步…) onPostExecute(结果)

下面是一个演示示例:

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {

    protected Long doInBackground(URL... urls) {
        int count = urls.length;
        long totalSize = 0;
        for (int i = 0; i < count; i++) {
            totalSize += Downloader.downloadFile(urls[i]);
            publishProgress((int) ((i / (float) count) * 100));

            // Escape early if cancel() is called
            if (isCancelled())
                break;
        }
        return totalSize;
    }

    protected void onProgressUpdate(Integer... progress) {
        setProgressPercent(progress[0]);
    }

    protected void onPostExecute(Long result) {
        showDialog("Downloaded " + result + " bytes");
    }
 }

一旦你创建了一个任务，执行起来非常简单:

new DownloadFilesTask().execute(url1, url2, url3);

带进度的AsyncTask示例示例

import android.animation.ObjectAnimator;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.DecelerateInterpolator;
import android.view.animation.LinearInterpolator;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;

public class AsyncTaskActivity extends AppCompatActivity implements View.OnClickListener {

    Button btn;
    ProgressBar progressBar;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn = (Button) findViewById(R.id.button1);
        btn.setOnClickListener(this);
        progressBar = (ProgressBar)findViewById(R.id.pbar);
    }

    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.button1:
                new LongOperation().execute("");
                break;
        }
    }

    private class LongOperation extends AsyncTask<String, Integer, String> {

        @Override
        protected String doInBackground(String... params) {
            Log.d("AsyncTask", "doInBackground");
            for (int i = 0; i < 5; i++) {
                try {
                    Log.d("AsyncTask", "task "+(i + 1));
                    publishProgress(i + 1);
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    Thread.interrupted();
                }
            }
            return "Completed";
        }

        @Override
        protected void onPostExecute(String result) {
            Log.d("AsyncTask", "onPostExecute");
            TextView txt = (TextView) findViewById(R.id.output);
            txt.setText(result);
            progressBar.setProgress(0);
        }

        @Override
        protected void onPreExecute() {
            Log.d("AsyncTask", "onPreExecute");
            TextView txt = (TextView) findViewById(R.id.output);
            txt.setText("onPreExecute");
            progressBar.setMax(500);
            progressBar.setProgress(0);
        }

        @Override
        protected void onProgressUpdate(Integer... values) {
            Log.d("AsyncTask", "onProgressUpdate "+values[0]);
            TextView txt = (TextView) findViewById(R.id.output);
            txt.setText("onProgressUpdate "+values[0]);

            ObjectAnimator animation = ObjectAnimator.ofInt(progressBar, "progress", 100 * values[0]);
            animation.setDuration(1000);
            animation.setInterpolator(new LinearInterpolator());
            animation.start();
        }
    }
}

更改代码如下所示:

@Override
protected void onPostExecute(String result) {

    runOnUiThread(new Runnable() {
        public void run() {
            TextView txt = (TextView) findViewById(R.id.output);
            txt.setText("Executed");
        }
    });
}

这里的概念和代码

我已经创建了一个简单的例子使用AsyncTask的Android。它从onPreExecute()， doInBackground()， publishProgress()开始，最后是onProgressUpdate()。

在这种情况下，doInBackground()作为后台线程工作，而其他线程在UI线程中工作。你不能访问doInBackground()中的UI元素。顺序和我之前提到的一样。

然而，如果你需要从doInBackground更新任何小部件，你可以从doInBackground发布进度，它会调用onProgressUpdate来更新你的UI小部件。

class TestAsync extends AsyncTask<Void, Integer, String> {
    String TAG = getClass().getSimpleName();

    protected void onPreExecute() {
        super.onPreExecute();
        Log.d(TAG + " PreExceute","On pre Exceute......");
    }

    protected String doInBackground(Void...arg0) {
        Log.d(TAG + " DoINBackGround", "On doInBackground...");

        for (int i=0; i<10; i++){
            Integer in = new Integer(i);
            publishProgress(i);
        }
        return "You are at PostExecute";
    }

    protected void onProgressUpdate(Integer...a) {
        super.onProgressUpdate(a);
        Log.d(TAG + " onProgressUpdate", "You are in progress update ... " + a[0]);
    }

    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        Log.d(TAG + " onPostExecute", "" + result);
    }
}

在你的活动中这样称呼它:

new TestAsync().execute();

开发人员参考资料

异步任务POST请求示例:

List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("key1", "value1"));
params.add(new BasicNameValuePair("key1", "value2"));
new WEBSERVICEREQUESTOR(URL, params).execute();

class WEBSERVICEREQUESTOR extends AsyncTask<String, Integer, String>
{
    String URL;
    List<NameValuePair> parameters;

    private ProgressDialog pDialog;

    public WEBSERVICEREQUESTOR(String url, List<NameValuePair> params)
    {
        this.URL = url;
        this.parameters = params;
    }

    @Override
    protected void onPreExecute()
    {
        pDialog = new ProgressDialog(LoginActivity.this);
        pDialog.setMessage("Processing Request...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params)
    {
        try
        {
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpEntity httpEntity = null;
            HttpResponse httpResponse = null;

            HttpPost httpPost = new HttpPost(URL);

            if (parameters != null)
            {
                httpPost.setEntity(new UrlEncodedFormEntity(parameters));
            }
            httpResponse = httpClient.execute(httpPost);

            httpEntity = httpResponse.getEntity();
            return EntityUtils.toString(httpEntity);

        }  catch (Exception e)
        {

        }
        return "";
    }

    @Override
    protected void onPostExecute(String result)
    {
        pDialog.dismiss();

        try
        {

        }
        catch (Exception e)
        {

        }
        super.onPostExecute(result);
    }
}