Question

对Android新手可以任何人建议我，哪里做错了？整个ManiActiviy.java

错误是'必须从UI线程调用方法getText，当前推断的线程是worker'

在这3行中，它给出了上述错误。

person = new Person();
person.setName(etName.getText().toString());
person.setCountry(etCountry.getText().toString());
person.setTwitter(etTwitter.getText().toString());

班级代码

import android.app.Activity;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.appindexing.Thing;
import com.google.android.gms.common.api.GoogleApiClient;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class MainActivity extends Activity implements OnClickListener {

    TextView tvIsConnected;
    EditText etName, etCountry, etTwitter;
    Button btnPost;

    Person person;
    /**
     * ATTENTION: This was auto-generated to implement the App Indexing API.
     * See https://g.co/AppIndexing/AndroidStudio for more information.
     */
    private GoogleApiClient client;

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

        // get reference to the views
        tvIsConnected = (TextView) findViewById(R.id.tvIsConnected);
        etName = (EditText) findViewById(R.id.etName);
        etCountry = (EditText) findViewById(R.id.etCountry);
        etTwitter = (EditText) findViewById(R.id.etTwitter);
        btnPost = (Button) findViewById(R.id.btnPost);

        // check if you are connected or not
        if (isConnected()) {
            tvIsConnected.setBackgroundColor(0xFF00CC00);
            tvIsConnected.setText("You are conncted");
        } else {
            tvIsConnected.setText("You are NOT conncted");
        }

        // add click listener to Button "POST"
        btnPost.setOnClickListener(this);

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
    }

    public static String POST(String url, Person person) {
        InputStream inputStream = null;
        String result = "";
        try {

            // 1. create HttpClient
            HttpClient httpclient = new DefaultHttpClient();

            // 2. make POST request to the given URL
            HttpPost httpPost = new HttpPost(url);

            String json = "";

            // 3. build jsonObject
            JSONObject jsonObject = new JSONObject();
            jsonObject.accumulate("name", person.getName());
            jsonObject.accumulate("country", person.getCountry());
            jsonObject.accumulate("twitter", person.getTwitter());

            // 4. convert JSONObject to JSON to String
            json = jsonObject.toString();

            // ** Alternative way to convert Person object to JSON string usin Jackson Lib
            // ObjectMapper mapper = new ObjectMapper();
            // json = mapper.writeValueAsString(person);

            // 5. set json to StringEntity
            StringEntity se = new StringEntity(json);

            // 6. set httpPost Entity
            httpPost.setEntity(se);

            // 7. Set some headers to inform server about the type of the content
            httpPost.setHeader("Accept", "application/json");
            httpPost.setHeader("Content-type", "application/json");

            // 8. Execute POST request to the given URL
            HttpResponse httpResponse = httpclient.execute(httpPost);

            // 9. receive response as inputStream
            inputStream = httpResponse.getEntity().getContent();

            // 10. convert inputstream to string
            if (inputStream != null)
                result = convertInputStreamToString(inputStream);
            else
                result = "Did not work!";

        } catch (Exception e) {
            Log.d("InputStream", e.getLocalizedMessage());
        }

        // 11. return result
        return result;
    }

    public boolean isConnected() {
        ConnectivityManager connMgr = (ConnectivityManager) getSystemService(Activity.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
        if (networkInfo != null && networkInfo.isConnected())
            return true;
        else
            return false;
    }

    @Override
    public void onClick(View view) {

        switch (view.getId()) {
            case R.id.btnPost:
                if (!validate())
                    Toast.makeText(getBaseContext(), "Enter some data!", Toast.LENGTH_LONG).show();
                // call AsynTask to perform network operation on separate thread
                new HttpAsyncTask().execute("http://hmkcode.appspot.com/jsonservlet");
                break;
        }

    }

    /**
     * ATTENTION: This was auto-generated to implement the App Indexing API.
     * See https://g.co/AppIndexing/AndroidStudio for more information.
     */
    public Action getIndexApiAction() {
        Thing object = new Thing.Builder()
                .setName("Main Page") // TODO: Define a title for the content shown.
                // TODO: Make sure this auto-generated URL is correct.
                .setUrl(Uri.parse("http:// http://192.168.0.51:1337/sensormessage/pushSensorData?MAC=18:fe:34:a5:df:8c&OC=0&ALS=3 &POW=100"))
                .build();
        return new Action.Builder(Action.TYPE_VIEW)
                .setObject(object)
                .setActionStatus(Action.STATUS_TYPE_COMPLETED)
                .build();
    }

    @Override
    public void onStart() {
        super.onStart();

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        client.connect();
        AppIndex.AppIndexApi.start(client, getIndexApiAction());
    }

    @Override
    public void onStop() {
        super.onStop();

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        AppIndex.AppIndexApi.end(client, getIndexApiAction());
        client.disconnect();
    }

    private class HttpAsyncTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... urls) {

            person = new Person();
            person.setName(etName.getText().toString());
            person.setCountry(etCountry.getText().toString());
            person.setTwitter(etTwitter.getText().toString());
            return POST(urls[0], person);

        }

        // onPostExecute displays the results of the AsyncTask.
        @Override
        protected void onPostExecute(String result) {
            Toast.makeText(getBaseContext(), "Data Sent!", Toast.LENGTH_LONG).show();
        }
    }

    private boolean validate() {
        if (etName.getText().toString().trim().equals(""))
            return false;
        else if (etCountry.getText().toString().trim().equals(""))
            return false;
        else if (etTwitter.getText().toString().trim().equals(""))
            return false;
        else
            return true;
    }

    private static String convertInputStreamToString(InputStream inputStream) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        String line = "";
        String result = "";
        while ((line = bufferedReader.readLine()) != null)
            result += line;

        inputStream.close();
        return result;

    }
}

And Person.java

package android.hmkcode.com.android_post_json;

/**
 * Created by HP on 2/2/2017.
 */

public class Person {

    private String name;
    private String country;
    private String twitter;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    public String getTwitter() {
        return twitter;
    }

    public void setTwitter(String twitter) {
        this.twitter = twitter;
    }
}

Answer 1

尝试将EditText变量与类HttpAsyncTask构造函数一起传递为：

private class HttpAsyncTask extends AsyncTask<String, Void, String> {
    EditText etName;
    EditText etCountry;
    EditText etTwitter;
    Context context;

    //Constructor to get the values
    public HttpAsyncTask(EditText etName, EditText etCountry, EditText etTwitter, Context context){
       this.etName = etName;
       this.etCountry = etCountry;
       this.etTwitter = etTwitter;
       this.context = context;
    }

    @Override
    protected String doInBackground(String... urls) {

        person = new Person();
        person.setName(etName.getText().toString());
        person.setCountry(etCountry.getText().toString());
        person.setTwitter(etTwitter.getText().toString());
        return POST(urls[0], person);

    }

    // onPostExecute displays the results of the AsyncTask.
    @Override
    protected void onPostExecute(String result) {
        Toast.makeText(context, "Data Sent!", Toast.LENGTH_LONG).show();
    }
}

并将editext变量传递给：

new HttpAsyncTask(etName, etCountry, etTwitter, MainActivity.this).execute("http://hmkcode.appspot.com/jsonservlet");

Answer 2

您无法访问后台线程（工作线程）中的视图

您可以像这样修改您的代码

private class HttpAsyncTask extends AsyncTask<String, Void, String> {

        @Override
        protected String doInBackground(String... urls) {

            person = new Person();
            person.setName(urls[1]); //name
            person.setCountry(urls[2]); //country
            person.setTwitter(urls[3]); // twitter
            return POST(urls[0], person);

        }

        // onPostExecute displays the results of the AsyncTask.
        @Override
        protected void onPostExecute(String result) {
            Toast.makeText(getBaseContext(), "Data Sent!", Toast.LENGTH_LONG).show();
        }
    }

并像这样打电话

new HttpAsyncTask().execute("http://hmkcode.appspot.com/jsonservlet",etName.getText().toString(),etCountry.getText().toString(),etTwitter.getText().toString());

Answer 3

除非使用Looper，否则无法访问工作线程中的UI组件（因为doInBackground创建工作线程）。
解决方案1： 在 onPreExecute（）方法中，您可以访问ui组件，因为它在UI线程本身中运行。请执行以下操作

private class HttpAsyncTask extends AsyncTask<String, Void, String> {
    Person person;

    @Override
    protected void onPreExecute(){
        person = new Person();
        person.setName(etName.getText().toString());
        person.setCountry(etCountry.getText().toString());
        person.setTwitter(etTwitter.getText().toString());
    }

    @Override
    protected String doInBackground(String... urls) {
        return POST(urls[0], person);

    }

解决方案2 只需在onClick之后创建一个Person，并在AsynTask（）

的构造函数中传递person对象

 @Override
    public void onClick(View view) {

        switch (view.getId()) {
            case R.id.btnPost:
                if (!validate())
                    Toast.makeText(getBaseContext(), "Enter some data!", Toast.LENGTH_LONG).show();
                person = new Person();
                person.setName(etName.getText().toString());
                person.setCountry(etCountry.getText().toString());
                person.setTwitter(etTwitter.getText().toString());
                // call AsynTask to perform network operation on separate thread
                new HttpAsyncTask(person).execute("http://hmkcode.appspot.com/jsonservlet");
                break;
        }

    }

在构造函数中，您需要以下内容。

private class HttpAsyncTask extends AsyncTask<String, Void, String> {
    Person person;
    Context context;

    //Constructor to get the values
    public HttpAsyncTask(Person person, Context context){
       this.person= person;
       this.context = context;
    }

    @Override
    protected String doInBackground(String... urls) {
        return POST(urls[0], person);

    }

Android错误方法getText必须从UI线程调用，当前推断的线程是worker

3 个答案: