Android:在单独的文本视图中使用字符串请求的结果

<uses-permission android:name="android.permission.INTERNET" />

<TextView
    android:id="@+id/resultTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class MainActivity extends AppCompatActivity {

    private TextView resultTextView;

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

        resultTextView = findViewById(R.id.resultTextView);

        // 发送字符串请求的异步任务
        new StringRequestTask().execute();
    }

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

        @Override
        protected String doInBackground(Void... voids) {
            try {
                OkHttpClient client = new OkHttpClient();
                Request request = new Request.Builder()
                        .url("http://example.com/api/string")
                        .build();
                Response response = client.newCall(request).execute();
                return response.body().string();
            } catch (Exception e) {
                e.printStackTrace();
                return null;
            }
        }

        @Override
        protected void onPostExecute(String result) {
            if (result != null) {
                resultTextView.setText(result);
            } else {
                resultTextView.setText("请求失败");
            }
        }
    }
}