我想从我从 httpurlconnection 获得的 json 数据中影响 TextView

Question

//[(START)File:ThirdActivity.java] -->
package com.example.caleb.splash_screen;

import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.io.IOException;
import java.io.OutputStream;


public class ThirdActivity extends AppCompatActivity {
  //public String  text = "https://jsonparsingdemo-cec5b.firebaseapp.com/jsonData/moviesDemoItem.txt";


    public TextView text;

    private void writeStream(OutputStream out){
        String output = "Hello world";

       // out.write(output.getBytes());
        //out.flush();
    }


    /*private String readStream(InputStream is) {
        try {`enter code here`
            ByteArrayOutputStream bo = new ByteArrayOutputStream();
            int i = is.read();
            while(i != -1) {
                bo.write(i);
                i = is.read();
            }
            return bo.toString();
        } catch (IOException e) {
            return "";
        }
    }*/

    //[(START) readStream -->
    private String readStream(InputStream in) throws IOException {
    BufferedReader bin = new BufferedReader(new InputStreamReader(in));
    //temporary
        try {
            StringBuilder sb = new StringBuilder();
            String inputLine;
            while ((inputLine = bin.readLine()) != null) {
                sb.append(inputLine);
            }
            return sb.toString();


        } finally {

        }
    }
    //[(END) readStream -->


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_third2);

        text = (TextView)findViewById(R.id.textView);

        new JSONTask().execute("https://jsonparsingdemo-cec5b.firebaseapp.com/jsonData/moviesDemoItem.txt");

    }

}
//[(END)File:ThirdActivity] -->







//[(START)File:JSONTask] -->

package com.example.caleb.splash_screen;

import android.app.Activity;
import android.content.Context;
import android.os.AsyncTask;
import android.support.v4.widget.TextViewCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

/**
 * Created by Caleb on 12/17/2017.
 */

public class JSONTask extends AsyncTask<String,String,String> {


//final TextView txt = (TextView)findViewById(R.id.textView);
    private Context context;

    public JSONTask(Activity ThirdActivity) {
        context = ThirdActivity;
    }

@Override
    protected String doInBackground(String... params) {
        BufferedReader reader = null;
        HttpURLConnection urlConnection = null;
        //{(START)] Working Connection:ALERT! Error within code will cause crash -->
        try {
            URL url = new URL(params[0]);
            Log.w("testing", "test");
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setRequestMethod("GET");
            urlConnection.setDoOutput(false);
            urlConnection.connect();
            //urlConnection.setChunkedStreamingMode(0);
            //OutputStream out = new BufferedOutputStream(urlConnection.getOutputStream());
            //writeStream(out);
            /*int a = urlConnection.getResponseCode();
            String b = String.valueOf(a);
            Log.e(b, "yesssssssssssssssss");*/

            InputStream in = urlConnection.getInputStream();
            //InputStream in = new BufferedInputStream(urlConnection.getInputStream());
            reader = new BufferedReader(new InputStreamReader(in));
            StringBuffer buffer = new StringBuffer();
            String line = "";
            while ((line = reader.readLine()) != null) {
                buffer.append(line);
            }
            /*String data = readStream(in);
            /*final TextView textView = (TextView) findViewById(R.id.textView);
            textView.setText("hello");
            */

            return buffer.toString();

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            throw new RuntimeException(e);

        } finally {
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        //{(END)] Working Connection -->
        return null;
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        TextView text = (TextView) ((AppCompatActivity) context).findViewById(R.id.textView);
        text.setText(result);

    }

}
//[(END)File:JSONTask] -->

/想要的效果/

块引用

我想从 url 指向的 json 文件中提取数据，并在名为 textView 的 UI 中更改 TextView。我不明白如何访问 AsyncTask 中的 findviewbyid。我在整个互联网上都找遍了，找不到任何东西:(任何建议都非常感谢！！

Answer 1

尝试弱引用以获取异步任务中的文本视图

//调用异步任务

new JSONTask(yourTextView).execute();

//在你的异步任务中

  private final WeakReference<TextView> textViewReference;

    public JSONTask (TextView textView){
         textViewReference = new WeakReference<TextView>( textView);
    }


    @Override
    protected void onPostExecute() {


            TextView textView = textViewReference.get();
            //set values to text view

    }

Answer 2

我正在使用 OkHttp 在我的应用程序中执行相同的任务

• HTTP/2 支持允许对同一主机的所有请求共享一个套接字。

• 连接池可减少请求延迟（如果 HTTP/2 不可用）。

• 透明 GZIP 可缩小下载大小。

• 响应缓存完全避免网络重复请求。

添加这个依赖

implementation 'com.squareup.okhttp3:okhttp:3.9.1'

然后创建/编码一个名为OkHttpHandler的新类

class OkHttpHandler extends AsyncTask<String, String, String> {

        OkHttpClient client = new OkHttpClient();
        private volatile String data;

        public String getResult() {
            return data;
        }

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

            try {
                Request.Builder builder = new Request.Builder();
                builder.url(params[0]);
                Request request = builder.build();

                Response response = client.newCall(request).execute();
                return response.body().string();
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            data = s;
        }
    }
}

并像这样使用它

String str = new OkHttpHandler().execute("http://www.<TEST>.com/json").get();

我还建议检查 Wi-fi-Connected/Bluetooth-Connected 或 PhoneData-Enabled 是否为 false if true/else，继续执行您的代码