//[(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] -->
/期望效果/
大段引用
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。我在整个互联网上看了一遍，找不到任何东西:(任何建议都非常感谢!!
尝试使用弱引用来获取asynctask中的textview
//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
}
我正在使用OkHttp在我的应用程序中执行相同的任务
添加此依赖项
implementation 'com.squareup.okhttp3:okhttp:3.9.1'
然后创建/编写一个名为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是否为假iftrue / else，继续你的代码