调用时 HttpURLConnection 方法为空
HttpURLConnection method empty when called
我打电话给
(getData()
应该 运行 HttpURLConnection 和 return 一个字符串（稍后将转换为 Long），该字符串应该是 URL 中的一行：
<a href="https://blockchain.info/tobtc?currency=USD&value=1" rel="nofollow">https://blockchain.info/tobtc?currency=USD&value=1</a>
试图查看它是否正在 returning 任何内容，我在 layout.xml 文件中显示 returned 字符串并显示祝酒词。但两者都显示为空白
请不要注意我是在主线程上做的，我只是想让它先工作。
我做错了什么？为什么它不 returning 字符串值。
谢谢
</p>
<pre><code> package app.com.cryptosudan.android.cryptosudan;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageButton sdg = (ImageButton) findViewById(R.id.imagesdg);
ImageButton btc = (ImageButton) findViewById(R.id.imagebtc);
final TextView display = (TextView) findViewById(R.id.display);
String price;
price = (getData());
display.setText(price);
Toast.makeText(this, price, Toast.LENGTH_LONG).show();
sdg.setOnClickListener(sdgpage);
btc.setOnClickListener(btcpage);
}
//to create an instance of button OnClickListener
View.OnClickListener sdgpage = new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, CalculateSdg.class));
}
};
//to create an instance of button OnClickListener
View.OnClickListener btcpage = new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, CalculateBtc.class));
}
};
public static String getData () {
BufferedReader reader = null;
try {
URL url = new URL("https://blockchain.info/tobtc?currency=USD&value=1");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
StringBuilder sb = new StringBuilder();
reader = new BufferedReader(new InputStreamReader(con.getInputStream()));
String line;
while((line = reader.readLine()) !=null) {
sb.append (line + "/n");
} return sb.toString();
}catch (Exception e){
e.printStackTrace();
return null;
}finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
对于主线程上的 http 请求，将 onCreate 方法更改为 StrictMode.ThreadPolicy.Builder().permitAll()
我不建议在主线程中进行 Http 请求!!!!
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageButton sdg = (ImageButton) findViewById(R.id.imagesdg);
ImageButton btc = (ImageButton) findViewById(R.id.imagebtc);
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
final TextView display = (TextView) findViewById(R.id.display);
String price;
price = (getData());
display.setText(price);
Toast.makeText(this, price, Toast.LENGTH_LONG).show();
sdg.setOnClickListener(sdgpage);
btc.setOnClickListener(btcpage);
}
我打电话给
(getData()
应该 运行 HttpURLConnection 和 return 一个字符串（稍后将转换为 Long），该字符串应该是 URL 中的一行：
<a href="https://blockchain.info/tobtc?currency=USD&value=1" rel="nofollow">https://blockchain.info/tobtc?currency=USD&value=1</a>
试图查看它是否正在 returning 任何内容，我在 layout.xml 文件中显示 returned 字符串并显示祝酒词。但两者都显示为空白
请不要注意我是在主线程上做的，我只是想让它先工作。
我做错了什么？为什么它不 returning 字符串值。
谢谢
</p>
<pre><code> package app.com.cryptosudan.android.cryptosudan;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageButton sdg = (ImageButton) findViewById(R.id.imagesdg);
ImageButton btc = (ImageButton) findViewById(R.id.imagebtc);
final TextView display = (TextView) findViewById(R.id.display);
String price;
price = (getData());
display.setText(price);
Toast.makeText(this, price, Toast.LENGTH_LONG).show();
sdg.setOnClickListener(sdgpage);
btc.setOnClickListener(btcpage);
}
//to create an instance of button OnClickListener
View.OnClickListener sdgpage = new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, CalculateSdg.class));
}
};
//to create an instance of button OnClickListener
View.OnClickListener btcpage = new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, CalculateBtc.class));
}
};
public static String getData () {
BufferedReader reader = null;
try {
URL url = new URL("https://blockchain.info/tobtc?currency=USD&value=1");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
StringBuilder sb = new StringBuilder();
reader = new BufferedReader(new InputStreamReader(con.getInputStream()));
String line;
while((line = reader.readLine()) !=null) {
sb.append (line + "/n");
} return sb.toString();
}catch (Exception e){
e.printStackTrace();
return null;
}finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
对于主线程上的 http 请求，将 onCreate 方法更改为 StrictMode.ThreadPolicy.Builder().permitAll()
我不建议在主线程中进行 Http 请求!!!!
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageButton sdg = (ImageButton) findViewById(R.id.imagesdg);
ImageButton btc = (ImageButton) findViewById(R.id.imagebtc);
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
final TextView display = (TextView) findViewById(R.id.display);
String price;
price = (getData());
display.setText(price);
Toast.makeText(this, price, Toast.LENGTH_LONG).show();
sdg.setOnClickListener(sdgpage);
btc.setOnClickListener(btcpage);
}