(getData()
应该运行HttpURLConnection
并返回一个字符串(稍后将被转换为Long),该字符串应该是此URL:
https://blockchain.info/tobtc?currency=USD&value=1
中的一行
尝试查看它是否返回任何内容,我在layout.xml文件中显示返回的字符串并显示toast。但两者都显示为空白
请不要注意我在主线程上这样做的事实,我只是想让它先工作。
我做错了什么?为什么它没有返回字符串值。
感谢
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);
}
}
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);
}
}
答案 0 :(得分:1)
对于主线程上的http请求,使用StrictMode.ThreadPolicy.Builder()更改onCreate方法.allowAll()
我不推荐主线程中的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);
}