我已经尝试了所有的解决方案，但是没有得到什么？
这是我的Android清单文件。
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.user.fuel_trade">
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
这是我的构建gradle
apply plugin: 'com.android.application'
android {
compileSdkVersion 27
defaultConfig {
applicationId "com.example.user.fuel_trade"
minSdkVersion 17
targetSdkVersion 27
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support.constraint:constraint-layout:1.1.2'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}
这是HTTP处理程序。 这是建立连接的类 在这里，我尝试打印返回的连接代码，但该语句未执行... 我可以说openConnection下面的LOG语句没有执行
package com.example.user.fuel_trade;
import android.net.ConnectivityManager;
import android.util.Log;
import java.io.BufferedInputStream;
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 User on 6/24/2018.
*/
public class HttpHandler {
private static final String TAG=HttpHandler.class.getSimpleName();
public HttpHandler(){}
public String makeServiceCall(String reqUrl)
{
HttpURLConnection conn=null;
String response=null;
try
{
int y;
Log.e(TAG,"I NA");
Log.e(TAG,"hey"+reqUrl);
URL url=new URL(reqUrl);
conn=(HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
y=conn.getResponseCode();
Log.e(HttpHandler.class.getSimpleName(),"code:"+y);
InputStream in=new BufferedInputStream(conn.getInputStream());
response=convertStreamToString(in);
}
catch(MalformedURLException e)
{
Log.e(HttpHandler.class.getSimpleName(),"Malformed");
}
catch (IOException e)
{
Log.e(HttpHandler.class.getSimpleName(),"io");
}
catch (Exception e)
{
}
finally {
conn.disconnect();
}
return response;
}
private String convertStreamToString(InputStream in) {
BufferedReader reader=new BufferedReader(new InputStreamReader(in));
Log.e(TAG,"reached here");
if(reader==null)
Log.e(HttpHandler.class.getSimpleName(),"no data");
StringBuilder sb=new StringBuilder();
String line;
try
{
while((line=reader.readLine())!=null)
{
Log.e(TAG,"line"+line);
sb.append(line).append('\n');
}
Log.e(TAG,"no");
}
catch (IOException e)
{
Log.e(TAG,"IOException");
}
finally {
try
{
in.close();
}
catch (IOException e)
{
Log.e(TAG,"IOException");
}
}
return sb.toString();
}
}
在这里，我主要活动是尝试打印从url返回但为空的响应
package com.example.user.fuel_trade;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import org.json.JSONException;
import org.json.JSONObject;
public class MainActivity extends AppCompatActivity {
String t;
TextView x;
//private static String url="http://still-tundra-35330.herokuapp.com/main/jaipur/petrol/price";
private static String url= "http://api.androidhive.info/contacts/";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
x=(TextView)findViewById(R.id.display);
HttpHandler sh=new HttpHandler();
String jsonStr=sh.makeServiceCall(url);
Log.e(MainActivity.class.getSimpleName(),"Response from url "+jsonStr);
if(jsonStr!=null)
{
try{
JSONObject jsonObj=new JSONObject(jsonStr);
t=jsonObj.getString("price");
x.setText(t);
} catch (JSONException e) {
e.printStackTrace();
Log.e(MainActivity.class.getSimpleName(),"jsonexception");
}
}
}
}
这是我的LOgcat
W/System: ClassLoader referenced unknown path: /data/app/com.example.user.fuel_trade-1/lib/arm
W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
E/HttpHandler: I NA
E/HttpHandler: heyhttp://api.androidhive.info/contacts/
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
E/MainActivity: Response from url null
I/Adreno: QUALCOMM build : 7d18700, I8ee426a9a2
Build Date : 10/07/16
OpenGL ES Shader Compiler Version: XE031.09.00.03
Local Branch : mybranch22308589
Remote Branch : quic/LA.BR.1.3.6_rb1.6
Remote Branch : NONE
Reconstruct Branch : NOTHING
I/OpenGLRenderer: Initialized EGL, version 1.4
D/OpenGLRenderer: Swap behavior 1