从服务器请求数据

---

1.实例化一个url对象
2.获取HttpUrlConnection对象
3.设置请求连接属性
4.获取响应码，判断是否连接成功
5.读取输入流并解析

---

---

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.studio.imoocdemo.MainActivity">

<TextView
 android:id="@+id/header"
android:layout_width="match_parent"
android:layout_height="48dp"
android:background="#3f51b5"
android:gravity="center"
android:paddingRight="15dp"
android:text="慕课"
android:textColor="#ffffff"
android:textSize="28sp" />

<ImageView
 android:id="@+id/banner"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:scaleType="fitXY" />

<ListView
 android:id="@+id/essay_view"
android:layout_width="match_parent"
android:layout_height="match_parent"></ListView>

</LinearLayout>

---

MainActivity.java

package com.studio.imoocdemo;

import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends Activity {

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

        initview();
    }

public void initview() {
        findViewById(R.id.header).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
                startActivity(new Intent(MainActivity.this, DetailActivity.class));
            }
        });
    }
}

---

activity_detail.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.studio.imoocdemo.DetailActivity">


<TextView
 android:id="@+id/name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="15dp"
android:gravity="center"
android:textSize="24sp" />

<TextView
 android:id="@+id/author"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="15dp"
android:gravity="right"
android:paddingRight="10dp"
android:textSize="20sp" />

<TextView
 android:id="@+id/content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="8dp"
android:layout_marginTop="15dp"
android:layout_weight="1"
android:lineSpacingMultiplier="1.5"
android:textSize="20sp" />

</LinearLayout>

---

DetailActivity.java

package com.studio.imoocdemo;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class DetailActivity extends AppCompatActivity {

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

        initData();
    }

public void initData() {
//HttpUrlConnection
/**
 * 1.实例化一个url对象
 * 2.获取HttpUrlConnection对象
 * 3.设置请求连接属性
 * 4.获取响应码，判断是否连接成功
 * 5.读取输入流并解析
 */
//参数：你要访问的接口地址
new Thread() {
@Override
public void run() {
super.run();
try {
                    URL url = new URL("http://www.imooc.com/api/teacher?type=3&cid=1");
                    HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                    httpURLConnection.setRequestMethod("GET");
                    httpURLConnection.setReadTimeout(6000);
//获取响应码
//200表示服务器成功返回网页;404（未找到）服务器找不到请求的网页;
//500（服务器内部错误）服务器遇到错误，无法完成请求;503服务不可用。
if (httpURLConnection.getResponseCode() == 200) {
//获取输入流
                        InputStream inputStream = httpURLConnection.getInputStream();
byte[] bytes = new byte[1024 * 512];
int len = 0;
//建立缓存流，保存所读取的字节数组
                        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
while ((len = inputStream.read(bytes)) > -1) {
                            byteArrayOutputStream.write(bytes, 0, len);
                        }
                        String msg = byteArrayOutputStream.toString();
                        Log.e("TAG", msg);

                    }
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }.start();

    }
}