android复习路之http网络访问

HttpURLConnection访问方式：

首先需要获取到HttpURLConnection的实例，一般需要new 一个URL并且传入访问地址，然后调用openConncetion()

URL url=new URL("https://www.baidu.com");

HttpURLConnection http= (HttpURLConnection) url.openConnection();

然后从服务器获得数据是GET:

http.setRequestMethod("GET");
可以设置连接超时还有读取超时
http.setConnectTimeout(8000);
http.setReadTimeout(8000);

调用getIuputStream()就可以获得字符流

InputStream in=http.getInputStream();
最后调用：disconnect();进行网络访问关闭。
例子：获得百度首页：
xlm布局：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.zobject.http.MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:text="Button" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Hello World!" />

    </ScrollView>
</RelativeLayout>
java代码：
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    TextView result;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button= (Button) findViewById(R.id.button);
        result= (TextView) findViewById(R.id.textView);
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        if (view.getId()==R.id.button){
            getresult();
        }
    }

    private void getresult() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                HttpURLConnection http=null;
                BufferedReader read=null;
                try {
                    URL url=new URL("https://www.baidu.com");
                    http= (HttpURLConnection) url.openConnection();
                    http.setRequestMethod("GET");
                    http.setConnectTimeout(8000);
                    http.setReadTimeout(8000);
                    InputStream in=http.getInputStream();
                    read=new BufferedReader(new InputStreamReader(in));
                    StringBuilder res=new StringBuilder();
                    String line;
                    while ((line=read.readLine())!=null){
                        res.append(line);

                    }
                    showresult(res.toString());
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }finally {
                    if (read!=null){
                        try {
                            read.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                    if (http!=null){
                        http.disconnect();
                    }
                }
            }
        }).start();
    }

    private void showresult(final String string) {

        runOnUiThread(new Runnable() {//切换到主线程进行ui更新
            @Override
            public void run() {
                result.setText(string);
            }
        });
    }
}

结果截图：

用okhttp进行网络访问：

okhttp是一个开源网络通信库，使用它可以让我们节省很多的时间：

首先使用okhttp需要添加依赖包：

compile 'com.squareup.okhttp3:okhttp:3.5.0'
使用首先要创建一个okhttp的实例
OkHttpClient client = new OkHttpClient();
发起请求需要创建一个Requst的实例:

Request request = new Request.Builder().build();

之后需要创建一个newcall对象并且调用execute方法获得服务器的数据：

Response response = client.newCall(request).execute();
response携带有数据可以通过以下方法获得数据：

String res = response.body().string();
同样的实例获取百度首页：

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    TextView result;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = (Button) findViewById(R.id.button);
        result = (TextView) findViewById(R.id.textView);
        button.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        if (view.getId() == R.id.button) {
            getresult();
        }
    }

    private void getresult() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                OkHttpClient client = new OkHttpClient();
                Request request = new Request.Builder().url("https://www.baidu.com").build();
                try {
                    Response response = client.newCall(request).execute();
                    String res = response.body().string();
                    showresult(res);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();

    }

    private void showresult(final String string) {

        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                result.setText(string);
            }
        });
    }
}
可以看到代码精简了很多。这里只是简单的实现和使用。后续进行深入的学习。效果是一样的都是获得百度首页的文件流，就不贴图了。