get请求 同步 和异步

//倒依赖

//布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:orientation="vertical"
    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" tools:context="com.example.ty.MainActivity">

    <TextView
        android:id="@+id/txt"
        android:text="测试"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <Button
        android:id="@+id/yibu"
        android:text="异步get"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <Button
        android:id="@+id/tb"
        android:text="同步"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
</LinearLayout>

package com.example.ty;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import java.io.IOException;
import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private static final String TAG = "MainActivity";
    private static final int RESPONSE_FLAG = 0x123;
    private Button yibu;
    private Button tb;
    private TextView txt;

    Handler  handler=new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            switch (msg.what){
                case RESPONSE_FLAG:
                    String str=(String) msg.obj;
                    txt.setText(str);
                    break;
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        yibu =(Button)findViewById(R.id.yibu);
        tb =(Button)findViewById(R.id.tb);
        txt =(TextView)findViewById(R.id.txt);
        //点击事件
        setListener();
    }

    private void setListener() {
        yibu.setOnClickListener(this);
        tb.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.yibu://异步
                OkHttpClient client=new OkHttpClient.Builder().build();
                //2Request对象
                final Request request = new Request.Builder()
                        .get()
                        .url("http://www.wuxirui.com/")
                        .build();
                Call call = client.newCall(request);
                call.enqueue(new Callback() {
                    @Override
                    public void onFailure(Call call, IOException e) {
                        Log.e(TAG, "onFailure: "+e.getMessage() );
                    }

                    @Override
                    public void onResponse(Call call, Response response) throws IOException {
                        // response.body().string()本质上是读流的操作  读完之后就没有了
                        final String a = response.body().string();
                       // Log.e(TAG, "onResponse: "+string );
                        runOnUiThread(new Runnable() {
                            @Override
                            public void run() {
                                txt.setText(a);//创建主线程更新UI
                            }
                        });
                    }
                });
                break;
            case R.id.tb://同步
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        OkHttpClient client3 = new OkHttpClient();
                        Request request3 = new Request.Builder()
                                .get()
                                .url("http://www.wuxirui.com/")
                                .build();
                        Call call3 = client3.newCall(request3);
                        try {
                            //是同步请求
                            // 默认是在当前线程执行的网络请求
                            //我们需要创建子线程    然后创建Handler主线程
                            //发送handler在主线程更新ui界面
                            Response execute = call3.execute();
                            String string = execute.body().string();

                            Message message = handler.obtainMessage();
                            message.what=RESPONSE_FLAG;
                            message.obj=string;
                            message.sendToTarget();

                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }).start();
                break;
        }
    }
}