安卓四大组件之一 Service简单实现

1、介绍：

• Service，服务，是四大组件之一, 和Activity 非常相似, 一般运行在后台, 没有用户界面, 可执行的程序
• Activity 和 Service的区别
  不同点：
  1、Activity : 可以和用户交互, 页面可见
  2、Service : 后台运行, 没有界面
  相同点：
  service 的用途：播放音乐；后台下载大文件

2、代码：

主类代码：

package com.example.day17;

import android.app.Service;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class Activity_day17 extends AppCompatActivity {

    Intent intent;
    MyService_1 myService_1;
    Button startbtn;
    Button stopbtn;
    ImageView img;
    ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            Log.e("ComponentName###",name.toString());
            myService_1 = ((MyService_1.MyBinder)service).getService();
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_day17);
        intent = new Intent(this,MyService_1.class);
        bindService(intent,connection, Service.BIND_AUTO_CREATE);
        startbtn = findViewById(R.id.start);
        stopbtn = findViewById(R.id.stop);
        img = findViewById(R.id.img);

        startbtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                myService_1.getLoad(img);
            }
        });
        stopbtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                unbindService(connection);
                Log.e("unbindService###","已解绑");
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unbindService(connection);
    }
}

服务代码：

从网络上去获取图片：

package com.example.day17;

import android.app.Service;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;
import android.widget.ImageView;

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

public class MyService_1 extends Service {
    @Override
    public void onCreate() {
        super.onCreate();

    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }

    @Override
    public IBinder onBind(Intent intent) {
        return new MyBinder();
    }

    /**
     * Binder类
     */
    class MyBinder extends Binder{
        public MyService_1 getService(){
            return MyService_1.this;
        }
    }

    public void getLoad(ImageView img){
        Log.e("Thread###","开启了线程");
        String str = "http://upload.jianshu.io/users/upload_avatars/6416344/5e103cde-c77d-49f9-8a47-2ed4418c564a.jpg";

        new MyAsync(str,img).execute();

    }
    public class MyAsync extends AsyncTask<String,String, Bitmap> {
        String urlstr;
        ImageView img;
        public MyAsync(String urlstr,ImageView img) {
            this.urlstr = urlstr;
            this.img = img;
        }
        @Override
        protected void onPostExecute(Bitmap bitmap) {
            super.onPostExecute(bitmap);
            img.setImageBitmap(bitmap);
        }
        @Override
        protected Bitmap doInBackground(String... strings) {
            Bitmap bitmap = null;
            try {
                URL url = new URL(urlstr);
                HttpURLConnection connection = (HttpURLConnection)url.openConnection();
                connection.setRequestMethod("GET");
                if(connection.getResponseCode() == 200){
                    InputStream is = connection.getInputStream();
                    ByteArrayOutputStream os = new ByteArrayOutputStream();
                    byte b[] = new byte[1024];
                    int len = 0;
                    while((len = is.read(b))!= -1){
                        os.write(b,0,len);
                    }
                    is.close();
                    os.close();
                    byte[] bs = os.toByteArray();
                    bitmap = BitmapFactory.decodeByteArray(bs, 0, bs.length);
                }

            } catch (Exception e) {
                e.printStackTrace();
            }
            return bitmap;
        }
    }
}

效果图：

点击前

点击启动服务之后：