android - BindService

关于安卓BindService 绑定问题

BindService 主要用于当用户想要将活动activity与service进行绑定，当activity结束时（调用者）service也跟着一起结束了；而startService()只能用来启动服务，当服务启动后，就与前台活动没有了关系；

当我们要从service外部获得service中的方法内容时，我们必须要Ibinder返回的service对象才能操作；所以我们必须利用bindservice的方式去绑定服务获取binder对象，利用binder的方式去获取service的方法内容；

使用bindservice的具体过程如下：

1）创建意图：Intent intent = new Intent(MainActivity.this,BindService.class);

2）创建bindservice对象：bindService(intent,conn,BIND_AUTO_CREATE);

3）创建内部类MyBinder、新建mybinder对象：

private  MyBinder myBinder = new MyBinder();
    class MyBinder extends Binder{
        public BindService getService(){
            return BindService.this;
        }
    }

4）onBind()返回mybinder对象：

public IBinder onBind(Intent intent) {
        return myBinder;
    }

5）通过serviceconnection获取Binder对象进一步来获取service对象，最后调用service中的方法：

ServiceConnection conn = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            BindService.MyBinder binder = (BindService.MyBinder)service;
            BindService bindService = binder.getService();
            bindService.print();
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };

示例代码：

MainActivity

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initEvent();
    }
    ServiceConnection conn = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            BindService.MyBinder binder = (BindService.MyBinder)service;
            BindService bindService = binder.getService();
            bindService.print();
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };

    private void initEvent() {
        findViewById(R.id.button4).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this,BindService.class);
                bindService(intent,conn,BIND_AUTO_CREATE);
            }
        });
        findViewById(R.id.button5).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                unbindService(conn);
            }
        });
    }
}

BindService

public class BindService extends Service {
    
    public void print(){
        Log.d(TAG, "print: BindService");
    }
    @Override
    public void onCreate() {
        super.onCreate();
        Log.d(TAG, "onCreate");
    }

    @Override
    public void onStart(Intent intent, int startId) {
        super.onStart(intent, startId);
        Log.d(TAG, "onStart");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(TAG, "onStartCommand");
        return super.onStartCommand(intent, flags, startId);
        
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy");
    }

    @Override
    public boolean onUnbind(Intent intent) {
        Log.d(TAG, "onUnbind:");
        return super.onUnbind(intent);
    }

    @Override
    public void onRebind(Intent intent) {
        Log.d(TAG, "onRebind");
        super.onRebind(intent);
    }

    private  MyBinder myBinder = new MyBinder();
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return myBinder;
    }
    class MyBinder extends Binder{
        public BindService getService(){
            return BindService.this;
        }
    }
}