android中处理程序的post()和sendMessage()有什么区别？

Question

我发现了post()和sendMessage()之间的一些信息差异

如果要组织发送到ui (来自后台线程的消息)或ui函数的内容，则使用looper.

• sendmessage()−将消息从后台线程发送到主线程。你应该使用sendMessage().

post ：Post()很清楚，我们从后台线程到主线程发布了一些内容。但是sendMessage()有什么不同？

Answer 1

post()和sendMessage()在内部的工作方式相同，但是对于sendMessage()，我们可以传递消息对象。

EXAMPLES

使用员额：

public class MainActivity extends AppCompatActivity {
    Handler mHandler = new Handler();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Handler Started", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();

                initHandler();
            }
        });
    }

    private void initHandler() {

        new Thread(new Runnable() {
            @Override
            public void run() {
                try{

                    mHandler.post(new Runnable() {
                        @Override
                        public void run() {
                            Toast.makeText(MainActivity.this,"Executed in background thread",Toast.LENGTH_LONG).show();
                        }
                    });
                }catch(Exception ex){
                    ex.printStackTrace();
                    Toast.makeText(MainActivity.this,ex.getMessage(),Toast.LENGTH_LONG).show();
                }
            }
        }).start();
    }


}

使用sendMessage

public class MainActivity extends AppCompatActivity {
    IncomingHandler msgHandler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        msgHandler = new IncomingHandler(MainActivity.this);
        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Handler Started", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();

                initHandler();
            }
        });
    }

    private void initHandler() {

        new Thread(new Runnable() {
            @Override
            public void run() {
                try{
                    Message msg = msgHandler.obtainMessage();
                    Bundle bundle = new Bundle();
                    bundle.putString("MSG_KEY", "Executed in background thread");
                    msg.setData(bundle);
                    msgHandler.sendMessage(msg);
                }catch(Exception ex){
                    ex.printStackTrace();
                    Toast.makeText(MainActivity.this,ex.getMessage(),Toast.LENGTH_LONG).show();
                }
            }
        }).start();
    }

    private static class IncomingHandler extends Handler{

        Handler mHandler = new Handler();
        Context context;

        public IncomingHandler(Context context) {
            this.context = context;
        }

        @Override
        public void handleMessage(@NonNull final Message msg) {
            super.handleMessage(msg);
            Bundle bundle = msg.getData();
            final String displayMessage = bundle.getString("MSG_KEY");
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(context ,displayMessage,Toast.LENGTH_LONG).show();
                }
            });
        }
    }


}