Android development-based Worker thread sends messages to the Main thread, androidworker

Android development-based Worker thread sends messages to the Main thread, androidworker

The Worker thread cannot modify the UI. Therefore, after receiving a message in the Worker thread, you must notify the main thread to update the UI.

The following is an example:

1 Layout

<RelativeLayout 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" android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">    <TextView android:text="default data."        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:id="@+id/textView" />    <Button android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_below="@id/textView"        android:text="download"        android:id="@+id/button"/></RelativeLayout>

Code 2

    private TextView textView;    private Button button;    private NetworkHandler handler_network;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        textView = (TextView)this.findViewById(R.id.textView);        button = (Button)this.findViewById(R.id.button);        button.setOnClickListener(new ButtonListener());        handler_network = new NetworkHandler();    }    class ButtonListener implements View.OnClickListener {        @Override        public void onClick(View v) {            NetworkThread thread = new NetworkThread();            thread.start();        }    }    class NetworkHandler extends Handler{        public void handleMessage(Message msg){            String str = (String)msg.obj;            textView.setText(str);        }    }    class NetworkThread extends Thread {        public void run() {            try {                Thread.sleep(2 * 1000);                String str = "data from net.";                Message msg = handler_network.obtainMessage();                msg.obj = str;                handler_network.sendMessage(msg);            } catch (Exception e) {                e.printStackTrace();            }        }    }

Result 3: