android_handler(二)

这篇是讲 workthread 模拟向网络访问数据，获得数据后，返回 message 发送给 mainthread ，并修改 textview 的 text。

1、layout：

<TextView 
        android:id="@+id/textViewId"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="数据"/>
    
    <Button
        android:id="@+id/buttonId"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/textViewId"
        android:text="发送消息" />

package com.away.b_07_handler02;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity {

	private TextView textView;
	private Button button;

	private Handler handler;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		textView = (TextView) findViewById(R.id.textViewId);
		button = (Button) findViewById(R.id.buttonId);

		handler = new MyHandler();

		button.setOnClickListener(new ButtonListener());
	}

	class MyHandler extends Handler {
		@Override
		public void handleMessage(Message msg) {
			System.out.println("handlerMessage ---->> :" + Thread.currentThread().getName());
			String s = (String) msg.obj;
			textView.setText(s);
		}
	}

	class ButtonListener implements OnClickListener {
		@Override
		public void onClick(View arg0) {
			Thread t = new NetworkThread();
			t.start();
		}
	}

	class NetworkThread extends Thread {
		@Override
		public void run() {
			System.out.println("network ---->> :" + Thread.currentThread().getName());

			// 模拟访问网络,所以说当线程休眠时,首先休眠2秒钟
			try {
				Thread.sleep(2 * 1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			// 变量s的值,模拟从网络当中获取的数据
			String s = "网络当中获取的数据";
			// textView.setText(s); 这种做法是错误的,因为在android系统当中,只有mainthread当中才能操作UI
			Message msg = handler.obtainMessage();
			msg.obj = s;
			// sendMessage()方法,无论是在主线程当中发送还是在workers thread当中发送,都是可以的
			handler.sendMessage(msg);
		}
	}

}

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