浅议事件异步处理底层实现原理

//主类
package cn.com.likeshow.bluetoothchat;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		final TextView tv=new TextView(getApplicationContext());
		MyButton  but=new MyButton(getApplicationContext());

		LinearLayout lin=new LinearLayout(getApplicationContext());
		lin.setOrientation(LinearLayout.VERTICAL);

		lin.addView(tv);
		lin.addView(but);
		setContentView(lin);

		//字定义按钮添加监听器
		//创建你匿名MyListener对象，传给but的setOnClickListener()方法
		but.setOnClickListener(new MyListener() {
			@Override
			public void onClick(MyEvent e) {
				tv.setText("MyEvent事件 "+e.getMessage());
			}
		});
	}

}

=====================================================================================================

//MyView接口
package cn.com.likeshow.bluetoothchat;

public interface MyView {
   //所有控件都用的方法，只能被系统调用
	public void systemEventMetod(MyEvent e);
}

========================================================================================

//MyListener接口
package cn.com.likeshow.bluetoothchat;

import android.view.View;

public interface MyListener {

	public void onClick(MyEvent e);
}

===================================================================

//MyEvent简单事件封装类
package cn.com.likeshow.bluetoothchat;

public class MyEvent {

	private String eventStr;
	public MyEvent(String eventStr)
	{
		this.eventStr=eventStr;
	}

	public String  getMessage()
	{
		return eventStr;
	}
}

=============================================

//自定义按钮
package cn.com.likeshow.bluetoothchat;

import java.util.Date;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.MotionEvent;
import android.view.View;

public class MyButton extends View implements MyView {

	private MyListener lis;

	public MyButton(Context context) {
		super(context);

	}

	/**
	 *
	 * 所用控件都实现的一组规范(即：函数   此处假定该函数是public void systemEventMetod(MyEvent e)  系统会调用该函数)
	 * 即：当该按钮被点击时，系统自动调用MyView基类中的systemEventMetod(MyEvent e)方法
	 */
	@Override
	public void systemEventMetod(MyEvent e) {
		//防止为调用 setOnClickListener(MyListener lis)时抛空指针异常
		if(lis==null)
			return;
		//通过多态完成调用自己实现的方法
		lis.onClick(e);
	}

	//注册
	public void setOnClickListener(MyListener lis)
	{
		this.lis=lis;
	}

	//绘制按钮界面
	@Override
	public void onDraw(Canvas canvas)
	{
		super.onDraw(canvas);
		Paint p=new Paint();
		p.setColor(Color.GRAY);

		canvas.drawRect(10,80,100,120, p);

		p.setColor(Color.RED);
		canvas.drawText("按钮", 20, 100, p);

	}

	//模拟点击按钮后，系统自动调用MyView基类中的  systemEventMetod(MyEvent e)方法
	//每当创建MyButton时，系统会得到该MyButton对象的引用，当系统获取到屏幕点击时，会自动调用MyButton
	//的  systemEventMetod(MyEvent e)方法
	@Override
    public boolean onTouchEvent(MotionEvent event) {
        String s=new Date().toLocaleString();

		this.systemEventMetod(new MyEvent(s));

        return super.onTouchEvent(event);
    }
}

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