Android 中Observer模式的使用

android实际上使用了大量的obverser 模式，最简单的就是onclicklistener,但是与一般的observer模式不同的是，view中定义了很多接口，如下所示：

 /**
     * Interface definition for a callback to be invoked when a touch event is
     * dispatched to this view. The callback will be invoked before the touch
     * event is given to the view.
     */
    public interface OnTouchListener {
        /**
         * Called when a touch event is dispatched to a view. This allows listeners to
         * get a chance to respond before the target view.
         *
         * @param v The view the touch event has been dispatched to.
         * @param event The MotionEvent object containing full information about
         *        the event.
         * @return True if the listener has consumed the event, false otherwise.
         */
        boolean onTouch(View v, MotionEvent event);
    }

    /**
     * Interface definition for a callback to be invoked when a view has been clicked and held.
     */
    public interface OnLongClickListener {
        /**
         * Called when a view has been clicked and held.
         *
         * @param v The view that was clicked and held.
         *
         * return True if the callback consumed the long click, false otherwise
         */
        boolean onLongClick(View v);
    }

    /**
     * Interface definition for a callback to be invoked when the focus state of
     * a view changed.
     */
    public interface OnFocusChangeListener {
        /**
         * Called when the focus state of a view has changed.
         *
         * @param v The view whose state has changed.
         * @param hasFocus The new focus state of v.
         */
        void onFocusChange(View v, boolean hasFocus);
    }

    /**
     * Interface definition for a callback to be invoked when a view is clicked.
     */
    public interface OnClickListener {
        /**
         * Called when a view has been clicked.
         *
         * @param v The view that was clicked.
         */
        void onClick(View v);
    }

    /**
     * Interface definition for a callback to be invoked when the context menu
     * for this view is being built.
     */
    public interface OnCreateContextMenuListener {
        /**
         * Called when the context menu for this view is being built. It is not
         * safe to hold onto the menu after this method returns.
         *
         * @param menu The context menu that is being built
         * @param v The view for which the context menu is being built
         * @param menuInfo Extra information about the item for which the
         *            context menu should be shown. This information will vary
         *            depending on the class of v.
         */
        void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo);
    }

每个接口执行不同的操作。

下面是一个相关的例子：

package com.fp.app.looper;

import com.fp.app.debug.DebugLog;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnFocusChangeListener;
import android.widget.Button;

public class Observer extends Activity implements OnClickListener ,OnFocusChangeListener{
	public static final String TITLE = "title";

	@Override
	public void setTitle(int titleId) {
		super.setTitle(titleId);
	}

	private Button btnMM;
	private Button btnMS;
	private Button btnSM;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.entry);
		findComponent();
		setOnClickListener();
		setOnFocusChangeListener();

	}

	private void setOnClickListener() {
		btnMM.setOnClickListener(this);
		btnMS.setOnClickListener(this);
		btnSM.setOnClickListener(this);
	}

	
	private void setOnFocusChangeListener() {
		btnMM.setOnFocusChangeListener(this);
		btnMS.setOnFocusChangeListener(this);
		btnSM.setOnFocusChangeListener(this);
	}
	
	private void findComponent() {
		btnMM = (Button) this.findViewById(R.id.btn_mm);
		btnMS = (Button) this.findViewById(R.id.btn_ms);
		btnSM = (Button) this.findViewById(R.id.btn_sm);
	}

	@Override
	public void onClick(View v) {
		int id = v.getId();
		switch (id) {
		case R.id.btn_mm:
			DebugLog.log("btnMM onclick");
			break;
		case R.id.btn_ms:
			DebugLog.log("btnMS onclick");
			break;
		case R.id.btn_sm:
			DebugLog.log("btnSM onclick");
			break;
		default:
			break;
		}

	}

	@Override
	public void onFocusChange(View v, boolean hasFocus) {
		int id = v.getId();
		switch (id) {
		case R.id.btn_mm:
			DebugLog.log("btnMM onFocusChange");
			break;
		case R.id.btn_ms:
			DebugLog.log("btnMS onFocusChange");
			break;
		case R.id.btn_sm:
			DebugLog.log("btnSM onFocusChange");
			break;
		default:
			break;
		}
		
	}

}

package com.fp.app.debug;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.Writer;

import android.util.Log;

public class DebugLog {
	public final static boolean DEBUG = true;

	public static void log(String message) {
		if (DEBUG) {
			String fullClassName = Thread.currentThread().getStackTrace()[3].getClassName();
			String className = fullClassName.substring(fullClassName.lastIndexOf(".") + 1);
			String methodName = Thread.currentThread().getStackTrace()[3].getMethodName();
			int lineNumber = Thread.currentThread().getStackTrace()[3].getLineNumber();

			Log.d(className + "." + methodName + "():" + lineNumber, message);
		}
	}
	
	
	public static void printThreadId(String message) {
		if (DEBUG) {
			Log.d(message, String.valueOf(Thread.currentThread().getId()));
		}
	}

	public static void log(String tag, String message) {
		if (DEBUG) {
			String methodName = Thread.currentThread().getStackTrace()[3].getMethodName();
			int lineNumber = Thread.currentThread().getStackTrace()[3].getLineNumber();

			Log.d(tag + "." + methodName + "():" + lineNumber, message);
		}
	}

	public static void printTrace(String message) {
		if (DEBUG) {
			printIllegalArgumentException("", message);
		}
	}

	public static String getStackTrace(Throwable throwable) {
		Writer writer = new StringWriter();
		PrintWriter printWriter = new PrintWriter(writer);
		throwable.printStackTrace(printWriter);
		return writer.toString();
	}

	public static void printIllegalArgumentException(String tag, String arg) {
		if (DEBUG) {
			final Throwable throwable = new IllegalArgumentException(arg);
			Log.w(tag, arg, throwable);
		}
	}

}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
	package="com.fp.app.looper" android:versionCode="1"
	android:versionName="1.0">
	<application android:icon="@drawable/icon" android:label="@string/app_name">
		<activity android:name=".Observer" android:label="@string/app_name">
			<intent-filter>
				<action android:name="android.intent.action.MAIN" />
				<category android:name="android.intent.category.LAUNCHER" />
			</intent-filter>
		</activity>
	</application>
</manifest> 

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    android:orientation="vertical"  
    android:layout_width="fill_parent"  
    android:layout_height="fill_parent"  
    >  
     
<Button android:id="@+id/btn_mm"   
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    android:text="main thread to main thread" />  
 <Button android:id="@+id/btn_ms"   
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    android:text="main thread to sub thread" />  
   <Button android:id="@+id/btn_sm"   
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    android:text="sub thread to main thread" />  
</LinearLayout>