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：

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;
        }
         
    }
 
}

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>