Android(安卓)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>

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