Java Adapter design pattern

This pattern is very useful especially when programming language such as Java which does not

support multiple-inheritance. Following example can achieve multiple-inheritance by implementing an

adapter design pattern.

package pattern;

public interface Dog {
    public String getDogSound();
}

package pattern;

public interface Cat {
    
    public String getCatSound();

}

package pattern;

public class AnimalAdapter implements Cat,Dog {

    @Override
    public String getCatSound() {
        return "Cat sound";
    }

    @Override
    public String getDogSound() {
        return "Dog sound";
    }

}

AnimalAdapter have both cat's voice and dog's voice.

package pattern;

public class Simulator {
    
    static boolean cat = true;
    public static void main(String[]args){
        AnimalAdapter aa = new AnimalAdapter();
        if(cat){
            System.out.println(aa.getCatSound());
        }else if(!cat){
            System.out.println(aa.getDogSound());
        }
    
    }
    
}

Therefore , simulator can produce cat voice or dog voice in different situations.
Reference:Wiki Article

Android FrameLayout

Activity在切換的時候會被移到背景去 

若使用FrameLayout的話可以讓View重疊顯示,而不會移到背景去

而visibility這個屬性可以定義元件是否要被看見.

visible:看得見
invisible:看不見,但還是佔有空間.
gone:看不見,也不占空間.

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <Button android:id="@+id/pop_btn"
        android:layout_width="50dp"
        android:layout_height="wrap_content"
        android:text="Click Me" 
        android:onClick="onClickBtn"
        />
    
    <Button android:id="@+id/pop_btn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Click Me" 
        android:onClick="onClickBtn"
        />
</FrameLayout>

Android popup window demo

MainActivity.java

package com.example.android.popwindow;

import com.example.android.R;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.PopupWindow;

public class MainActivity extends Activity {
    
    PopupWindow pw = null;

    boolean isClicked = false;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.popup_main);
        LayoutInflater inflater = (LayoutInflater) this
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        pw = new PopupWindow(inflater.inflate(R.layout.pop_content,
                null, false), 100, 100, true);
        pw.setFocusable(false);
        
    }
    
    public void onClickBtn(View v){
        if(isClicked == true){
            pw.dismiss();
            isClicked = false;
        }else if(isClicked == false){
            pw.showAsDropDown(this.findViewById(R.id.pop_btn));
            isClicked = true;
        }
    }

}

We can use showAtLocation  to replace the showAsDropDown. Because this method is

more flexibile than the prior one.

res/layout/pop_content.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Content"
         />

</LinearLayout>

res/layout/pop_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <Button android:id="@+id/pop_btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Click Me" 
        android:onClick="onClickBtn"
        />
</LinearLayout>

AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.android"
    android:versionCode="1"
    android:versionName="1.0">

    <uses-sdk android:minSdkVersion="3" android:targetSdkVersion="14" />

    <application android:label="@string/app_name"
        android:icon="@drawable/ic_launcher"
        android:theme="@style/AppTheme">
        
        <activity android:name="com.example.android.popwindow.MainActivity" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

Reference: Android Developer Guide