<?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">  <ImageView android:id="@+id/imageView" android:layout_width="wrap_content"  android:layout_height="wrap_content"  android:layout_gravity="center_horizontal"  android:src="@drawable/icon" />  <Button android:id="@+id/alpha_plus"  android:layout_width="wrap_content" android:layout_height="wrap_content"  android:text="透明度增加" android:layout_gravity="center_horizontal"  />  <Button android:id="@+id/alpha_minus"  android:layout_width="wrap_content" android:layout_height="wrap_content"  android:text="透明度減少" android:layout_gravity="center_horizontal"  /></LinearLayout>

import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.view.View;import android.widget.Button;import android.widget.ImageView;public class TOUMINGDU extends Activity {  private ImageView imageView=null;  private Button alpha_plus=null; //透明度增加  private Button alpha_minus=null; //透明度減少  private int alpha=255; //記錄ImageView的透明度  Boolean flag=true;  @Override    public void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.main);    imageView=(ImageView)findViewById(R.id.imageView);    alpha_plus=(Button)findViewById(R.id.alpha_plus);    alpha_minus=(Button)findViewById(R.id.alpha_minus);    alpha_plus.setOnClickListener(listener);    alpha_minus.setOnClickListener(listener);  }  private View.OnClickListener listener = new View.OnClickListener(){    public void onClick(View v) {      //加加      if(v==alpha_plus){        alpha+=10;        if(alpha>255){          alpha=255;        }        imageView.setAlpha(alpha);      }      //減減      if(v==alpha_minus){        alpha-=10;        if(alpha<0){          alpha=0;        }        imageView.setAlpha(alpha);      }    }  };}