Android控件之ImageView探究
ImageView控件是一个图片控件，负责显示图片。
以下模拟手机图片查看器
目录结构
main.xml布局文件
<?
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/p1
"
/>
<
LinearLayout xmlns:android
=
"
http://schemas.android.com/apk/res/android
"
android:orientation
=
"
horizontal
"
android:layout_width
=
"
fill_parent
"
android:layout_height
=
"
wrap_content
"
android:layout_gravity
=
"
center_horizontal
"
>
<
Button android:id
=
"
@+id/previous
"
android:layout_width
=
"
wrap_content
"
android:layout_height
=
"
wrap_content
"
android:text
=
"
上一张
"
android:layout_gravity
=
"
center_horizontal
"
/>
<
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
=
"
透明度减少
"
android:layout_gravity
=
"
center_horizontal
"
/>
<
Button android:id
=
"
@+id/next
"
android:layout_width
=
"
wrap_content
"
android:layout_height
=
"
wrap_content
"
android:text
=
"
下一张
"
android:layout_gravity
=
"
center_horizontal
"
/>
</
LinearLayout
>
</
LinearLayout
>
ImageViewActivity类
package
com.ljq.iv;
import
android.app.Activity;
import
android.os.Bundle;
import
android.view.View;
import
android.widget.Button;
import
android.widget.ImageView;
public
class
ImageViewActivity
extends
Activity {
private
ImageView imageView
=
null
;
private
Button previous
=
null
;
//
上一张
private
Button next
=
null
;
//
下一张
private
Button alpha_plus
=
null
;
//
透明度增加
private
Button alpha_minus
=
null
;
//
透明度减少
private
int
currentImgId
=
0
;
//
记录当前ImageView显示的图片id
private
int
alpha
=
255
;
//
记录ImageView的透明度
int
[] imgId
=
{
//
ImageView显示的图片数组
R.drawable.p1,
R.drawable.p2,
R.drawable.p3,
R.drawable.p4,
R.drawable.p5,
R.drawable.p6,
R.drawable.p7,
R.drawable.p8,
};
@Override
public
void
onCreate(Bundle savedInstanceState) {
super
.onCreate(savedInstanceState);
setContentView(R.layout.main);
imageView
=
(ImageView)findViewById(R.id.imageView);
previous
=
(Button)findViewById(R.id.previous);
next
=
(Button)findViewById(R.id.next);
alpha_plus
=
(Button)findViewById(R.id.alpha_plus);
alpha_minus
=
(Button)findViewById(R.id.alpha_minus);
previous.setOnClickListener(listener);
next.setOnClickListener(listener);
alpha_plus.setOnClickListener(listener);
alpha_minus.setOnClickListener(listener);
}
private
View.OnClickListener listener
=
new
View.OnClickListener(){
public
void
onClick(View v) {
if
(v
==
previous){
currentImgId
=
(currentImgId
-
1
+
imgId.length)
%
imgId.length;
imageView.setImageResource(imgId[currentImgId]);
}
if
(v
==
next){
currentImgId
=
(currentImgId
+
1
)
%
imgId.length;
imageView.setImageResource(imgId[currentImgId]);
}
if
(v
==
alpha_plus){
alpha
+=
10
;
if
(alpha
>
255
){
alpha
=
255
;
}
imageView.setAlpha(alpha);
}
if
(v
==
alpha_minus){
alpha
-=
10
;
if
(alpha
<
0
){
alpha
=
0
;
}
imageView.setAlpha(alpha);
}
}
};
}
运行结果
