Android Gallery用法（自定义边框+底部小圆点）

最近在项目中用到图片轮播，试了Gallery，ViewFlipper，ViewPager,感觉Gallery最符合需求，但是Gallery的系统边框很难看，项目中要求用自己的背景图片。

下面来看一下使用Gallery实现图片轮播

运行效果：

布局文件：

 <FrameLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingLeft="16dp"
        android:paddingRight="16dp"
        android:paddingTop="10dp" >

        <Gallery
            android:id="@+id/gallery"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:fadingEdge="none"
            android:spacing="0dp" />

        <RelativeLayout
            android:layout_width="fill_parent"
            android:layout_height="18dp"
            android:layout_gravity="bottom"
            android:layout_marginBottom="3dp"
            android:layout_marginLeft="3dp"
            android:layout_marginRight="3dp"
            android:background="#80776f63"
            android:gravity="center" >

            <ImageView
                android:id="@+id/dot_1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:src="@drawable/ic_dot_normal" />

            <ImageView
                android:id="@+id/dot_2"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="10dp"
                android:layout_toRightOf="@+id/dot_1"
                android:src="@drawable/ic_dot_normal" />

            <ImageView
                android:id="@+id/dot_3"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="10dp"
                android:layout_marginRight="10dp"
                android:layout_toRightOf="@+id/dot_2"
                android:src="@drawable/ic_dot_normal" />
        </RelativeLayout>
    </FrameLayout>

其中， android:fadingEdge="none"消除图片两边的阴影。使用FrameLayout在底部显示小圆点

public class MainActivity extends Activity {

    private Gallery mGallery;
    private int index = 0;// 记录选中的图片位置
    private ImageView[] mImageViewIds;// 小圆点ImageView数组
    private static final int IMAGE_COUNT = 3;// 小圆点个数

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findViews();
        mImageViewIds[0].setImageDrawable(getBaseContext().getResources()
                .getDrawable(R.drawable.ic_dot_focused));
        ImageAdapteradapter = new ImageAdapter(this);
        mGallery.setAdapter(adapter);
        Timer timer = new Timer();
        timer.schedule(task, 2000, 2000);
        mGallery.setOnItemSelectedListener(onItemSelectedListener);
        mGallery.setOnItemClickListener(onItemClickListener);
    }

    private void findViews() {
        mGallery = (Gallery) findViewById(R.id.gallery);
        mImageViewIds = new ImageView[] { (ImageView) findViewById(R.id.dot_1),
                (ImageView) findViewById(R.id.dot_2),
                (ImageView) findViewById(R.id.dot_3) };
    }

    private TimerTask task = new TimerTask() {

        @Override
        public void run() {
            Message message = new Message();
            message.what = 2;
            index = mGallery.getSelectedItemPosition();
            index++;
            handler.sendMessage(message);
        }
    };

    /**
     * 开一个线程执行耗时操作
     */
    private Handler handler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            switch (msg.what) {
            case 2:
                mGallery.setSelection(index);
                break;
            default:
                break;
            }
        }

    };
    /**
     * 设置小圆点显示，position会一直增加，如果要循环显示图片，需要对position取余，否则数组越界
     */
    private OnItemSelectedListener onItemSelectedListener = new OnItemSelectedListener() {

        @Override
        public void onItemSelected(AdapterView<?> parent, View view,
                int position, long id) {
            int pos = position % IMAGE_COUNT;
            mImageViewIds[pos].setImageDrawable(getBaseContext().getResources()
                    .getDrawable(R.drawable.ic_dot_focused));
            if (pos > 0) {
                mImageViewIds[pos - 1].setImageDrawable(getBaseContext()
                        .getResources().getDrawable(R.drawable.ic_dot_normal));
            }
            if (pos < (IMAGE_COUNT - 1)) {
                mImageViewIds[pos + 1].setImageDrawable(getBaseContext()
                        .getResources().getDrawable(R.drawable.ic_dot_normal));
            }
            if (pos == 0) {
                mImageViewIds[IMAGE_COUNT - 1]
                        .setImageDrawable(getBaseContext().getResources()
                                .getDrawable(R.drawable.ic_dot_normal));
            }
        }

        @Override
        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub

        }
    };

    /**
     * 点击事件，点击图片进入SecondActivity
     */
    private OnItemClickListener onItemClickListener = new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1, int pos,
                long arg3) {
            Intent intent = new Intent();
            intent.setClass(MainActivity.this, SecondActivity.class);
            startActivity(intent);
        }
    };
}
ImageAdapter类，重写android.widget.BaseAdapter，用于描述图像信息。
public class ImageAdapter extends BaseAdapter {
    private Context context;
    private int[] mImages = { R.drawable.bg_timeline_01,
            R.drawable.bg_timeline_02, R.drawable.bg_timeline_03 };
    private static final int IMAGE_PX_HEIGHT = 198;

    public ImageAdapter(Context context) {
        this.context = context;
    }

    @Override
    public int getCount() {
        return Integer.MAX_VALUE;//实现循环显示
    }

    @Override
    public Object getItem(int position) {
        return position;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView = new ImageView(context);
        imageView.setImageResource(mImages[position % mImages.length]);
        imageView.setScaleType(ImageView.ScaleType.CENTER);
        imageView.setLayoutParams(new Gallery.LayoutParams(
                Gallery.LayoutParams.FILL_PARENT, IMAGE_PX_HEIGHT));

        RelativeLayout borderImg = new RelativeLayout(context);
        borderImg.setPadding(2, 2, 2, 2);
        borderImg.setBackgroundResource(R.drawable.bg_gallery);//设置ImageView边框
        borderImg.addView(imageView);
        return borderImg;
    }

}

如果用系统背景，可以这样写
int mGalleryItemBackground;
private Context mContext;
 
public ImageAdapter(Context context)
{
mContext = context;
// 获得Gallery组件的属性
TypedArray typedArray = obtainStyledAttributes(R.styleable.Gallery);
mGalleryItemBackground = typedArray.getResourceId(
R.styleable.Gallery_android_galleryItemBackground, 0); 
}

在getview中设置
imageView.setBackgroundResource(mGalleryItemBackground);
Gallery组件属性信息定义在res\values\attrs.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="Gallery">
<attr name="android:galleryItemBackground" />
</declare-styleable>
</resources>

详细讲解见http://www.eoeandroid.com/forum.php?mod=viewthread&tid=182297

自定义边框参考http://stackoverflow.com/questions/4830173/change-border-style-in-gallery