Android应用开发控件——Gallery和ImageSwitcher

Gallery组件主要用于横向显示图像列表，不过按常规做法。Gallery组件只能有限地显示指定的图像。也就是说，如果为Gallery组件指定了10张图像，那么当Gallery组件显示到第10张时，就不会再继续显示了。这虽然在大多数时候没有什么关系，但在某些情况下，我们希望图像显示到最后一张时再重第1张开始显示，也就是循环显示。要实现这种风格的Gallery组件，就需要对Gallery的Adapter对象进行一番改进。

以下通过Gallery模拟循环显示图像，在单击某一个Gallery组件中的图像时在下方显示一个放大的图像（使用ImageSwitcher组件）。

最终效果图如下：

View Code

package cn.moon.contact;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageButton;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;
import android.widget.ViewSwitcher.ViewFactory;

public class AddContactActivity extends Activity {
ImageButton ibtnImgChoose;
AlertDialog imgChooseDialog;
Gallery gallery;
ImageSwitcher imageSwitcher;
int selectedImage;

private int[] images = { R.drawable.png0001, R.drawable.png0002,
R.drawable.png0003, R.drawable.png0004, R.drawable.png0005,
R.drawable.png0006, R.drawable.png0007, R.drawable.png0008,
R.drawable.png0009, R.drawable.png0010, };

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.addcontact);
System.out.println("AddContact");
ibtnImgChoose = (ImageButton) findViewById(R.id.ibtnHead);
ibtnImgChoose.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
initImageChoose();
imgChooseDialog.show();
}
});
}

private void initImageChoose() {
LayoutInflater layoutInflater = LayoutInflater.from(this);
View view = layoutInflater.inflate(R.layout.userheadchoose, null);
gallery = (Gallery) view.findViewById(R.id.img_gallery);
gallery.setAdapter(new imageAdapter(this));
gallery.setSelection(images.length / 2);
imageSwitcher = (ImageSwitcher) view.findViewById(R.id.img_switcher);
imageSwitcher.setFactory(new switcherFactory(this));
gallery.setOnItemSelectedListener(new OnItemSelectedListener() {

public void onItemSelected(AdapterView<?> arg0, View arg1,
int arg2, long arg3) {
imageSwitcher.setImageResource(images[arg2]);
selectedImage = arg2;
}

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

}
});
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("请选择图像");
builder.setPositiveButton("确认", new OnClickListener() {

public void onClick(DialogInterface dialog, int which) {
ibtnImgChoose.setImageResource(images[selectedImage]);
}
});
builder.setNegativeButton("取消", new OnClickListener() {

public void onClick(DialogInterface dialog, int which) {

}
});
builder.setView(view);
imgChooseDialog = builder.create();
}

class imageAdapter extends BaseAdapter {
private Context context;

public imageAdapter(Context context) {
super();
this.context = context;
}

public int getCount() {
return images.length;
}

public Object getItem(int arg0) {
// TODO Auto-generated method stub
return null;
}

public long getItemId(int position) {
// TODO Auto-generated method stub
return 0;
}

public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageView = new ImageView(context);// 构造一个ImageView
imageView.setImageResource(images[position]);// 设置ImageView图片源
imageView.setAdjustViewBounds(true);
imageView.setScaleType(ScaleType.FIT_XY);// 自适应高和宽
imageView.setLayoutParams(new Gallery.LayoutParams(80, 80));// 设置显示图处的大小
imageView.setPadding(10, 5, 10, 5);// 设置四边的距离
return imageView;
}
}

class switcherFactory implements ViewFactory {
private Context context;

public switcherFactory(Context context) {
super();
this.context = context;
}

public View makeView() {
ImageView imageView = new ImageView(context);
imageView.setLayoutParams(new ImageSwitcher.LayoutParams(90, 90));
return imageView;
}

}
}