目的：了解如何应用非本地图片资源制作Gallery widget。
Layout 源代码 (XML)：
主程序源代码 (Java)：
import java.io.BufferedInputStream; import java.io.IOException; import java.io.InputStream; import java.net.URL; import java.net.URLConnection; import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.Gallery; import android.widget.ImageView; public class GalleryExample extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.main); /* Find the gallery defined in the main.xml * Apply a new (custom) ImageAdapter to it. */ ((Gallery) findViewById(R.id.gallery)) .setAdapter(new ImageAdapter(this)); } public class ImageAdapter extends BaseAdapter { /** The parent context */ private Context myContext; /** URL-Strings to some remote images. */ private String[] myRemoteImages = { "http://www.anddev.org/images/tiny_tutheaders/weather_forecast.png", "http://www.anddev.org/images/tiny_tutheaders/cellidtogeo.png", "http://www.anddev.org/images/tiny_tutheaders/droiddraw.png" }; /** Simple Constructor saving the 'parent' context. */ public ImageAdapter(Context c) { this.myContext = c; } /** Returns the amount of images we have defined. */ public int getCount() { return this.myRemoteImages.length; } /* Use the array-Positions as unique IDs */ public Object getItem(int position) { return position; } public long getItemId(int position) { return position; } /** Returns a new ImageView to * be displayed, depending on * the position passed. */ public View getView(int position, View convertView, ViewGroup parent) { ImageView i = new ImageView(this.myContext); try { /* Open a new URL and get the InputStream to load data from it. */ URL aURL = new URL(myRemoteImages[position]); URLConnection conn = aURL.openConnection(); conn.connect(); InputStream is = conn.getInputStream(); /* Buffered is always good for a performance plus. */ BufferedInputStream bis = new BufferedInputStream(is); /* Decode url-data to a bitmap. */ Bitmap bm = BitmapFactory.decodeStream(bis); bis.close(); is.close(); /* Apply the Bitmap to the ImageView that will be returned. */ i.setImageBitmap(bm); } catch (IOException e) { i.setImageResource(R.drawable.error); Log.e("DEBUGTAG", "Remtoe Image Exception", e); } /* Image should be scaled as width/height are set. */ i.setScaleType(ImageView.ScaleType.FIT_CENTER); /* Set the Width/Height of the ImageView. */ i.setLayoutParams(new Gallery.LayoutParams(150, 150)); return i; } /** Returns the size (0.0f to 1.0f) of the views * depending on the 'offset' to the center. */ public float getScale(boolean focused, int offset) { /* Formula: 1 / (2 ^ offset) */ return Math.max(0, 1.0f / (float)Math.pow(2, Math.abs(offset))); } } }
Posted in Resource, Tutorial |
EGGer June 10th, 2009 at 7:04 pm
延时肯定存在，任何操作都存在一定程度的延时，这么说有点抬杠的成分。根据用户所处的网络环境而定，一般情况下不会有出现明显的不良反应。