Android检索图像

public class MainActivity extends Activity {private final static int DISPLAY_HEIGHT=200;private final static int DISPLAY_WIDTH=200;@SuppressWarnings("deprecation")protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);    ListView listView = (ListView) findViewById(R.id.img_listview);String[] columns = { Media.DATA};//使用共享内容提供者。Cursor cursor = getContentResolver().query(Media.EXTERNAL_CONTENT_URI, columns, null, null, null);    //构建一个简单的适配器SimpleAdapter  sAdapter = new SimpleAdapter(getApplicationContext(), getImageMap(cursor),                                    R.layout.listview_layout,                                    new String[]{"img"},                                    new int[]{R.id.img});//存入binersAdapter.setViewBinder(new ViewBinder() {@Overridepublic boolean setViewValue(View view, Object data,String textRepresentation) {//判断是否是ImageView类型  if(view instanceof ImageView){  ImageView image = (ImageView) view;  //把map里的value取出来.  String imageFilePath = (String) data;  //显示图像  image.setImageBitmap(getBitmap(imageFilePath));  }return true;}});listView.setAdapter(sAdapter);        }private List<Map<String,Object>> getImageMap(Cursor sc){  List<Map<String,Object>> list = new ArrayList<Map<String,Object>>();  Map<String,Object> map =null;  while(sc.moveToNext()){  map = new HashMap<String,Object>();  map.put("img",sc.getString(0));  System.out.println("image path:"+sc.getString(0));  list.add(map);  }  return list;  }private Bitmap getBitmap(String imageFilePath) {//加载图像的尺寸而不是图像的本身BitmapFactory.Options  opts = new BitmapFactory.Options();opts.inJustDecodeBounds  = true;    Bitmap bp =  BitmapFactory.decodeFile(imageFilePath, opts);int heightRatio  = (int) Math.ceil(opts.outHeight/(float)DISPLAY_HEIGHT);int widthRatio   =(int) Math.ceil(opts.outHeight/(float)DISPLAY_WIDTH);System.out.println("heightRatio :"+heightRatio);System.out.println("widthRatio  :"+widthRatio);//如果两个比率都大于1，那么图像 的一条边大于屏幕if(widthRatio>1&&heightRatio>1){ if(heightRatio>widthRatio) //若高度比率较大，则根据它进行缩放opts.inSampleSize = heightRatio; else  //若宽度比率较大，则根据它进行缩放 opts.inSampleSize = widthRatio;}//-----------------------------------------------------////对它进行解码opts.inJustDecodeBounds =false;bp = BitmapFactory.decodeFile(imageFilePath, opts);    return bp;}}

activity_main.xml :文件如下

<LinearLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <ListView android:id="@+id/img_listview"              android:layout_height="wrap_content"              android:layout_width="match_parent"              android:dividerHeight="1dip"/></LinearLayout>

listview_layout.xml 文件如下:

<LinearLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <ListView android:id="@+id/img_listview"              android:layout_height="wrap_content"              android:layout_width="match_parent"              android:dividerHeight="1dip"/></LinearLayout>

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