在GridView中展示sd卡中的图片
package blog.android.sdcard;import android.app.Activity;import android.content.Context;import android.content.Intent;import android.database.Cursor;import android.net.Uri;import android.os.Bundle;import android.provider.MediaStore;import android.view.Menu;import android.view.MenuInflater;import android.view.MenuItem;import android.view.View;import android.view.ViewGroup;import android.widget.AdapterView;import android.widget.BaseAdapter;import android.widget.GridView;import android.widget.ImageView;import android.widget.AdapterView.OnItemClickListener;/** * Displays images from an SD card. */public class SDCardImagesActivity extends Activity { /** * Cursor used to access the results from querying for images on the SD card. */ private Cursor cursor; /* * Column index for the Thumbnails Image IDs. */ private int columnIndex; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.sdcard); // Set up an array of the Thumbnail Image ID column we want String[] projection = {MediaStore.Images.Thumbnails._ID}; // Create the cursor pointing to the SDCard cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, projection, // Which columns to return null, // Return all rows null, MediaStore.Images.Thumbnails.IMAGE_ID); // Get the column index of the Thumbnails Image ID columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID); GridView sdcardImages = (GridView) findViewById(R.id.sdcard); sdcardImages.setAdapter(new ImageAdapter(this)); // Set up a click listener sdcardImages.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView parent, View v, int position, long id) { // Get the data location of the image String[] projection = {MediaStore.Images.Media.DATA}; cursor = managedQuery( MediaStore.Images.Media.EXTERNAL_CONTENT_URI, projection, // Which columns to return null, // Return all rows null, null); columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA); cursor.moveToPosition(position); // Get image filename String imagePath = cursor.getString(columnIndex); // Use this path to do further processing, i.e. full screen display } }); } /** * Adapter for our image files. */ private class ImageAdapter extends BaseAdapter { private Context context; public ImageAdapter(Context localContext) { context = localContext; } public int getCount() { return cursor.getCount(); } public Object getItem(int position) { return position; } public long getItemId(int position) { return position; } public View getView(int position, View convertView, ViewGroup parent) { ImageView picturesView; if (convertView == null) { picturesView = new ImageView(context); // Move cursor to current position cursor.moveToPosition(position); // Get the current value for the requested column int imageID = cursor.getInt(columnIndex); // Set the content of the image based on the provided URI picturesView.setImageURI(Uri.withAppendedPath( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, "" + imageID)); picturesView.setScaleType(ImageView.ScaleType.FIT_CENTER); picturesView.setPadding(8, 8, 8, 8); picturesView.setLayoutParams(new GridView.LayoutParams(100, 100)); } else { picturesView = (ImageView)convertView; } return picturesView; } }}The layout of the main activity is shown below:<?xml version="1.0" encoding="utf-8"?><GridView xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/sdcard" android:layout_width="fill_parent" android:layout_height="fill_parent" android:padding="10dp" android:verticalSpacing="10dp" android:horizontalSpacing="10dp" android:numColumns="auto_fit" android:columnWidth="90dp" android:stretchMode="columnWidth" android:gravity="center"/> 注意 通常最好是自己在sd卡中已经弄成了一些小图片MediaStore.Images.Thumbnails._ID 换成MediaStore.Images.Thumbnails.IMAGE_ID 是因为有时候小图片不显示，而且有时候还会出现错误的路径所以使用
cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
projection, // Which columns to return
null, // Return all rows
null,
MediaStore.Images.Thumbnails.IMAGE_ID);
而不是
cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
projection, // Which columns to return
null, // Return all rows
null,
null);
main.xml
<?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/sdcard"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="10dp"
android:verticalSpacing="10dp"
android:horizontalSpacing="10dp"
android:numColumns="auto_fit"
android:columnWidth="90dp"
android:stretchMode="columnWidth"
android:gravity="center"
/>
改进一下
package blog.android.sdcard2;import java.io.BufferedInputStream;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.util.ArrayList;import android.app.Activity;import android.content.Context;import android.database.Cursor;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.drawable.BitmapDrawable;import android.net.Uri;import android.os.AsyncTask;import android.os.Bundle;import android.provider.MediaStore;import android.view.Display;import android.view.View;import android.view.ViewGroup;import android.view.Window;import android.view.WindowManager;import android.widget.AdapterView;import android.widget.BaseAdapter;import android.widget.GridView;import android.widget.ImageView;import android.widget.AdapterView.OnItemClickListener;/** * Loads images from SD card.** @author Mihai Fonoage * */public class LoadImagesFromSDCardActivity extends Activity implementsOnItemClickListener { /** * Grid view holding the images. */ private GridView sdcardImages; /** * Image adapter for the grid view. */ private ImageAdapter imageAdapter; /** * Display used for getting the width of the screen. */ private Display display; /** * Creates the content view, sets up the grid, the adapter, and the click listener. * * @see android.app.Activity#onCreate(android.os.Bundle) */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Request progress bar requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS); setContentView(R.layout.sdcard); display = ((WindowManager) getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay(); setupViews(); loadImages(); } /** * Free up bitmap related resources. */ protected void onDestroy() { super.onDestroy(); final GridView grid = sdcardImages; final int count = grid.getChildCount(); ImageView v = null; for (int i = 0; i < count; i++) { v = (ImageView) grid.getChildAt(i); ((BitmapDrawable) v.getDrawable()).setCallback(null); } } /** * Setup the grid view. */ private void setupViews() { sdcardImages = (GridView) findViewById(R.id.sdcard); sdcardImages.setNumColumns(display.getWidth()/95); sdcardImages.setClipToPadding(false); sdcardImages.setOnItemClickListener(LoadImagesFromSDCardActivity.this); imageAdapter = new ImageAdapter(getApplicationContext()); sdcardImages.setAdapter(imageAdapter); } /** * Load images. */ private void loadImages() { final Object data = getLastNonConfigurationInstance(); if (data == null) { new LoadImagesFromSDCard().execute(); } else { final LoadedImage[] photos = (LoadedImage[]) data; if (photos.length == 0) { new LoadImagesFromSDCard().execute(); } for (LoadedImage photo : photos) { addImage(photo); } } } /** * Add image(s) to the grid view adapter. * * @param value Array of LoadedImages references */ private void addImage(LoadedImage... value) { for (LoadedImage image : value) { imageAdapter.addPhoto(image); imageAdapter.notifyDataSetChanged(); } } /** * Save bitmap images into a list and return that list. * * @see android.app.Activity#onRetainNonConfigurationInstance() */ @Override public Object onRetainNonConfigurationInstance() { final GridView grid = sdcardImages; final int count = grid.getChildCount(); final LoadedImage[] list = new LoadedImage; for (int i = 0; i < count; i++) { final ImageView v = (ImageView) grid.getChildAt(i); list = new LoadedImage(((BitmapDrawable) v.getDrawable()).getBitmap()); } return list; } /** * Async task for loading the images from the SD card. * * @author Mihai Fonoage * */ class LoadImagesFromSDCard extends AsyncTask<Object, LoadedImage, Object> { /** * Load images from SD Card in the background, and display each image on the screen. * * @see android.os.AsyncTask#doInBackground(Params[]) */ @Override protected Object doInBackground(Object... params) { setProgressBarIndeterminateVisibility(true); Bitmap bitmap = null; Bitmap newBitmap = null; Uri uri = null; // Set up an array of the Thumbnail Image ID column we want String[] projection = {MediaStore.Images.Thumbnails._ID}; // Create the cursor pointing to the SDCard Cursor cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, projection, // Which columns to return null, // Return all rows null, null); int columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID); int size = cursor.getCount(); // If size is 0, there are no images on the SD Card. if (size == 0) { //No Images available, post some message to the user } int imageID = 0; for (int i = 0; i < size; i++) { cursor.moveToPosition(i); imageID = cursor.getInt(columnIndex); uri = Uri.withAppendedPath(MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, "" + imageID); try { bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri)); if (bitmap != null) { newBitmap = Bitmap.createScaledBitmap(bitmap, 70, 70, true); bitmap.recycle(); if (newBitmap != null) { publishProgress(new LoadedImage(newBitmap)); } } } catch (IOException e) { //Error fetching image, try to recover } } cursor.close(); return null; } /** * Add a new LoadedImage in the images grid. * * @param value The image. */ @Override public void onProgressUpdate(LoadedImage... value) { addImage(value); } /** * Set the visibility of the progress bar to false. * * @see android.os.AsyncTask#onPostExecute(java.lang.Object) */ @Override protected void onPostExecute(Object result) { setProgressBarIndeterminateVisibility(false); } } /** * Adapter for our image files. * * @author Mihai Fonoage * */ class ImageAdapter extends BaseAdapter { private Context mContext; private ArrayList<LoadedImage> photos = new ArrayList<LoadedImage>(); public ImageAdapter(Context context) { mContext = context; } public void addPhoto(LoadedImage photo) { photos.add(photo); } public int getCount() { return photos.size(); } public Object getItem(int position) { return photos.get(position); } public long getItemId(int position) { return position; } public View getView(int position, View convertView, ViewGroup parent) { final ImageView imageView; if (convertView == null) { imageView = new ImageView(mContext); } else { imageView = (ImageView) convertView; } imageView.setScaleType(ImageView.ScaleType.FIT_CENTER); imageView.setPadding(8, 8, 8, 8); imageView.setImageBitmap(photos.get(position).getBitmap()); return imageView; } } /** * A LoadedImage contains the Bitmap loaded for the image. */ private static class LoadedImage { Bitmap mBitmap; LoadedImage(Bitmap bitmap) { mBitmap = bitmap; } public Bitmap getBitmap() { return mBitmap; } } /** * When an image is clicked, load that image as a puzzle. */ public void onItemClick(AdapterView<?> parent, View v, int position, long id) { int columnIndex = 0; String[] projection = {MediaStore.Images.Media.DATA}; Cursor cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, projection, null, null, null); if (cursor != null) { columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA); cursor.moveToPosition(position); String imagePath = cursor.getString(columnIndex); FileInputStream is = null; BufferedInputStream bis = null; try { is = new FileInputStream(new File(imagePath)); bis = new BufferedInputStream(is); Bitmap bitmap = BitmapFactory.decodeStream(bis); Bitmap useThisBitmap = Bitmap.createScaledBitmap(bitmap, parent.getWidth(), parent.getHeight(), true); bitmap.recycle(); //Display bitmap (useThisBitmap) } catch (Exception e) { //Try to recover } finally { try { if (bis != null) { bis.close(); } if (is != null) { is.close(); } cursor.close(); projection = null; } catch (Exception e) { } } } }}
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