如何检索并显示媒体库中的图片

上一篇中实例讲解了Android中的Camera的调用和图片的存储，这篇文章，我们将学习如何检索并显示媒体库中的图片。

这里有个问题需要注意，如果你在模拟器已经启动的情况下，push了几张图片到SDCard中，建议将模拟器关了，再重新启动

一下，否则，刚刚添加的图片，是没有办法获取到的。这是因为Android是在系统启动的时候来扫描模拟器上SDCard中多媒体文件的。

闲话少说，看代码：

package demo.camera; import android.app.Activity; import android.database.Cursor; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.Bundle; import android.provider.MediaStore.Images.Media; import android.util.Log; import android.view.View; import android.widget.ImageButton; import android.widget.TextView; /** * 该类完成图片的检索，显示功能 * @author Administrator * */ public class PhotoManager extends Activity { public static final float DISPLAY_WIDTH = 200; public static final float DISPLAY_HEIGHT = 200; //这里采用ImageButton的原因是有Button的作用 private ImageButton photoView; private TextView nameView; private Cursor cursor; private String photoPath; //存放某张图片对应的位置信息 private Bitmap currPhoto; //这三个变量主要用来保存Media.DATA,Media.TITLE,Media.DISPLAY_NAME的索引号，来获取每列的数据 private int photoIndex; //private int titleIndex; private int nameIndex; public void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); setContentView(R.layout.photo_view); photoView = (ImageButton)this.findViewById(R.id.image_view); photoView.setOnClickListener(clickListener); nameView = (TextView)this.findViewById(R.id.view_name); //指定获取的列 String columns[] = new String[]{ Media.DATA,Media._ID,Media.TITLE,Media.DISPLAY_NAME }; //cursor = this.managedQuery(Media.EXTERNAL_CONTENT_URI, columns, null, null, null); cursor = this.getContentResolver().query(Media.EXTERNAL_CONTENT_URI, columns, null, null, null); photoIndex = cursor.getColumnIndexOrThrow(Media.DATA); //titleIndex = cursor.getColumnIndexOrThrow(Media.TITLE); nameIndex = cursor.getColumnIndexOrThrow(Media.DISPLAY_NAME); Log.v("HERE First:", "First Debug"); //显示第一张图片，但是首先要判断一下，Cursor是否有值 if(cursor.moveToFirst()){ showImage(); } } private View.OnClickListener clickListener = new View.OnClickListener() { @Override public void onClick(View v) { if(cursor.moveToNext()){ showImage(); } } }; /** * 显示图像信息 */ private void showImage(){ photoPath = cursor.getString(photoIndex); //这里获取到的就是图片存储的位置信息 //这里怎样获取图片呢？看decodeBitmap Log.v("Photo Path:", photoPath); currPhoto = decodeBitmap(photoPath); photoView.setImageBitmap(currPhoto); nameView.setText(cursor.getString(nameIndex)); } /** * 从path中获取图片信息 * @param path * @return */ private Bitmap decodeBitmap(String path){ BitmapFactory.Options op = new BitmapFactory.Options(); op.inJustDecodeBounds = true; Bitmap bmp = BitmapFactory.decodeFile(path, op); //获取尺寸信息 //获取比例大小 int wRatio = (int)Math.ceil(op.outWidth/DISPLAY_WIDTH); int hRatio = (int)Math.ceil(op.outHeight/DISPLAY_HEIGHT); //如果超出指定大小，则缩小相应的比例 if(wRatio > 1 && hRatio > 1){ if(wRatio > hRatio){ op.inSampleSize = wRatio; }else{ op.inSampleSize = hRatio; } } op.inJustDecodeBounds = false; bmp = BitmapFactory.decodeFile(path, op); return bmp; } } package demo.camera;import android.app.Activity;import android.database.Cursor;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.Bundle;import android.provider.MediaStore.Images.Media;import android.util.Log;import android.view.View;import android.widget.ImageButton;import android.widget.TextView;/** * 该类完成图片的检索，显示功能 * @author Administrator * */public class PhotoManager extends Activity {public static final float DISPLAY_WIDTH = 200;public static final float DISPLAY_HEIGHT = 200;//这里采用ImageButton的原因是有Button的作用private ImageButton photoView;private TextView nameView;private Cursor cursor;private String photoPath; //存放某张图片对应的位置信息private Bitmap currPhoto;//这三个变量主要用来保存Media.DATA,Media.TITLE,Media.DISPLAY_NAME的索引号，来获取每列的数据private int photoIndex;//private int titleIndex;private int nameIndex;public void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.photo_view);photoView = (ImageButton)this.findViewById(R.id.image_view);photoView.setOnClickListener(clickListener);nameView = (TextView)this.findViewById(R.id.view_name);//指定获取的列String columns[] = new String[]{Media.DATA,Media._ID,Media.TITLE,Media.DISPLAY_NAME};//cursor = this.managedQuery(Media.EXTERNAL_CONTENT_URI, columns, null, null, null);cursor = this.getContentResolver().query(Media.EXTERNAL_CONTENT_URI, columns, null, null, null);photoIndex = cursor.getColumnIndexOrThrow(Media.DATA);//titleIndex = cursor.getColumnIndexOrThrow(Media.TITLE);nameIndex = cursor.getColumnIndexOrThrow(Media.DISPLAY_NAME);Log.v("HERE First:", "First Debug");//显示第一张图片，但是首先要判断一下，Cursor是否有值if(cursor.moveToFirst()){showImage();}}private View.OnClickListener clickListener = new View.OnClickListener() {@Overridepublic void onClick(View v) {if(cursor.moveToNext()){showImage();}}};/** * 显示图像信息 */private void showImage(){photoPath = cursor.getString(photoIndex); //这里获取到的就是图片存储的位置信息//这里怎样获取图片呢？看decodeBitmapLog.v("Photo Path:", photoPath);currPhoto = decodeBitmap(photoPath);photoView.setImageBitmap(currPhoto);nameView.setText(cursor.getString(nameIndex));}/** * 从path中获取图片信息 * @param path * @return */private Bitmap decodeBitmap(String path){BitmapFactory.Options op = new BitmapFactory.Options();op.inJustDecodeBounds = true;Bitmap bmp = BitmapFactory.decodeFile(path, op); //获取尺寸信息//获取比例大小int wRatio = (int)Math.ceil(op.outWidth/DISPLAY_WIDTH);int hRatio = (int)Math.ceil(op.outHeight/DISPLAY_HEIGHT);//如果超出指定大小，则缩小相应的比例if(wRatio > 1 && hRatio > 1){if(wRatio > hRatio){op.inSampleSize = wRatio;}else{op.inSampleSize = hRatio;}}op.inJustDecodeBounds = false;bmp = BitmapFactory.decodeFile(path, op);return bmp;}}