如何在显示图库视图之前从SD卡调整图像大小？

Question

如果我把存储在SD卡中的图像的正常大小放到一个图库视图中，它会非常慢，所以在图库视图中显示它之前是否有任何方法自动调整大小？ 谢谢。

private Gallery g; 
private ImageView imv; 

private Uri[] mUrls; 
String[] mFiles=null; 

class ImageFilter implements FilenameFilter 
{ 
    public boolean accept(File dir, String name) 
    { 
     return (name.endsWith(".JPG")|| name.endsWith(".jpg")); 
    } 
} 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main);  

    File images = new File("/sdcard/DCIM/Camera/"); 
    File[] imagelist = images.listFiles(new ImageFilter()); 

    mFiles = new String[imagelist.length]; 

    for(int i= 0 ; i< imagelist.length; i++){ 
     mFiles[i] = imagelist[i].getAbsolutePath(); 
    } 

    mUrls = new Uri[mFiles.length]; 

    for(int i=0; i < mFiles.length; i++){ 
     mUrls[i] = Uri.parse(mFiles[i]); 
    } 

    imv = (ImageView)findViewById(R.id.ImageView01);  

    g = (Gallery) findViewById(R.id.gallery); 
    g.setAdapter(new ImageAdapter(this)); 
    g.setFadingEdgeLength(40); 
    g.setOnItemClickListener(new OnItemClickListener() { 
     public void onItemClick(AdapterView<?> parent, View v, int position, long id) { 
      imv.setImageURI(mUrls[position]);    
     } 
    }); 
} 

public class ImageAdapter extends BaseAdapter { 
    int mGalleryItemBackground; 
    private Context mContext; 

    public ImageAdapter(Context c) { 
     mContext = c; 
     TypedArray a = obtainStyledAttributes(R.styleable.HelloGallery); 
     mGalleryItemBackground = a.getResourceId(R.styleable.HelloGallery_android_galleryItemBackground, 0); 
     a.recycle(); 
    } 

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

    public Object getItem(int position) { 
     return position; 
    } 

    public long getItemId(int position) { 
     return position; 
    } 

    public View getView(int position, View convertView, ViewGroup parent) { 
     ImageView i = new ImageView(mContext); 

     i.setImageURI(mUrls[position]);    
     i.setLayoutParams(new Gallery.LayoutParams(150, 100)); 
     i.setScaleType(ImageView.ScaleType.FIT_XY); 
     i.setBackgroundResource(mGalleryItemBackground); 

     return i; 
    } 
} 

Answer 1

import android.content.Context; 
import android.graphics.Canvas; 
import android.graphics.drawable.BitmapDrawable; 
import android.util.AttributeSet; 
import android.util.Log; 
import android.view.MotionEvent; 
import android.view.ScaleGestureDetector; 
import android.view.View; 

public class MyImageView extends View { 

private static final int INVALID_POINTER_ID = -1; 

    private Drawable mImage; 
    private float mPosX; 
    private float mPosY; 

    private float mLastTouchX; 
    private float mLastTouchY; 
    private int mActivePointerId = INVALID_POINTER_ID; 

    private ScaleGestureDetector mScaleDetector; 
    private float mScaleFactor = 1.f; 

    public MyImageView(Context context) { 
     this(context, null, 0); 
    mImage = Drawable.createFromPath("/sdcard/filename"); 

     mImage.setBounds(0, 0, width, height); 
    } 

    public MyImageView(Context context, AttributeSet attrs) { 
     this(context, attrs, 0); 
    } 

    public MyImageView(Context context, AttributeSet attrs, int defStyle) { 
     super(context, attrs, defStyle); 
     mScaleDetector = new ScaleGestureDetector(context, new ScaleListener()); 
    } 

    @Override 
    public boolean onTouchEvent(MotionEvent ev) { 
     // Let the ScaleGestureDetector inspect all events. 
     mScaleDetector.onTouchEvent(ev); 

     final int action = ev.getAction(); 
     switch (action & MotionEvent.ACTION_MASK) { 
     case MotionEvent.ACTION_DOWN: { 
      final float x = ev.getX(); 
      final float y = ev.getY(); 

      mLastTouchX = x; 
      mLastTouchY = y; 
      mActivePointerId = ev.getPointerId(0); 
      break; 
     } 

     case MotionEvent.ACTION_MOVE: { 
      final int pointerIndex = ev.findPointerIndex(mActivePointerId); 
      final float x = ev.getX(pointerIndex); 
      final float y = ev.getY(pointerIndex); 

      // Only move if the ScaleGestureDetector isn't processing a gesture. 
      if (!mScaleDetector.isInProgress()) { 
       final float dx = x - mLastTouchX; 
       final float dy = y - mLastTouchY; 

       mPosX += dx; 
       mPosY += dy; 

       invalidate(); 
      } 

      mLastTouchX = x; 
      mLastTouchY = y; 

      break; 
     } 

     case MotionEvent.ACTION_UP: { 
      mActivePointerId = INVALID_POINTER_ID; 
      break; 
     } 

     case MotionEvent.ACTION_CANCEL: { 
      mActivePointerId = INVALID_POINTER_ID; 
      break; 
     } 

     case MotionEvent.ACTION_POINTER_UP: { 
      final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) 
        >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; 
      final int pointerId = ev.getPointerId(pointerIndex); 
      if (pointerId == mActivePointerId) { 
       // This was our active pointer going up. Choose a new 
       // active pointer and adjust accordingly. 
       final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 
       mLastTouchX = ev.getX(newPointerIndex); 
       mLastTouchY = ev.getY(newPointerIndex); 
       mActivePointerId = ev.getPointerId(newPointerIndex); 
      } 
      break; 
     } 
     } 

     return true; 
    } 

    @Override 
    public void onDraw(Canvas canvas) { 
     super.onDraw(canvas); 

     canvas.save(); 
     Log.d("DEBUG", "X: "+mPosX+" Y: "+mPosY); 
     canvas.translate(mPosX, mPosY); 
     canvas.scale(mScaleFactor, mScaleFactor); 
     mImage.draw(canvas); 
     canvas.restore(); 
    } 

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener { 
     @Override 
     public boolean onScale(ScaleGestureDetector detector) { 
      mScaleFactor *= detector.getScaleFactor(); 

      // Don't let the object get too small or too large. 
      mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f)); 

      invalidate(); 
      return true; 
     } 
    } 

} 

在您的活动调用这个，的setContentView（新MyImageView（本））;