解决关于图片过大而造成OutOfMemoryError方法

╰半夏微凉° 2024-02-19 18:53 60阅读 0赞

1.首先在Activity中获得屏幕分辨率  
final DisplayMetrics dm = new DisplayMetrics();  
getWindowManager().getDefaultDisplay().getMetrics(dm);  
int height = dm.heightPixels;  
int width = dm.widthPixels;  
2.当图片过大，或图片数量较多时使用BitmapFactory解码图片会出java.lang.OutOfMemoryError: bitmap size exceeds VM budget，要想正常使用则需分配更少的内存，具体的解决办法是修改采样值BitmapFactory.Options.inSampleSize，例如：www.2cto.comBitmapFactory.Options opts = new BitmapFactory.Options();  
opts.inSampleSize = 4;  
  
Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);如何设置恰当的inSampleSize  
  
设置恰当的inSampleSize是解决该问题的关键之一。BitmapFactory.Options提供了另一个成员inJustDecodeBounds。  
  
BitmapFactory.Options opts = new BitmapFactory.Options();  
opts.inJustDecodeBounds = true;  
Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);  
  
设置inJustDecodeBounds为true后，decodeFile并不分配空间，但可计算出原始图片的长度和宽度，即opts.width和opts.height。有了这两个参数，再通过一定的算法，即可得到一个恰当的inSampleSize。  
  
查看Android源码，Android提供了一种动态计算的方法。  
  
创建ImageTools类（参照原文http://www.2cto.com/kf/201206/136907.html）

/**
    * 
    */
    package com.cmdi.util;
    
    import android.graphics.BitmapFactory;
    
    /**
    * @author wu
    *为了避免导入图片过大而造成内存溢出
    */
    public class ImgTools {
    
    public static int computeSampleSize(BitmapFactory.Options options,
    int minSideLength, int maxNumOfPixels) {
    int initialSize = computeInitialSampleSize(options, minSideLength,maxNumOfPixels);
    int roundedSize;
    if (initialSize <= 8 ) {
    roundedSize = 1;
    while (roundedSize < initialSize) {
    roundedSize <<= 1;
    }
    } else {
    roundedSize = (initialSize + 7) / 8 * 8;
    }
    return roundedSize;
    }
    
    private static int computeInitialSampleSize(BitmapFactory.Options options,int minSideLength, int maxNumOfPixels) {
    double w = options.outWidth;
    double h = options.outHeight;
    
    int lowerBound = (maxNumOfPixels == -1) ? 1 :
    (int) Math.ceil(Math.sqrt(w * h / maxNumOfPixels));
    int upperBound = (minSideLength == -1) ? 128 :
    (int) Math.min(Math.floor(w / minSideLength),
    Math.floor(h / minSideLength));
    
    if (upperBound < lowerBound) {
    // return the larger one when there is no overlapping zone.
    return lowerBound;
    }
    if ((maxNumOfPixels == -1) &&
    (minSideLength == -1)) {
    return 1;
    } else if (minSideLength == -1) {
    return lowerBound;
    } else {
    return upperBound;
    }
    }
    }

3.调用ImgTools

// 通过图片的路径获得Bitmap
    	public void setImage(String path,int height,int width) {
    		File f = new File(path);
    		
    		if (f != null && f.isFile()) {
    			BitmapFactory.Options opts = new BitmapFactory.Options();
    			opts.inJustDecodeBounds = true;
    			BitmapFactory.decodeFile(path, opts);
    			opts.inSampleSize = ImgTools.computeSampleSize(opts, -1, height*width);
    			opts.inJustDecodeBounds = false;
    			try {
    				mBitmap = BitmapFactory.decodeFile(path,opts).copy(
    						Bitmap.Config.ARGB_8888, true);
    			} catch (OutOfMemoryError err) {
    				
    			}
    			// 从资源中获取Bitmap并根据该位图的大小产生一个新位图
    			/*mBitmap = BitmapFactory.decodeFile(path,opts).copy(
    					Bitmap.Config.ARGB_8888, true);*/
    			calculateAspectQuotient();
    			// 刷新View,把之前的旧的view从主UI线程队列中pop掉
    			invalidate();
    			
    		} else {
    			;
    		}
    		
    	}

注：同时需要通过onDestory()及时回收内存

@Override
    	protected void onDestroy(){
    		super.onDestroy();
    		//及时回收内存
    		if (mBitmap != null){
    			mBitmap.recycle();
    		}
    	}