Android之等比例显示图片

　　在android中，由于密度的影响，如果想得到图片的宽高是不行的，具体为什么我就大概说一下，具体的请搜索度娘或者古哥吧。原因是如果你把图片放在drawable-mdpi里，而手机是属于drawable-hdpi的话，图片是被自动放大，就这样取到的宽与高未必就是正确的。那么如何让android上面显示的图片是基于原来图片的比例呢，首先你可以在res目录下创建一个drawable-nodpi的目录，这个目录下的图片是不根据dpi的多少来进行拉伸或者缩小滴。然后，就是根据屏幕的宽和图片的宽高得出图片在屏幕显示的高，宽是固定的，就是屏幕的宽，所以不用算了。

private void getWidth_Height() {        Display display = getWindowManager().getDefaultDisplay();        int width = display.getWidth(); // deprecated        int height = display.getHeight(); // deprecated        Bitmap mBitmap = createImageWithResouce(R.drawable.history4);        image.setLayoutParams(new LayoutParams(width, width / getBitmapWidth(mBitmap) * getBitmapHeight(mBitmap)));        image.setImageBitmap(createImageWithResouce(R.drawable.history4));    }    private Bitmap createImageWithResouce(int resourceID) {        Bitmap bit = BitmapFactory.decodeResource(getResources(), R.drawable.history4);        return bit;    }        private int getBitmapWidth(Bitmap bitmap){        return bitmap.getWidth();    }    private int getBitmapHeight(Bitmap bitmap){        return bitmap.getHeight();    }        // 释放bitmap    private void releaseBitmap(Bitmap bitmap){        if (bitmap!=null && !bitmap.isRecycled()) {            bitmap.recycle();            bitmap = null;        }    }

建议使用如下的这种，应用了LruCache作为管理

public class ImageUtil {    private LruCache<String, Bitmap> mMemoryCache;    private final Context mContext;    private static ImageUtil imageUtil;    private static Object obj = new Object();    private int memClass;    private int cacheSize;    private ImageUtil(Context mContext) {        this.mContext = mContext;        createLruCache(mContext);    }    private void createLruCache(Context mContext) {        memClass = ((ActivityManager) mContext.getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass();        cacheSize = 1024 * 1024 * memClass / 8;        mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {            @Override            protected int sizeOf(String key, Bitmap value) {                // TODO Auto-generated method stub                return value.getRowBytes();            }        };    }    public static ImageUtil getInstance(Context mContext) {        if (imageUtil == null) {            synchronized (obj) {                if (imageUtil == null) {                    imageUtil = new ImageUtil(mContext);                }            }        }        return imageUtil;    }    public void adjustImageSize(ImageView imageView, int imageResourceId) {        Bitmap mBitmap = null;        Display display = ((MainActivity) mContext).getWindowManager().getDefaultDisplay();        int width = display.getWidth(); // deprecated        int height = display.getHeight(); // deprecated        Bitmap bitmapCache = mMemoryCache.get(imageResourceId + "");        if (bitmapCache != null) {            mBitmap = bitmapCache;        } else {            mBitmap = createImageWithResouce(mContext, imageResourceId);            mMemoryCache.put(imageResourceId + "", mBitmap);        }        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(width, width                / getBitmapWidth(mBitmap) * getBitmapHeight(mBitmap));        layoutParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);        imageView.setLayoutParams(layoutParams);        imageView.setBackgroundDrawable(new BitmapDrawable(mBitmap));        // imageView.setImageBitmap(mBitmap);    }    private static Bitmap createImageWithResouce(Context context, int resourceID) {        Bitmap bit = BitmapFactory.decodeResource(context.getResources(), R.drawable.ic_launcher);        return bit;    }    private int getBitmapWidth(Bitmap bitmap) {        return bitmap.getWidth();    }    private int getBitmapHeight(Bitmap bitmap) {        return bitmap.getHeight();    }}

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