Android加載大圖片到內存

在android中要加載一張大圖片到內存中如果通過如下方式進行

    Bitmap bitmap= BitmapFactory.decodeFile("/sdcard/a.jpg");  
     iv.setImageBitmap(bitmap);  

正確的做法應該是這樣的：

    public class MainActivity extends Activity {

        private ImageView iv;

        private int windowHeight;

        private int windowWidth;


    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
        iv = (ImageView) findViewById(R.id.iv);  
        WindowManager win = (WindowManager) getSystemService(WINDOW_SERVICE);  
        windowHeight = win.getDefaultDisplay().getHeight();  
        windowWidth = win.getDefaultDisplay().getWidth();  
    }  

    @Override  
    public boolean onCreateOptionsMenu(Menu menu) {  
        // Inflate the menu; this adds items to the action bar if it is present.  
        getMenuInflater().inflate(R.menu.main, menu);  
        return true;  
    }  

    public void load(View view) {  

    /*   Bitmap bitmap= BitmapFactory.decodeFile("/sdcard/a.jpg"); 
         iv.setImageBitmap(bitmap);*/  

        // 圖片解析的配置  
        BitmapFactory.Options options = new Options();  
        // 不去真的解析圖片，只是獲取圖片的頭部信息寬，高  
        options.inJustDecodeBounds = true;  
        BitmapFactory.decodeFile("/sdcard/a.jpg", options);  
        int imageHeight = options.outHeight;  
        int imageWidth = options.outWidth;  
        // 計算縮放比例  
        int scaleX = imageWidth / windowWidth;  
        int scaleY = imageHeight / windowHeight;  
        int scale = 1;  
        if (scaleX > scaleY & scaleY >= 1) {  
            scale = scaleX;  

        }else if (scaleY > scaleX & scaleX >= 1) {  
            scale = scaleY;  

        }  
        //真的解析圖片  
        options.inJustDecodeBounds=false;  
        //設置采樣率  
        options.inSampleSize=scale;  
        Bitmap bitmap=BitmapFactory.decodeFile("/sdcard/a.jpg", options);  
        iv.setImageBitmap(bitmap);  
    }  

}  </pre><br />

xml文件 
    <LinearLayout xmlns:android="
        xmlns:tools="
        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:orientation="vertical"

        tools:context=".MainActivity" >


    <Button  
        android:onClick="load"  
        android:layout_width="match_parent"  
        android:layout_height="wrap_content"  
        android:text="加載大圖片到內存" />  

    <ImageView  
        android:id="@+id/iv"  
        android:layout_width="match_parent"  
        android:layout_height="match_parent" />  

</LinearLayout>  </pre><br />

在這種情況下，是將大分辨率的圖片按照一定的比例縮小然后加載進內存，就不會出現內存溢出的現象了。