Android loads large images to memory,

Android loads large images to memory,

This article demonstrates how to load images to memory in android

First, design the interface:

The Code is as follows:

<LinearLayout xmlns: android = "http://schemas.android.com/apk/res/android" xmlns: tools = "http://schemas.android.com/tools" android: layout_width = "match_parent" android: layout_height = "match_parent" android: orientation = "vertical" tools: context = ". mainActivity "> <Button android: layout_width =" wrap_content "android: layout_height =" wrap_content "android: onClick =" load "android: text = "loading images to memory"/> <ImageView android: id = "@ + id/iv" android: layout_width = "fill_parent" android: layout_height = "fill_parent"/> </LinearLayout>

Upload test images to mnt/sdcard

Add the logic code:

public class MainActivity extends Activity {    private ImageView iv;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        iv = (ImageView) findViewById(R.id.iv);    }    public void load() {        Bitmap bitmap = BitmapFactory.decodeFile("/sdcard/a.jpg");        iv.setImageBitmap(bitmap);    }}

Run the code to generate an error because the image is too large (select a large photo)

You can use static Options in BitmapFactory to obtain the image width and height without parsing the image information:

BitmapFactory. options opts = new Options (); // do not parse the image information, just get the width and height of the image header opts. inJustDecodeBounds = true; BitmapFactory. decodeFile ("/sdcard/a.jpg", opts); int imageHeight = opts. outHeight; int imagewidth = opts. outWidth; System. out. println ("Image Width:" + imagewidth); System. out. println ("Image Height" + imageHeight );

 

Run:

09-04 06:09:10. 519: I/System. out (1812): Image Width: 2560
09-04 06:09:10. 519: I/System. out (1812): The image height is 1920.

The following figure shows the screen width and height of the mobile phone:

// Obtain the WindowManager wm = (WindowManager) getSystemService (WINDOW_SERVICE); int height = wm. getdefadisplay display (). getHeight (); int width = wm. getdefadisplay display (). getWidth ();

We can see that the getHeight and getWidth methods are outdated. Use the following method instead:

// Obtain the WindowManager wm = (WindowManager) getSystemService (WINDOW_SERVICE); Point outSize = new Point (); wm. getdefadisplay display (). getSize (outSize); // Versions later than 3.0 can be used

The complete code is as follows:

Package com. wuyudong. loadimage; import android. OS. bundle; import android. annotation. suppressLint; import android. app. activity; import android. graphics. bitmap; import android. graphics. bitmapFactory; import android. graphics. bitmapFactory. options; import android. graphics. point; import android. view. menu; import android. view. view; import android. view. windowManager; import android. widget. imageView; public class MainActivity extends Activity {private ImageView iv; private int running wheight; private int running wwidth; protected void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. activity_main); iv = (ImageView) findViewById (R. id. iv); // obtain the width and height of the mobile phone screen. WindowManager wm = (WindowManager) getSystemService (WINDOW_SERVICE); then wheight = wm. getdefadisplay display (). getHeight (); expires wwidth = wm. getdefadisplay display (). getWidth (); // Point outSize = new Point (); // wm. getdefadisplay display (). getSize (outSize); // Versions later than 3.0 can be used // optional wheight = outSize. y; // required wwidth = outSize. x;} public void load (View view) {// Bitmap bitmap = BitmapFactory. decodeFile ("/sdcard/a.jpg"); // iv. setImageBitmap (bitmap); // configure BitmapFactory for Image Parsing. options opts = new Options (); // do not parse the image information, just get the width and height of the image header opts. inJustDecodeBounds = true; BitmapFactory. decodeFile ("/sdcard/a.jpg", opts); int imageHeight = opts. outHeight; int imagewidth = opts. outWidth; System. out. println ("Image Width:" + imagewidth); System. out. println ("Image Height" + imageHeight); // calculate the zoom ratio of int scaleX = imagewidth/expires wwidth; int scaleY = imageHeight/rotate wheight; int scale = 1; if (scaleX> scaleY & scaleY> = 1) {scale = scaleX;} if (scaleY> scaleX & scaleX> = 1) {scale = scaleY;} // parse image opts. inJustDecodeBounds = false; // sampling rate opts. inSampleSize = scale; Bitmap bitmap = BitmapFactory. decodeFile ("/sdcard/a.jpg", opts); iv. setImageBitmap (bitmap );}}