Androidj basics: Download images from the Internet,

Androidj basics: Download images from the Internet,

I. layout files

On the settings page, add an ImageView and two Button to set its attributes and id.

<ImageView android: id = "@ + id/ImageView" android: layout_width = "match_parent" android: layout_height = "wrap_content" android: layout_centerInParent = "true" android: background = "# ffffff"/> <LinearLayout android: layout_width = "match_parent" android: layout_height = "wrap_content" android: layout_alignParentBottom = "true"> <Button android: id = "@ + id/bt1" android: layout_width = "wrap_content" android: layout_height = "wrap_content" android: layout_weight = "1" android: text = "Download image"/> <Button android: id = "@ + id/bt2" android: layout_width = "wrap_content" android: layout_height = "wrap_content" android: layout_weight = "1" android: layout_toRightOf = "@ + id/bt1" android: text = "read image"/>

2. Declare network Permissions

Because you need to add permissions to use the network function, modify the AndroidManifest. xml file to add permission declaration statements.

 <uses-permission android:name="android.permission.INTERNET"/>

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.administrator.httpexe">    <uses-permission android:name="android.permission.INTERNET"/>

</manifest>

3. Edit the ManActivity. java file.

Import... // The import Statement is automatically generated.
Public class MainActivity extends AppCompatActivity {ImageView imageView; Button button Button; Button button1; @ Override protected void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. activity_main); imageView = (ImageView) findViewById (R. id. imageView); button = (Button) findViewById (R. id. bt1); button1 = (Button) findViewById (R. id. bt2); button. setOnClickLis Tener (new View. onClickListener () {@ Override public void onClick (View v) {MyTask task = new MyTask (); // create an asynchronous task object task.exe cute ("https://www.baidu.com/img/bd_logo1.png "); // create download task}); button1.setOnClickListener (new View. onClickListener () {// read image @ Override public void onClick (View v) {Bitmap bmp = null; try {FileInputStream FS = openFileInput ("a.png"); bmp = BitmapFactory. decodeStream (FCM); if (bmp! = Null) {imageView. setImageBitmap (bmp) ;}} catch (Exception ex) {}});} public class MyTask extends AsyncTask <String, Void, Bitmap >{// bmp Bitmap, generic @ Override protected Bitmap doInBackground (String... params) {// download String urlStr = params [0]; // obtain the first variable parameter Bitmap bmp = null; try {URL url = new URL (urlStr ); bmp = BitmapFactory. decodeStream (url. openStream (); // bitmap factory, returns bitmap InputStream is = url. openStre Am (); byte [] buffer = new byte [4096]; // byte [] buffer FileOutputStream fos = MainActivity. this. openFileOutput ("a.png", MainActivity. MODE_PRIVATE); int hasRead = is. read (buffer); while (hasRead> 0) {fos. write (buffer, 0, hasRead); // file size, starting position, read Amount hasRead = is. read (buffer);} fos. close (); // close is. close (); // close} catch (Exception ex) {} finally {} return bmp;} @ Override protected void onPostExecute (Bitmap bitmap) {I F (bitmap! = Null) {imageView. setImageBitmap (bitmap );}}}

 

Iv. Running results

Click Download to download the image. Function of the read image button: After a download, you do not need to download the image again..

Note:

When the java code is entered, some of them will automatically pop up and match the corresponding package, and an error will be reported directly.