通过JSON从mysql数据库中获取BLOB映像

Question

I have an image stored as BLOB in my MySQL database. I am returning the image back to the android app via PHP JSON array like this: $row_array['image'] = base64_encode($row['image']); Now I am getting the value in android like this String image = c.getString(TAG_IMAGE); where c is a JSON Object. Then I tried decoding it

byte[] b = Base64.decode(image, 0);

Bitmap bmp = BitmapFactory.decodeByteArray(b, 0, b.length);

But this just gives me a null pointer exception and crashes. What am I doing wrong here?

Logcat:

05-16 15:40:47.469: E/AndroidRuntime(30925): FATAL EXCEPTION: main
05-16 15:40:47.469: E/AndroidRuntime(30925): java.lang.NullPointerException
05-16 15:40:47.469: E/AndroidRuntime(30925):    at com.example.shareity.ListNew$JSONParse.onPostExecute(ListNew.java:254)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at com.example.shareity.ListNew$JSONParse.onPostExecute(ListNew.java:1)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.os.AsyncTask.finish(AsyncTask.java:631)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.os.AsyncTask.access$600(AsyncTask.java:177)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.os.Handler.dispatchMessage(Handler.java:99)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.os.Looper.loop(Looper.java:137)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at android.app.ActivityThread.main(ActivityThread.java:4745)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at java.lang.reflect.Method.invokeNative(Native Method)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at java.lang.reflect.Method.invoke(Method.java:511)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-16 15:40:47.469: E/AndroidRuntime(30925):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

Suppose the event is the table name , image is the column name that holds the BLOB Image and user_id is the id of the user/row . To extract the image from the BLOB, You should create an EXTRA PHP File. which would like something like this.

get_image.php

<?php 
$db = mysql_connect("localhost","user","password") or die(mysql_error()); 
mysql_select_db("shareity",$db) or die(mysql_error()); 
$userId = $_GET['eid']; 
$query = "SELECT image FROM event WHERE eid='$userId'"; 
$result = mysql_query($query) or die(mysql_error()); 
$photo = mysql_fetch_array($result); 
header('Content-Type:image/jpeg'); 
echo $photo['image']; 
?>

Now,get_image.php is like an image. if you pass a user_id through GET to the get_image.php will throw the user_image.

So when ever you encode the json from server side,add a field which append the user id with the get_image.php like this

{
 'ID':1,
 'userName':'John',
 'image_url':'http://your-host-name/get_image.php?ID=1'
}

So from the Android, you can decode the image like this

try {
    URL url = new URL("http://your-host-name/get_image.php?ID=1");
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setDoInput(true);
    connection.connect();
    InputStream input = connection.getInputStream();
    Bitmap myBitmap = BitmapFactory.decodeStream(input);
} catch (IOException e) {
    // Log exception
    return null;
}

More clarification can be fnd here