从中下载图像时应用程序崩溃

Question

While Clicking on download button app is crashing and showing java.lang.NullPointerException

at com.$$$$$$.fieldforce.adapter.InstallDocAdapter.saveToGallery

Here is the logcat

Exception java.lang.NullPointerException:
  at android.graphics.Bitmap.compress (Bitmap.java:1434)
  at com.$$$$$$.fieldforce.adapter.InstallDocAdapter.saveToGallery (InstallDocAdapter.java:123)
  at com.$$$$$$.fieldforce.adapter.InstallDocAdapter.access$100 (InstallDocAdapter.java:40)
  at com.$$$$$$.fieldforce.adapter.InstallDocAdapter$1.onClick (InstallDocAdapter.java:75)
  at android.view.View.performClick (View.java:7488)
  at android.view.View.performClickInternal (View.java:7464)
  at android.view.View.access$3700 (View.java:841)
  at android.view.View$PerformClick.run (View.java:28911)
  at android.os.Handler.handleCallback (Handler.java:938)
  at android.os.Handler.dispatchMessage (Handler.java:99)
  at android.os.Looper.loopOnce (Looper.java:233)
  at android.os.Looper.loop (Looper.java:344)
  at android.app.ActivityThread.main (ActivityThread.java:8212)
  at java.lang.reflect.Method.invoke
  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run (RuntimeInit.java:584)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1034)

Here is the function used in it

private void saveToGallery(String attachment){
    byte [] encodeByte = Base64.decode(attachment,Base64.DEFAULT);
    Bitmap bitmap = BitmapFactory.decodeByteArray(encodeByte, 0, encodeByte.length);

    FileOutputStream outputStream = null;
    File file = Environment.getExternalStorageDirectory();
    File dir = new File(file.getAbsolutePath() + "/$$$$$$ Downloads");
    dir.mkdirs();

    String filename = String.format("%d.png",System.currentTimeMillis());
    File outFile = new File(dir,filename);
    try{
        outputStream = new FileOutputStream(outFile);
    }catch (Exception e){
        e.printStackTrace();
    }
    bitmap.compress(Bitmap.CompressFormat.PNG,100,outputStream);
    try{
        outputStream.flush();
    }catch (Exception e){
        e.printStackTrace();
    }
    try{
        outputStream.close();
        Toast.makeText(context,"Downloaded image ....",Toast.LENGTH_LONG).show();
    }
    catch (Exception e){
        e.printStackTrace();
    }
}

Here is the screenshot of the above code

Answer 1

Exception java.lang.NullPointerException:
  at android.graphics.Bitmap.compress (Bitmap.java:1434)
  at com.$$$$$$.fieldforce.adapter.InstallDocAdapter.saveToGallery (InstallDocAdapter.java:123)

You're getting this because saveToGallery calls Bitmap.compress at line 123 and passes null as a parameter that shouldn't be null. I'm assuming it's this line:

bitmap.compress(Bitmap.CompressFormat.PNG,100,outputStream);

The first two parameters are fine so it'll be outputStream that's null. Which means this:

try{
    outputStream = new FileOutputStream(outFile);
}catch (Exception e){
    e.printStackTrace();
}

is failing because an exception is being thrown, so outputStream (which is initialised as null ) isn't being assigned.

The docs for FileOutputStream explain which exceptions are thrown under what circumstances, and you're printing the stacktrace to your logs in the catch block, so find out why it's failing. If you've made a mistake, fix it - if it's a valid scenario that can happen , then you need to handle that possibility in your code.