NullPointerException in createBitmap() from View

问题

I am using the below code for getting a Bitmap from a View :

private static Bitmap loadBitmapFromView(View yourView) {
        Bitmap snapshot = null;
        Drawable drawable = null;
        yourView.setDrawingCacheEnabled(true);
        yourView.setDrawingCacheQuality(View.DRAWING_CACHE_QUALITY_HIGH); //Quality of the snpashot
        try {
            snapshot = Bitmap.createBitmap(yourView.getDrawingCache());
            drawable = new BitmapDrawable(snapshot);
        } finally {
            yourView.setDrawingCacheEnabled(false);
        }
        return snapshot;
    }

But I am getting NullPointerException on the following line:

snapshot = Bitmap.createBitmap(yourView.getDrawingCache());

Here is the Logcat:

09-19 15:39:15.481: E/AndroidRuntime(8704): FATAL EXCEPTION: main
09-19 15:39:15.481: E/AndroidRuntime(8704): java.lang.NullPointerException
09-19 15:39:15.481: E/AndroidRuntime(8704):     at android.graphics.Bitmap.createBitmap(Bitmap.java:455)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at com.scb.bonuspartner.utils.MapUtility.loadBitmapFromView(MapUtility.java:85)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at com.scb.bonuspartner.utils.MapUtility.createMarker(MapUtility.java:74)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at com.scb.bonuspartner.offeractivity.fragments.MapOfferFragment.onLocationChanged(MapOfferFragment.java:70)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at android.location.LocationManager$ListenerTransport._handleMessage(LocationManager.java:227)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at android.location.LocationManager$ListenerTransport.access$000(LocationManager.java:160)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at android.location.LocationManager$ListenerTransport$1.handleMessage(LocationManager.java:176)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at android.os.Looper.loop(Looper.java:154)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at android.app.ActivityThread.main(ActivityThread.java:4624)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at java.lang.reflect.Method.invokeNative(Native Method)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at java.lang.reflect.Method.invoke(Method.java:511)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:809)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:576)
09-19 15:39:15.481: E/AndroidRuntime(8704):     at dalvik.system.NativeStart.main(Native Method)

回答1:

Try this way

private static Bitmap loadBitmapFromView(View yourView) {
        Bitmap snapshot = null;
        Drawable drawable = null;
        yourView.setDrawingCacheEnabled(true);
        yourView.setDrawingCacheQuality(View.DRAWING_CACHE_QUALITY_HIGH); //Quality of the snpashot
        try {
            yourView.buildDrawingCache(); // UPDATE HERE
            snapshot = Bitmap.createBitmap(yourView.getDrawingCache());
            drawable = new BitmapDrawable(snapshot);
        } finally {
            yourView.setDrawingCacheEnabled(false);
        }
        return snapshot;
    }

Explanation :

For the knowledge Bitmap is final class. So it's priority for garbage collector(GC) is very low and it is very memory expensive.By default view does not creates the bitmap from the canvas because if it do so one bitmap will be generate in memory for each view inflated and it may cause buildDrawingCache. So buildDrawingCache() method is given that you can generate the bitmap when it is required.

回答2:

Should the code be

snapshot = snapshot.createBitmap(yourView.getDrawingCache());

as youve already cast snapshot as Bitmap there

Bitmap snapshot = null;

来源：https://stackoverflow.com/questions/18891657/nullpointerexception-in-createbitmap-from-view

标签

android

view

nullpointerexception

drawable