将动态列表视图保存为sdcard中的图像

Question

此函数给出空指针异常

public static Bitmap getWholeListViewItemsToBitmap() {

    ListView listview    = Result_Activity.mFocusedListView;
    ListAdapter adapter  = listview.getAdapter(); 
    int itemscount       = adapter.getCount();
    int allitemsheight   = 0;
    List<Bitmap> bmps    = new ArrayList<Bitmap>();

    for (int i = 0; i < itemscount; i++) {

        View childView      = adapter.getView(i, null, listview);
        childView.measure(MeasureSpec.makeMeasureSpec(listview.getWidth(), MeasureSpec.EXACTLY), 
                MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));

        childView.layout(0, 0, childView.getMeasuredWidth(), childView.getMeasuredHeight());
        childView.setDrawingCacheEnabled(true);
        childView.buildDrawingCache();
        bmps.add(childView.getDrawingCache());
        allitemsheight+=childView.getMeasuredHeight();
    }

    Bitmap bigbitmap    = Bitmap.createBitmap(listview.getMeasuredWidth(), allitemsheight, Bitmap.Config.ARGB_8888);
    Canvas bigcanvas    = new Canvas(bigbitmap);

    Paint paint = new Paint();
    int iHeight = 0;

    for (int i = 0; i < bmps.size(); i++) {
        Bitmap bmp = bmps.get(i);
        bigcanvas.drawBitmap(bmp, 0, iHeight, paint);
        iHeight+=bmp.getHeight();

        bmp.recycle();
        bmp=null;
    }


    return bigbitmap;
}

我直接用它的名字来称呼它。任何人都可以如何将列表视图保存为图像？

这是它的原木猫

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02-10 16:58:09.371: E/AndroidRuntime(5214): FATAL EXCEPTION: main
02-10 16:58:09.371: E/AndroidRuntime(5214): java.lang.NullPointerException
02-10 16:58:09.371: E/AndroidRuntime(5214):     at com.mothistorycheck.Result_Activity.getWholeListViewItemsToBitmap(Result_Activity.java:196)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at com.mothistorycheck.Result_Activity.onClick(Result_Activity.java:141)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at android.view.View.performClick(View.java:4191)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at android.view.View$PerformClick.run(View.java:17229)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at android.os.Handler.handleCallback(Handler.java:615)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at android.os.Handler.dispatchMessage(Handler.java:92)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at android.os.Looper.loop(Looper.java:137)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at android.app.ActivityThread.main(ActivityThread.java:4960)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at java.lang.reflect.Method.invokeNative(Native Method)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at java.lang.reflect.Method.invoke(Method.java:511)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
02-10 16:58:09.371: E/AndroidRuntime(5214):     at dalvik.system.NativeStart.main(Native Method)
02-10 16:58:23.991: I/Process(5214): Sending signal. PID: 5214 SIG: 9
02-10 17:00:18.701: D/ActivityThread(5549): setTargetHeapUtilization:0.25