In the lunar lander example, if I add the following two lines to the
top of the doDraw method, the app crashes immediately on the second
line with a NullPointerException:
Matrix m = canvas.getMatrix();
canvas.setMatrix( null );
Stack trace is:
FATAL EXCEPTION: Thread-8
java.lang.NullPointerException
at android.graphics.Matrix.preConcat(Matrix.java:233)
at android.view.Surface$CompatibleCanvas.setMatrix(Surface.java:
259)
at com.example.android.lunarlander.LunarView
$LunarThread.doDraw(LunarView.java:617)
at com.example.android.lunarlander.LunarView
$LunarThread.run(LunarView.java:360)
The canvas documentation for setMatrix states that "If the matrix
parameter is null, then the current matrix is reset to identity", so
there's no reason this should crash.
Also, if I do *not* call getMatrix before calling setMatrix(null),
then setMatrix(null) is *successful*. So somehow it is the
combination of the two calls that causes the problem.
Can anyone help me figure out what's going on here?
Thanks!
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