Android canvas setMatrix(null) crashes (if preceded by a getMatrix)

In the lunar lander example, if I add the following two lines to the top of the doDraw method, the app crashes immediately 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 are causing a problem.

Whats going on here?!

ansaurus

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Android canvas setMatrix(null) crashes (if preceded by a getMatrix)

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