Setting a TextView in an Inner Static Class - Android

Question

I am currently editing the AprilTags code from GitHub found here: https://github.com/johnjwang/apriltag-android/tree/master/src/main. I am trying to set a TextView in an inner static class.

static class LinesProgram {
    private static final String vertexShaderCode =
            "uniform mat4 uMVPMatrix;\n" +
            "attribute vec4 aPosition;\n" +
            "void main() {\n" +
            "    gl_Position = uMVPMatrix * aPosition;\n" +
            "}\n";

    private static final String fragmentShaderCode =
            "precision mediump float;\n" +
            "uniform vec4 uColor;\n" +
            "void main() {\n" +
            "    gl_FragColor = uColor;\n" +
            "}\n";

    private FloatBuffer buffer;
    private Context context;

    int programId;

    int aPositionLoc;
    int uMVPMatrixLoc;
    int uColorLoc;

    public LinesProgram(Context context) {
        // Compile the shader code into a GL program
        this.context = context;
        int vid = loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
        int fid = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
        programId = GLES20.glCreateProgram();
        checkGlError("glCreateProgram");
        GLES20.glAttachShader(programId, vid);
        checkGlError("glAttachShader");
        GLES20.glAttachShader(programId, fid);
        checkGlError("glAttachShader");
        GLES20.glLinkProgram(programId);
        int[] linkStatus = new int[1];
        GLES20.glGetProgramiv(programId, GLES20.GL_LINK_STATUS, linkStatus, 0);
        if (linkStatus[0] != GLES20.GL_TRUE) {
            Log.e(TAG, "Could not link program: ");
            Log.e(TAG, GLES20.glGetProgramInfoLog(programId));
            GLES20.glDeleteProgram(programId);
        }

        // Get handles to attributes and uniforms
        aPositionLoc = GLES20.glGetAttribLocation(programId, "aPosition");
        checkGlError("get aPosition");
        uMVPMatrixLoc = GLES20.glGetUniformLocation(programId, "uMVPMatrix");
        checkGlError("get uMVPMatrix");
        uColorLoc = GLES20.glGetUniformLocation(programId, "uColor");
        checkGlError("get uColor");
    }

    // points = [x0 y0 x1 y1 ...]
    // npoints = number of xy pairs in points (e.g. points is expected to have
    //           a length of at least 2*npoints)
    public void draw(float[] PVM, float[] points, int npoints, float[] rgba, int type) {
        // Reuse points buffer if possible
        if (buffer == null || 2*npoints > buffer.capacity()) {
            int nbytes = 4 * 2*npoints;
            ByteBuffer bb = ByteBuffer.allocateDirect(nbytes);
            bb.order(ByteOrder.nativeOrder());
            buffer = bb.asFloatBuffer();
        }
        buffer.position(0);
        buffer.put(points, 0, 2*npoints);
        buffer.position(0);

        GLES20.glUseProgram(programId);
        checkGlError("glUseProgram");

        GLES20.glUniformMatrix4fv(uMVPMatrixLoc, 1, false, PVM, 0);
        checkGlError("glUniformMatrix4fv");

        GLES20.glUniform4fv(uColorLoc, 1, rgba, 0);
        checkGlError("glUniform4fv");

        // Render frame
        GLES20.glEnableVertexAttribArray(aPositionLoc);
        GLES20.glVertexAttribPointer(aPositionLoc, 2,
                GLES20.GL_FLOAT, false, 8, buffer);

        GLES20.glLineWidth(4.0f);
        GLES20.glDrawArrays(type, 0, npoints);

        GLES20.glDisableVertexAttribArray(aPositionLoc);
        GLES20.glUseProgram(0);

        TextView coordinates = (TextView) ((Activity)context).findViewById(R.id.textView1);
        //for (int i = 0; i < points.length; i++) {
        //    coordinates.setText(String.valueOf(points[i]));
        //}

    }
}

However, I am getting this error:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.app.Activity.findViewById(int)' on a null object reference

and the app crashes when it gets to where I set the TextView.

I'm sure the text view id is the same as defined in the main.xml file. The TextView is within a FrameLayout if that is important.

In the onCreate function I defined at the top, public TextView coordinates;.