create simple skia app for android using jni

experimental/HelloSkia/jni/helloskia.cpp

+#include <math.h>
+#include <time.h>
+#include <jni.h>
+#include <android/bitmap.h>
+
+#include "SkCanvas.h"
+#include "SkGraphics.h"
+#include "SkSurface.h"
+#include "SkString.h"
+#include "SkTime.h"
+
+
+static float get_seconds()

[djsollen, 2013/06/04 00:26:35]

doesn't look like you call this function

[Zach Reizner, 2013/06/04 14:35:45]

Done.

+{
+    struct timespec currentTime;
+    clock_gettime(CLOCK_REALTIME, &currentTime);
+    return currentTime.tv_sec + (float)currentTime.tv_nsec / 1e9;
+}
+
+/**
+ * Draws something into the given bitmap
+ * @param  env
+ * @param  thiz
+ * @param  dstBitmap   The bitmap to place the results of skia into
+ * @param  elapsedTime The number of milliseconds since the app was started
+ */
+extern "C"
+JNIEXPORT void JNICALL Java_com_example_HelloSkiaActivity_drawIntoBitmap(JNIEnv* env,
+        jobject thiz, jobject dstBitmap, jlong elapsedTime)
+{
+    // Grab the dst bitmap info and pixels
+    AndroidBitmapInfo dstInfo;
+    void* dstPixels;
+    AndroidBitmap_getInfo(env, dstBitmap, &dstInfo);
+    AndroidBitmap_lockPixels(env, dstBitmap, &dstPixels);
+
+    SkImage::Info info = {
+        dstInfo.width, dstInfo.height, SkImage::kPMColor_ColorType, SkImage::kPremul_AlphaType
+    };
+
+    // Create a surface from the given bitmap
+    SkAutoTUnref<SkSurface> surface(SkSurface::NewRasterDirect(info, dstPixels, dstInfo.stride));
+    SkCanvas* canvas = surface->getCanvas();
+

[djsollen, 2013/06/04 00:26:35]

keep the basic text drawing as well, but I like your animation idea! That is
interesting. :)

[Zach Reizner, 2013/06/04 14:35:45]

Done.

+    // Draw something "interesting"
+
+    // Clear the canvas with a white color
+    canvas->drawColor(SK_ColorWHITE);
+
+    // Draw some interesting lines using trig functions
+    SkPaint paint;
+    paint.setColor(0xFF0000FF); // This is a solid blue color for our lines
+    paint.setStrokeWidth(SkIntToScalar(2)); // This makes the lines have a thickness of 2 pixels
+    for (int i = 0; i < 100; i++)
+    {
+        float x = (float)i / 99.0f;
+        float offset = elapsedTime / 1000.0f;
+        canvas->drawLine(sin(x * M_PI + offset) * 800.0f, 0,   // first endpoint
+                         cos(x * M_PI + offset) * 800.0f, 800, // second endpoint
+                         paint);
+    }
+
+    // Unlock the dst's pixels
+    AndroidBitmap_unlockPixels(env, dstBitmap);
+}