if (!mActive) {//绘制开始 处于活动状态mActive = true;notify();}// Lock the canvas for drawing. //拿到 surface的 canvas ,开始绘制这个canvasCanvas canvas = mSurfaceHolder.lockCanvas();if (canvas == null) {Log.i("WindowSurface", "Failure locking canvas");continue;}// Update graphics.if (!mInitialized) {mInitialized = true;mPoint1.init(canvas.getWidth(), canvas.getHeight(), mMinStep);mPoint2.init(canvas.getWidth(), canvas.getHeight(), mMinStep);mColor.init(127, 127, 1);} else {mPoint1.step(canvas.getWidth(), canvas.getHeight(),mMinStep, mMaxStep);mPoint2.step(canvas.getWidth(), canvas.getHeight(),mMinStep, mMaxStep);mColor.step(127, 127, 1, 3);}mBrightLine+=2;if (mBrightLine > (NUM_OLD*2)) {mBrightLine = -2;}// Clear background. 绘制背景 也是清空canvas.drawColor(mBackground.getColor());// Draw old lines.绘制旧的线条for (int i=mNumOld-1; i>=0; i--) {mForeground.setColor(mOldColor[i] | makeGreen(i)); //开始绿色的传递mForeground.setAlpha(((NUM_OLD-i) * 255) / NUM_OLD);int p = i*4;canvas.drawLine(mOld[p], mOld[p+1], mOld[p+2], mOld[p+3], mForeground);}// Draw new line.int red = (int)mColor.x + 128;if (red > 255) red = 255;int blue = (int)mColor.y + 128;if (blue > 255) blue = 255;int color = 0xff000000 | (red<<16) | blue;//这里可能是设置红色的?mForeground.setColor(color | makeGreen(-2));//新的线条canvas.drawLine(mPoint1.x, mPoint1.y, mPoint2.x, mPoint2.y, mForeground);// Add in the new line.if (mNumOld > 1) {System.arraycopy(mOld, 0, mOld, 4, (mNumOld-1)*4);System.arraycopy(mOldColor, 0, mOldColor, 1, mNumOld-1);}if (mNumOld < NUM_OLD) mNumOld++;mOld[0] = mPoint1.x;mOld[1] = mPoint1.y;mOld[2] = mPoint2.x;mOld[3] = mPoint2.y;mOldColor[0] = color;// All done!完成 ,然后 是否canvas 显示在屏幕mSurfaceHolder.unlockCanvasAndPost(canvas); }}}}
}