对Android4.0中Launcher2一些调试记录

最近项目打板了，板子跑起来后发现Launcher的所有程序界面不能全屏(两边有黑框，只在中上部显示)，但是主界面看上去是全屏显示的(后面证实也非全屏显示。)

我们的屏是21寸的，分辨率为1980*1080。

最开始以为是uboot里的屏幕参数没设置好，后面check之后发现没问题。没办法，只有去看Launcher的代码。

首先，在我最开始就有一个误解，这个误解浪费我很多时间。由于最开始的时候主界面(也就是workspace)是没有黑框的，所以我一直认为workspace的代码是没问题的。

后面经验证主界面也没有按屏幕的实际分辨率显示！Workspace.java中构造函数有如下代码：

final float smallestScreenDim = res.getConfiguration().smallestScreenWidthDp;
 cellCountX = 1;
            while (CellLayout.widthInPortrait(res, cellCountX + 1) <= smallestScreenDim) {
                
                cellCountX++;
            }

            cellCountY = 1;
            while (actionBarHeight + CellLayout.heightInLandscape(res, cellCountY + 1)
                <= smallestScreenDim - systemBarHeight) {
                cellCountY++;
            }
        }

smallestScreenDim 按字面理解意思应该是屏幕宽度的最小值(以DP为单位)，cellCountX初始化为1，然后通过一个while循环去计算X、Y方向各能放多少个应用。
我们看看widthInPortrait方法：

    static int widthInPortrait(Resources r, int numCells) {
        // We use this method from Workspace to figure out how many rows/columns Launcher should
        // have. We ignore the left/right padding on CellLayout because it turns out in our design
        // the padding extends outside the visible screen size, but it looked fine anyway.
        int cellWidth = r.getDimensionPixelSize(R.dimen.workspace_cell_width);
        int minGap = Math.min(r.getDimensionPixelSize(R.dimen.workspace_width_gap),
                r.getDimensionPixelSize(R.dimen.workspace_height_gap));
        return minGap * (numCells - 1) + cellHeight * numCells;
    }

getDimensionPixelSize方法实际上是把dimens.xml中设置的cellWidth大小由dp转换成px！

widthInPortrait计算后的返回值会与smallestScreenDim进行比较，如果比smallestScreenDim 小，那么说明能够再放一个APP，cellCount进行加一。
循环比较之后就会得出在该屏幕上能放多少行，多少列个应用。
既然cellWidth的单位为px,那与通过他计算后得到的值进行比较的smallestScreenDim单位应该也是px，而不是像他字面所说的dp！

通过加log进一步确认，我发现android4.0默认的smallestScreenDim为720！也就是720px，而我的屏实际像素宽度为1920！
将smallestScreenDim强制设置为1920后all apps界面能全屏了，主界面的workspace也大了很多！说明之前主界面的全屏都是假象。。。
我们可以在代码里得到屏幕的宽度，然后赋值给smallestScreenDim以便于支持更多的屏幕。
至于之前的主界面为什么没有黑色的边框，我估计是壁纸设置的原因，具体细节没去深究了。

后面发现系统默认的图标在大屏幕上显示效果不太好，有点偏小，直接修改res/values-sw600dp/dimens.xml中的app_icon_size。
改完make之后发现图标并没有变大。。。
跟踪代码Launcher.java[onCreate]--->[setLauncher]--->LauncherApplication[onCreate]--->[new LauncherModel]--->[createIconBitmap]

static Bitmap createIconBitmap(Drawable icon, Context context) {
        synchronized (sCanvas) { // we share the statics :-(
            if (sIconWidth == -1) {
                initStatics(context);
            }

            int width = sIconWidth;
            int height = sIconHeight;
            
            Log.i("Info","In createIconBitmap width is: "+width);
            Log.i("Info","In createIconBitmap height is: "+height);
            if (icon instanceof PaintDrawable) {
                Log.i("Info","Icon type is PaintDrawable" );
                PaintDrawable painter = (PaintDrawable) icon;
                painter.setIntrinsicWidth(width);
                painter.setIntrinsicHeight(height);
            } else if (icon instanceof BitmapDrawable) {
                // Ensure the bitmap has a density.
                Log.i("Info","Icon type is BitmapDrawable" );
                BitmapDrawable bitmapDrawable = (BitmapDrawable) icon;
                Bitmap bitmap = bitmapDrawable.getBitmap();
                if (bitmap.getDensity() == Bitmap.DENSITY_NONE) {
                    bitmapDrawable.setTargetDensity(context.getResources().getDisplayMetrics());
                }
            }
            int sourceWidth = icon.getIntrinsicWidth();
            int sourceHeight = icon.getIntrinsicHeight();
            Log.i("Info","IntrinsicWidth is: "+sourceWidth);
            Log.i("Info","IntrinsicHeight is: "+sourceHeight);
            if (sourceWidth > 0 && sourceHeight > 0) {
                // There are intrinsic sizes.
                if (width < sourceWidth || height < sourceHeight) {
                    // It's too big, scale it down.
                    final float ratio = (float) sourceWidth / sourceHeight;
                    if (sourceWidth > sourceHeight) {
                        height = (int) (width / ratio);
                    } else if (sourceHeight > sourceWidth) {
                        width = (int) (height * ratio);
                    }
                } else if (sourceWidth < width && sourceHeight < height) {
                    // Don't scale up the icon
                    //width = sourceWidth;
                    //height = sourceHeight;
                    width = sIconWidth;
                    height = sIconHeight;
                }
            }

            // no intrinsic size --> use default size
            int textureWidth = sIconTextureWidth;
            int textureHeight = sIconTextureHeight;
            Log.i("Info","textureWidth is: "+textureWidth);
            Log.i("Info","textureHeight is: "+textureHeight);

            final Bitmap bitmap = Bitmap.createBitmap(textureWidth, textureHeight,
                    Bitmap.Config.ARGB_8888);
            final Canvas canvas = sCanvas;
            canvas.setBitmap(bitmap);

            final int left = (textureWidth-width) / 2;
            final int top = (textureHeight-height) / 2;

            if (false) {
                // draw a big box for the icon for debugging
                canvas.drawColor(sColors[sColorIndex]);
                if (++sColorIndex >= sColors.length) sColorIndex = 0;
                Paint debugPaint = new Paint();
                debugPaint.setColor(0xffcccc00);
                canvas.drawRect(left, top, left+width, top+height, debugPaint);
            }

            sOldBounds.set(icon.getBounds());
            icon.setBounds(left, top, left+width, top+height);
            icon.draw(canvas);
            icon.setBounds(sOldBounds);
            canvas.setBitmap(null);

            return bitmap;
        }
    }
private static void initStatics(Context context) {
        final Resources resources = context.getResources();
        final DisplayMetrics metrics = resources.getDisplayMetrics();
        final float density = metrics.density;

        //default is 72*density
        sIconWidth = sIconHeight = (int) resources.getDimension(R.dimen.app_icon_size);
        sIconTextureWidth = sIconTextureHeight = sIconWidth;

        sBlurPaint.setMaskFilter(new BlurMaskFilter(5 * density, BlurMaskFilter.Blur.NORMAL));
        sGlowColorPressedPaint.setColor(0xffffc300);
        sGlowColorPressedPaint.setMaskFilter(TableMaskFilter.CreateClipTable(0, 30));
        sGlowColorFocusedPaint.setColor(0xffff8e00);
        sGlowColorFocusedPaint.setMaskFilter(TableMaskFilter.CreateClipTable(0, 30));

        ColorMatrix cm = new ColorMatrix();
        cm.setSaturation(0.2f);
        sDisabledPaint.setColorFilter(new ColorMatrixColorFilter(cm));
        sDisabledPaint.setAlpha(0x88);
    }

经过分析，发现在这个方法里对图片大小进行了判断，如果大于默认的图片大小96dp，那么强制将图片大小设置为96dp！
稍作修改图标就能放大了，细节不说了，大家看看代码就知道了。