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：
1 final float smallestScreenDim = res.getConfiguration().smallestScreenWidthDp; 2 cellCountX = 1; 3 while (CellLayout.widthInPortrait(res, cellCountX + 1) <= smallestScreenDim) { 4 5 cellCountX++; 6 } 7 8 cellCountY = 1; 9 while (actionBarHeight + CellLayout.heightInLandscape(res, cellCountY + 1) 10 <= smallestScreenDim - systemBarHeight) { 11 cellCountY++; 12 } 13 }
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：
1 static int widthInPortrait(Resources r, int numCells) { 2 // We use this method from Workspace to figure out how many rows/columns Launcher should 3 // have. We ignore the left/right padding on CellLayout because it turns out in our design 4 // the padding extends outside the visible screen size, but it looked fine anyway. 5 int cellWidth = r.getDimensionPixelSize(R.dimen.workspace_cell_width); 6 int minGap = Math.min(r.getDimensionPixelSize(R.dimen.workspace_width_gap), 7 r.getDimensionPixelSize(R.dimen.workspace_height_gap)); 8 return minGap * (numCells - 1) + cellHeight * numCells; 9 }
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]
1 static Bitmap createIconBitmap(Drawable icon, Context context) { 2 synchronized (sCanvas) { // we share the statics :-( 3 if (sIconWidth == -1) { 4 initStatics(context); 5 } 6 7 int width = sIconWidth; 8 int height = sIconHeight; 9 10 Log.i("Info","In createIconBitmap width is: "+width); 11 Log.i("Info","In createIconBitmap height is: "+height); 12 if (icon instanceof PaintDrawable) { 13 Log.i("Info","Icon type is PaintDrawable" ); 14 PaintDrawable painter = (PaintDrawable) icon; 15 painter.setIntrinsicWidth(width); 16 painter.setIntrinsicHeight(height); 17 } else if (icon instanceof BitmapDrawable) { 18 // Ensure the bitmap has a density. 19 Log.i("Info","Icon type is BitmapDrawable" ); 20 BitmapDrawable bitmapDrawable = (BitmapDrawable) icon; 21 Bitmap bitmap = bitmapDrawable.getBitmap(); 22 if (bitmap.getDensity() == Bitmap.DENSITY_NONE) { 23 bitmapDrawable.setTargetDensity(context.getResources().getDisplayMetrics()); 24 } 25 } 26 int sourceWidth = icon.getIntrinsicWidth(); 27 int sourceHeight = icon.getIntrinsicHeight(); 28 Log.i("Info","IntrinsicWidth is: "+sourceWidth); 29 Log.i("Info","IntrinsicHeight is: "+sourceHeight); 30 if (sourceWidth > 0 && sourceHeight > 0) { 31 // There are intrinsic sizes. 32 if (width < sourceWidth || height < sourceHeight) { 33 // It's too big, scale it down. 34 final float ratio = (float) sourceWidth / sourceHeight; 35 if (sourceWidth > sourceHeight) { 36 height = (int) (width / ratio); 37 } else if (sourceHeight > sourceWidth) { 38 width = (int) (height * ratio); 39 } 40 } else if (sourceWidth < width && sourceHeight < height) { 41 // Don't scale up the icon 42 //width = sourceWidth; 43 //height = sourceHeight; 44 width = sIconWidth; 45 height = sIconHeight; 46 } 47 } 48 49 // no intrinsic size --> use default size 50 int textureWidth = sIconTextureWidth; 51 int textureHeight = sIconTextureHeight; 52 Log.i("Info","textureWidth is: "+textureWidth); 53 Log.i("Info","textureHeight is: "+textureHeight); 54 55 final Bitmap bitmap = Bitmap.createBitmap(textureWidth, textureHeight, 56 Bitmap.Config.ARGB_8888); 57 final Canvas canvas = sCanvas; 58 canvas.setBitmap(bitmap); 59 60 final int left = (textureWidth-width) / 2; 61 final int top = (textureHeight-height) / 2; 62 63 if (false) { 64 // draw a big box for the icon for debugging 65 canvas.drawColor(sColors[sColorIndex]); 66 if (++sColorIndex >= sColors.length) sColorIndex = 0; 67 Paint debugPaint = new Paint(); 68 debugPaint.setColor(0xffcccc00); 69 canvas.drawRect(left, top, left+width, top+height, debugPaint); 70 } 71 72 sOldBounds.set(icon.getBounds()); 73 icon.setBounds(left, top, left+width, top+height); 74 icon.draw(canvas); 75 icon.setBounds(sOldBounds); 76 canvas.setBitmap(null); 77 78 return bitmap; 79 } 80 } 81 private static void initStatics(Context context) { 82 final Resources resources = context.getResources(); 83 final DisplayMetrics metrics = resources.getDisplayMetrics(); 84 final float density = metrics.density; 85 86 //default is 72*density 87 sIconWidth = sIconHeight = (int) resources.getDimension(R.dimen.app_icon_size); 88 sIconTextureWidth = sIconTextureHeight = sIconWidth; 89 90 sBlurPaint.setMaskFilter(new BlurMaskFilter(5 * density, BlurMaskFilter.Blur.NORMAL)); 91 sGlowColorPressedPaint.setColor(0xffffc300); 92 sGlowColorPressedPaint.setMaskFilter(TableMaskFilter.CreateClipTable(0, 30)); 93 sGlowColorFocusedPaint.setColor(0xffff8e00); 94 sGlowColorFocusedPaint.setMaskFilter(TableMaskFilter.CreateClipTable(0, 30)); 95 96 ColorMatrix cm = new ColorMatrix(); 97 cm.setSaturation(0.2f); 98 sDisabledPaint.setColorFilter(new ColorMatrixColorFilter(cm)); 99 sDisabledPaint.setAlpha(0x88); 100 }
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。