在做Android app开发的时候，为了验证不同屏幕分辨率和dpi下界面的布局情况。你可以使用android emulator来实现，也可以找不同屏幕配置的手机来验证。当然，你可以找台Android原生系统的手机来验证如Nexus 4/Nexus 5系列的手机来验证。Android系统中有一个wm命令，可以设置显示窗口的尺寸（重新设置屏幕的罗辑分辩率）和屏幕的dpi。
- 设置显示窗口的尺寸
$ adb shell wm size 540x960
显示窗口的尺寸可以比屏幕的物理分辨率大，也可以比它小。重置用如下命令：
$ adb shell wm size reset
设置完之后，你会发现SurfaceFlinger中的Layer的尺寸也发生的变化。
以Nexus4为例，原来Live Wallpaper: PhaseBeam Layer的尺寸为768×1280：
$ adb shell dumpsys SurfaceFlinger
...
+ Layer 0xb7bbf3b0 ()
Region transparentRegion (this=0xb7bbf510, count=1)
[ 0, 0, 0, 0]
Region visibleRegion (this=0xb7bbf3b8, count=1)
[ 0, 50, 768, 1184]
layerStack= 0, z= 21000, pos=(0,0), size=( 768,1280), crop=( 0, 50, 768,1184), isOpaque=1, invalidate=0, alpha=0xff, flags=0x00000002, tr=[1.00, 0.00][0.00, 1.00]
client=0xb7bad728
format= 2, activeBuffer=[ 768x1280: 768, 3], queued-frames=0, mRefreshPending=0
mTexName=10 mCurrentTexture=0
mCurrentCrop=[0,0,0,0] mCurrentTransform=0
mAbandoned=0
-BufferQueue mMaxAcquiredBufferCount=1, mDequeueBufferCannotBlock=0, default-size=[768x1280], default-format=2, transform-hint=00, FIFO(0)={}
>[00:0xb7bbef08] state=ACQUIRED, 0xb7b18260 [ 768x1280: 768, 3]
[01:0xb7baf328] state=FREE , 0xb7badaa8 [ 768x1280: 768, 3]
[02:0xb7b1a5d0] state=FREE , 0xb7bad9a0 [ 768x1280: 768, 3]
...
将显示窗口的尺寸设为1080×1920之后：
$ adb shell dumpsys SurfaceFlinger
...
+ Layer 0xb7d596b8 ()
Region transparentRegion (this=0xb7d59818, count=1)
[ 0, 0, 0, 0]
Region visibleRegion (this=0xb7d596c0, count=1)
[ 0, 50, 1080, 1824]
layerStack= 0, z= 21000, pos=(0,0), size=(1080,1920), crop=( 0, 50,1080,1824), isOpaque=1, invalidate=0, alpha=0xff, flags=0x00000002, tr=[1.00, 0.00][0.00, 1.00]
client=0xb7dbf270
format= 2, activeBuffer=[1080x1920:1152, 3], queued-frames=0, mRefreshPending=0
mTexName=10 mCurrentTexture=2
mCurrentCrop=[0,0,0,0] mCurrentTransform=0
mAbandoned=0
-BufferQueue mMaxAcquiredBufferCount=1, mDequeueBufferCannotBlock=0, default-size=[1080x1920], default-format=2, transform-hint=00, FIFO(0)={}
[00:0xb7dd1fb0] state=FREE , 0xb7dd0048 [1080x1920:1152, 3]
[01:0xb7d5c2c8] state=FREE , 0xb7d39ca8 [1080x1920:1152, 3]
>[02:0xb7d1d578] state=ACQUIRED, 0xb7d5cb18 [1080x1920:1152, 3]
...
可以想象得到，系统把这个layer对应的窗口当成了一个1080p屏幕来布局和绘制了。
- 设置屏幕的dpi
$ adb shell wm density 320
常用的dpi有160(mdpi), 240(hdpi), 320(xhdpi), 480(xxhdpi)。重置可用如下命令：
$ adb shell wm density reset
- 如何实现 ，以设置显示窗口尺寸为例(@android-5.1.1)
首先看一下wm命令如何通知WindowManagerService更新配置：
代码：frameworks/base/cmds/wm/src/com/android/commands/wm/
public class Wm extends BaseCommand {
...
public void onRun() throws Exception {
mWm = ((
Context.WINDOW_SERVICE));
if (mWm == null) {
(NO_SYSTEM_ERROR_CODE);
throw new AndroidException("Can't connect to window manager; is the system running?");
}
String op = nextArgRequired();
if (("size")) {
runDisplaySize();
} else if (("density")) {
runDisplayDensity();
} else if (("overscan")) {
runDisplayOverscan();
} else {
showError("Error: unknown command '" + op + "'");
return;
}
}
...
private void runDisplaySize() throws Exception {
String size = nextArg();
int w, h;
if (size == null) {
Point initialSize = new Point();
Point baseSize = new Point();
try {
(Display.DEFAULT_DISPLAY, initialSize);
(Display.DEFAULT_DISPLAY, baseSize);
("Physical size: " + + "x" + );
if (!(baseSize)) {
("Override size: " + + "x" + );
}
} catch (RemoteException e) {
}
return;
} else if ("reset".equals(size)) {
w = h = -1;
} else {
int div = ('x');
if (div <= 0 || div >= (()-1)) {
("Error: bad size " + size);
return;
}
String wstr = (0, div);
String hstr = (div+1);
try {
w = (wstr);
h = (hstr);
} catch (NumberFormatException e) {
("Error: bad number " + e);
return;
}
}
try {
if (w >= 0 && h >= 0) {
// TODO(multidisplay): For now Configuration only applies to main screen.
(Display.DEFAULT_DISPLAY, w, h);
} else {
(Display.DEFAULT_DISPLAY);
}
} catch (RemoteException e) {
}
}
...
}
先获取WindowManagerService再调用它的setForcedDisplaySize()方法。
代码：frameworks/base/services/core/java/com/android/server/wm/
public class WindowManagerService extends
implements , {
...
@Override
public void setForcedDisplaySize(int displayId, int width, int height) {
if ((
.WRITE_SECURE_SETTINGS) !=
PackageManager.PERMISSION_GRANTED) {
throw new SecurityException("Must hold permission " +
.WRITE_SECURE_SETTINGS);
}
if (displayId != Display.DEFAULT_DISPLAY) {
throw new IllegalArgumentException("Can only set the default display");
}
final long ident = ();
try {
synchronized(mWindowMap) {
// Set some sort of reasonable bounds on the size of the display that we
// will try to emulate.
final int MIN_WIDTH = 200;
final int MIN_HEIGHT = 200;
final int MAX_SCALE = 2;
final DisplayContent displayContent = getDisplayContentLocked(displayId);
if (displayContent != null) {
width = ((width, MIN_WIDTH),
* MAX_SCALE);
height = ((height, MIN_HEIGHT),
* MAX_SCALE);
setForcedDisplaySizeLocked(displayContent, width, height);
((),
.DISPLAY_SIZE_FORCED, width + "," + height);
}
}
} finally {
(ident);
}
}
...
// displayContent must not be null
private void setForcedDisplaySizeLocked(DisplayContent displayContent, int width, int height) {
(TAG, "Using new display size: " + width + "x" + height);
synchronized() {
= width;
= height;
}
reconfigureDisplayLocked(displayContent);
}
...
// displayContent must not be null
private void reconfigureDisplayLocked(DisplayContent displayContent) {
// TODO: Multidisplay: for now only use with default display.
configureDisplayPolicyLocked(displayContent);
= true;
boolean configChanged = updateOrientationFromAppTokensLocked(false);
();
= ;
if (computeScreenConfigurationLocked(mTempConfiguration)) {
if ((mTempConfiguration) != 0) {
configChanged = true;
}
}
if (configChanged) {
mWaitingForConfig = true;
startFreezingDisplayLocked(false, 0, 0);
(H.SEND_NEW_CONFIGURATION);
}
performLayoutAndPlaceSurfacesLocked();
}
...
}
setForcedDisplaySize()->setForcedDisplaySizeLocked()->reconfigureDisplayLocked()->SEND_NEW_CONFIGURATION
这里可以看到可以设置的屏幕窗口最小为(200,200),最大小显示屏分辨率的两倍。
而WindowManagerService又是如何通知DisplayManagerService更新配置：
WindowsManagerService$(SEND_NEW_CONFIGURATION)
->()
->() x2
->()
->()
->()
->()
->DisplayManagerService$()
->$4200()
->()
->()
->()
->()
到这里就会去设置layer stack的尺寸和在屏幕上的位置：
final class LogicalDisplay {
...
/**
* Applies the layer stack and transformation to the given display device
* so that it shows the contents of this logical display.
*
* We know that the given display device is only ever showing the contents of
* a single logical display, so this method is expected to blow away all of its
* transformation properties to make it happen regardless of what the
* display device was previously showing.
*
* The caller must have an open Surface transaction.
*
* The display device may not be the primary display device, in the case
* where the display is being mirrored.
*
* @param device The display device to modify.
* @param isBlanked True if the device is being blanked.
*/
public void configureDisplayInTransactionLocked(DisplayDevice device,
boolean isBlanked) {
final DisplayInfo displayInfo = getDisplayInfoLocked();
final DisplayDeviceInfo displayDeviceInfo = ();
// Set the layer stack.
(isBlanked ? BLANK_LAYER_STACK : mLayerStack);
// Set the refresh rate
(mRequestedRefreshRate);
// Set the viewport.
// This is the area of the logical display that we intend to show on the
// display device. For now, it is always the full size of the logical display.
(0, 0, , );
// Set the orientation.
// The orientation specifies how the physical coordinate system of the display
// is rotated when the contents of the logical display are rendered.
int orientation = Surface.ROTATION_0;
if (( & DisplayDeviceInfo.FLAG_ROTATES_WITH_CONTENT) != 0) {
orientation = ;
}
// Apply the physical rotation of the display device itself.
orientation = (orientation + ) % 4;
// Set the frame.
// The frame specifies the rotated physical coordinates into which the viewport
// is mapped. We need to take care to preserve the aspect ratio of the viewport.
// Currently we maximize the area to fill the display, but we could try to be
// more clever and match resolutions.
boolean rotated = (orientation == Surface.ROTATION_90
|| orientation == Surface.ROTATION_270);
int physWidth = rotated ? : ;
int physHeight = rotated ? : ;
// Determine whether the width or height is more constrained to be scaled.
// physWidth / => letter box
// or physHeight / => pillar box
//
// We avoid a division (and possible floating point imprecision) here by
// multiplying the fractions by the product of their denominators before
// comparing them.
int displayRectWidth, displayRectHeight;
if (physWidth *
< physHeight * ) {
// Letter box.
displayRectWidth = physWidth;
displayRectHeight = * physWidth / ;
} else {
// Pillar box.
displayRectWidth = * physHeight / ;
displayRectHeight = physHeight;
}
int displayRectTop = (physHeight - displayRectHeight) / 2;
int displayRectLeft = (physWidth - displayRectWidth) / 2;
(displayRectLeft, displayRectTop,
displayRectLeft + displayRectWidth, displayRectTop + displayRectHeight);
(orientation, mTempLayerStackRect, mTempDisplayRect);
}
...
}
->()
通知SurfaceFlinger:
abstract class DisplayDevice {
...
/**
* Sets the display projection while in a transaction.
*
* @param orientation defines the display's orientation
* @param layerStackRect defines which area of the window manager coordinate
* space will be used
* @param displayRect defines where on the display will layerStackRect be
* mapped to. displayRect is specified post-orientation, that is
* it uses the orientation seen by the end-user
*/
public final void setProjectionInTransactionLocked(int orientation,
Rect layerStackRect, Rect displayRect) {
if (mCurrentOrientation != orientation
|| mCurrentLayerStackRect == null
|| !(layerStackRect)
|| mCurrentDisplayRect == null
|| !(displayRect)) {
mCurrentOrientation = orientation;
if (mCurrentLayerStackRect == null) {
mCurrentLayerStackRect = new Rect();
}
(layerStackRect);
if (mCurrentDisplayRect == null) {
mCurrentDisplayRect = new Rect();
}
(displayRect);
SurfaceControl.setDisplayProjection(mDisplayToken,
orientation, layerStackRect, displayRect);
}
}
...
}
最后，SurfaceFlinger就会跟据这些信息对Layer进行合成，显示在屏幕上。
代码：frameworks/native/services/surfaceflinger/
void DisplayDevice::setProjection(int orientation,
const Rect& newViewport, const Rect& newFrame) {
Rect viewport(newViewport);
Rect frame(newFrame);
const int w = mDisplayWidth;
const int h = mDisplayHeight;
Transform R;
DisplayDevice::orientationToTransfrom(orientation, w, h, &R);
if (!()) {
// the destination frame can be invalid if it has never been set,
// in that case we assume the whole display frame.
frame = Rect(w, h);
}
if (()) {
// viewport can be invalid if it has never been set, in that case
// we assume the whole display size.
// it's also invalid to have an empty viewport, so we handle that
// case in the same way.
viewport = Rect(w, h);
if (() & Transform::ROT_90) {
// viewport is always specified in the logical orientation
// of the display (ie: post-rotation).
swap(, );
}
}
(getBounds());
Transform TL, TP, S;
float src_width = ();
float src_height = ();
float dst_width = ();
float dst_height = ();
if (src_width != dst_width || src_height != dst_height) {
float sx = dst_width / src_width;
float sy = dst_height / src_height;
(sx, 0, 0, sy);
}
float src_x = ;
float src_y = ;
float dst_x = ;
float dst_y = ;
(-src_x, -src_y);
(dst_x, dst_y);
// The viewport and frame are both in the logical orientation.
// Apply the logical translation, scale to physical size, apply the
// physical translation and finally rotate to the physical orientation.
mGlobalTransform = R * TP * S * TL;
const uint8_t type = ();
mNeedsFiltering = (!() ||
(type >= Transform::SCALE));
mScissor = (viewport);
if (()) {
mScissor = getBounds();
}
mOrientation = orientation;
mViewport = viewport;
mFrame = frame;
}
- 在三星A9上将屏幕的density由原来的480更改为320，重启后发现显示的效果不太好：
- 三星Launcher的主页只在屏幕的上半部显示
- camera的界面只显示在了屏幕的右上方
- 输入法界面也显示不正常
- 常用的应用如计算器、收音机、智能管理器。。。好多应用布局都有问题。
看来还是google原生系统处理得比较好，系在统重启之后，还没有找到有问题的布局（bootanimation会显示不正常）。