AndroidManifest.xml初识
AndroidManifest.xml这个文件用来告诉android系统，这里面有关于APP的配置信息，你需要根据里面的设置的配置信息来运行这个app。
——根节点 ——应用节点，必须有 ， ， 描述应用的组件，作为 的子节点 ——用户特征标签，描述应用所依赖的硬件或者软件条件。在应用商店搜索的时候进行过滤。 ——用户权限标签，描述应用需要的权限
minSdkVersion 和 targetSdkVersion 和 compileSdkVersion
minSdkVersion和targetSdkVersion设置的值表示这两个区间的设备能正常使用这个app，表示您已经在您指定的版本上测试了应用程序(大概包括该版本)。这更像是一个认证或签署，你是给Android操作系统作为一个提示，它应该如何处理您的应用程序的操作系统功能。
（设备的android系统版本的使用的sdkversion是不一样的，比如Android5.0对应的targetSDK设置为21）。一般来说每次发布新的版本，targetSdkVersion应该递增以匹配最新的api级别，如果有变，然后在相应的平台版本上彻底测试应用程序。
而compileSdkVersion可以不变，除非你需要要最新的sdk中功能，那么需要相应的改变compileSdkVersion，举一个样例：
假如你想给你的app增加大量的手势操作（sdk
7才引入的），然而这些手势操作能够被Button啊或menu等取代，在这样的情况下，手势操作就是一个额外的加分功能，而不是一个必须的功能。然后你所要做的就是要在代码里推断版本号，假设是大于等于7的版本号中就使用手势操作，小于7的版本号中就使用button等取代。然后你把targetSDK设置为7，把minSDK设置为低一些。这样使用了新手机的用户就能够体验到你app中酷炫的新功能了，老用户也能正常运行。
Android 10.0 修改导航栏横屏固定在底部显示
路径：framework/base/core/res/res/values/config.xml -true +false
DisplayPolicy(WindowManagerService service, DisplayContent displayContent) {
mService = service;
mContext = displayContent.isDefaultDisplay ? service.mContext
: service.mContext.createDisplayContext(displayContent.getDisplay());
mDisplayContent = displayContent;
mLock = service.getWindowManagerLock();
final int displayId = displayContent.getDisplayId();
mStatusBarController = new StatusBarController(displayId);
mNavigationBarController = new BarController("NavigationBar",
displayId,
View.NAVIGATION_BAR_TRANSIENT,
View.NAVIGATION_BAR_UNHIDE,
View.NAVIGATION_BAR_TRANSLUCENT,
StatusBarManager.WINDOW_NAVIGATION_BAR,
FLAG_TRANSLUCENT_NAVIGATION,
View.NAVIGATION_BAR_TRANSPARENT);
final Resources r = mContext.getResources();
mCarDockEnablesAccelerometer = r.getBoolean(R.bool.config_carDockEnablesAccelerometer);
mDeskDockEnablesAccelerometer = r.getBoolean(R.bool.config_deskDockEnablesAccelerometer);
mForceShowSystemBarsFromExternal = r.getBoolean(R.bool.config_forceShowSystemBars);
mAccessibilityManager = (AccessibilityManager) mContext.getSystemService(
Context.ACCESSIBILITY_SERVICE);
if (!displayContent.isDefaultDisplay) {
mAwake = true;
mScreenOnEarly = true;
mScreenOnFully = true;
}
final Looper looper = UiThread.getHandler().getLooper();
mHandler = new PolicyHandler(looper);
mSystemGestures = new SystemGesturesPointerEventListener(mContext, mHandler,
new SystemGesturesPointerEventListener.Callbacks() {
@Override
public void onSwipeFromTop() {
if (mStatusBar != null) {
requestTransientBars(mStatusBar);
}
}
@Override
public void onSwipeFromBottom() {
if (mNavigationBar != null && mNavigationBarPosition == NAV_BAR_BOTTOM) {
requestTransientBars(mNavigationBar);
}
}
@Override
public void onSwipeFromRight() {
final Region excludedRegion;
synchronized (mLock) {
excludedRegion = mDisplayContent.calculateSystemGestureExclusion();
}
final boolean sideAllowed = mNavigationBarAlwaysShowOnSideGesture
|| mNavigationBarPosition == NAV_BAR_RIGHT;
if (mNavigationBar != null && sideAllowed
&& !mSystemGestures.currentGestureStartedInRegion(excludedRegion)) {
requestTransientBars(mNavigationBar);
}
}
@Override
public void onSwipeFromLeft() {
final Region excludedRegion;
synchronized (mLock) {
excludedRegion = mDisplayContent.calculateSystemGestureExclusion();
}
final boolean sideAllowed = mNavigationBarAlwaysShowOnSideGesture
|| mNavigationBarPosition == NAV_BAR_LEFT;
if (mNavigationBar != null && sideAllowed
&& !mSystemGestures.currentGestureStartedInRegion(excludedRegion)) {
requestTransientBars(mNavigationBar);
}
}
@Override
public void onFling(int duration) {
if (mService.mPowerManagerInternal != null) {
mService.mPowerManagerInternal.powerHint(
PowerHint.INTERACTION, duration);
}
}
@Override
public void onDebug() {
// no-op
}
private WindowOrientationListener getOrientationListener() {
final DisplayRotation rotation = mDisplayContent.getDisplayRotation();
return rotation != null ? rotation.getOrientationListener() : null;
}
@Override
public void onDown() {
final WindowOrientationListener listener = getOrientationListener();
if (listener != null) {
listener.onTouchStart();
}
}
@Override
public void onUpOrCancel() {
final WindowOrientationListener listener = getOrientationListener();
if (listener != null) {
listener.onTouchEnd();
}
}
@Override
public void onMouseHoverAtTop() {
mHandler.removeMessages(MSG_REQUEST_TRANSIENT_BARS);
Message msg = mHandler.obtainMessage(MSG_REQUEST_TRANSIENT_BARS);
msg.arg1 = MSG_REQUEST_TRANSIENT_BARS_ARG_STATUS;
mHandler.sendMessageDelayed(msg, 500 );
}
@Override
public void onMouseHoverAtBottom() {
mHandler.removeMessages(MSG_REQUEST_TRANSIENT_BARS);
Message msg = mHandler.obtainMessage(MSG_REQUEST_TRANSIENT_BARS);
msg.arg1 = MSG_REQUEST_TRANSIENT_BARS_ARG_NAVIGATION;
mHandler.sendMessageDelayed(msg, 500 );
}
@Override
public void onMouseLeaveFromEdge() {
mHandler.removeMessages(MSG_REQUEST_TRANSIENT_BARS);
}
});
displayContent.registerPointerEventListener(mSystemGestures);
displayContent.mAppTransition.registerListenerLocked(
mStatusBarController.getAppTransitionListener());
mImmersiveModeConfirmation = new ImmersiveModeConfirmation(mContext, looper,
mService.mVrModeEnabled);
mAcquireSleepTokenRunnable = () -> {
if (mWindowSleepToken != null) {
return;
}
mWindowSleepToken = service.mAtmInternal.acquireSleepToken(
"WindowSleepTokenOnDisplay" + displayId, displayId);
};
mReleaseSleepTokenRunnable = () -> {
if (mWindowSleepToken == null) {
return;
}
mWindowSleepToken.release();
mWindowSleepToken = null;
};
// TODO: Make it can take screenshot on external display
mScreenshotHelper = displayContent.isDefaultDisplay
? new ScreenshotHelper(mContext) : null;
if (mDisplayContent.isDefaultDisplay) {
mHasStatusBar = true;
mHasNavigationBar = mContext.getResources().getBoolean(R.bool.config_showNavigationBar);
// Allow a system property to override this. Used by the emulator.
// See also hasNavigationBar().
String navBarOverride = SystemProperties.get("qemu.hw.mainkeys");
if ("1".equals(navBarOverride)) {
mHasNavigationBar = false;
} else if ("0".equals(navBarOverride)) {
mHasNavigationBar = true;
}
} else {
mHasStatusBar = false;
mHasNavigationBar = mDisplayContent.supportsSystemDecorations();
}
mRefreshRatePolicy = new RefreshRatePolicy(mService,
mDisplayContent.getDisplayInfo(),
mService.mHighRefreshRateBlacklist);
}
void systemReady() {
mSystemGestures.systemReady();
if (mService.mPointerLocationEnabled) {
setPointerLocationEnabled(true);
}
}
private int getDisplayId() {
return mDisplayContent.getDisplayId();
}
public boolean hasNavigationBar() {
return mHasNavigationBar;
}
public boolean hasStatusBar() {
return mHasStatusBar;
}
public boolean navigationBarCanMove() {
return mNavigationBarCanMove;
}
@NavigationBarPosition
int navigationBarPosition(int displayWidth, int displayHeight, int displayRotation) {
if (navigationBarCanMove() && displayWidth > displayHeight) {
if (displayRotation == Surface.ROTATION_270) {
return NAV_BAR_LEFT;
} else if (displayRotation == Surface.ROTATION_90) {
return NAV_BAR_RIGHT;
}
}
return NAV_BAR_BOTTOM;
}
boolean canNavigationBarMove() {
return mNavigationBarCanMove;
}
void updateConfigurationAndScreenSizeDependentBehaviors() {
final Resources res = getCurrentUserResources();
mNavigationBarCanMove =
mDisplayContent.mBaseDisplayWidth != mDisplayContent.mBaseDisplayHeight
&& res.getBoolean(R.bool.config_navBarCanMove);
mAllowSeamlessRotationDespiteNavBarMoving =
res.getBoolean(R.bool.config_allowSeamlessRotationDespiteNavBarMoving);
}
从上述代码可以看出
在navigationBarPosition(int displayWidth, int displayHeight, int displayRotation)中
来判断导航栏显示的方向 当navigationBarCanMove()为false的时候 就会显示在底部
所以就是
boolean canNavigationBarMove() {
return mNavigationBarCanMove;
}
就是mNavigationBarCanMove的参数值
mNavigationBarCanMove =
mDisplayContent.mBaseDisplayWidth != mDisplayContent.mBaseDisplayHeight
&& res.getBoolean(R.bool.config_navBarCanMove);
就是由config_navBarCanMove 属性值决定的 查看config.xml
路径：framework/base/core/res/res/values/config.xml
true
在config中为true
