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前言

• 分屏：是指一个屏幕分出多个窗口，分别显示不同应用的界面，这在当前的手机设备中很常见。
• 多屏：是指一个设备存在多个屏幕，这些可能是虚拟屏幕或者实体硬件屏幕，不同的应用同时显示在不同的屏幕中，或者相同应用的不同页面同时现在在不同的屏幕中。

在我们日常生活中所接触的大部分以Android系统为载体的智能化硬件设备，大多都只有一个屏幕，但是有的时候会出现需要多个屏幕的场景，特别是随着新能源汽车行业竞争的白热化，越来越多的车厂倾向于通过多屏幕来获得消费者的青睐，比如为汽车主驾副驾所对应的主屏副屏等等，这就导致车机系统的多屏幕场景越来越多；而在智能手机端，多屏协助的场景也越来越多，比如将手机屏幕内容实时投放到大屏电视上已得到更好的视觉体验；

一、模拟辅助设备

1.1、模拟辅助设备功能开关

1、在Android开发者选项里面有一个模拟辅助设备功能开关。

2、此功能默认为无，当我们点击并选择一个分辨率的时候，屏幕上会多出来一个小窗口。

这个小窗口其实就是系统新创建的一个虚拟屏幕，只不过Android系统将该虚拟屏幕的视图实时绘制在了此窗口上。

1.2、屏幕设备信息

1、我们通过adb执行dumpsys display指令，可以看到系统中当前存在的屏幕设备的相关信息。

  Logical Displays: size=1Display 0:mDisplayId=0mPhase=1mLayerStack=0mHasContent=truemDesiredDisplayModeSpecs={baseModeId=1 allowGroupSwitching=false primaryRefreshRateRange=[0 60] appRequestRefreshRateRange=[0 60]}mRequestedColorMode=0mDisplayOffset=(0, 0)mDisplayScalingDisabled=falsemPrimaryDisplayDevice=内置屏幕mBaseDisplayInfo=DisplayInfo{"内置屏幕", displayId 0", displayGroupId 0, FLAG_SECURE, FLAG_SUPPORTS_PROTECTED_BUFFERS, FLAG_TRUSTED, real 1080 x 2400, largest app 1080 x 2400, smallest app 1080 x 2400, appVsyncOff 1000000, presDeadline 16666666, mode 1, defaultMode 1, modes [{id=1, width=1080, height=2400, fps=60.000004, alternativeRefreshRates=[90.0, 120.00001]}, {id=2, width=1080, height=2400, fps=120.00001, alternativeRefreshRates=[60.000004, 90.0]}, {id=3, width=1080, height=2400, fps=90.0, alternativeRefreshRates=[60.000004, 120.00001]}], hdrCapabilities HdrCapabilities{mSupportedHdrTypes=[1, 2, 3, 4], mMaxLuminance=420.0, mMaxAverageLuminance=210.1615, mMinLuminance=0.323}, userDisabledHdrTypes [], minimalPostProcessingSupported false, rotation 0, state ON, type INTERNAL, uniqueId "local:4630946545580055170", app 1080 x 2400, density 440 (419.449 x 419.257) dpi, layerStack 0, colorMode 0, supportedColorModes [0, 7, 9], address {port=130, model=0x40446d58ef1f1a}, deviceProductInfo DeviceProductInfo{name=, manufacturerPnpId=QCM, productId=1, modelYear=null, manufactureDate=ManufactureDate{week=27, year=2006}, connectionToSinkType=0}, removeMode 0, refreshRateOverride 0.0, brightnessMinimum 0.0, brightnessMaximum 1.0, brightnessDefault 0.07496032, installOrientation ROTATION_0}mOverrideDisplayInfo=DisplayInfo{"内置屏幕", displayId 0", displayGroupId 0, FLAG_SECURE, FLAG_SUPPORTS_PROTECTED_BUFFERS, FLAG_TRUSTED, real 1080 x 2400, largest app 2313 x 2269, smallest app 1080 x 949, appVsyncOff 1000000, presDeadline 16666666, mode 1, defaultMode 1, modes [{id=1, width=1080, height=2400, fps=60.000004, alternativeRefreshRates=[90.0, 120.00001]}, {id=2, width=1080, height=2400, fps=120.00001, alternativeRefreshRates=[60.000004, 90.0]}, {id=3, width=1080, height=2400, fps=90.0, alternativeRefreshRates=[60.000004, 120.00001]}], hdrCapabilities HdrCapabilities{mSupportedHdrTypes=[1, 2, 3, 4], mMaxLuminance=420.0, mMaxAverageLuminance=210.1615, mMinLuminance=0.323}, userDisabledHdrTypes [], minimalPostProcessingSupported false, rotation 0, state ON, type INTERNAL, uniqueId "local:4630946545580055170", app 1080 x 2269, density 440 (419.449 x 419.257) dpi, layerStack 0, colorMode 0, supportedColorModes [0, 7, 9], address {port=130, model=0x40446d58ef1f1a}, deviceProductInfo DeviceProductInfo{name=, manufacturerPnpId=QCM, productId=1, modelYear=null, manufactureDate=ManufactureDate{week=27, year=2006}, connectionToSinkType=0}, removeMode 0, refreshRateOverride 0.0, brightnessMinimum 0.0, brightnessMaximum 1.0, brightnessDefault 0.07496032, installOrientation ROTATION_0}mRequestedMinimalPostProcessing=falsemFrameRateOverrides=[]mPendingFrameRateOverrideUids={}

2、默认情况下系统只有一个屏幕设备信息，而在我们开启模拟辅助显示设备功能开关之后，Android系统中便会多出来一个屏幕设备信息。

  Logical Displays: size=2Display 0:mDisplayId=0mPhase=1mLayerStack=0mHasContent=truemDesiredDisplayModeSpecs={baseModeId=1 allowGroupSwitching=false primaryRefreshRateRange=[0 60] appRequestRefreshRateRange=[0 60]}    mRequestedColorMode=0mDisplayOffset=(0, 0)mDisplayScalingDisabled=falsemPrimaryDisplayDevice=内置屏幕mBaseDisplayInfo=DisplayInfo{"内置屏幕", displayId 0", displayGroupId 0, FLAG_SECURE, FLAG_SUPPORTS_PROTECTED_BUFFERS, FLAG_TRUSTED, real 1080 x 2400, largest app 1080 x 2400, smallest app 1080 x 2400, appVsyncOff 1000000, presDeadline 16666666, mode 1, defaultMode 1, modes [{id=1, width=1080, height=2400, fps=60.000004, alternativeRefreshRates=[90.0, 120.00001]}, {id=2, width=1080, height=2400, fps=120.00001, alternativeRefreshRates=[60.000004, 90.0]}, {id=3, width=1080, height=2400, fps=90.0, alternativeRefreshRates=[60.000004, 120.00001]}], hdrCapabilities HdrCapabilities{mSupportedHdrTypes=[1, 2, 3, 4], mMaxLuminance=420.0, mMaxAverageLuminance=210.1615, mMinLuminance=0.323}, userDisabledHdrTypes [], minimalPostProcessingSupported false, rotation 0, state ON, type INTERNAL, uniqueId "local:4630946545580055170", app 1080 x 2400, density 440 (419.449 x 419.257) dpi, layerStack 0, colorMode 0, supportedColorModes [0, 7, 9], address {port=130, model=0x40446d58ef1f1a}, deviceProductInfo DeviceProductInfo{name=, manufacturerPnpId=QCM, productId=1, modelYear=null, manufactureDate=ManufactureDate{week=27, year=2006}, connectionToSinkType=0}, removeMode 0, refreshRateOverride 0.0, brightnessMinimum 0.0, brightnessMaximum 1.0, brightnessDefault 0.07496032, installOrientation ROTATION_0}mOverrideDisplayInfo=DisplayInfo{"内置屏幕", displayId 0", displayGroupId 0, FLAG_SECURE, FLAG_SUPPORTS_PROTECTED_BUFFERS, FLAG_TRUSTED, real 1080 x 2400, largest app 2313 x 2269, smallest app 1080 x 949, appVsyncOff 1000000, presDeadline 16666666, mode 1, defaultMode 1, modes [{id=1, width=1080, height=2400, fps=60.000004, alternativeRefreshRates=[90.0, 120.00001]}, {id=2, width=1080, height=2400, fps=120.00001, alternativeRefreshRates=[60.000004, 90.0]}, {id=3, width=1080, height=2400, fps=90.0, alternativeRefreshRates=[60.000004, 120.00001]}], hdrCapabilities HdrCapabilities{mSupportedHdrTypes=[1, 2, 3, 4], mMaxLuminance=420.0, mMaxAverageLuminance=210.1615, mMinLuminance=0.323}, userDisabledHdrTypes [], minimalPostProcessingSupported false, rotation 0, state ON, type INTERNAL, uniqueId "local:4630946545580055170", app 1080 x 2269, density 440 (419.449 x 419.257) dpi, layerStack 0, colorMode 0, supportedColorModes [0, 7, 9], address {port=130, model=0x40446d58ef1f1a}, deviceProductInfo DeviceProductInfo{name=, manufacturerPnpId=QCM, productId=1, modelYear=null, manufactureDate=ManufactureDate{week=27, year=2006}, connectionToSinkType=0}, removeMode 0, refreshRateOverride 0.0, brightnessMinimum 0.0, brightnessMaximum 1.0, brightnessDefault 0.07496032, installOrientation ROTATION_0}mRequestedMinimalPostProcessing=falsemFrameRateOverrides=[]mPendingFrameRateOverrideUids={}Display 2:mDisplayId=2mPhase=1mLayerStack=2mHasContent=falsemDesiredDisplayModeSpecs={baseModeId=4 allowGroupSwitching=false primaryRefreshRateRange=[0 60] appRequestRefreshRateRange=[0 60]}    mRequestedColorMode=0mDisplayOffset=(0, 0)mDisplayScalingDisabled=falsemPrimaryDisplayDevice=叠加视图 #1mBaseDisplayInfo=DisplayInfo{"叠加视图 #1", displayId 2", displayGroupId 0, FLAG_PRESENTATION, FLAG_TRUSTED, real 1280 x 720, largest app 1280 x 720, smallest app 1280 x 720, appVsyncOff 0, presDeadline 33333332, mode 4, defaultMode 4, modes [{id=4, width=1280, height=720, fps=60.000004, alternativeRefreshRates=[]}], hdrCapabilities null, userDisabledHdrTypes [], minimalPostProcessingSupported false, rotation 0, state ON, type OVERLAY, uniqueId "overlay:1", app 1280 x 720, density 213 (213.0 x 213.0) dpi, layerStack 2, colorMode 0, supportedColorModes [0], deviceProductInfo null, removeMode 0, refreshRateOverride 0.0, brightnessMinimum 0.0, brightnessMaximum 0.0, brightnessDefault 0.0, installOrientation ROTATION_0}mOverrideDisplayInfo=DisplayInfo{"叠加视图 #1", displayId 2", displayGroupId 0, FLAG_PRESENTATION, FLAG_TRUSTED, real 1280 x 720, largest app 1280 x 1280, smallest app 720 x 720, appVsyncOff 0, presDeadline 33333332, mode 4, defaultMode 4, modes [{id=4, width=1280, height=720, fps=60.000004, alternativeRefreshRates=[]}], hdrCapabilities null, userDisabledHdrTypes [], minimalPostProcessingSupported false, rotation 0, state ON, type OVERLAY, uniqueId "overlay:1", app 1280 x 720, density 213 (213.0 x 213.0) dpi, layerStack 2, colorMode 0, supportedColorModes [0], deviceProductInfo null, removeMode 0, refreshRateOverride 0.0, brightnessMinimum 0.0, brightnessMaximum 0.0, brightnessDefault 0.0, installOrientation ROTATION_0}mRequestedMinimalPostProcessing=falsemFrameRateOverrides=[]mPendingFrameRateOverrideUids={}

可以发现此事屏幕变成了两个。

二、将页面显示到特定屏幕中

2.1 获取当前屏幕设备信息

1、在Android系统默认情况下，我们新建一个Activity，并将其启动。

DisplayInfoActivity.java

public class DisplayInfoActivity extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main_activity);TextView tvDisplayInfo = findViewById(R.id.tv_display_info);Display display = getDisplay();tvDisplayInfo.setText(display.toString());}
}

main_activity.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextViewandroid:id="@+id/tv_display_info"android:layout_width="match_parent"android:layout_height="200dp"android:gravity="center"android:text="屏幕设备信息"android:textColor="#F00"android:textSize="30sp" /></LinearLayout>

2、默认显示效果如下所示。

通过Activity显示的信息我们可以发现，该页面当前显示的屏幕设备id为0，名字叫做内置屏幕。

2.2 将页面显示到其他屏幕上

1、当我们为Android系统开启了模拟辅助显示设备的功能之后，此时我们通过代码打开一个新的Activity，并为其指定displayid为2，这样这个新的Activity就会显示到这个新的虚拟屏幕中。

DisplayInfoActivity.java

public class DisplayInfoActivity extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main_activity);TextView tvDisplayInfo = findViewById(R.id.tv_display_info);Display display = getDisplay();tvDisplayInfo.setText(display.toString());findViewById(R.id.btn_open_activity).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {Intent intent = new Intent(DisplayInfoActivity.this, DisplayInfoActivity.class);ActivityOptions activityOptions = ActivityOptions.makeBasic();activityOptions.setLaunchDisplayId(2);//指定要显示到displayid为2的屏幕设备上startActivity(intent, activityOptions.toBundle());}});}}

main_activity.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextViewandroid:id="@+id/tv_display_info"android:layout_width="match_parent"android:layout_height="200dp"android:gravity="center"android:text="屏幕设备信息"android:textColor="#F00"android:textSize="30sp" /><Buttonandroid:id="@+id/btn_open_activity"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="在模拟辅助设备中显示新页面" />
</LinearLayout>

2、当我们点击按钮的时候，当前页面会从主屏幕消失，并显示到模拟辅助功能所开启的窗口里面。

通过Activity显示的信息我们可以发现，该页面当前显示的屏幕设备id为2，名字叫做叠加视图，也就是新增的虚拟屏幕设备ID。