Android應用如何支持屏幕多尺寸多分辨率問題

作為Android應用程序開發者都知道android是一個“碎片化”的世界。多種系統版本、多種尺寸、多種分辨率、多種機型,還有不同的廠商定制的不同ROM，你開發的應用會在不可預期的手機上報錯。這給開發適配帶來不小的難度。這篇文章會告訴我們怎麼解決這個問題。

 

1、Android碎片化

1.1、android系統版本

Android更新較大的版本如下：

 

 

上面只有當前可用版本，Android L作為開發者版本沒有出現其中，未來會有更多的版本。下圖給出Android各個版本的占有率，這個是googleplay統計的近期數據。googleplay只支持2.2以上的手機，所以統計中缺少2.2以下版本。

 

1.2、Android中不同尺寸、不同分辨率市場占有情況

 

3、Android不同機型

這是OpenSignal在2013年的調查調查結果，Android系統設備覆蓋了11,868不同機型，現在肯定會更多。

2、基本概念

Android“碎片化”如此嚴重，那麼我們怎麼解決Android應用適配問題呢。Android官方文檔給出了解決方案，這篇文章也是參考總結的官方文檔。

解決Android“碎片化”化問題，我們需要了解一些基礎概念。

 

屏幕大小

根據屏幕對角線實際測量的物理大小（android已經根據屏幕大小分為四類small, normal, large, extra large），具體怎麼劃分的下面會提到。

屏幕密度
屏幕物理區域一個單位（一般用英寸）的像素數量，一般簡稱dpi（dots per inch，每英寸上的點數，記住DPI這個概念很重要）屏幕密度也分為四類 low, medium, high, extra high，他們的比例關系是 0.75:1:1.5:2，具體的值為120:160:240:320。

屏幕方向
屏幕方向分為橫屏和豎屏。

分辨率
一個物理屏幕上像素點的總數。一般我們的App不會直接使用分辨率，而是使用密度和屏幕大小。

 

獨立像素單位（Density-independent pixel (dp)）
一個虛擬的單位，用來決定UI布局的。用來表述布局的尺寸或者位置。
dp是一個與屏幕密度有關系的單位，dp與像素的換算關系為 px = dp * (dpi / 160)。例如在240密度（dpi）的屏幕上一個dp等於1.5個像素。以後我們應該盡量使用dp單位布局，不要使用像素單位。這樣會使你的app屏幕兼容性更好

Android1.6開始就支持多屏幕和密度了，這都是為了更好的用戶體驗，為了簡化我們多屏幕的開發，當然這要聲明或者大於4。android提供了一組范圍讓我們使用，見下圖：

 

3、Android中資源配置

Android工程中經常看到下圖的資源文件配置，一般會包含animator、anim、color、drawable、layout、menu、raw、value、xml等。

命名規則是-。
：資源文件名
：特定條件下可以使用這種資源

 

 

config_qualifier可以使用多種：

 

 

Configuration Qualifier Values Description MCC and MNC Examples:mcc310mcc310-mnc004mcc208-mnc00etc. The mobile country code (MCC), optionally followed by mobile network code (MNC) from the SIM card in the device. For example, mcc310 is U.S. on any carrier,mcc310-mnc004 is U.S. on Verizon, and mcc208-mnc00 is France on Orange.
If the device uses a radio connection (GSM phone), the MCC and MNC values come from the SIM card.
You can also use the MCC alone (for example, to include country-specific legal resources in your application). If you need to specify based on the language only, then use the language and region qualifier instead (discussed next). If you decide to use the MCC and MNC qualifier, you should do so with care and test that it works as expected.
Also see the configuration fields mcc, and mnc, which indicate the current mobile country code and mobile network code, respectively. Language and region Examples:enfren-rUSfr-rFRfr-rCAetc. The language is defined by a two-letter ISO 639-1 language code, optionally followed by a two letter ISO 3166-1-alpha-2 region code (preceded by lowercase r).
The codes are not case-sensitive; the r prefix is used to distinguish the region portion. You cannot specify a region alone.
This can change during the life of your application if the user changes his or her language in the system settings. See Handling Runtime Changes for information about how this can affect your application during runtime.
See Localization for a complete guide to localizing your application for other languages.
Also see the locale configuration field, which indicates the current locale. Layout Direction ldrtlldltr The layout direction of your application. ldrtl means layout-direction-right-to-left. ldltr means layout-direction-left-to-right and is the default implicit value.
This can apply to any resource such as layouts, drawables, or values.
For example, if you want to provide some specific layout for the Arabic language and some generic layout for any other right-to-left language (like Persian or Hebrew) then you would have:
res/
layout/
main.xml (Default layout)
layout-ar/
main.xml (Specific layout for Arabic)
layout-ldrtl/
main.xml (Any right-to-left language, except
for Arabic, because the ar language qualifier
has a higher precedence.)

Note: To enable right-to-left layout features for your app, you must setsupportsRtl to true and set targetSdkVersion to 17 or higher.
Added in API level 17. smallestWidth swdpExamples:sw320dpsw600dpsw720dpetc. The fundamental size of a screen, as indicated by the shortest dimension of the available screen area. Specifically, the device's smallestWidth is the shortest of the screen's available height and width (you may also think of it as the smallest possible width for the screen). You can use this qualifier to ensure that, regardless of the screen's current orientation, your application has at least dps of width available for its UI.
For example, if your layout requires that its smallest dimension of screen area be at least 600 dp at all times, then you can use this qualifer to create the layout resources, res/layout-sw600dp/. The system will use these resources only when the smallest dimension of available screen is at least 600dp, regardless of whether the 600dp side is the user-perceived height or width. The smallestWidth is a fixed screen size characteristic of the device; the device's smallestWidth does not change when the screen's orientation changes.
The smallestWidth of a device takes into account screen decorations and system UI. For example, if the device has some persistent UI elements on the screen that account for space along the axis of the smallestWidth, the system declares the smallestWidth to be smaller than the actual screen size, because those are screen pixels not available for your UI. Thus, the value you use should be the actual smallest dimension required by your layout (usually, this value is the smallest width that your layout supports, regardless of the screen's current orientation).
Some values you might use here for common screen sizes:
320, for devices with screen configurations such as:
240x320 ldpi (QVGA handset)
320x480 mdpi (handset)
480x800 hdpi (high density handset)
480, for screens such as 480x800 mdpi (tablet/handset).
600, for screens such as 600x1024 mdpi (7 tablet).
720, for screens such as 720x1280 mdpi (10 tablet).
When your application provides multiple resource directories with different values for the smallestWidth qualifier, the system uses the one closest to (without exceeding) the device's smallestWidth.
Added in API level 13.
Also see the android:requiresSmallestWidthDp attribute, which declares the minimum smallestWidth with which your application is compatible, and thesmallestScreenWidthDp configuration field, which holds the device's smallestWidth value.
For more information about designing for different screens and using this qualifier, see the Supporting Multiple Screens developer guide. Available width wdpExamples:w720dpw1024dpetc. Specifies a minimum available screen width, in dp units at which the resource should be used—defined by the value. This configuration value will change when the orientation changes between landscape and portrait to match the current actual width.
When your application provides multiple resource directories with different values for this configuration, the system uses the one closest to (without exceeding) the device's current screen width. The value here takes into account screen decorations, so if the device has some persistent UI elements on the left or right edge of the display, it uses a value for the width that is smaller than the real screen size, accounting for these UI elements and reducing the application's available space.
Added in API level 13.
Also see the screenWidthDp configuration field, which holds the current screen width.
For more information about designing for different screens and using this qualifier, see the Supporting Multiple Screens developer guide. Available height hdpExamples:h720dph1024dpetc. Specifies a minimum available screen height, in dp units at which the resource should be used—defined by the value. This configuration value will change when the orientation changes between landscape and portrait to match the current actual height.
When your application provides multiple resource directories with different values for this configuration, the system uses the one closest to (without exceeding) the device's current screen height. The value here takes into account screen decorations, so if the device has some persistent UI elements on the top or bottom edge of the display, it uses a value for the height that is smaller than the real screen size, accounting for these UI elements and reducing the application's available space. Screen decorations that are not fixed (such as a phone status bar that can be hidden when full screen) are not accounted for here, nor are window decorations like the title bar or action bar, so applications must be prepared to deal with a somewhat smaller space than they specify.
Added in API level 13.
Also see the screenHeightDp configuration field, which holds the current screen width.
For more information about designing for different screens and using this qualifier, see the Supporting Multiple Screens developer guide. Screen size smallnormallargexlarge small: Screens that are of similar size to a low-density QVGA screen. The minimum layout size for a small screen is approximately 320x426 dp units. Examples are QVGA low density and VGA high density.
normal: Screens that are of similar size to a medium-density HVGA screen. The minimum layout size for a normal screen is approximately 320x470 dp units. Examples of such screens a WQVGA low density, HVGA medium density, WVGA high density.
large: Screens that are of similar size to a medium-density VGA screen. The minimum layout size for a large screen is approximately 480x640 dp units. Examples are VGA and WVGA medium density screens.
xlarge: Screens that are considerably larger than the traditional medium-density HVGA screen. The minimum layout size for an xlarge screen is approximately 720x960 dp units. In most cases, devices with extra large screens would be too large to carry in a pocket and would most likely be tablet-style devices. Added in API level 9.
Note: Using a size qualifier does not imply that the resources are only for screens of that size. If you do not provide alternative resources with qualifiers that better match the current device configuration, the system may use whichever resources are the best match.
Caution: If all your resources use a size qualifier that is larger than the current screen, the system will not use them and your application will crash at runtime (for example, if all layout resources are tagged with the xlarge qualifier, but the device is a normal-size screen).
Added in API level 4.
See Supporting Multiple Screens for more information.
Also see the screenLayout configuration field, which indicates whether the screen is small, normal, or large. Screen aspect longnotlong long: Long screens, such as WQVGA, WVGA, FWVGA
notlong: Not long screens, such as QVGA, HVGA, and VGA
Added in API level 4.
This is based purely on the aspect ratio of the screen (a long screen is wider). This is not related to the screen orientation.
Also see the screenLayout configuration field, which indicates whether the screen is long. Screen orientation portland port: Device is in portrait orientation (vertical)
land: Device is in landscape orientation (horizontal)
This can change during the life of your application if the user rotates the screen. See Handling Runtime Changes for information about how this affects your application during runtime.
Also see the orientation configuration field, which indicates the current device orientation. UI mode cardesktelevisionappliancewatch car: Device is displaying in a car dock
desk: Device is displaying in a desk dock
television: Device is displaying on a television, providing a ten foot experience where its UI is on a large screen that the user is far away from, primarily oriented around DPAD or other non-pointer interaction
appliance: Device is serving as an appliance, with no display
watch: Device has a display and is worn on the wrist
Added in API level 8, television added in API 13, watch added in API 20.
For information about how your app can respond when the device is inserted into or removed from a dock, read Determining and Monitoring the Docking State and Type.
This can change during the life of your application if the user places the device in a dock. You can enable or disable some of these modes using UiModeManager. SeeHandling Runtime Changes for information about how this affects your application during runtime. Night mode nightnotnight night: Night time
notnight: Day time
Added in API level 8.
This can change during the life of your application if night mode is left in auto mode (default), in which case the mode changes based on the time of day. You can enable or disable this mode using UiModeManager. See Handling Runtime Changes for information about how this affects your application during runtime. Screen pixel density (dpi) ldpimdpihdpixhdpinodpitvdpi ldpi: Low-density screens; approximately 120dpi.
mdpi: Medium-density (on traditional HVGA) screens; approximately 160dpi.
hdpi: High-density screens; approximately 240dpi.
xhdpi: Extra high-density screens; approximately 320dpi. Added in API Level 8
nodpi: This can be used for bitmap resources that you do not want to be scaled to match the device density.
tvdpi: Screens somewhere between mdpi and hdpi; approximately 213dpi. This is not considered a primary density group. It is mostly intended for televisions and most apps shouldn't need it—providing mdpi and hdpi resources is sufficient for most apps and the system will scale them as appropriate. This qualifier was introduced with API level 13.
There is a 3:4:6:8 scaling ratio between the four primary densities (ignoring the tvdpi density). So, a 9x9 bitmap in ldpi is 12x12 in mdpi, 18x18 in hdpi and 24x24 in xhdpi.
If you decide that your image resources don't look good enough on a television or other certain devices and want to try tvdpi resources, the scaling factor is 1.33*mdpi. For example, a 100px x 100px image for mdpi screens should be 133px x 133px for tvdpi.
Note: Using a density qualifier does not imply that the resources are only for screens of that density. If you do not provide alternative resources with qualifiers that better match the current device configuration, the system may use whichever resources are the best match.
See Supporting Multiple Screens for more information about how to handle different screen densities and how Android might scale your bitmaps to fit the current density. Touchscreen type notouchfinger notouch: Device does not have a touchscreen.
finger: Device has a touchscreen that is intended to be used through direction interaction of the user's finger.
Also see the touchscreen configuration field, which indicates the type of touchscreen on the device. Keyboard availability keysexposedkeyshiddenkeyssoft keysexposed: Device has a keyboard available. If the device has a software keyboard enabled (which is likely), this may be used even when the hardware keyboard is not exposed to the user, even if the device has no hardware keyboard. If no software keyboard is provided or it's disabled, then this is only used when a hardware keyboard is exposed.
keyshidden: Device has a hardware keyboard available but it is hidden and the device does not have a software keyboard enabled.
keyssoft: Device has a software keyboard enabled, whether it's visible or not.
If you provide keysexposed resources, but not keyssoft resources, the system uses the keysexposed resources regardless of whether a keyboard is visible, as long as the system has a software keyboard enabled.
This can change during the life of your application if the user opens a hardware keyboard. See Handling Runtime Changes for information about how this affects your application during runtime.
Also see the configuration fields hardKeyboardHidden and keyboardHidden, which indicate the visibility of a hardware keyboard and and the visibility of any kind of keyboard (including software), respectively. Primary text input method nokeysqwerty12key nokeys: Device has no hardware keys for text input.
qwerty: Device has a hardware qwerty keyboard, whether it's visible to the user or not.
12key: Device has a hardware 12-key keyboard, whether it's visible to the user or not.
Also see the keyboard configuration field, which indicates the primary text input method available. Navigation key availability navexposednavhidden navexposed: Navigation keys are available to the user.
navhidden: Navigation keys are not available (such as behind a closed lid).
This can change during the life of your application if the user reveals the navigation keys. See Handling Runtime Changes for information about how this affects your application during runtime.
Also see the navigationHidden configuration field, which indicates whether navigation keys are hidden. Primary non-touch navigation method nonavdpadtrackballwheel nonav: Device has no navigation facility other than using the touchscreen.
dpad: Device has a directional-pad (d-pad) for navigation.
trackball: Device has a trackball for navigation.
wheel: Device has a directional wheel(s) for navigation (uncommon).
Also see the navigation configuration field, which indicates the type of navigation method available. Platform Version (API level) Examples:v3v4v7etc. The API level supported by the device. For example, v1 for API level 1 (devices with Android 1.0 or higher) and v4 for API level 4 (devices with Android 1.6 or higher). See the Android API levels document for more information about these values.

 

資源文件可以配置多種選擇條件。
Android系統是怎樣找到最合適的資源的請參考：

http://developer.android.com/guide/topics/resources/providing-resources.html#BestMatch

 

4、怎麼解決這些問題

其實給出的解決方法也是官方文檔中，這裡會簡單的寫一點，有條件可以看一下參考中的鏈接。

4.1 Supporting Different Devices

4.1.1支持不同的語言

這一點是應用怎麼實現國際化，使用values文件添加config_qualifier屬性，例如：

 

 

MyProject/
    res/
       values/
           strings.xml
       values-es/
           strings.xml
       values-fr/
           strings.xml

 

4.1.2支持不同的屏幕

Android手機的屏幕有兩個屬性，屏幕尺寸、屏幕密度。前面也介紹了屏幕的尺寸、密度。解決這個問題，我們需要聲明不同的布局，不同的圖片資源。屏幕的方向（橫屏、豎屏）也是在這處理的。這個和前面國際化處理一樣的，使用資源文件添加config_qualifier屬性。

 

4.1.2.1 Create Different Layouts

Android中一般分為四種尺寸： small, normal, large, xlarge。
一般創建不同的布局來適配這四種尺寸。

適配不同尺寸可以創建下面目錄：

 

MyProject/
    res/
        layout/
            main.xml
        layout-large/
            main.xml

 

 

適配橫屏、豎屏可以創建如下目錄：

 

MyProject/
    res/
        layout/
            main.xml
        layout-land/
            main.xml

 

如果需要同時適配，需要更多的條件：

 

MyProject/
    res/
        layout/              # default (portrait)
            main.xml
        layout-land/         # landscape
            main.xml
        layout-large/        # large (portrait)
            main.xml
        layout-large-land/   # large landscape
            main.xml

 

 

Android3.2中為了適配平板的開發，增加了smallestWidth屬性。詳情參考。

4.1.2.2 Create Different Bitmaps

Android中圖片資源是必不可少的，並且建議提供四種圖片以適應不同的屏幕密度。Android中廣義的屏幕密度分為4種（ low, medium, high and extra-high ）。他們的比例關系如下：

xhdpi: 2.0
hdpi: 1.5
mdpi: 1.0 (baseline)
ldpi: 0.75

如果你在mdpi中放置200x200的圖片，建議你在mdpi中放置100x100的圖片。

圖片資源文件如下：

MyProject/
    res/
        drawable-xhdpi/
            awesomeimage.png
        drawable-hdpi/
            awesomeimage.png
        drawable-mdpi/
            awesomeimage.png
        drawable-ldpi/
            awesomeimage.png

現在已經不建議使用ldpi，因為這樣的手機基本沒了。

 

4.1.3支持不同的平台版本

 

Android版本的升級就會帶來新的api，我們怎麼適配不同的系統版本呢。

 

1、使用 Android Support Library

2、AndroidManifest文件配置minSdk、targetSdk。

 

    
    ...

 

3、檢測版本號，根據版本號調用api

 

private void setUpActionBar() {
    // Make sure we're running on Honeycomb or higher to use ActionBar APIs
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        ActionBar actionBar = getActionBar();
        actionBar.setDisplayHomeAsUpEnabled(true);
    }
}

4、使用平台的Styles and Themes

 

 

 

 

4.2 Designing for Multiple Screens

Android設備包含phone、glass、watch、autocar等等，這些屏幕尺寸從小到watch大到電視，我們的應用能夠兼容這麼多的尺寸是很重要的。

 

4.2.1支持不同屏幕尺寸

 

 

4.2.1.1 Use wrap_content and match_parent

UI實現中view和layout的高度、寬度使用wrap_content and match_parent，不使用固定值。

4.2.1.2 Use RelativeLayout

UI實現中layout盡量使用RelativeLayout，這樣可以控制相對位置，還能減少布局的層級。

4.2.1.3 Use Size Qualifiers

 

 

 

距離使用dp和字體使用sp作為單位，不使用px。

 

 

 

4.2.1.4 Use the Smallest-width Qualifier

 

 

 

使用Smallest-width Qualifier，這個是Android3.2開始支持的，以適配平板。

 

 

 

res/layout-sw600dp/main.xml

 

 

 

4.2.1.5 Use Layout Aliases

 

 

 

使用Layout的別名，以適配不同尺寸的屏幕。

 

 

 

4.2.1.6 Use Orientation Qualifiers

 

 

 

使用屏幕方向屬性，以支持橫屏、豎屏。

 

 

 

4.2.1.7 Use Nine-patch Bitmaps

 

 

 

使用.9圖片，.9圖片能很好地支持橫向、豎向拉伸。

 

 

 

 

4.2.2支持不同屏幕密度

 

見4.1.2.2 Create Different Bitmaps

 

4.2.3創建自適應界面

這裡主要是運行時檢測，什麼是運行時檢測呢，就是在java代碼中判斷需要的view是否找到（是否為空），例如下面的代碼。

 

 

public class NewsReaderActivity extends FragmentActivity {
    boolean mIsDualPane;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);

        View articleView = findViewById(R.id.article);
        mIsDualPane = articleView != null && 
                        articleView.getVisibility() == View.VISIBLE;
    }
}

 

這一方面的，可以參考《Android UI開發第三十篇——使用Fragment構建靈活的桌面》。

 

 

Android應用如何支持屏幕多尺寸多分辨率問題基本就這些，更多經驗需要從實踐中總結。

 

後記：很久的時候和一位小伙伴討論過應用適配的問題，說好了要總結出來的，現在權當實現諾言，寫的有些凌亂，有讀不通的通信請留言。