Why does DP not fit well?

Take blue Lake 360DP wide design draft, 60DP wide control as an example

Screen fit is to make the actual screen size ratio of the control the same as in the design draft

Toutiao adaptation scheme

Px = DP * density

Assume that the width of the design draft is 360DP. Based on this, in order to achieve the adaptation effect, the wide DP value of all devices should be 360DP. The device’s width PX value is physically fixed and the density can be modified to achieve this goal

fun customerDensity(app: Application) { 
    val displayMetrics = app.resources.displayMetrics 
    // Get the screen width
    val screenWidth = displayMetrics.widthPixels // density = px / dp 
    val targetDensity = screenWidth / 360f 
    val targetDensityDpi = (160 * targetDensity).toInt() 
    displayMetrics.density = targetDensity 
    displayMetrics.densityDpi = targetDensityDpi 
}
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advantages

1. Low cost, easy to implement
2. Low intrusion and easy rollback
3. Global adaptation

disadvantages

1. Global adaptation, when the third-party library UI design rules are too different, the actual adaptation effect is very different

SmallestWidth qualifier fit

The principle of

The system will match dimens. XML in the values-SWdp folder according to the minimum screen width of the current device (smallestWidth). If not found, the system will look for the values-SWdp folder less than or equal to sw

Take the 360DP design draft as an example

Create dimens. XML under values-sw360dp as follows:

<resources> 
    <dimen name="dp_1">1dp</dimen> 
    <dimen name="dp_2">2dp</dimen>. <dimen name="dp_359">359dp</dimen> 
    <dimen name="dp_360">360dp</dimen> 
</resources>
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Based on the width of 360DP, the unit value of dimens. XML under values -SW380dp is 380/360=1.05555

<resources> 
    <dimen name="dp_1">1.05555 dp</dimen> 
    <dimen name="dp_2">2.11111 dp</dimen>. <dimen name="dp_359">378.944dp</dimen> 
    <dimen name="dp_360">380dp</dimen> 
</resources>
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advantages

1. Stable, no performance loss
2. Customize the adaptation range

disadvantages

1. It is highly intrusive and difficult to maintain
2. Model coverage is limited, the wider the adaptation range, the larger the corresponding inclusion size

ConstraintLayout Percentage width and height

<View
    android:layout_width="0dp"
    android:layout_height="0dp"
    app:layout_constraintWidth_percent="0.5"
    app:layout_constraintHeight_percent="0.1"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"/>
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