CODEWITHSUNDEEP
androidandroid-constraintlayout
MohammadReza Hosseini
MohammadReza Hosseini

Reputation: 359

In ConstraintLayout when I set a layoutDirection of a view to "rtl" some thing go wrong. How to avoid this?

my sample xml file to introduce my problem is this:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/toBeUpdated"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layoutDirection="rtl"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@+id/guideline"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:text="@string/update_text_view"
        android:onClick="updateTextView"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <android.support.constraint.Guideline
        android:id="@+id/guideline"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_begin="274dp" />

</android.support.constraint.ConstraintLayout>

I want my (toBeUpdated) textView to have "rtl" layoutDirection. With this code we have above every thing is ok until the time textView must be updated. After (for any reason) I update this textView at run time the view jump to the left of the Guideline. I found what's wrong. The reason behind this sudden jump is that when direction is right to left so right is the start and left is the end of view (as you know completely reverse of usual). So my new and corrected version of this xml file to solve this issue is new version of xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/toBeUpdated"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layoutDirection="rtl"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toEndOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/guideline"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:text="@string/update_text_view"
        android:onClick="updateTextView"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <android.support.constraint.Guideline
        android:id="@+id/guideline"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_begin="274dp" />

</android.support.constraint.ConstraintLayout>

in this version, at first, textView is in wrong place but after it is updated, it jump where I want. Completely reverse of first situation where the textView was in correct place until It was not updated and after that, jump happens. In both cases a sudden unwanted jump happen. It may overlaps some other view or be overlapped by them. And the most important thing is that maybe I don't want it to be updated even one time and that is an static title. What shall I do? Is this a Bug or something?

build.gradle (Module: app)

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "example.com.testconstraintlayout"
        minSdkVersion 21
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

Upvotes: 3

Views: 1749

Answers (1)

Cheticamp
Cheticamp

Reputation: 62831

I can't think of any reason why the text view should jump when the contents are updated. I think that this is a bug and that it is probably related to left/right and start/end confusion that crops up now and again.

You don't show screen shots and I can't be sure of what you are trying to achieve, but I think a work-around for you is to use left/right instead of start/end for the text view as follows:

<TextView
    android:id="@+id/toBeUpdated"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layoutDirection="rtl"
    android:text="Hello World!"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintLeft_toRightOf="@+id/guideline"
    app:layout_constraintTop_toTopOf="parent" />

I have tried this out and the view does not jump as it does with start/end.

Upvotes: 4

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