Exemple d'accessibilité des affichages personnalisés pour Android TV

Ce guide présente un exemple illustrant certaines des bonnes pratiques avec des vues personnalisées dans une application Android TV. Ce guide vous explique comment créer une activité simple qui utilise l'API Canvas pour dessiner quatre images sélectionnables et permettre aux services d'accessibilité de naviguer entre eux.

Créer un fichier XML de mise en page

Créez un fichier de mise en page pour l'activité de vue personnalisée.

<?xml version="1.0" encoding="utf-8">
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    <LinearLayout xmlns:app="http://schemas.android.com/apk/res-auto"
            xmlns:tools="http://schemas.android.com/tools"
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            tools:context=".custom.CustomViewActivity">

    <com.example.tvcustomviews.SampleCustomView
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />

    </LinearLayout>

</LinearLayout>

Les sections suivantes définissent com.example.tvcustomviews.SampleCustomView.

Définir une activité simple

Créez une activité simple pour charger le fichier XML de mise en page.

Kotlin

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle

class CustomViewBestPracticeActivity:AppCompatActivity() {

  protected fun onCreate(savedInstanceState:Bundle) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.custom_view_best_practices)
  }
}

Java

package com.example.tvcustomviews;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;

public class CustomViewBestPracticeActivity extends AppCompatActivity{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.custom_view_best_practices);
    }

}

Définir la classe SampleCustomView

Ensuite, définissez la classe et dessinez quatre images à l'aide d'un canevas.

Kotlin

package com.example.tvcustomviews

import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import android.graphics.Rect
import android.util.AttributeSet
import android.view.View
import androidx.annotation.Nullable
import androidx.core.view.ViewCompat
import java.util.HashMap

class SampleCustomView:View {

  internal val virtualIdRectMap:Map<Int, VirtualRect> = HashMap<Int, VirtualRect>()
  private val rectangleId = 1

  internal class VirtualRect(rect:Rect, paint:Paint, id:Int) {
    val rect:Rect
    val paint:Paint
    val id:Int = 0
    init{
      this.rect = rect
      this.paint = paint
      this.id = id
    }
  }

  constructor(context:Context) : super(context) {
    init()
  }

  constructor(context:Context, @Nullable attrs:AttributeSet) : super(context, attrs) {
    init()
  }

  constructor(context:Context, @Nullable attrs:AttributeSet, defStyleAttr:Int) : super(context, attrs, defStyleAttr) {
    init()
  }

  private fun init() {
    setRectangle()
    ViewCompat.setAccessibilityDelegate(this,
                                        SampleExploreByTouchHelper(this))
  }

  protected fun onDraw(canvas:Canvas) {
    super.onDraw(canvas)
    for (mapElement in virtualIdRectMap.entries)
    {
      val virtualRect = mapElement.value
      canvas.drawRect(virtualRect.rect, virtualRect.paint)
    }
  }

  private fun setRectangle() {
    val paint = Paint(Paint.ANTI_ALIAS_FLAG)
    paint.setColor(RECTANGLE_COLOR)

    val leftTopRectangle = Rect()
    leftTopRectangle.left = RECTANGLE_START_POINT_LEFT
    leftTopRectangle.right = leftTopRectangle.left + RECTANGLE_WIDTH
    leftTopRectangle.top = RECTANGLE_START_POINT_TOP
    leftTopRectangle.bottom = leftTopRectangle.top + RECTANGLE_HEIGHT
    virtualIdRectMap.put(rectangleId, VirtualRect(leftTopRectangle, paint, rectangleId++))

    val rightTopRectangle = Rect()
    rightTopRectangle.left = leftTopRectangle.right + HORIZONTAL_PADDING
    rightTopRectangle.right = rightTopRectangle.left + RECTANGLE_WIDTH
    rightTopRectangle.top = leftTopRectangle.top
    rightTopRectangle.bottom = rightTopRectangle.top + RECTANGLE_HEIGHT
    virtualIdRectMap.put(rectangleId, VirtualRect(rightTopRectangle, paint, rectangleId++))

    val leftBottomRectangle = Rect()
    leftBottomRectangle.left = leftTopRectangle.left
    leftBottomRectangle.right = leftBottomRectangle.left + RECTANGLE_WIDTH
    leftBottomRectangle.top = leftTopRectangle.bottom + VERTICAL_PADDING
    leftBottomRectangle.bottom = leftBottomRectangle.top + RECTANGLE_HEIGHT
    virtualIdRectMap.put(rectangleId, VirtualRect(leftBottomRectangle, paint, rectangleId++))

    val rightBottomRectangle = Rect()
    rightBottomRectangle.left = leftBottomRectangle.right + HORIZONTAL_PADDING
    rightBottomRectangle.right = rightBottomRectangle.left + RECTANGLE_WIDTH
    rightBottomRectangle.top = leftBottomRectangle.top
    rightBottomRectangle.bottom = rightBottomRectangle.top + RECTANGLE_HEIGHT
    virtualIdRectMap.put(rectangleId, VirtualRect(rightBottomRectangle, paint, rectangleId++))
  }

  companion object {
    private val RECTANGLE_START_POINT_LEFT = 50
    private val RECTANGLE_START_POINT_TOP = 100
    private val RECTANGLE_WIDTH = 200
    private val RECTANGLE_HEIGHT = 100
    private val HORIZONTAL_PADDING = 50
    private val VERTICAL_PADDING = 100
    private val RECTANGLE_COLOR = Color.argb(100, 0, 163, 245)
  }
}

Java

package com.example.tvcustomviews;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.View;
import androidx.annotation.Nullable;
import androidx.core.view.ViewCompat;
import java.util.HashMap;
import java.util.Map;

public class SampleCustomView extends View {

  final Map<Integer, VirtualRect> virtualIdRectMap = new HashMap<>();

  private static final int RECTANGLE_START_POINT_LEFT = 50;
  private static final int RECTANGLE_START_POINT_TOP = 100;
  private static final int RECTANGLE_WIDTH = 200;
  private static final int RECTANGLE_HEIGHT = 100;
  private static final int HORIZONTAL_PADDING = 50;
  private static final int VERTICAL_PADDING = 100;
  private static final int RECTANGLE_COLOR = Color.argb(100, 0, 163, 245);

  private int rectangleId = 1;

  static class VirtualRect {
    final Rect rect;
    final Paint paint;
    final int id;

    VirtualRect(Rect rect, Paint paint, int id) {
      this.rect = rect;
      this.paint = paint;
      this.id = id;
    }
  }

  public SampleCustomView(Context context) {
    super(context);
    init();
  }

  public SampleCustomView(Context context, @Nullable AttributeSet attrs) {
    super(context, attrs);
    init();
  }

  public SampleCustomView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    init();
  }

  private void init() {
    setRectangle();
  }

  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    for (Map.Entry<Integer, VirtualRect> mapElement :
        virtualIdRectMap.entrySet()) {
      VirtualRect virtualRect = mapElement.getValue();
      canvas.drawRect(virtualRect.rect, virtualRect.paint);
    }
  }

  private void setRectangle() {
    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setColor(RECTANGLE_COLOR);
    Rect leftTopRectangle = new Rect();
    leftTopRectangle.left = RECTANGLE_START_POINT_LEFT;
    leftTopRectangle.right = leftTopRectangle.left + RECTANGLE_WIDTH;
    leftTopRectangle.top = RECTANGLE_START_POINT_TOP;
    leftTopRectangle.bottom = leftTopRectangle.top + RECTANGLE_HEIGHT;
    virtualIdRectMap.put(rectangleId, new VirtualRect(leftTopRectangle, paint, rectangleId++));

    Rect rightTopRectangle = new Rect();
    rightTopRectangle.left = leftTopRectangle.right + HORIZONTAL_PADDING;
    rightTopRectangle.right = rightTopRectangle.left + RECTANGLE_WIDTH;
    rightTopRectangle.top = leftTopRectangle.top;
    rightTopRectangle.bottom = rightTopRectangle.top + RECTANGLE_HEIGHT;
    virtualIdRectMap.put(rectangleId, new VirtualRect(rightTopRectangle, paint, rectangleId++));

    Rect leftBottomRectangle = new Rect();
    leftBottomRectangle.left = leftTopRectangle.left;
    leftBottomRectangle.right = leftBottomRectangle.left + RECTANGLE_WIDTH;
    leftBottomRectangle.top = leftTopRectangle.bottom + VERTICAL_PADDING;
    leftBottomRectangle.bottom = leftBottomRectangle.top + RECTANGLE_HEIGHT;
    virtualIdRectMap.put(rectangleId, new VirtualRect(leftBottomRectangle, paint, rectangleId++));

    Rect rightBottomRectangle = new Rect();
    rightBottomRectangle.left = leftBottomRectangle.right + HORIZONTAL_PADDING;
    rightBottomRectangle.right = rightBottomRectangle.left + RECTANGLE_WIDTH;
    rightBottomRectangle.top = leftBottomRectangle.top;
    rightBottomRectangle.bottom = rightBottomRectangle.top + RECTANGLE_HEIGHT;
    virtualIdRectMap.put(rectangleId, new VirtualRect(rightBottomRectangle, paint, rectangleId++));
  }
}

L'application dans cet état affiche quatre rectangles bleus sur l'écran lorsqu'il s'exécute. Toutefois, lorsque TalkBack est activé, vous ne pouvez pas accéder rectangles. En d'autres termes, ces rectangles ne peuvent pas avoir de focus d'accessibilité.

Définir ExplorerByTouchHelper pour exposer AccessiblityNodeInfo

Définissez SampleExploreByTouchHelper en héritant de ExploreByTouchHelper et à mettre en œuvre ses méthodes.

Kotlin

package com.example.tvcustomviews

import android.graphics.Rect
import android.os.Bundle
import android.util.Log
import android.widget.ImageView
import androidx.annotation.NonNull
import androidx.annotation.Nullable
import androidx.core.view.accessibility.AccessibilityNodeInfoCompat
import androidx.core.view.accessibility.AccessibilityNodeInfoCompat.AccessibilityActionCompat
import androidx.customview.widget.ExploreByTouchHelper
import com.example.tvcustomviews.SampleCustomView.VirtualRect
import java.util.Objects

internal class SampleExploreByTouchHelper(parentView:SampleCustomView):ExploreByTouchHelper(parentView) {

  private val TAG = SampleExploreByTouchHelper::class.java!!.getName()
  private val parentView:SampleCustomView

  init{
    this.parentView = parentView
  }

  /**
   * Define AccessibilityNodeInfo objects with necessary attributes.
   * Set required attributes into the AccessibilityNodeInfo for the UI
   * component whose virtualID is the virtualViewId.
   * @param virtualViewId: virtual ID for the component.
   * @param node: the AccessibilityNodeInfoCompat used to set the attribute.
   */
  protected fun onPopulateNodeForVirtualView(
    virtualViewId:Int, @NonNull node:AccessibilityNodeInfoCompat) {
    val rectEle = parentView.virtualIdRectMap.get(virtualViewId)

    assert(rectEle != null)
    node.setContentDescription("Selected rect " + rectEle.id)
    node.setClassName(ImageView::class.java!!.getName())
    node.setPackageName(BuildConfig.APPLICATION_ID)
    node.setVisibleToUser(true)
    node.addAction(AccessibilityActionCompat.ACTION_CLICK)
    // *****************************************************************
    // It is very important to set the rectangle area for each node so
    // the accessibility service knows where to set accessibility focus.
    // *****************************************************************
    node.setBoundsInParent(
      Objects.requireNonNull(parentView.virtualIdRectMap.get(
        virtualViewId)).rect)
  }

  protected fun getVirtualViewAt(x:Float, y:Float):Int {
    for (mapElement in parentView.virtualIdRectMap.entrySet())
    {
      val rect = mapElement.value.rect
      if ((rect.left <= x && x <= rect.right
           && rect.top <= y && y <= rect.bottom))
      {
        return mapElement.value.id
      }
    }

    return ExploreByTouchHelper.INVALID_ID
  }

  protected fun getVisibleVirtualViews(virtualViewIds:List<Int>) {
    for (mapElement in parentView.virtualIdRectMap.entrySet())
    {
      virtualViewIds.add(mapElement.key)
    }
  }

  protected fun onPerformActionForVirtualView(
    virtualViewId:Int, action:Int, @Nullable arguments:Bundle):Boolean {
    when (action) {
      // After Talkback is turned on, if you want to handle
      // DPAD_CENTER key event with your own logic,
      // implement it under ACTION_CLICK action.
      AccessibilityNodeInfoCompat.ACTION_CLICK -> {
        Log.e(TAG, "ACTION_CLICK action handled here.")
        return true
      }
    }

    // All the DPAD directional keys are handled by
    // Accessibility based on the AccessibilityNodeInfo Tree
    // defined above.
    // fall through
    return false
  }
}

Java

package com.example.tvcustomviews;

import android.graphics.Rect;
import android.os.Bundle;
import android.util.Log;
import android.widget.ImageView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.core.view.accessibility.AccessibilityNodeInfoCompat;
import androidx.core.view.accessibility.AccessibilityNodeInfoCompat.AccessibilityActionCompat;
import androidx.customview.widget.ExploreByTouchHelper;
import com.example.tvcustomviews.SampleCustomView.VirtualRect;
import java.util.List;
import java.util.Map;
import java.util.Objects;

class SampleExploreByTouchHelper extends ExploreByTouchHelper {

  private final String TAG = SampleExploreByTouchHelper.class.getName();

  private SampleCustomView parentView;

  SampleExploreByTouchHelper(SampleCustomView parentView) {
    super(parentView);
    this.parentView = parentView;
  }

  /**
   * Define AccessibilityNodeInfo objects with necessary attributes.
   * Set required attributes into the AccessibilityNodeInfo for the UI
   * component whose virtualID is the virtualViewId.
   * @param virtualViewId: virtual ID for the component.
   * @param node: the AccessibilityNodeInfoCompat used to set the attribute.
   */
  @Override
  protected void onPopulateNodeForVirtualView(
      int virtualViewId, @NonNull AccessibilityNodeInfoCompat node) {
    VirtualRect rectEle = parentView.virtualIdRectMap.get(virtualViewId);

    assert rectEle != null;
    node.setContentDescription("Selected rect " + rectEle.id);
    node.setClassName(ImageView.class.getName());
    node.setPackageName(BuildConfig.APPLICATION_ID);
    node.setVisibleToUser(true);
    node.addAction(AccessibilityActionCompat.ACTION_CLICK);
    // *****************************************************************
    // It is very important to set the rectangle area for each node so
    // the accessibility service knows where to set accessibility focus.
    // *****************************************************************
    node.setBoundsInParent(
        Objects.requireNonNull(parentView.virtualIdRectMap.get(
            virtualViewId)).rect);
  }

  @Override
  protected int getVirtualViewAt(float x, float y) {
    for (Map.Entry<Integer, VirtualRect> mapElement :
        parentView.virtualIdRectMap.entrySet()) {
      Rect rect = mapElement.getValue().rect;
      if (rect.left <= x && x <= rect.right
          && rect.top <= y && y <= rect.bottom) {
        return mapElement.getValue().id;
      }
    }
    return ExploreByTouchHelper.INVALID_ID;
  }

  @Override
  protected void getVisibleVirtualViews(List<Integer> virtualViewIds) {
    for (Map.Entry<Integer, VirtualRect> mapElement :
        parentView.virtualIdRectMap.entrySet()) {
      virtualViewIds.add(mapElement.getKey());
    }
  }

  @Override
  protected boolean onPerformActionForVirtualView(
      int virtualViewId, int action, @Nullable Bundle arguments) {
    switch (action) {
      // After Talkback is turned on, if you want to handle
      // DPAD_CENTER key event with your own logic,
      // implement it under ACTION_CLICK action.
      case AccessibilityNodeInfoCompat.ACTION_CLICK:
        Log.e(TAG, "ACTION_CLICK action handled here.");
        return true;
    // All the DPAD directional keys are handled by
    // Accessibility based on the AccessibilityNodeInfo Tree
    // defined above.
      default:
        // fall through
    }

    return false;
  }
}

Enfin, appelez setAccessibilityDelegate() lors de l'instanciation de la vue personnalisée.

Kotlin

private fun init(@Nullable attrs:AttributeSet) {
  ...
  ViewCompat.setAccessibilityDelegate(this,
                                      SampleExploreByTouchHelper(this))
}

Java

  private void init(@Nullable AttributeSet attrs) {
        ...
        ViewCompat.setAccessibilityDelegate(this,
        new SampleExploreByTouchHelper(this));
    }

Lorsque TalkBack est activé, la sélection de l'accessibilité peut désormais accéder à les quatre images dans la vue personnalisée. Si vous appuyez sur la touche DPAD_CENTER d'un clavier, l'application enregistre cet événement en tant qu'événement ACTION_CLICK.