Beispiel für eine benutzerdefinierte Ansicht mit Bedienungshilfen für Android TV

In diesem Leitfaden werden einige Best Practices zur Unterstützung Bedienungshilfen mit benutzerdefinierten Ansichten in einer Android TV-App In diesem Leitfaden erfahren Sie, wie Sie eine einfache Aktivität zu erstellen, bei der mit der Canvas API vier Bilder gezeichnet werden, fokussierbar sind, sodass Bedienungshilfen zwischen ihnen wechseln können.

Layout-XML-Datei erstellen

Erstellen Sie eine Layoutdatei für die Aktivität der benutzerdefinierten Ansicht.

<?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>

In den folgenden Abschnitten werden die Klasse com.example.tvcustomviews.SampleCustomView.

Einfache Aktivität definieren

Erstellen Sie eine einfache Aktivität zum Laden der Layout-XML-Datei.

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);
    }

}

SampleCustomView-Klasse definieren

Definieren Sie als Nächstes die Klasse und zeichnen Sie vier Bilder auf einem Canvas.

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++));
  }
}

In der Anwendung werden in diesem Zustand vier blaue Rechtecke auf der Seite Bildschirm, wenn er läuft. Wenn TalkBack jedoch aktiviert ist, Rechtecke. Mit anderen Worten, diese Rechtecke dürfen keinen Fokus auf Barrierefreiheit haben.

ExploreByTouchHelper definieren, um AccessiblityNodeInfo anzuzeigen

Definieren Sie SampleExploreByTouchHelper, indem Sie ExploreByTouchHelper und die Implementierung ihrer Methoden.

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;
  }
}

Rufen Sie schließlich setAccessibilityDelegate() auf, wenn Sie die benutzerdefinierte Ansicht instanziieren.

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));
    }

Wenn TalkBack aktiviert ist, kann der Bedienungshilfefokus jetzt korrekt zu die vier Bilder in der benutzerdefinierten Ansicht an. Wenn Sie die DPAD_CENTER-Taste auf einem Wähltastatur verwenden, registriert die App dieses Ereignis als ACTION_CLICK-Ereignis.