Questa guida illustra i passaggi di un esempio che illustra alcune best practice a supporto l'accessibilità con visualizzazioni personalizzate in un'app per Android TV. La guida mostra come creare un'attività semplice che utilizzi l'API Canvas per disegnare quattro immagini che attivabile e consente ai servizi di accessibilità di passare da uno all'altro.
Crea file XML di layout
Crea un file di layout per l'attività di visualizzazione personalizzata.
<?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>
Le sezioni seguenti definiscono
com.example.tvcustomviews.SampleCustomView
corso.
Definisci un'attività semplice
Creare un'attività semplice per caricare il file XML di layout.
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); } }
Definisci la classe SampleCustomView
A questo punto, definisci la classe e disegna quattro immagini utilizzando un 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++)); } }
L'applicazione in questo stato mostra quattro rettangoli blu schermata durante l'esecuzione. Tuttavia, quando TalkBack è attivo, non puoi accedere alla rettangoli. In altre parole, questi rettangoli non possono essere incentrati sull'accessibilità.
Definisci ExploreByTouchHelper per esporre AccessiblityNodeInfo
Definisci SampleExploreByTouchHelper
ereditando ExploreByTouchHelper
e
a implementare i propri metodi.
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; } }
Infine, richiama setAccessibilityDelegate()
quando crei un'istanza della vista personalizzata.
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)); }
Con TalkBack attivato, ora lo stato attivo dell'accessibilità è in grado di navigare correttamente verso
le quattro immagini nella visualizzazione personalizzata. Se premi il tasto DPAD_CENTER
su una
l'app registra questo evento come evento ACTION_CLICK
.