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BasicAccessibility / src / com.example.android.basicaccessibility /

DialView.java

       
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        /*
       
       
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        * Copyright (C) 2013 The Android Open Source Project
       
       
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        *
       
       
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        * Licensed under the Apache License, Version 2.0 (the "License");
       
       
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        * you may not use this file except in compliance with the License.
       
       
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        * You may obtain a copy of the License at
       
       
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        *
       
       
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        *      http://www.apache.org/licenses/LICENSE-2.0
       
       
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        *
       
       
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        * Unless required by applicable law or agreed to in writing, software
       
       
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        * distributed under the License is distributed on an "AS IS" BASIS,
       
       
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        * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
       
       
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        * See the License for the specific language governing permissions and
       
       
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        * limitations under the License.
       
       
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        */
       
       
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        package com.example.android.basicaccessibility;
       
       
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        import android.annotation.TargetApi;
       
       
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        import android.content.Context;
       
       
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        import android.graphics.Canvas;
       
       
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        import android.graphics.Color;
       
       
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        import android.graphics.Paint;
       
       
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        import android.os.Build;
       
       
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        import android.util.AttributeSet;
       
       
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        import android.view.View;
       
       
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        import android.view.accessibility.AccessibilityEvent;
       
       
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        /**
       
       
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        * Custom view to demonstrate accessibility.
       
       
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        *
       
       
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        * <p>This view does not use any framework widgets, so does not get any accessibility features
       
       
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        * automatically. Instead, we use {@link android.view.accessibility.AccessibilityEvent} to provide accessibility hints to
       
       
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        * the OS.
       
       
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        *
       
       
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        * <p>For example, if TalkBack is enabled, users will be able to receive spoken feedback as they
       
       
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        * interact with this view.
       
       
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        *
       
       
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        * <p>More generally, this view renders a multi-position "dial" that can be used to select a value
       
       
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        * between 1 and 4. Each time the dial is clicked, the next position will be selected (modulo
       
       
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        * the maximum number of positions).
       
       
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        */
       
       
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        public class DialView extends View {
       
       
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        private static int SELECTION_COUNT = 4;
       
       
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        private static float FONT_SIZE = 40f;
       
       
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        private float mWidth;
       
       
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        private float mHeight;
       
       
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        private float mWidthPadded;
       
       
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        private float mHeightPadded;
       
       
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        private Paint mTextPaint;
       
       
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        private Paint mDialPaint;
       
       
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        private float mRadius;
       
       
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        private int mActiveSelection;
       
       
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        /**
       
       
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        * Constructor that is called when inflating a view from XML. This is called
       
       
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        * when a view is being constructed from an XML file, supplying attributes
       
       
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        * that were specified in the XML file.
       
       
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        *
       
       
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        * <p>In our case, this constructor just calls init().
       
       
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        *
       
       
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        * @param context The Context the view is running in, through which it can
       
       
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        *                access the current theme, resources, etc.
       
       
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        * @param attrs   The attributes of the XML tag that is inflating the view.
       
       
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        * @see #View(android.content.Context, android.util.AttributeSet, int)
       
       
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        */
       
       
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        public DialView(Context context, AttributeSet attrs) {
       
       
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        super(context, attrs);
       
       
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        init();
       
       
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        }
       
       
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        /**
       
       
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        * Helper method to initialize instance variables. Called by constructor.
       
       
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        */
       
       
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        private void init() {
       
       
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        // Paint styles used for rendering are created here, rather than at render-time. This
       
       
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        // is a performance optimization, since onDraw() will get called frequently.
       
       
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        mTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
       
       
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        mTextPaint.setColor(Color.BLACK);
       
       
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        mTextPaint.setStyle(Paint.Style.FILL_AND_STROKE);
       
       
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        mTextPaint.setTextAlign(Paint.Align.CENTER);
       
       
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        mTextPaint.setTextSize(FONT_SIZE);
       
       
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        mDialPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
       
       
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        mDialPaint.setColor(Color.GRAY);
       
       
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        // Initialize current selection. This will store where the dial's "indicator" is pointing.
       
       
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        mActiveSelection = 0;
       
       
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        // Setup onClick listener for this view. Rotates between each of the different selection
       
       
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        // states on each click.
       
       
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        //
       
       
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        // Notice that we call sendAccessibilityEvent here. Some AccessibilityEvents are generated
       
       
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        // by the system. However, custom views will typically need to send events manually as the
       
       
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        // user interacts with the view. The type of event sent will vary, depending on the nature
       
       
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        // of the view and how the user interacts with it.
       
       
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        //
       
       
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        // In this case, we are sending TYPE_VIEW_SELECTED rather than TYPE_VIEW_CLICKED, because
       
       
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        // clicking on this view selects a new value.
       
       
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        //
       
       
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        // We will give our AccessibilityEvent further information about the state of the view in
       
       
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        // onPopulateAccessibilityEvent(), which will be called automatically by the system
       
       
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        // for each AccessibilityEvent.
       
       
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        setOnClickListener(new OnClickListener() {
       
       
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        @Override
       
       
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        public void onClick(View v) {
       
       
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        // Rotate selection to the next valid choice.
       
       
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        mActiveSelection = (mActiveSelection + 1) % SELECTION_COUNT;
       
       
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        // Send an AccessibilityEvent, since the user has interacted with the view.
       
       
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        sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_SELECTED);
       
       
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        // Redraw the entire view. (Inefficient, but this is sufficient for demonstration
       
       
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        // purposes.)
       
       
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        invalidate();
       
       
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        }
       
       
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        });
       
       
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        }
       
       
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        /**
       
       
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        * This is where a View should populate outgoing accessibility events with its text content.
       
       
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        * While this method is free to modify event attributes other than text content, doing so
       
       
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        * should normally be performed in
       
       
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        * {@link #onInitializeAccessibilityEvent(android.view.accessibility.AccessibilityEvent)}.
       
       
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        * <p/>
       
       
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        * <p>Note that the behavior of this method will typically vary, depending on the type of
       
       
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        * accessibility event is passed into it. The allowed values also very, and are documented
       
       
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        * in {@link android.view.accessibility.AccessibilityEvent}.
       
       
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        * <p/>
       
       
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        * <p>Typically, this is where you'll describe the state of your custom view. You may also
       
       
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        * want to provide custom directions when the user has focused your view.
       
       
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        *
       
       
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        * @param event The accessibility event which to populate.
       
       
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        */
       
       
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        @Override
       
       
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        @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
       
       
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        public void onPopulateAccessibilityEvent(AccessibilityEvent event) {
       
       
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        super.onPopulateAccessibilityEvent(event);
       
       
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        // Detect what type of accessibility event is being passed in.
       
       
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        int eventType = event.getEventType();
       
       
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        // Common case: The user has interacted with our view in some way. State may or may not
       
       
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        // have been changed. Read out the current status of the view.
       
       
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        //
       
       
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        // We also set some other metadata which is not used by TalkBack, but could be used by
       
       
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        // other TTS engines.
       
       
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        if (eventType == AccessibilityEvent.TYPE_VIEW_SELECTED ||
       
       
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        eventType == AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUSED) {
       
       
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        event.getText().add("Mode selected: " + Integer.toString(mActiveSelection + 1) + ".");
       
       
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        event.setItemCount(SELECTION_COUNT);
       
       
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        event.setCurrentItemIndex(mActiveSelection);
       
       
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        }
       
       
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        // When a user first focuses on our view, we'll also read out some simple instructions to
       
       
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        // make it clear that this is an interactive element.
       
       
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        if (eventType == AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUSED) {
       
       
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        event.getText().add("Tap to change.");
       
       
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        }
       
       
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        }
       
       
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        /**
       
       
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        * This is called during layout when the size of this view has changed. If
       
       
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        * you were just added to the view hierarchy, you're called with the old
       
       
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        * values of 0.
       
       
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        *
       
       
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        * <p>This is where we determine the drawing bounds for our custom view.
       
       
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        *
       
       
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        * @param w    Current width of this view.
       
       
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        * @param h    Current height of this view.
       
       
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        * @param oldw Old width of this view.
       
       
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        * @param oldh Old height of this view.
       
       
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        */
       
       
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        @Override
       
       
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        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
       
       
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        // Account for padding
       
       
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        float xPadding = (float) (getPaddingLeft() + getPaddingRight());
       
       
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        float yPadding = (float) (getPaddingTop() + getPaddingBottom());
       
       
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        // Compute available width/height
       
       
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        mWidth = w;
       
       
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        mHeight = h;
       
       
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        mWidthPadded = w - xPadding;
       
       
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        mHeightPadded = h - yPadding;
       
       
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        mRadius = (float) (Math.min(mWidth, mHeight) / 2 * 0.8);
       
       
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        }
       
       
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        /**
       
       
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        * Render view content.
       
       
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        *
       
       
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        * <p>We render an outer grey circle to serve as our "dial", and then render a smaller black
       
       
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        * circle to server as our indicator. The position for the indicator is determined based
       
       
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        * on mActiveSelection.
       
       
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        *
       
       
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        * @param canvas the canvas on which the background will be drawn
       
       
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        */
       
       
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        @Override
       
       
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        protected void onDraw(Canvas canvas) {
       
       
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        super.onDraw(canvas);
       
       
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        // Draw dial
       
       
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        canvas.drawCircle(mWidth / 2, mHeight / 2, (float) mRadius, mDialPaint);
       
       
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        // Draw text labels
       
       
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        final float labelRadius = mRadius + 10;
       
       
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        for (int i = 0; i < SELECTION_COUNT; i++) {
       
       
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        float[] xyData = computeXYForPosition(i, labelRadius);
       
       
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        float x = xyData[0];
       
       
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        float y = xyData[1];
       
       
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        canvas.drawText(Integer.toString(i + 1), x, y, mTextPaint);
       
       
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        }
       
       
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        // Draw indicator mark
       
       
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        final float markerRadius = mRadius - 35;
       
       
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        float[] xyData = computeXYForPosition(mActiveSelection, markerRadius);
       
       
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        float x = xyData[0];
       
       
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        float y = xyData[1];
       
       
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        canvas.drawCircle(x, y, 20, mTextPaint);
       
       
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        }
       
       
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        /**
       
       
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        * Compute the X/Y-coordinates for a label or indicator, given the position number and radius
       
       
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        * where the label should be drawn.
       
       
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        *
       
       
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        * @param pos    Zero based position index
       
       
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        * @param radius Radius where label/indicator is to be drawn.
       
       
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        * @return 2-element array. Element 0 is X-coordinate, element 1 is Y-coordinate.
       
       
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        */
       
       
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        private float[] computeXYForPosition(final int pos, final float radius) {
       
       
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        float[] result = new float[2];
       
       
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        Double startAngle = Math.PI * (9 / 8d);   // Angles are in radiansq
       
       
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        Double angle = startAngle + (pos * (Math.PI / 4));
       
       
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        result[0] = (float) (radius * Math.cos(angle)) + (mWidth / 2);
       
       
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        result[1] = (float) (radius * Math.sin(angle)) + (mHeight / 2);
       
       
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        return result;
       
       
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        }
       
       
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        }