camera/ui/Switch.java

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.camera.ui;

import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.ColorStateList;
import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.text.Layout;
import android.text.StaticLayout;
import android.text.TextPaint;
import android.text.TextUtils;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.ViewConfiguration;
import android.view.accessibility.AccessibilityEvent;
import android.view.accessibility.AccessibilityNodeInfo;
import android.widget.CompoundButton;

import com.android.camera2.R;

/**
 * A Switch is a two-state toggle switch widget that can select between two
 * options. The user may drag the "thumb" back and forth to choose the selected option,
 * or simply tap to toggle as if it were a checkbox.
 */
public class Switch extends CompoundButton {
    private static final int TOUCH_MODE_IDLE = 0;
    private static final int TOUCH_MODE_DOWN = 1;
    private static final int TOUCH_MODE_DRAGGING = 2;

    private Drawable mThumbDrawable;
    private Drawable mTrackDrawable;
    private int mThumbTextPadding;
    private int mSwitchMinWidth;
    private int mSwitchTextMaxWidth;
    private int mSwitchPadding;
    private CharSequence mTextOn;
    private CharSequence mTextOff;

    private int mTouchMode;
    private int mTouchSlop;
    private float mTouchX;
    private float mTouchY;
    private VelocityTracker mVelocityTracker = VelocityTracker.obtain();
    private int mMinFlingVelocity;

    private float mThumbPosition;
    private int mSwitchWidth;
    private int mSwitchHeight;
    private int mThumbWidth; // Does not include padding

    private int mSwitchLeft;
    private int mSwitchTop;
    private int mSwitchRight;
    private int mSwitchBottom;

    private TextPaint mTextPaint;
    private ColorStateList mTextColors;
    private Layout mOnLayout;
    private Layout mOffLayout;

    private final Rect mTempRect = new Rect();

    private static final int[] CHECKED_STATE_SET = {
        android.R.attr.state_checked
    };

    /**
     * Construct a new Switch with default styling, overriding specific style
     * attributes as requested.
     *
     * @param context The Context that will determine this widget's theming.
     * @param attrs Specification of attributes that should deviate from default styling.
     */
    public Switch(Context context, AttributeSet attrs) {
        this(context, attrs, R.attr.switchStyle);
    }

    /**
     * Construct a new Switch with a default style determined by the given theme attribute,
     * overriding specific style attributes as requested.
     *
     * @param context The Context that will determine this widget's theming.
     * @param attrs Specification of attributes that should deviate from the default styling.
     * @param defStyle An attribute ID within the active theme containing a reference to the
     *                 default style for this widget. e.g. android.R.attr.switchStyle.
     */
    public Switch(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        mTextPaint = new TextPaint(Paint.ANTI_ALIAS_FLAG);
        Resources res = getResources();
        DisplayMetrics dm = res.getDisplayMetrics();
        mTextPaint.density = dm.density;
        mThumbDrawable = res.getDrawable(R.drawable.switch_inner_holo_dark);
        mTrackDrawable = res.getDrawable(R.drawable.switch_track_holo_dark);
        mTextOn = res.getString(R.string.capital_on);
        mTextOff = res.getString(R.string.capital_off);
        mThumbTextPadding = res.getDimensionPixelSize(R.dimen.thumb_text_padding);
        mSwitchMinWidth = res.getDimensionPixelSize(R.dimen.switch_min_width);
        mSwitchTextMaxWidth = res.getDimensionPixelSize(R.dimen.switch_text_max_width);
        mSwitchPadding = res.getDimensionPixelSize(R.dimen.switch_padding);
        setSwitchTextAppearance(context, android.R.style.TextAppearance_Holo_Small);

        ViewConfiguration config = ViewConfiguration.get(context);
        mTouchSlop = config.getScaledTouchSlop();
        mMinFlingVelocity = config.getScaledMinimumFlingVelocity();

        // Refresh display with current params
        refreshDrawableState();
        setChecked(isChecked());
    }

    /**
     * Sets the switch text color, size, style, hint color, and highlight color
     * from the specified TextAppearance resource.
     */
    public void setSwitchTextAppearance(Context context, int resid) {
        Resources res = getResources();
        mTextColors = getTextColors();
        int ts = res.getDimensionPixelSize(R.dimen.thumb_text_size);
        if (ts != mTextPaint.getTextSize()) {
            mTextPaint.setTextSize(ts);
            requestLayout();
        }
    }

    @Override
    public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        if (mOnLayout == null) {
            mOnLayout = makeLayout(mTextOn, mSwitchTextMaxWidth);
        }
        if (mOffLayout == null) {
            mOffLayout = makeLayout(mTextOff, mSwitchTextMaxWidth);
        }

        mTrackDrawable.getPadding(mTempRect);
        final int maxTextWidth = Math.min(mSwitchTextMaxWidth,
                Math.max(mOnLayout.getWidth(), mOffLayout.getWidth()));
        final int switchWidth = Math.max(mSwitchMinWidth,
                maxTextWidth * 2 + mThumbTextPadding * 4 + mTempRect.left + mTempRect.right);
        final int switchHeight = mTrackDrawable.getIntrinsicHeight();

        mThumbWidth = maxTextWidth + mThumbTextPadding * 2;

        mSwitchWidth = switchWidth;
        mSwitchHeight = switchHeight;

        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        final int measuredHeight = getMeasuredHeight();
        final int measuredWidth = getMeasuredWidth();
        if (measuredHeight < switchHeight) {
            setMeasuredDimension(measuredWidth, switchHeight);
        }
    }

    @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
    @Override
    public void onPopulateAccessibilityEvent(AccessibilityEvent event) {
        super.onPopulateAccessibilityEvent(event);
        CharSequence text = isChecked() ? mOnLayout.getText() : mOffLayout.getText();
        if (!TextUtils.isEmpty(text)) {
            event.getText().add(text);
        }
    }

    private Layout makeLayout(CharSequence text, int maxWidth) {
        int actual_width = (int) Math.ceil(Layout.getDesiredWidth(text, mTextPaint));
        StaticLayout l = new StaticLayout(text, 0, text.length(), mTextPaint,
                actual_width,
                Layout.Alignment.ALIGN_NORMAL, 1.f, 0, true,
                TextUtils.TruncateAt.END,
                (int) Math.min(actual_width, maxWidth));
        return l;
    }

    /**
     * @return true if (x, y) is within the target area of the switch thumb
     */
    private boolean hitThumb(float x, float y) {
        mThumbDrawable.getPadding(mTempRect);
        final int thumbTop = mSwitchTop - mTouchSlop;
        final int thumbLeft = mSwitchLeft + (int) (mThumbPosition + 0.5f) - mTouchSlop;
        final int thumbRight = thumbLeft + mThumbWidth +
                mTempRect.left + mTempRect.right + mTouchSlop;
        final int thumbBottom = mSwitchBottom + mTouchSlop;
        return x > thumbLeft && x < thumbRight && y > thumbTop && y < thumbBottom;
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        mVelocityTracker.addMovement(ev);
        final int action = ev.getActionMasked();
        switch (action) {
            case MotionEvent.ACTION_DOWN: {
                final float x = ev.getX();
                final float y = ev.getY();
                if (isEnabled() && hitThumb(x, y)) {
                    mTouchMode = TOUCH_MODE_DOWN;
                    mTouchX = x;
                    mTouchY = y;
                }
                break;
            }

            case MotionEvent.ACTION_MOVE: {
                switch (mTouchMode) {
                    case TOUCH_MODE_IDLE:
                        // Didn't target the thumb, treat normally.
                        break;

                    case TOUCH_MODE_DOWN: {
                        final float x = ev.getX();
                        final float y = ev.getY();
                        if (Math.abs(x - mTouchX) > mTouchSlop ||
                                Math.abs(y - mTouchY) > mTouchSlop) {
                            mTouchMode = TOUCH_MODE_DRAGGING;
                            getParent().requestDisallowInterceptTouchEvent(true);
                            mTouchX = x;
                            mTouchY = y;
                            return true;
                        }
                        break;
                    }

                    case TOUCH_MODE_DRAGGING: {
                        final float x = ev.getX();
                        final float dx = x - mTouchX;
                        float newPos = Math.max(0,
                                Math.min(mThumbPosition + dx, getThumbScrollRange()));
                        if (newPos != mThumbPosition) {
                            mThumbPosition = newPos;
                            mTouchX = x;
                            invalidate();
                        }
                        return true;
                    }
                }
                break;
            }

            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL: {
                if (mTouchMode == TOUCH_MODE_DRAGGING) {
                    stopDrag(ev);
                    return true;
                }
                mTouchMode = TOUCH_MODE_IDLE;
                mVelocityTracker.clear();
                break;
            }
        }

        return super.onTouchEvent(ev);
    }

    private void cancelSuperTouch(MotionEvent ev) {
        MotionEvent cancel = MotionEvent.obtain(ev);
        cancel.setAction(MotionEvent.ACTION_CANCEL);
        super.onTouchEvent(cancel);
        cancel.recycle();
    }

    /**
     * Called from onTouchEvent to end a drag operation.
     *
     * @param ev Event that triggered the end of drag mode - ACTION_UP or ACTION_CANCEL
     */
    private void stopDrag(MotionEvent ev) {
        mTouchMode = TOUCH_MODE_IDLE;
        // Up and not canceled, also checks the switch has not been disabled during the drag
        boolean commitChange = ev.getAction() == MotionEvent.ACTION_UP && isEnabled();

        cancelSuperTouch(ev);

        if (commitChange) {
            boolean newState;
            mVelocityTracker.computeCurrentVelocity(1000);
            float xvel = mVelocityTracker.getXVelocity();
            if (Math.abs(xvel) > mMinFlingVelocity) {
                newState = xvel > 0;
            } else {
                newState = getTargetCheckedState();
            }
            animateThumbToCheckedState(newState);
        } else {
            animateThumbToCheckedState(isChecked());
        }
    }

    private void animateThumbToCheckedState(boolean newCheckedState) {
        setChecked(newCheckedState);
    }

    private boolean getTargetCheckedState() {
        return mThumbPosition >= getThumbScrollRange() / 2;
    }

    private void setThumbPosition(boolean checked) {
        mThumbPosition = checked ? getThumbScrollRange() : 0;
    }

    @Override
    public void setChecked(boolean checked) {
        super.setChecked(checked);
        setThumbPosition(checked);
        invalidate();
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);

        setThumbPosition(isChecked());

        int switchRight;
        int switchLeft;

        switchRight = getWidth() - getPaddingRight();
        switchLeft = switchRight - mSwitchWidth;

        int switchTop = 0;
        int switchBottom = 0;
        switch (getGravity() & Gravity.VERTICAL_GRAVITY_MASK) {
            default:
            case Gravity.TOP:
                switchTop = getPaddingTop();
                switchBottom = switchTop + mSwitchHeight;
                break;

            case Gravity.CENTER_VERTICAL:
                switchTop = (getPaddingTop() + getHeight() - getPaddingBottom()) / 2 -
                        mSwitchHeight / 2;
                switchBottom = switchTop + mSwitchHeight;
                break;

            case Gravity.BOTTOM:
                switchBottom = getHeight() - getPaddingBottom();
                switchTop = switchBottom - mSwitchHeight;
                break;
        }

        mSwitchLeft = switchLeft;
        mSwitchTop = switchTop;
        mSwitchBottom = switchBottom;
        mSwitchRight = switchRight;
    }

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

        // Draw the switch
        int switchLeft = mSwitchLeft;
        int switchTop = mSwitchTop;
        int switchRight = mSwitchRight;
        int switchBottom = mSwitchBottom;

        mTrackDrawable.setBounds(switchLeft, switchTop, switchRight, switchBottom);
        mTrackDrawable.draw(canvas);

        canvas.save();

        mTrackDrawable.getPadding(mTempRect);
        int switchInnerLeft = switchLeft + mTempRect.left;
        int switchInnerTop = switchTop + mTempRect.top;
        int switchInnerRight = switchRight - mTempRect.right;
        int switchInnerBottom = switchBottom - mTempRect.bottom;
        canvas.clipRect(switchInnerLeft, switchTop, switchInnerRight, switchBottom);

        mThumbDrawable.getPadding(mTempRect);
        final int thumbPos = (int) (mThumbPosition + 0.5f);
        int thumbLeft = switchInnerLeft - mTempRect.left + thumbPos;
        int thumbRight = switchInnerLeft + thumbPos + mThumbWidth + mTempRect.right;

        mThumbDrawable.setBounds(thumbLeft, switchTop, thumbRight, switchBottom);
        mThumbDrawable.draw(canvas);

        // mTextColors should not be null, but just in case
        if (mTextColors != null) {
            mTextPaint.setColor(mTextColors.getColorForState(getDrawableState(),
                    mTextColors.getDefaultColor()));
        }
        mTextPaint.drawableState = getDrawableState();

        Layout switchText = getTargetCheckedState() ? mOnLayout : mOffLayout;

        canvas.translate((thumbLeft + thumbRight) / 2 - switchText.getEllipsizedWidth() / 2,
                (switchInnerTop + switchInnerBottom) / 2 - switchText.getHeight() / 2);
        switchText.draw(canvas);

        canvas.restore();
    }

    @Override
    public int getCompoundPaddingRight() {
        int padding = super.getCompoundPaddingRight() + mSwitchWidth;
        if (!TextUtils.isEmpty(getText())) {
            padding += mSwitchPadding;
        }
        return padding;
    }

    private int getThumbScrollRange() {
        if (mTrackDrawable == null) {
            return 0;
        }
        mTrackDrawable.getPadding(mTempRect);
        return mSwitchWidth - mThumbWidth - mTempRect.left - mTempRect.right;
    }

    @Override
    protected int[] onCreateDrawableState(int extraSpace) {
        final int[] drawableState = super.onCreateDrawableState(extraSpace + 1);

        if (isChecked()) {
            mergeDrawableStates(drawableState, CHECKED_STATE_SET);
        }
        return drawableState;
    }

    @Override
    protected void drawableStateChanged() {
        super.drawableStateChanged();

        int[] myDrawableState = getDrawableState();

        // Set the state of the Drawable
        // Drawable may be null when checked state is set from XML, from super constructor
        if (mThumbDrawable != null) mThumbDrawable.setState(myDrawableState);
        if (mTrackDrawable != null) mTrackDrawable.setState(myDrawableState);

        invalidate();
    }

    @Override
    protected boolean verifyDrawable(Drawable who) {
        return super.verifyDrawable(who) || who == mThumbDrawable || who == mTrackDrawable;
    }

    @Override
    public void jumpDrawablesToCurrentState() {
        super.jumpDrawablesToCurrentState();
        mThumbDrawable.jumpToCurrentState();
        mTrackDrawable.jumpToCurrentState();
    }

    @Override
    public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
        super.onInitializeAccessibilityEvent(event);
        event.setClassName(Switch.class.getName());
    }

    @Override
    public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
        super.onInitializeAccessibilityNodeInfo(info);
        info.setClassName(Switch.class.getName());
        CharSequence switchText = isChecked() ? mTextOn : mTextOff;
        if (!TextUtils.isEmpty(switchText)) {
            CharSequence oldText = info.getText();
            if (TextUtils.isEmpty(oldText)) {
                info.setText(switchText);
            } else {
                StringBuilder newText = new StringBuilder();
                newText.append(oldText).append(' ').append(switchText);
                info.setText(newText);
            }
        }
    }
}