core/java/android/widget/ToggleButton.java

/*
 * Copyright (C) 2007 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 android.widget;

import android.annotation.FloatRange;
import android.annotation.NonNull;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.LayerDrawable;
import android.util.AttributeSet;
import android.view.inspector.InspectableProperty;

import com.android.internal.R;

/**
 * Displays checked/unchecked states as a button
 * with a "light" indicator and by default accompanied with the text "ON" or "OFF".
 *
 * <p>See the <a href="{@docRoot}guide/topics/ui/controls/togglebutton.html">Toggle Buttons</a>
 * guide.</p>
 * 
 * @attr ref android.R.styleable#ToggleButton_textOn
 * @attr ref android.R.styleable#ToggleButton_textOff
 * @attr ref android.R.styleable#ToggleButton_disabledAlpha
 */
public class ToggleButton extends CompoundButton {
    private CharSequence mTextOn;
    private CharSequence mTextOff;
    
    private Drawable mIndicatorDrawable;

    private static final int NO_ALPHA = 0xFF;
    private float mDisabledAlpha;

    public ToggleButton(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);

        final TypedArray a = context.obtainStyledAttributes(
                attrs, com.android.internal.R.styleable.ToggleButton, defStyleAttr, defStyleRes);
        saveAttributeDataForStyleable(context, com.android.internal.R.styleable.ToggleButton,
                attrs, a, defStyleAttr, defStyleRes);
        mTextOn = a.getText(com.android.internal.R.styleable.ToggleButton_textOn);
        mTextOff = a.getText(com.android.internal.R.styleable.ToggleButton_textOff);
        mDisabledAlpha = a.getFloat(com.android.internal.R.styleable.ToggleButton_disabledAlpha, 0.5f);
        syncTextState();
        // Default state is derived from on/off-text, so state has to be updated when on/off-text
        // are updated.
        setDefaultStateDescritption();
        a.recycle();
    }

    public ToggleButton(Context context, AttributeSet attrs, int defStyleAttr) {
        this(context, attrs, defStyleAttr, 0);
    }

    public ToggleButton(Context context, AttributeSet attrs) {
        this(context, attrs, com.android.internal.R.attr.buttonStyleToggle);
    }

    public ToggleButton(Context context) {
        this(context, null);
    }

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

    private void syncTextState() {
        boolean checked = isChecked();
        if (checked && mTextOn != null) {
            setText(mTextOn);
        } else if (!checked && mTextOff != null) {
            setText(mTextOff);
        }
    }

    /**
     * Returns the text for when the button is in the checked state.
     * 
     * @return The text.
     */
    @InspectableProperty
    public CharSequence getTextOn() {
        return mTextOn;
    }

    /**
     * Sets the text for when the button is in the checked state.
     *  
     * @param textOn The text.
     */
    public void setTextOn(CharSequence textOn) {
        mTextOn = textOn;
        // Default state is derived from on/off-text, so state has to be updated when on/off-text
        // are updated.
        setDefaultStateDescritption();
    }

    /**
     * Returns the text for when the button is not in the checked state.
     * 
     * @return The text.
     */
    @InspectableProperty
    public CharSequence getTextOff() {
        return mTextOff;
    }

    /**
     * Sets the text for when the button is not in the checked state.
     * 
     * @param textOff The text.
     */
    public void setTextOff(CharSequence textOff) {
        mTextOff = textOff;
        // Default state is derived from on/off-text, so state has to be updated when on/off-text
        // are updated.
        setDefaultStateDescritption();
    }

    /**
     * Returns the alpha value of the button when it is disabled
     *
     * @return the alpha value, 0.0-1.0
     */
    @InspectableProperty
    @FloatRange(from = 0.0, to = 1.0)
    public float getDisabledAlpha() {
        return mDisabledAlpha;
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        
        updateReferenceToIndicatorDrawable(getBackground());
    }

    @Override
    public void setBackgroundDrawable(Drawable d) {
        super.setBackgroundDrawable(d);
        
        updateReferenceToIndicatorDrawable(d);
    }

    private void updateReferenceToIndicatorDrawable(Drawable backgroundDrawable) {
        if (backgroundDrawable instanceof LayerDrawable) {
            LayerDrawable layerDrawable = (LayerDrawable) backgroundDrawable;
            mIndicatorDrawable =
                    layerDrawable.findDrawableByLayerId(com.android.internal.R.id.toggle);
        } else {
            mIndicatorDrawable = null;
        }
    }
    
    @Override
    protected void drawableStateChanged() {
        super.drawableStateChanged();
        
        if (mIndicatorDrawable != null) {
            mIndicatorDrawable.setAlpha(isEnabled() ? NO_ALPHA : (int) (NO_ALPHA * mDisabledAlpha));
        }
    }

    @Override
    public CharSequence getAccessibilityClassName() {
        return ToggleButton.class.getName();
    }

    /** @hide **/
    @Override
    @NonNull
    protected CharSequence getButtonStateDescription() {
        if (isChecked()) {
            return mTextOn == null ? getResources().getString(R.string.capital_on) : mTextOn;
        } else {
            return mTextOff == null ? getResources().getString(R.string.capital_off) : mTextOff;
        }
    }
}