android/preference/TwoStatePreference.java

/*
 * Copyright (C) 2010 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.preference;

import android.content.Context;
import android.content.SharedPreferences;
import android.content.res.TypedArray;
import android.os.Parcel;
import android.os.Parcelable;
import android.text.TextUtils;
import android.util.AttributeSet;
import android.view.View;
import android.view.accessibility.AccessibilityEvent;
import android.view.accessibility.AccessibilityManager;
import android.widget.TextView;

/**
 * Common base class for preferences that have two selectable states, persist a
 * boolean value in SharedPreferences, and may have dependent preferences that are
 * enabled/disabled based on the current state.
 */
public abstract class TwoStatePreference extends Preference {

    private CharSequence mSummaryOn;
    private CharSequence mSummaryOff;
    boolean mChecked;
    private boolean mCheckedSet;
    private boolean mSendClickAccessibilityEvent;
    private boolean mDisableDependentsState;


    public TwoStatePreference(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    public TwoStatePreference(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

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

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

        boolean newValue = !isChecked();

        mSendClickAccessibilityEvent = true;

        if (!callChangeListener(newValue)) {
            return;
        }

        setChecked(newValue);
    }

    /**
     * Sets the checked state and saves it to the {@link SharedPreferences}.
     *
     * @param checked The checked state.
     */
    public void setChecked(boolean checked) {
        // Always persist/notify the first time; don't assume the field's default of false.
        final boolean changed = mChecked != checked;
        if (changed || !mCheckedSet) {
            mChecked = checked;
            mCheckedSet = true;
            persistBoolean(checked);
            if (changed) {
                notifyDependencyChange(shouldDisableDependents());
                notifyChanged();
            }
        }
    }

    /**
     * Returns the checked state.
     *
     * @return The checked state.
     */
    public boolean isChecked() {
        return mChecked;
    }

    @Override
    public boolean shouldDisableDependents() {
        boolean shouldDisable = mDisableDependentsState ? mChecked : !mChecked;
        return shouldDisable || super.shouldDisableDependents();
    }

    /**
     * Sets the summary to be shown when checked.
     *
     * @param summary The summary to be shown when checked.
     */
    public void setSummaryOn(CharSequence summary) {
        mSummaryOn = summary;
        if (isChecked()) {
            notifyChanged();
        }
    }

    /**
     * @see #setSummaryOn(CharSequence)
     * @param summaryResId The summary as a resource.
     */
    public void setSummaryOn(int summaryResId) {
        setSummaryOn(getContext().getString(summaryResId));
    }

    /**
     * Returns the summary to be shown when checked.
     * @return The summary.
     */
    public CharSequence getSummaryOn() {
        return mSummaryOn;
    }

    /**
     * Sets the summary to be shown when unchecked.
     *
     * @param summary The summary to be shown when unchecked.
     */
    public void setSummaryOff(CharSequence summary) {
        mSummaryOff = summary;
        if (!isChecked()) {
            notifyChanged();
        }
    }

    /**
     * @see #setSummaryOff(CharSequence)
     * @param summaryResId The summary as a resource.
     */
    public void setSummaryOff(int summaryResId) {
        setSummaryOff(getContext().getString(summaryResId));
    }

    /**
     * Returns the summary to be shown when unchecked.
     * @return The summary.
     */
    public CharSequence getSummaryOff() {
        return mSummaryOff;
    }

    /**
     * Returns whether dependents are disabled when this preference is on ({@code true})
     * or when this preference is off ({@code false}).
     *
     * @return Whether dependents are disabled when this preference is on ({@code true})
     *         or when this preference is off ({@code false}).
     */
    public boolean getDisableDependentsState() {
        return mDisableDependentsState;
    }

    /**
     * Sets whether dependents are disabled when this preference is on ({@code true})
     * or when this preference is off ({@code false}).
     *
     * @param disableDependentsState The preference state that should disable dependents.
     */
    public void setDisableDependentsState(boolean disableDependentsState) {
        mDisableDependentsState = disableDependentsState;
    }

    @Override
    protected Object onGetDefaultValue(TypedArray a, int index) {
        return a.getBoolean(index, false);
    }

    @Override
    protected void onSetInitialValue(boolean restoreValue, Object defaultValue) {
        setChecked(restoreValue ? getPersistedBoolean(mChecked)
                : (Boolean) defaultValue);
    }

    void sendAccessibilityEvent(View view) {
        // Since the view is still not attached we create, populate,
        // and send the event directly since we do not know when it
        // will be attached and posting commands is not as clean.
        AccessibilityManager accessibilityManager = AccessibilityManager.getInstance(getContext());
        if (mSendClickAccessibilityEvent && accessibilityManager.isEnabled()) {
            AccessibilityEvent event = AccessibilityEvent.obtain();
            event.setEventType(AccessibilityEvent.TYPE_VIEW_CLICKED);
            view.onInitializeAccessibilityEvent(event);
            view.dispatchPopulateAccessibilityEvent(event);
            accessibilityManager.sendAccessibilityEvent(event);
        }
        mSendClickAccessibilityEvent = false;
    }

    /**
     * Sync a summary view contained within view's subhierarchy with the correct summary text.
     * @param view View where a summary should be located
     */
    void syncSummaryView(View view) {
        // Sync the summary view
        TextView summaryView = (TextView) view.findViewById(com.android.internal.R.id.summary);
        if (summaryView != null) {
            boolean useDefaultSummary = true;
            if (mChecked && !TextUtils.isEmpty(mSummaryOn)) {
                summaryView.setText(mSummaryOn);
                useDefaultSummary = false;
            } else if (!mChecked && !TextUtils.isEmpty(mSummaryOff)) {
                summaryView.setText(mSummaryOff);
                useDefaultSummary = false;
            }

            if (useDefaultSummary) {
                final CharSequence summary = getSummary();
                if (!TextUtils.isEmpty(summary)) {
                    summaryView.setText(summary);
                    useDefaultSummary = false;
                }
            }

            int newVisibility = View.GONE;
            if (!useDefaultSummary) {
                // Someone has written to it
                newVisibility = View.VISIBLE;
            }
            if (newVisibility != summaryView.getVisibility()) {
                summaryView.setVisibility(newVisibility);
            }
        }
    }

    @Override
    protected Parcelable onSaveInstanceState() {
        final Parcelable superState = super.onSaveInstanceState();
        if (isPersistent()) {
            // No need to save instance state since it's persistent
            return superState;
        }

        final SavedState myState = new SavedState(superState);
        myState.checked = isChecked();
        return myState;
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state) {
        if (state == null || !state.getClass().equals(SavedState.class)) {
            // Didn't save state for us in onSaveInstanceState
            super.onRestoreInstanceState(state);
            return;
        }

        SavedState myState = (SavedState) state;
        super.onRestoreInstanceState(myState.getSuperState());
        setChecked(myState.checked);
    }

    static class SavedState extends BaseSavedState {
        boolean checked;

        public SavedState(Parcel source) {
            super(source);
            checked = source.readInt() == 1;
        }

        @Override
        public void writeToParcel(Parcel dest, int flags) {
            super.writeToParcel(dest, flags);
            dest.writeInt(checked ? 1 : 0);
        }

        public SavedState(Parcelable superState) {
            super(superState);
        }

        public static final Parcelable.Creator<SavedState> CREATOR =
                new Parcelable.Creator<SavedState>() {
            public SavedState createFromParcel(Parcel in) {
                return new SavedState(in);
            }

            public SavedState[] newArray(int size) {
                return new SavedState[size];
            }
        };
    }
}