【起航计划 031】2015 起航计划 Android APIDemo的魔鬼步伐 30 App->Preferences->Advanced preferences 自定义preference OnPreferenceChangeListener

    <com.example.android.apis.preference.MyPreference
            android:key="my_preference"
            android:title="@string/title_my_preference"
            android:summary="@string/summary_my_preference"
            android:defaultValue="100" />

public class MyPreference extends Preference

    // This is the constructor called by the inflater
    public MyPreference(Context context, AttributeSet attrs) {
        super(context, attrs);

        setWidgetLayoutResource(R.layout.preference_widget_mypreference);
    }

    @Override
    protected void onBindView(View view) {
        super.onBindView(view);

        // Set our custom views inside the layout
        final TextView myTextView = (TextView) view.findViewById(R.id.mypreference_widget);
        if (myTextView != null) {
            myTextView.setText(String.valueOf(mClickCounter));
        }
    }

    @Override
    protected Object onGetDefaultValue(TypedArray a, int index) {
        // This preference type‘s value type is Integer, so we read the default
        // value from the attributes as an Integer.
        return a.getInteger(index, 0);
    }

    @Override
    protected void onSetInitialValue(boolean restoreValue, Object defaultValue) {
        if (restoreValue) {
            // Restore state
            mClickCounter = getPersistedInt(mClickCounter);
        } else {
            // Set state
            int value = (Integer) defaultValue;
            mClickCounter = value;
            persistInt(value);
        }
    }

    @Override
    protected Parcelable onSaveInstanceState() {
        /*
         * Suppose a client uses this preference type without persisting. We
         * must save the instance state so it is able to, for example, survive
         * orientation changes.
         */

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

        // Save the instance state
        final SavedState myState = new SavedState(superState);
        myState.clickCounter = mClickCounter;
        return myState;
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state) {
        if (!state.getClass().equals(SavedState.class)) {
            // Didn‘t save state for us in onSaveInstanceState
            super.onRestoreInstanceState(state);
            return;
        }

        // Restore the instance state
        SavedState myState = (SavedState) state;
        super.onRestoreInstanceState(myState.getSuperState());
        mClickCounter = myState.clickCounter;
        notifyChanged();
    }

    @Override
    protected void onClick() {
        int newValue = mClickCounter + 1;
        // Give the client a chance to ignore this change if they deem it
        // invalid
        if (!callChangeListener(newValue)) {
            // They don‘t want the value to be set
            return;
        }

        // Increment counter
        mClickCounter = newValue;

        // Save to persistent storage (this method will make sure this
        // preference should be persistent, along with other useful checks)
        persistInt(mClickCounter);

        // Data has changed, notify so UI can be refreshed!
        notifyChanged();
    }

public class AdvancedPreferences extends PreferenceActivity implements OnSharedPreferenceChangeListener {
    public static final String KEY_MY_PREFERENCE = "my_preference";
    public static final String KEY_ADVANCED_CHECKBOX_PREFERENCE = "advanced_checkbox_preference";

    private CheckBoxPreference mCheckBoxPreference;
    private Handler mHandler = new Handler();

    /**
     * This is a simple example of controlling a preference from code.
     */
    private Runnable mForceCheckBoxRunnable = new Runnable() {
        public void run() {
            if (mCheckBoxPreference != null) {
                mCheckBoxPreference.setChecked(!mCheckBoxPreference.isChecked());
            }

            // Force toggle again in a second
            mHandler.postDelayed(this, 1000);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Load the XML preferences file
        addPreferencesFromResource(R.xml.advanced_preferences);

        // Get a reference to the checkbox preference
        mCheckBoxPreference = (CheckBoxPreference)getPreferenceScreen().findPreference(
                KEY_ADVANCED_CHECKBOX_PREFERENCE);
    }

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

        // Start the force toggle
        mForceCheckBoxRunnable.run();

        // Set up a listener whenever a key changes
        getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
    }

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

        // Unregister the listener whenever a key changes
        getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);

        mHandler.removeCallbacks(mForceCheckBoxRunnable);
    }

    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        // Let‘s do something when my counter preference value changes
        if (key.equals(KEY_MY_PREFERENCE)) {
            Toast.makeText(this, "Thanks! You increased my count to "
                    + sharedPreferences.getInt(key, 0), Toast.LENGTH_SHORT).show();
        }
    }

}