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Android example source code file (StateSet.java)

This example Android source code file (StateSet.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

android, e, f, p, stateset, string, stringbuilder, w, wild_card

The StateSet.java Android example source code

/*
 * 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.util;

import com.android.internal.R;

/**
 * State sets are arrays of positive ints where each element
 * represents the state of a {@link android.view.View} (e.g. focused,
 * selected, visible, etc.).  A {@link android.view.View} may be in
 * one or more of those states.
 *
 * A state spec is an array of signed ints where each element
 * represents a required (if positive) or an undesired (if negative)
 * {@link android.view.View} state.
 *
 * Utils dealing with state sets.
 *
 * In theory we could encapsulate the state set and state spec arrays
 * and not have static methods here but there is some concern about
 * performance since these methods are called during view drawing.
 */

public class StateSet {

    public static final int[] WILD_CARD = new int[0];

    /**
     * Return whether the stateSetOrSpec is matched by all StateSets.
     * 
     * @param stateSetOrSpec a state set or state spec.
     */
    public static boolean isWildCard(int[] stateSetOrSpec) {
        return stateSetOrSpec.length == 0 || stateSetOrSpec[0] == 0;
    }

    /**
     * Return whether the stateSet matches the desired stateSpec.
     * 
     * @param stateSpec an array of required (if positive) or
     *        prohibited (if negative) {@link android.view.View} states.
     * @param stateSet an array of {@link android.view.View} states
     */
    public static boolean stateSetMatches(int[] stateSpec, int[] stateSet) {
        if (stateSet == null) {
            return (stateSpec == null || isWildCard(stateSpec));
        }
        int stateSpecSize = stateSpec.length;
        int stateSetSize = stateSet.length;
        for (int i = 0; i < stateSpecSize; i++) {
            int stateSpecState = stateSpec[i];
            if (stateSpecState == 0) {
                // We've reached the end of the cases to match against.
                return true;
            }
            final boolean mustMatch;
            if (stateSpecState > 0) {
                mustMatch = true;
            } else {
                // We use negative values to indicate must-NOT-match states.
                mustMatch = false;
                stateSpecState = -stateSpecState;
            }
            boolean found = false;
            for (int j = 0; j < stateSetSize; j++) {
                final int state = stateSet[j];
                if (state == 0) {
                    // We've reached the end of states to match.
                    if (mustMatch) {
                        // We didn't find this must-match state.
                        return false;
                    } else {
                        // Continue checking other must-not-match states.
                        break;
                    }
                }
                if (state == stateSpecState) {
                    if (mustMatch) {
                        found = true;
                        // Continue checking other other must-match states.
                        break;
                    } else {
                        // Any match of a must-not-match state returns false.
                        return false;
                    }
                }
            }
            if (mustMatch && !found) {
                // We've reached the end of states to match and we didn't
                // find a must-match state.
                return false;
            }
        }
        return true;
    }

    /**
     * Return whether the state matches the desired stateSpec.
     * 
     * @param stateSpec an array of required (if positive) or
     *        prohibited (if negative) {@link android.view.View} states.
     * @param state a {@link android.view.View} state
     */
    public static boolean stateSetMatches(int[] stateSpec, int state) {
        int stateSpecSize = stateSpec.length;
        for (int i = 0; i < stateSpecSize; i++) {
            int stateSpecState = stateSpec[i];
            if (stateSpecState == 0) {
                // We've reached the end of the cases to match against.
                return true;
            }
            if (stateSpecState > 0) {
                if (state != stateSpecState) {
                   return false;
                }
            } else {
                // We use negative values to indicate must-NOT-match states.
                if (state == -stateSpecState) {
                    // We matched a must-not-match case.
                    return false;
                }
            }
        }
        return true;
    }

    public static int[] trimStateSet(int[] states, int newSize) {
        if (states.length == newSize) {
            return states;
        }

        int[] trimmedStates = new int[newSize];
        System.arraycopy(states, 0, trimmedStates, 0, newSize);
        return trimmedStates;
    }
    
    public static String dump(int[] states) {
        StringBuilder sb = new StringBuilder();
        
        int count = states.length;
        for (int i = 0; i < count; i++) {
            
            switch (states[i]) {
            case R.attr.state_window_focused:
                sb.append("W ");
                break;
            case R.attr.state_pressed:
                sb.append("P ");
                break;
            case R.attr.state_selected:
                sb.append("S ");
                break;
            case R.attr.state_focused:
                sb.append("F ");
                break;
            case R.attr.state_enabled:
                sb.append("E ");
                break;
            }
        }
        
        return sb.toString();
    }
}

Other Android examples (source code examples)

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