android判斷應用安裝狀況

public class InstalledPackageQuerier {
    
    public static final int VERSION_CODE_NONE = -1;
    private static final Integer EMPTY_VERSION = new Integer(VERSION_CODE_NONE);
    private static InstalledPackageQuerier sInstance;

    private Context mContext;
    private Map<String, Integer> mInstalledApps;
    private Map<String, List<WeakReference<InstalledPackageQuerierListener>>> mListeners = new HashMap<String, List<WeakReference<InstalledPackageQuerierListener>>>();
    private ArrayList<WeakReference<InstalledPackageQuerierListener>> mGlobalListener = new ArrayList<>();

    public static void init (Context context) {
        sInstance = new InstalledPackageQuerier(context);
    }

    public static InstalledPackageQuerier getInstance () {
        return sInstance;
    }

    private InstalledPackageQuerier (Context context) {
        mContext = context.getApplicationContext();
        mInstalledApps = new HashMap<>();
        registerReceiver();
    }

    private void registerReceiver () {
        IntentFilter filter = new IntentFilter();
        filter.addAction(Intent.ACTION_PACKAGE_ADDED);
        filter.addAction(Intent.ACTION_PACKAGE_REMOVED);
        filter.setPriority(Integer.MAX_VALUE); // 設置級別
        filter.addDataScheme("package");
        mContext.registerReceiver(new AppInstallReceiver(), filter);
    }

    public int getInstalledAppVersionCode (String packageName) {

        Integer versionCode = mInstalledApps.get(packageName);
        if (versionCode == null) {    //還沒緩存
            PackageInfo info = getPackageInfo(packageName);
            if (info != null) {
                mInstalledApps.put(packageName, info.versionCode);
                return info.versionCode;
            } else {
                mInstalledApps.put(packageName, EMPTY_VERSION);
                return VERSION_CODE_NONE;
            }
        } else {
            return versionCode.intValue();
        }
    }

    public boolean isInstalled (String packageName) {
        return getInstalledAppVersionCode(packageName) != VERSION_CODE_NONE;
    }

    private PackageInfo getPackageInfo (String packageName) {
        try {
            return mContext.getPackageManager().getPackageInfo(packageName, 0);
        } catch (NameNotFoundException e) {
        }
        return null;
    }

    public class AppInstallReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {

            String packageName = intent.getDataString().substring(8);

            if (Intent.ACTION_PACKAGE_ADDED.equals(intent.getAction())) {
                if (mInstalledApps.containsKey(packageName)) {
                    PackageInfo info = getPackageInfo(packageName);
                    if (info != null) {
                        mInstalledApps.put(packageName, info.versionCode);
                    }
                }
                dispatchAppChanged(packageName, true);
            } else if (Intent.ACTION_PACKAGE_REMOVED.equals(intent.getAction())) {
                if (mInstalledApps.containsKey(packageName)) {
                    mInstalledApps.put(packageName, EMPTY_VERSION);
                }
                dispatchAppChanged(packageName, false);
            }

        }
    }

    private void dispatchAppChanged (String appPackage, boolean addOrRemove) {

        dispatchForList(mGlobalListener, appPackage, addOrRemove);

        List<WeakReference<InstalledPackageQuerierListener>> appListeners = mListeners.get(appPackage);
        if (appListeners != null) {
            dispatchForList(appListeners, appPackage, addOrRemove);
        }
    }

    private void dispatchForList (List<WeakReference<InstalledPackageQuerierListener>> list, String appPackage, boolean addOrRemove) {
        Iterator<WeakReference<InstalledPackageQuerierListener>> it = list.iterator();
        while (it.hasNext()) {
            WeakReference<InstalledPackageQuerierListener> ref = it.next();
            InstalledPackageQuerierListener listener = ref.get();
            if (listener != null) {
                if (addOrRemove) {
                    listener.onAppAdded(appPackage);
                } else {
                    listener.onAppRemoved(appPackage);
                }
            } else {
                it.remove();
            }
        }
    }

    public void addInstalledPackageQuerierListener (InstalledPackageQuerierListener listener) {
        if (listener != null) {
            mGlobalListener.add(new WeakReference<>(listener));
        }
    }

    public void removeInstalledPackageQuerierListener (InstalledPackageQuerierListener listener) {
        if (listener != null) {
            Iterator<WeakReference<InstalledPackageQuerierListener>> it = mGlobalListener.iterator();
            while (it.hasNext()) {
                WeakReference<InstalledPackageQuerierListener> ref = it.next();
                if (ref.get() == listener || ref.get() == null) {
                    it.remove();
                    break;
                }
            }
        }
    }

    public void addInstalledPackageQuerierListener (String appPackage, InstalledPackageQuerierListener listener) {
        if (listener != null) {
            List<WeakReference<InstalledPackageQuerierListener>> appListeners = mListeners.get(appPackage);
            if (appListeners == null) {
                appListeners = new ArrayList<>();
                mListeners.put(appPackage, appListeners);
            }
            appListeners.add(new WeakReference<>(listener));
        }
    }

    public void removeInstalledPackageQuerierListener (String appPackage, InstalledPackageQuerierListener listener) {
        if (listener != null) {
            List<WeakReference<InstalledPackageQuerierListener>> appListeners = mListeners.get(appPackage);
            if (appListeners != null) {
                Iterator<WeakReference<InstalledPackageQuerierListener>> it = appListeners.iterator();
                while (it.hasNext()) {
                    WeakReference<InstalledPackageQuerierListener> ref = it.next();
                    if (ref.get() == listener || ref.get() == null) {
                        it.remove();
                        break;
                    }
                }
            }
        }
    }

    public interface InstalledPackageQuerierListener {         void onAppAdded(String appPackage);         void onAppRemoved(String appPackage);     } }