Android判断应用是否已经安装

  /** 
     * 判断应用是否已安装 
     *  
     * @param context 
     * @param packageName 
     * @return 
     */  
    private boolean isInstalled(Context context, String packageName) {  
        boolean hasInstalled = false;  
        PackageManager pm = context.getPackageManager();  
        List<PackageInfo> list = pm  
                .getInstalledPackages(PackageManager.PERMISSION_GRANTED);  
        for (PackageInfo p : list) {  
            if (packageName != null && packageName.equals(p.packageName)) {  
                hasInstalled = true;  
                break;  
            }  
        }  
        return hasInstalled;  
    }